Fluke Power Supply 2620A User Manual

®
2620A/2625A  
Hydra Series II Data Acquisition Unit  
Hydra Series II Data Logger  
Users Manual  
PN 686675  
November 1997  
© 1997 Fluke Corporation, All rights reserved. Printed in U.S.A.  
All product names are trademarks of their respective companies.  
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Table of Contents  
Chapter  
1
Title  
Page  
Introduction........................................................................................ 1-1  
The Hydra Series II Data Acquisition Unit....................................................... 1-3  
The Hydra Series II Data Logger ...................................................................... 1-3  
Options and Accessories ................................................................................... 1-3  
Applications Software................................................................................... 1-3  
IEEE-488 Interface Assembly....................................................................... 1-3  
Connector Set (2620A-100).......................................................................... 1-3  
Accessories.................................................................................................... 1-5  
Where to go From Here..................................................................................... 1-5  
2
Overview............................................................................................. 2-1  
Introduction ....................................................................................................... 2-3  
Setting Up the Instrument.................................................................................. 2-3  
Unpacking and Inspecting the Instrument..................................................... 2-3  
Adjusting the Handle .................................................................................... 2-3  
Line Power .................................................................................................... 2-4  
Front/Rear Panel Features............................................................................. 2-4  
Input Channels .............................................................................................. 2-9  
Operating Modes ............................................................................................... 2-9  
Turning the Instrument On................................................................................ 2-9  
Front Panel Display........................................................................................... 2-10  
Reading the Display .......................................................................................... 2-10  
Left Display................................................................................................... 2-10  
Right Display ................................................................................................ 2-10  
Specific Annunciators................................................................................... 2-10  
Front Panel Buttons........................................................................................... 2-11  
Selecting a Channel....................................................................................... 2-11  
Using the Buttons.......................................................................................... 2-11  
Setting up a Channel.......................................................................................... 2-12  
Setting Alarm Limits and Mx+B Scaling Values.............................................. 2-14  
Alarm Limits................................................................................................. 2-14  
Mx+B Scaling ............................................................................................... 2-15  
Setting the Scan Interval.................................................................................... 2-15  
Using the Monitor Function .............................................................................. 2-16  
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Users Manual  
Using the Scan Function.................................................................................... 2-16  
Reviewing Channel Data................................................................................... 2-16  
Viewing the Totalizer Count............................................................................. 2-17  
Using External DC Power ................................................................................. 2-17  
Using the Rack Mount Kit................................................................................. 2-18  
3
Operating the Instrument from the Front Panel............................... 3-1  
Introduction ....................................................................................................... 3-3  
Operating Modes ............................................................................................... 3-3  
Other Displayed Data ........................................................................................ 3-4  
What is the Present Configuration?................................................................... 3-4  
If Power is Interrupted .................................................................................. 3-4  
If the Configuration is Reset......................................................................... 3-4  
Channel Configuration ...................................................................................... 3-4  
Selecting Channel, Function, and Range ...................................................... 3-4  
Setting Alarms............................................................................................... 3-9  
Alarm Limits............................................................................................. 3-9  
Alarm Indications ..................................................................................... 3-10  
Resetting Alarm Conditions ..................................................................... 3-11  
Using the Digital I/O Lines........................................................................... 3-11  
Mx+B Scaling ............................................................................................... 3-12  
Instrument Configuration .................................................................................. 3-14  
Entering and Changing Numeric Values....................................................... 3-14  
Selecting Scan Interval.................................................................................. 3-15  
Selecting the Measurement Rate................................................................... 3-15  
Triggering...................................................................................................... 3-16  
External Triggering....................................................................................... 3-16  
Changing the Temperature Unit.................................................................... 3-16  
Setting Date and Time of Day....................................................................... 3-17  
Measurement Connections ................................................................................ 3-17  
DC Volts, AC Volts, Frequency, and Thermocouples.................................. 3-18  
Resistance and RTD...................................................................................... 3-20  
Totalizing........................................................................................................... 3-22  
General.......................................................................................................... 3-22  
Connections................................................................................................... 3-22  
Review Array..................................................................................................... 3-22  
List Button Functions........................................................................................ 3-23  
Autoprint ........................................................................................................... 3-25  
Memory Storage ................................................................................................ 3-25  
Front Panel Lock out Conditions....................................................................... 3-26  
Front Panel Review Only Function............................................................... 3-26  
Front Panel Monitor Only Function.............................................................. 3-26  
Computer Interface-Initiated Lockouts......................................................... 3-27  
REM Annunciator ............................................................................................. 3-27  
Calibration......................................................................................................... 3-27  
4
Using the Computer Interface........................................................... 4-1  
Introduction ....................................................................................................... 4-3  
Front Panel and Computer Interface Operations........................................... 4-3  
Types of Computer Interface ........................................................................ 4-3  
Using the RS-232 Computer Interface .............................................................. 4-3  
Setting Communication Parameters (RS-232).............................................. 4-4  
Autoprint and Memory Storage (RS-232)..................................................... 4-5  
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Contents (continued)  
Autoprint: Computer Interface Control .................................................... 4-5  
Autoprint: Output Format......................................................................... 4-5  
Memory Storage: Computer Interface Control......................................... 4-6  
Memory Retrieval..................................................................................... 4-6  
Memory Full Operation ............................................................................ 4-7  
Clearing Memory...................................................................................... 4-7  
Cabling the Instrument to a Host or Printer (RS-232) .................................. 4-7  
Installation Test............................................................................................. 4-8  
RS-232 Information....................................................................................... 4-8  
Character Echoing .................................................................................... 4-8  
Character Deletion.................................................................................... 4-8  
Device Clear Using Ctrl C........................................................................ 4-8  
RS-232 Prompts........................................................................................ 4-9  
Sample Program Using the RS-232 Computer Interface .............................. 4-9  
Using the IEEE-488 Interface............................................................................ 4-9  
IEEE-488 Operating Limitations .................................................................. 4-9  
Installing the IEEE-488 Interface.................................................................. 4-9  
Enabling the IEEE-488 Interface .................................................................. 4-12  
Installation Test............................................................................................. 4-13  
General Information (RS-232 and IEEE-488)................................................... 4-13  
How the Instrument Processes Input............................................................. 4-13  
Input Strings.............................................................................................. 4-14  
Input Terminators ..................................................................................... 4-14  
Typical Input Strings ................................................................................ 4-14  
Sending Numeric Values to the Instrument (RS-232 and IEEE-488) ...... 4-16  
Sending Input Strings to the Instrument ................................................... 4-16  
How the Instrument Processes Output.......................................................... 4-16  
Service Requests (IEEE-488 only) and Status Registers.............................. 4-17  
Event Status and Event Status Enable Registers ...................................... 4-19  
Status Byte Register.................................................................................. 4-19  
Reading the Status Byte Register ............................................................. 4-20  
Service Request Enable Register.............................................................. 4-21  
Instrument Event Register ........................................................................ 4-21  
Computer Interface Command Set .................................................................... 4-22  
5
Additional Considerations ................................................................ 5-1  
Introduction ....................................................................................................... 5-3  
Measurement Rate............................................................................................. 5-3  
Advanced Trigger Mechanisms......................................................................... 5-3  
Front Panel Trigger Control.......................................................................... 5-3  
Computer Interface Trigger Control ............................................................. 5-3  
Both External and Monitor Alarms Disabled (Type 0) ................................ 5-4  
External Trigger Enabled (Type 1)............................................................... 5-4  
Monitor Alarm Enabled (Type 2) ................................................................. 5-6  
Thermal Voltages .............................................................................................. 5-6  
When Measuring Resistance or Temperature (RTD)........................................ 5-6  
True RMS Measurements.................................................................................. 5-8  
Effects of Internal Noise in AC Measurements ............................................ 5-8  
Waveform Comparison (True RMS vs Average Responding) ..................... 5-8  
Making Mixed Measurements........................................................................... 5-9  
Using Shielded Wiring...................................................................................... 5-11  
General Rule ................................................................................................. 5-11  
Alternate Suggestions ................................................................................... 5-11  
Non-Isolated Sensor Configuration .......................................................... 5-11  
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Isolated and Shielded Sensor Configuration ............................................ 5-11  
In More Detail............................................................................................... 5-12  
6
Maintenance....................................................................................... 6-1  
Introduction ....................................................................................................... 6-3  
Cleaning............................................................................................................. 6-3  
Line Fuse ........................................................................................................... 6-3  
Self-Test Diagnostics and Error Codes ............................................................. 6-3  
Performance Tests............................................................................................. 6-4  
Accuracy Verification Test........................................................................... 6-7  
Channel Integrity Test................................................................................... 6-7  
Thermocouple Measurement Range Accuracy Test ..................................... 6-9  
4-Terminal Resistance Test........................................................................... 6-10  
Thermocouple Temperature Accuracy Test.................................................. 6-11  
Open Thermocouple Response Test ............................................................. 6-13  
RTD Temperature Accuracy Test................................................................. 6-14  
RTD Temperature Accuracy Test (Using Decade Resistance Source).... 6-14  
RTD Temperature Accuracy Test (Using DIN/IEC 751)......................... 6-15  
Digital Input/Output Verification Tests........................................................ 6-15  
Digital Output Test ................................................................................... 6-16  
Digital Input Test...................................................................................... 6-16  
Totalizer Test............................................................................................ 6-17  
Totalizer Sensitivity Test.......................................................................... 6-18  
Dedicated Alarm Output Test ....................................................................... 6-19  
External Trigger Input Test........................................................................... 6-21  
Calibration......................................................................................................... 6-21  
Variations in the Display................................................................................... 6-22  
Service............................................................................................................... 6-22  
Appendices  
A Specifications.............................................................................................. A-1  
B ASCII & IEEE-488 Bus Codes ................................................................... B-1  
C IEEE-488.2 Devise Documentation Requirements..................................... C-1  
D Making Mixed Measurements .................................................................... D-1  
E
F
Binary Upload of Logged Data (LOG_BIN?) (2625A only)...................... E-1  
RS-232 Cabling........................................................................................... F-1  
Index  
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List of Tables  
Table  
Title  
Page  
1-1. Hydra Features....................................................................................................... 1-4  
1-2. Accessories ............................................................................................................ 1-5  
2-1. Display Annunciators ............................................................................................ 2-7  
2-2. Front Panel Pushbuttons ........................................................................................ 2-11  
2-3. Review Array......................................................................................................... 2-17  
3-1. Configuration Reset Settings................................................................................. 3-5  
3-2. DC Voltage, AC Voltage....................................................................................... 3-6  
3-3. Resistance .............................................................................................................. 3-7  
3-4. Frequency............................................................................................................... 3-7  
3-5. Thermocouple Temperature................................................................................... 3-8  
3-6. RTD Temperature.................................................................................................. 3-9  
3-7. Alarm Selection ..................................................................................................... 3-10  
3-8. Initial Alarm Assignments, Digital I/O Lines 4 Through 7................................... 3-12  
3-9. Mx+B Selection..................................................................................................... 3-14  
3-10. Scan Interval .......................................................................................................... 3-15  
3-11. Measurement Rate Selection ................................................................................. 3-16  
3-12. Trigger Type Selection .......................................................................................... 3-16  
3-13. Date/Time Selection .............................................................................................. 3-17  
3-14. Thermocouple Ranges ........................................................................................... 3-20  
3-15. Review Array......................................................................................................... 3-23  
3-16. List Button Operation ............................................................................................ 3-24  
3-17. Autoprint/Memory Storage Selection.................................................................... 3-26  
3-18. Clearing Memory Storage...................................................................................... 3-26  
3-19. REM Annunciation................................................................................................ 3-27  
4-1. RS-232 Setup ......................................................................................................... 4-4  
4-2. IEEE-488.1 Capabilities ........................................................................................ 4-12  
4-3. IEEE-488 Setup ..................................................................................................... 4-12  
4-4. Status Byte Register............................................................................................... 4-19  
4-5. Event Status Register............................................................................................. 4-20  
4-6. Instrument Event Register (IER) ........................................................................... 4-22  
4-7. Command and Query Summary............................................................................. 4-23  
4-8. Command and Query Reference............................................................................ 4-26  
5-1. Ohms Test Voltage ................................................................................................ 5-8  
6-1. Power-Up Error Codes........................................................................................... 6-5  
6-2. Recommended Test Equipment............................................................................. 6-6  
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Users Manual  
6-3. Performance Tests (Voltage, Resistance, and Frequency) .................................... 6-8  
6-4. Performance Tests for Thermocouple Temperature Function (IPTS-68/ITS-90) . 6-13  
6-5. Performance Tests for RTD Temperature Function (Resistance) (DIN/IEC 751  
Amendment 1) (IPTS-68) ...................................................................................... 6-14  
6-6. Performance Tests for RTD Temperature Function (DIN/IEC 751 Amendment 1)  
(IPTS-68) ............................................................................................................... 6-15  
6-7. Digital Input Values............................................................................................... 6-17  
E-1. Floating Point Format............................................................................................ E-4  
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List of Figures  
Figure  
Title  
Page  
2-1. Adjusting Handle................................................................................................... 2-3  
2-2. Front Panel............................................................................................................. 2-5  
2-3. Left Display ........................................................................................................... 2-6  
2-4. Right Display......................................................................................................... 2-6  
2-5. Annunciators.......................................................................................................... 2-6  
2-6. Rear View.............................................................................................................. 2-8  
3-1. Configuration Mode............................................................................................... 3-3  
3-2. Input Module Connections .................................................................................... 3-19  
3-3. 2-Terminal and 4-Terminal Connections............................................................... 3-21  
3-4. Totalizing Connection ........................................................................................... 3-22  
4-1. Data/Stop Bits........................................................................................................ 4-4  
4-2. Sample Program..................................................................................................... 4-10  
4-3. Typical Input Strings ............................................................................................. 4-15  
4-4. Overview of Status Data Registers........................................................................ 4-18  
5-1. External Trigger Timing........................................................................................ 5-5  
5-2. 2T and 4T-Connections ......................................................................................... 5-7  
5-3. Comparison of Common Waveforms .................................................................... 5-10  
6-1. Replacing the Line Fuse ........................................................................................ 6-4  
6-2. 4-Terminal Connections to 5700A ........................................................................ 6-12  
6-3. 4-Terminal Connections to Decade Resistance Box ............................................. 6-13  
6-4. Dedicated Alarms Output Test .............................................................................. 6-20  
6-5. External Trigger Test............................................................................................. 6-21  
E-1. ASCII String Decoding.......................................................................................... E-2  
E-2. Floating Point Conversion ..................................................................................... E-5  
E-3. Example ................................................................................................................. E-6  
F-1. Summary of RS-232 Connections ......................................................................... F-3  
F-2. Hydra (DB-9) to PC (DB-9) RS-232 Connection (Generic) ................................. F-4  
F-3. Hydra (DB-9) to PC (DB-25) RS-232 Connection................................................ F-5  
F-4. Hydra (DB-9) to Modem (DB-25) RS-232 Connection ........................................ F-6  
F-5. Hydra (DB-9) to Printer (DB-25) RS-232 Connection.......................................... F-7  
F-6. RS-232 DB9 and DB-25 Connectors..................................................................... F-8  
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Caution  
THIS IS AN IEC SAFETY CLASS 1 PRODUCT. BEFORE USING, THE GROUND WIRE IN THE  
LINE CORD OR THE REAR PANEL BINDING POST MUST BE CONNECTED FOR SAFETY.  
Interference Information  
This equipment generates and uses radio frequency energy and if not installed and used in strict  
accordance with the manufacturer’s instructions, may cause interference to radio and television  
reception. It has been type tested and found to comply with the limits for a Class B computing  
device in accordance with the specifications of Part 15 of FCC Rules, which are designed to  
provide reasonable protection against such interference in a residential installation.  
Operation is subject to the following two conditions:  
This device may not cause harmful interference.  
This device must accept any interference received, including interference that may cause  
undesired operation.  
There is no guarantee that interference will not occur in a particular installation. If this equipment  
does cause interference to radio or television reception, which can be determined by turning the  
equipment off and on, the user is encouraged to try to correct the interference by one of more of  
the following measures:  
Reorient the receiving antenna  
Relocate the equipment with respect to the receiver  
Move the equipment away from the receiver  
Plug the equipment into a different outlet so that the computer and receiver are on different  
branch circuits  
If necessary, the user should consult the dealer or an experienced radio/television technician for  
additional suggestions. The user may find the following booklet prepared by the Federal  
Communications Commission helpful: How to Identify and Resolve Radio-TV Interference  
Problems. This booklet is available from the U.S. Government Printing Office, Washington, D.C.  
20402. Stock No. 004-000-00345-4.  
Declaration of the Manufacturer or Importer  
We hereby certify that the Fluke Model 2620A Data Acquisition Unit and 2625A Data Logger are in  
compliance with BMPT Vfg 243/1991 and is RFI suppressed. The normal operation of some  
equipment (e.g. signal generators) may be subject to specific restrictions. Please observe the  
notices in the users manual. The marketing and sales of the equipment was reported to the  
Central Office for Telecommunication Permits (BZT). The right to retest this equipment to verify  
compliance with the regulation was given to the BZT.  
Bescheinigung des Herstellers/Importeurs  
Hiermit wird bescheinigt, daβ Fluke Model 2620A Data Acquisition Unit and 2625A Data Logger in  
Übereinstimung mit den Bestimmungen der BMPT-AmtsblVfg 243/1991 funk-entstört ist. Der  
vorschriftsmäßige Betrieb mancher Geräte (z.B. Meßsender) kann allerdings gewissen  
Einschränkungen unterliegen. Beachten Sie deshalb die Hinweise in der Bedienungsanleitung.  
Dem Bundesamt für Zulassungen in der Telekcommunikation wurde das Inverkehrbringen dieses  
Gerätes angezeigt und die Berechtigung zur Überprüfung der Seire auf Einhaltung der  
Bestimmungen eingeräumt.  
Fluke Corporation  
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Safety Terms in this Manual  
This instrument has been designed and tested in accordance with IEC publication 1010,  
Safety Requirements for Electrical Measuring, control and Laboratory Equipment. This  
Users Manual contains information, warnings, and cautions that must be followed to  
ensure safe operation and to maintain the instrument in a safe condition. Use of this  
equipment in a manner not specified herein may impair the protection provided by the  
equipment.  
The meter is designed for IEC 664, Installation Category II use. It is not designed for use  
in circuits rated over 4800VA.  
Warning statements identify conditions or practices that could result in personal injury  
or loss of life.  
Caution statements identify conditions or practices that could result in damage to  
equipment.  
Symbols Marked on Equipment  
Danger - High voltage.  
Ground (earth) terminal.  
Protective ground (earth) terminal. Must be connected to safety earth  
ground when the power cord is not used. See Chapter 2.  
Attention - refer to the manual. This symbol indicates that information  
about usage of a feature is contained in the manual. This symbol appears  
in the following two places on the instrument rear panel:  
1. Ground Binding Post (left of line power connector). Refer to "Using  
External DC Power" in Chapter 2.  
2. Alarm Outputs/Digital I/O Connectors. Refer to Appendix A,  
Specifications.  
Warning  
To avoid electric shock:  
When the input module is installed, consider all channels  
with connections as accessible terminals that may be  
hazardous live.  
Disconnect the input module before touching or changing  
external wiring.  
Remove inputs from live voltages before opening the input  
module.  
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2620A/2625A  
Users Manual  
AC Power Source  
The instrument is intended to operate from an ac power source that will not apply more  
than 264V ac rms between the supply conductors or between either supply conductor and  
ground. A protective ground connection by way of the grounding conductor in the power  
cord is required for safe operation.  
DC Power Source  
The instrument may also be operated from a 9 to 16V dc power source when either the  
rear panel ground binding post or the power cord grounding conductor is properly  
connected.  
Use the Proper Fuse  
To avoid fire hazard, use only a fuse identical in type, voltage rating, and current rating  
as specified on the rear panel fuse rating label.  
Grounding the Instrument  
The instrument utilizes controlled overvoltage techniques that require the instrument to  
be grounded whenever normal mode or common mode ac voltages or transient voltages  
may occur. The enclosure must be grounded through the grounding conductor of the  
power cord, or if operated on battery with the power cord unplugged, through the rear  
panel ground binding post.  
Use the Proper Power Cord  
Use only the power cord and connector appropriate for the voltage and plug  
configuration in your country.  
Use only a power cord that is in good condition.  
Refer cord and connector changes to qualified service personnel.  
Do Not Operate in Explosive Atmospheres  
To avoid explosion, do not operate the instrument in an atmosphere of explosive gas.  
Do Not Remove Cover  
To avoid personal injury or death, do not remove the instrument cover. Do not operate  
the instrument without the cover properly installed. Normal calibration is accomplished  
with the cover closed, and there are no user-serviceable parts inside the instrument, so  
there is no need for the operator to ever remove the cover. Access procedures and the  
warnings for such procedures are contained in the Service Manual. Service procedures  
are for qualified service personnel only.  
Do Not Attempt to Operate if Protection may be Impaired  
If the instrument appears damaged or operates abnormally, protection may be impaired.  
Do not attempt to operate it. When in doubt, have the instrument serviced.  
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Getting Started  
Introduction  
This section will have you operating Hydra in a matter of minutes. All basic operating  
information is covered in this short Getting Started guide. Subsequent chapters of the  
manual cover the instrument in more detail.  
Note  
This manual contains information and warnings that must be followed to  
ensure safe operation and retain the instrument in safe condition.  
The Basics  
Hydra has 21 input channels: channel 0 is on the front panel, and channels 1 through 20  
are on the rear input module.  
There are two ways Hydra takes measurements (these can be used separately or  
together):  
A Scan function, which measures all channels at a specified scan interval.  
A Monitor function, which repeatedly measures any one channel.  
The instrument has three different modes of operation:  
Active Mode - when the Scan and/or Monitor functions are on.  
Configuration Mode - when any of the setup parameters are being changed.  
Inactive mode - when the instrument is powered up, and sitting idle (i.e., not in  
Active Mode or Configuration Mode).  
Turning On the Instrument  
Press R ON. The entire display lights up as the instrument steps through a series of  
self tests. (Refer to Chapter 6 if any error messages are displayed during this self-test  
sequence.) When the self-tests are finished, the instrument resumes whatever mode it  
was in the last time power went off.  
Normally it will go to Inactive Mode, and sit idle with a channel number on the right-  
hand display. You can change the displayed channel with G and D. Other annunciators  
are lit dimly to provide a summary description of the selected channels setup.  
The initial setup for all channels should be "off": as you scroll through the channels with  
G or D, the "OFF" annunciator should be on dimly. If any of the channels are set up  
otherwise, or if the instrument immediately starts taking measurements after the self-test  
sequence, then it still contains the previous users setup. You can quickly get the  
instrument back to the initial setup by performing a "Configuration Reset".  
To perform a Configuration Reset, press R OFF. Then hold C in, while pressing  
R ON; keep C pressed until the self-test sequence is finished and the instrument  
beeps one time.  
Setting Up a Channel  
1. Press G, D to select a channel to modify. For this example, start with channel 0.  
2. Press F to access the function setup menu.  
The "SET" and "FUNC" annunciators come on, and the instrument goes into  
Configuration Mode. The present function for this channel is also highlighted (for  
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2620A/2625A  
Users Manual  
this example, "OFF" is lit if youre working with channel 0, and have already  
performed the Configuration Reset).  
3. Press G, D to cycle through the choices for measurement function. For now, select  
"V AC", to set up the channel for AC voltage measurements.  
4. Press E to confirm your choice. The instrument then offers a choice of  
measurement ranges for this function, starting with "Auto" for autoranging.  
5. Press G, D to cycle through the choices for range. Select the 300v range. (300v is  
available only on channels 0, 1 and 11.)  
6. Press E to confirm your choice.  
This completes setting up channel 0 to measure AC voltage. The instrument returns to  
Inactive Mode, and the new setup for channel 0 is shown dimly on the display.  
The sequence for setting up a channel to measure DC Voltage, Frequency or Resistance  
is very similar:  
1. Press G, D to select a channel to set up.  
2. Press F to access the function setup menu.  
3. Press G, D to cycle through the choices for measurement function, then press  
E.  
4. Press G, D to cycle through the choices for range, then press E. This  
completes the setup for the channel and the instrument returns to Inactive Mode.  
When you set up a channel to measure resistance, the instrument also lets you choose 2-  
Terminal or 4-Terminal measurements ("2T" or "4T") before returning to Inactive Mode.  
Note that 4-Terminal measurements are supported only on channels 1 - 10.  
The sequence for setting up a channel to measure temperature is similar:  
1. Press G, D to select a channel to set up.  
2. Press F to access the function setup menu.  
3. Press G, D to select "°C" from the list of measurement functions, then press E.  
(Chapter 3 of the manual explains how to change temperature measurement units.)  
4. The instrument then offers a choice of 9 different thermocouple types, as well as  
"Pt" for platinum RTDs.  
Press G, D to select a thermocouple type, then press E. This completes the setup  
for the channel and the instrument returns to Inactive Mode.  
When setting up a channel to measure RTDs, the instrument also prompts for 2-  
Terminal vs 4-Terminal measurements, and then allows you to specify a value for R0.  
(Note that Channel 0 cannot be set up to measure thermocouples or 4-Terminal RTDs.)  
Subsequent sections of the manual explain how to set up alarm values and Mx+B linear  
scaling for each channel.  
Selecting the Scan Data Destination  
The 2620A will always send the scan data to the RS-232 printer port, following each  
scan. The 2625A can be configured to send the scan data to the RS-232 printer port, or to  
the internal Memory Storage, or to both simultaneously. Begin this procedure by  
selecting MODE (shift print). Select the scan data destination (“dESt” in the right  
display) as “Print” (left display) to send the data to the RS-232 port, as “StoreE” to send  
the data to Memory Storage, or as “both” for simultaneous storage and printing. Then  
xii  
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Getting Started (continued)  
select the mode (“Mode” in right display) from “All” to output all scan data, “ALAr” to  
output only alarm data, or “trAnS” to output data scanned only when the Hydra goes into  
or out of alarm.  
Once the destination and mode have been set, enable Memory Storage by pressing: print.  
The “PRN” annunciator lights to indicate that Memory Storage is enabled.  
Warning  
No data will be saved unless the “PRN” annunciator is lit on the  
on the Hydra from panel florescent display.  
Memory contents can be sent to the RS-232 port for listing directly to a printer (refer to  
Table 3-16 in Chapter 3) or through the computer interface.  
Taking Measurements  
Before taking any measurements, you might want to set up a few more channels... set up  
three additional channels, as described below. (Remember, use G or D when in  
inactive Mode to select a channel, and then press F.)  
Channel  
Function  
0
1
V AC, 300V range  
V DC, 30V range  
2
3
4
(leave set up as "OFF")  
Resistance, 3 mrange  
Thermocouple Temperature ("°C" or "°F")  
(leave set up as "OFF")  
5 .. 20  
Warning  
Inputs may be connected to live voltages. To avoid electric  
shock remove inputs from live voltages before opening this  
module.  
You need to connect wires to these channels before taking measurements. Insert a pair of  
test leads into the jacks on the front panel for channel 0. For channels on the rear Input  
Module, proceed as follows:  
1. Remove the input module from the rear panel.  
2. Loosen the two large screws on top and open the module.  
3. Connect wires to the pairs of terminals for channels 1 and 3. Weve enclosed some  
thermocouple wire for you to connect to channel 4; the thermocouples red lead must  
be connected to the "low" input terminal, labeled "L". (Note that the enclosed  
thermocouple is for demonstration purposes only. Measurements taken with it may  
be off by 1 - 2 degrees.) Refer to Table 3-14 in Chapter 3 to identify the type of  
thermocouple by positive lead color. This table also shows the appropriate usable  
temperature range.  
4. Thread the wires through the strain-relief pins and out the back of the module.  
5. Close the cover, secure the screws, and insert the module back in the instrument.  
The instrument is now ready to take measurements. Start with the Monitor function,  
which takes repeated measurements on a channel.  
Press G, D to select a channel to Monitor.  
Press M to activate the monitor function.  
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2620A/2625A  
Users Manual  
Note  
You cannot activate the Monitor function if the selected channel is set up  
as OFF; the instrument gives a long beep and ignores your request.  
The "MON" annunciator comes on, and the instrument starts taking measurements on the  
selected channel. If you havent connected the input leads to a signal, the instrument  
simply displays a nominal noise reading; on channels set up to measure resistance, "OL"  
is displayed for overload. (The instrument also displays "OL", or "otc" for open  
thermocouple, when attempting to measure temperatures on channels to which no sensor  
has been connected.)  
Press G, D to scroll through other channels and take additional measurements. Note  
that the instrument automatically skips over channels that are not set up (i.e., those  
channels still set to "OFF").  
Press M to deactivate the Monitor function when youre through. ( M toggles the  
Monitor function on and off.)  
Next, press Q to activate the Scan function. The "Scan" annunciator comes on, and the  
instrument begins taking measurements on all the channels youve set up.  
When the scan completes, the instrument normally then counts down the time interval  
remaining until the next scan is due. (the countdown appears on the right display.)  
However, if you performed a Configuration Reset, then the scan interval has been set  
back to 0:00:00. Under this condition, the instrument performs continuous scanning.  
Subsequent sections of the manual explain how to change the scan interval.  
Even with the scan function on, you can still use the Monitor function to watch a  
channel:  
Press M to activate the Monitor function.  
Press G, D to change the monitor channel, as desired. (The instrument continues to  
take scan measurements in the background.)  
Press M to deactivate the Monitor function when you are through.  
Similarly, press Q to deactivate the Scan function when you are through.  
Viewing Minimum, Maximum, and Last Data Values  
While taking scan measurements, the instrument also collects Minimum, Maximum and  
Last values for each channel. These values are stored in the "Review Array." You can  
examine the data in the Review array when the instrument is in Active Mode or Inactive  
Mode. If you are in Active Mode, (i.e. the Scan and/or Monitor functions are on), the  
instrument will continue to take measurements in the background while you examine the  
Review data.  
Press N to call up the Review array onto the display.  
Use the four arrow buttons to examine different entries in the Review array. The arrow  
buttons move around in the Review array, as illustrated below.  
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Getting Started (continued)  
20  
LAST  
MIN  
MAX  
.
.
.
.
.
.
.
LAST  
MIN  
MAX  
0
oo24f.eps  
Press N or C to remove the Review data from the display when youre through.  
The remainder of this manual covers all aspects of using Hydra. Glance over the Table  
of Contents; youll find that each section presents an additional layer of information. You  
can use as little as (or as much as) you need for your Hydra application.  
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2620A/2625A  
Users Manual  
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Chapter 1  
Introduction  
Title  
Page  
The Hydra Series II Data Acquisition Unit....................................................... 1-3  
The Hydra Series II Data Logger ...................................................................... 1-3  
Options and Accessories ................................................................................... 1-3  
Applications Software....................................................................................... 1-3  
IEEE-488 Interface Assembly........................................................................... 1-3  
Connector Set (2620A-100) .............................................................................. 1-3  
Accessories........................................................................................................ 1-5  
Where to go From Here..................................................................................... 1-5  
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2620A, 2625A  
Users Manual  
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Introduction  
The Hydra Series II Data Acquisition Unit  
1
Note  
This manual contains information and warnings that must be followed to  
ensure safe operation and retain the instrument in safe condition.  
The Hydra Series II Data Acquisition Unit  
The Hydra Series II Data Acquisition Unit (Model 2620A) is a multi-channel data  
acquisition unit able to measure ac and dc voltages, temperature via thermocouples and  
RTDs, resistance, and frequency. It features 21 measurement channels, 8 digital  
input/output lines, a Totalizer input, and 4 alarm output lines. The Data Acquisition Unit  
is easily carried by hand and can be ac or dc powered. The user can choose  
communications with a host computer over an RS-232 (standard) or IEEE-488  
(2620A/05) computer interface. Refer to Table 1-1 for a list of operating features.  
The Hydra Series II Data Logger  
The Hydra Series II Data Logger (Model 2625A) combines data logging memory with  
the features of the Data Acquisition Unit. The RS-232 computer interface is standard  
(IEEE-488 capability is not available.)  
Options and Accessories  
Applications Software  
The following software packages are available for the instrument:  
Hydra Starter (included with instrument)  
Allows for communication from an IBM-compatible personal computer through the  
RS-232 interface, emphasizing transfer of measurement and configuration settings to  
and from the instrument.  
Hydra Logger Package (order separately)  
Hydra Logger (model 2635A-901) is a Windows-based package that allows  
complete set up and data collection and data conversion from up to 2 Hydra units.  
Logger communicates over the RS-232 port on a personal computer and may be used  
with telephone modems. Hydra Logger with Trending (model 2635A-902) includes a  
comprehensive trending package that simulates a chart recorder. A brochure with  
complete details is available.  
IEEE-488 Interface Assembly  
Model 2620A/05 includes an IEEE-488 Interface. Commands for the IEEE-488 interface  
are virtually identical to those used with the RS-232 Interface  
If your Hydra Series II Data Acquisition Unit does not have an IEEE-488 Interface, a  
field-installable kit (2620A-05K) is available. The Hydra Series II Data Logger cannot  
be equipped with an IEEE-488 Interface.  
Connector Set (2620A-100)  
The 2620A-100 is a complete set of input connectors (one Input Module and two Digital  
I/O Connectors). These connectors allow for additional wiring setups so that a single  
Hydra Series II Data Acquisition Unit or Data Logger can then be moved among  
multiple installations.  
1-3  
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2620A, 2625A  
Users Manual  
Table 1-1. Hydra Features  
Channel Scanning  
Can be continuous scanning, scanning at an interval time, single scans, or triggered (internal or  
external) scans.  
Channel Monitoring  
Make measurements on a single channel and view these measurements on the display.  
Channel Scanning and Monitoring  
View measurements made for the monitor channel while scanning of all active channels continues.  
Multi-Function Display  
Left (numeric) display shows measurement readings; also used when setting numeric parameters.  
Right (alphanumeric) display used for numeric entries, channel number selection and display, status  
information, and operator prompts.  
Front-Panel Operation  
Almost all operations can be readily controlled with the buttons on the front panel.  
Measurement Input Function and Range  
Volts dc (VDC), volts ac (VAC), frequency (Hz), and resistance () inputs can be specified in a fixed  
measurement range. Autoranging, which allows the instrument to use the measurement range  
providing the optimum resolution, can also be selected.  
Temperature Measurement  
Thermocouple types J, K, E, T, N, R, S, and B, and Hoskins Engineering Co. type C are supported.  
Also, DIN/IEC 751 Platinum RTDs are supported.  
Totalize Events on the Totalizing Input  
Alarm Limits and Digital Output Alarm Indication  
4-Terminal Resistance Measurements (Channels 1 through 10 only)  
RS-232 Computer Interface Operation  
Measurement Rate Selection  
Nonvolatile Memory  
Storage of minimum, maximum, and most recent measurements for all scanned channels.  
Storage of Computer Interface setup, channel configurations, and calibration values.  
Storage of measurement data: storage for 2047 scans of up to 21 channels, representing up to  
42,987 readings (Hydra Data Logger only).  
1-4  
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Introduction  
Where to go From Here  
1
Accessories  
Accessories available for the instrument are described in Table 1-2.  
Table 1-2. Accessories  
Description  
Model  
80I-410  
80i-1010  
80J-10  
Clamp-On DC/AC Current Probes.  
Current Shunt.  
2620A-05K  
2620A-901  
C40  
Field-installable IEEE-488 Option kit (Hydra Data Acquisition Unit only).  
Hydra Data Logger Applications Package.  
Soft carrying case. Provides padded protection for the instrument. Includes a pocket for  
the manual and pouch for the line cord.  
M00-200-634  
Rackmount Kit. Provides standard 19-inch rack mounting for one instrument (right or left  
side).  
PM 8922  
RS40  
Switchable x1, x10 passive probe.  
Shielded RS-232 terminal interface cable. Connects the instrument to any terminal or  
printer with properly configured DTE connector (DB-25 socket), including an IBM PC(\R),  
IBM PC/XT(\R) or IBM PS/2 (models 25, 30, 50, P60, 70, and 80).  
RS41  
Shielded RS-232 modem cable. Connects the instrument to a modem with properly  
configured DB-25 male pin connector. Use an RS40 and an RS41 cable in series to  
connect with an IBM PC/AT(\R).  
RS42  
TL20  
Serial printer cable. Contact Fluke for list of compatible printers.  
Industrial test lead set.  
TL70  
Test lead set.  
Y8021  
Y8022  
Y8023  
Y9109  
Shielded IEEE-488 one-meter cable, with plug and jack at each end.  
Shielded IEEE-488 two-meter cable, with plug and jack at each end.  
Shielded IEEE-488 four-meter cable, with plug and jack at each end.  
Binding post to BNC plug.  
Fluke PN  
268789  
10Precision Resistor, metal film, +/- 1%, 1/8 watt, 100 ppm. For use with 4 - 20 mA  
signals.  
Where to go From Here  
You might want take a minute to familiarize yourself with this manual. Glance through  
the table of contents at the front to see the overall layout of the manual and the major  
parts of the instrument. If you have questions about specific topics, the Index at the end  
of the manual will be useful. Or, just fan through the headers at the top of each page;  
each header reveals the chapter number and the chief subject for that page.  
The chapters are summarized in the following paragraphs:  
1-5  
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2620A, 2625A  
Users Manual  
Getting Started  
Provides a quick introduction to instrument setup and operation.  
Chapter 1 Introduction  
Describes standard features, options, and accessories for the Fluke Hydra Series II Data  
Acquisition Unit and Hydra Series II Data Logger. Also, this chapter discusses the  
organization and intended uses of this manual.  
Chapter 2 Overview  
Brings the instrument from its shipping container to operating status. This chapter  
provides brief descriptions and a quick walk-through of instrument operation. Read this  
chapter to gain a feel for instrument use. But please dont avoid reading Chapter 3 (for  
in-depth operation from the front panel) and Chapter 4 (for computer interface  
operation); the instrument is far more powerful than suggested in Chapter 2.  
Chapter 3 Operating the Instrument from the Front Panel  
Describes all capabilities available through front panel control. The features introduced  
in Chapter 2 are described more fully, including descriptions for setting up and using  
each type of measurement input (dc volts, thermocouple, etc.) and digital input  
(Totalizer, etc.) or output (such as alarms). Other features of the Hydra Series II Data  
Acquisition Unit and the Hydra Series II Data Logger are also more fully explained.  
Chapter 4 Using the Computer Interface  
Describes connecting the instrument to a terminal or host computer and operating the  
instrument over the RS-232 Interface. For the Hydra Series II Data Acquisition Unit  
only, use of the optional IEEE-488 Interface is also described here. This chapter is  
detailed and requires a good knowledge of instrument operation via the front panel (see  
Sections 2 and 3).  
Chapter 5 Additional Considerations  
Provides detailed operating information not provided elsewhere. This chapter also  
describes instrument operation for the advanced user. This chapter is written with the  
assumption that you have full knowledge of instrument operation from the front panel  
(Chapter 3).  
Chapter 6 Maintenance  
Provides performance tests (suitable as acceptance testing procedures) and routine  
maintenance information. Refer to this chapter for explanation of error codes  
encountered during instrument operation. Also, this chapter provides parts ordering  
information for such commonly used items as fuses, accessories, and publications.  
Refer to the "Hydra Series II Service Manual" (P/N 688868) for complete service, repair,  
and parts ordering information.  
Appendices  
A. Specifications  
B. ASCII/IEEE-488 Bus Codes  
C. IEEE-488.2 Device Documentation Requirements  
D. Making Mixed Measurements Service Centers  
E. Binary Upload of Logged Data (LOG_BIN?) (2625A only)  
Index  
1-6  
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Chapter 2  
Overview  
Title  
Page  
Introduction ....................................................................................................... 2-3  
Setting Up the Instrument.................................................................................. 2-3  
Unpacking and Inspecting the Instrument..................................................... 2-3  
Adjusting the Handle .................................................................................... 2-3  
Line Power .................................................................................................... 2-4  
Front/Rear Panel Features............................................................................. 2-4  
Input Channels .............................................................................................. 2-9  
Operating Modes ............................................................................................... 2-9  
Turning the Instrument On................................................................................ 2-9  
Front Panel Display........................................................................................... 2-10  
Reading the Display .......................................................................................... 2-10  
Left Display................................................................................................... 2-10  
Right Display ................................................................................................ 2-10  
Specific Annunciators................................................................................... 2-10  
Front Panel Buttons........................................................................................... 2-11  
Selecting a Channel....................................................................................... 2-11  
Using the Buttons.......................................................................................... 2-11  
Setting up a Channel.......................................................................................... 2-12  
Setting Alarm Limits and Mx+B Scaling Values.............................................. 2-14  
Alarm Limits................................................................................................. 2-14  
Mx+B Scaling ............................................................................................... 2-15  
Setting the Scan Interval.................................................................................... 2-15  
Using the Monitor Function .............................................................................. 2-16  
Using the Scan Function.................................................................................... 2-16  
Reviewing Channel Data................................................................................... 2-16  
Viewing the Totalizer Count............................................................................. 2-17  
Using External DC Power ................................................................................. 2-17  
Using the Rack Mount Kit................................................................................. 2-18  
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2620A, 2625A  
Users Manual  
2-2  
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Overview  
Introduction  
2
Introduction  
Chapter 2 provides an overview of the major features of the instrument. Comprehensive  
details on all instrument features are found in Chapter 3 (for front panel operation) and  
Chapter 4 (for computer interface operation.)  
Setting Up the Instrument  
Unpacking and Inspecting the Instrument  
The following items are included in the shipping container:  
This manual  
Hydra Series II Starter Software  
Hydra Series II Data Acquisition Unit (2620A) or Hydra Series II Data Logger  
(2625A)  
Input Module  
Digital I/O and Alarms Connector  
Test leads  
Line cord  
Carefully remove the instrument from its shipping container and inspect it for possible  
damage or missing items. If the instrument is damaged or something is missing, contact  
the place of purchase immediately. Save the container and packing material in case you  
have to return the instrument.  
Rotate the rear feet 180 degrees so that their support pads extend slightly below the  
bottom of the case.  
Adjusting the Handle  
The handle can be positioned to four angles: one for carrying, two for viewing, and one  
for handle removal. To change the angle, simultaneously pull both handle ends outward  
to hard stops (about 1/4 inch on each side) and then rotate the handle to one of the four  
stop positions shown in Figure 2-1. With the handle in the straight-up removal position  
(4 in Figure 2-1), you can disengage and free one handle side at a time.  
2. Alternate Viewing Position  
1. Viewing Position  
Pull One End Out and Towards You.  
Then Pull the Other End Out.  
4. Removal Position  
(to Remove, Pull Ends Out)  
COM  
V
3. Carrying Position  
300V  
MAX  
oo01f.eps  
Figure 2-1. Adjusting Handle  
2-3  
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2620A, 2625A  
Users Manual  
Line Power  
Warning  
To avoid shock hazard, connect the instrument power cord to a  
power receptacle with earth ground.  
Plug the line cord into the connector on the rear of the instrument. The instrument  
operates on any line voltage between 90 and 264V ac without adjustment, and at any  
frequency between 45 and 440 Hz. However, the instrument is warranted to meet  
published specifications only at 50/60 Hz.  
Front/Rear Panel Features  
The Front Panel (shown in Figure 2-2) provides a two-terminal input for channel 0, a  
multipurpose display, and a set of control buttons. The display includes the following  
elements:  
A major numeric chapter (called the Left Display). See Figure 2-3.  
An auxiliary alphanumeric chapter (called the Right Display). See Figure 2-4.  
A set of Display Annunciators. See Figure 2-5 and Table 2-1.  
The buttons control all instrument operations: channel configuration, instrument  
configuration, measurement functions, and print/communications selections. The buttons  
are introduced in this chapter, with a more detailed description following in Chapter 3.  
The Rear Panel (shown in Figure 2-6) provides input and output connections: power  
input, measurement input, digital input/output, Totalizer input, alarm output, and  
computer interface connections. These connections are introduced in this chapter and  
explained in greater detail in subsequent chapters of this manual. Inputs and outputs are  
described with their related functions (Measuring DC Voltage, Totalizing, etc.) in  
Chapter 3. RS-232 and IEEE-488 Computer Interface connections are detailed in  
Chapter 4.  
2-4  
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Overview  
Setting Up the Instrument  
2
1
2
FUNC  
ALARM  
°C °F RO  
F
MAX REM SCAN SET  
MIN AUTO MON Mx+B  
REVIEW  
LAST  
PRN CH  
OFF  
CAL EXT TR  
mV AC DC LIMIT HI  
COM  
V
CAL  
ENABLE  
x1MkHz  
1
2
LO  
INTVL  
PRINT  
REVIEW  
FUNC  
Mx+B  
ALRM  
SCAN  
SINGLE  
MON  
300V  
MAX  
COCK  
MODE  
CLEAR  
RATE  
CANCL  
ENTER  
SHIFT  
LIST  
TOTAL  
TRIGS  
LOCAL  
COMM  
ZERO  
POWER  
8
7
6
5
4
3
1
2
3
INPUT TERMINALS (Channel 0)  
7
OTHER BUTTONS  
These buttons are used to both  
configure and operate the  
instrument:  
DISPLAY (See Figures 2-3, 2-4, and 2-5)  
ACTIVE MODE BUTTONS  
,
,
,
SINGLE (  
)
ZERO (  
)
)
4
5
POWER BUTTON  
PRINT/COMMUNICATIONS BUTTONS  
CLEAR (  
MODE (  
COMM (  
)
CHANNEL CONFIGURATION  
BUTTONS  
8
)
LOCAL (  
)
6
INSTRUMENT CONFIGURATION  
BUTTONS  
TRIGS (  
)
RATE (  
)
CLOCK (  
)
oo02f.eps  
Figure 2-2. Front Panel  
2-5  
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2620A, 2625A  
Users Manual  
FUNC  
F
SET  
Mx+B  
MAX REM SCAN  
MIN AUTO MON  
REVIEW  
LAST  
ALARM  
°C °F RO  
PRN CH  
EXT TR  
OFF  
CAL  
mV AC DC  
HI  
LIMIT  
1 2 LO  
x1Mk  
Hz  
oo03f.eps  
oo04f.eps  
oo05f.eps  
Figure 2-3. Left Display  
FUNC  
F
SET  
Mx+B  
MAX REM SCAN  
MIN AUTO MON  
REVIEW  
LAST  
ALARM  
°C °F RO  
PRN CH  
EXT TR  
OFF  
CAL  
mV AC DC LIMIT HI  
x1Mk Hz  
1 2 LO  
Figure 2-4. Right Display  
FUNC  
ALARM  
°C °F RO  
F
SET  
Mx+B  
MAX REM SCAN  
MIN AUTO MON  
REVIEW  
LAST  
PRN CH  
EXT TR  
OFF  
CAL  
mV AC DC LIMIT HI  
x1Mk Hz  
1 2 LO  
Figure 2-5. Annunciators  
2-6  
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Overview  
Setting Up the Instrument  
2
Table 2-1. Display Annunciators  
MON  
Indicates that the Monitor function is enabled.  
SCAN  
Indicates that the Scan function is enabled. Scanning can be enabled as a single  
scan (SINGLE K Q), with a scan interval, with an alarm-triggered scan, or as an  
externally triggered scan.  
CH  
Indicates that the channel number is displayed immediately above, in the right  
display.  
SET  
Lit when the instrument is in Configuration Mode.  
Mx+B  
Lit while Mx+B scaling is being defined and when a measurement on the display  
has been scaled with an M value other than 1 and/or a B value other than 0. Also  
dimly lit when in the Inactive Mode to indicate that an M value other than 1 and/or a  
B value other than 0 has been defined for this channel.  
FUNC  
Lit when a measurement function is being defined for this channel.  
ALARM  
Lit when alarm values are being defined for this channel or when an alarm limit has  
been exceeded while measuring.  
V
Indicates that the measurement function is volts for this channel (used with the AC  
or DC annunciator).  
DC  
AC  
Indicates that the measurement function is dc voltage for this channel.  
Indicates that the measurement function is ac voltage for this channel.  
Indicates that the measurement function is resistance for this channel.  
Indicates that the measurement function is frequency for this channel.  
Hz  
°C  
Indicates that the measurement function is temperature for this channel and that the  
degree unit is Celsius.  
°F  
m
Indicates that the measurement function is temperature for this channel and that the  
degree unit is Fahrenheit.  
(milli) a multiplier for the displayed value, e.g., mV for millivolts. Also used when  
defining alarm and Mx+B values.  
x1  
k
(times 1) a multiplier for the displayed value. Used when defining alarm and Mx+B  
values.  
(kilo) a multiplier for the displayed value, e.g., kHz for kilohertz. Also used when  
defining alarm and Mx+B values.  
M
(mega) a multiplier for the displayed value, e.g., Mfor megohms. Also used when  
defining alarm and Mx+B values.  
R0  
OFF  
Lit when the ice point resistance is being defined for RTD measurements on the  
displayed channel.  
Indicates there is no measurement function defined for the displayed channel; OFF  
channels are skipped over when scanning. OFF is also used when defining an  
alarm value to indicate that the alarm limit is to be ignored.  
AUTO  
LIMIT  
Indicates that autoranging is enabled for the displayed channel.  
Used with the S and T annunciators when you are setting an alarm limit value. Also  
lit when displaying a measurement value (LAST, Monitor) which has exceeded an  
alarm limit.  
2-7  
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2620A, 2625A  
Users Manual  
Table 2-1. Display Annunciators (cont)  
"1"  
Lit when alarm limit 1 is being defined. Also lit when displaying a measurement  
value (LAST, Monitor) which has exceeded alarm limit 1.  
"2"  
Lit when alarm limit 2 is being defined. Also lit when displaying a measurement  
value (LAST, Monitor) which has exceeded alarm limit 2.  
HI, LO  
REVIEW  
MIN, MAX  
LAST  
Identifies alarm limit sensing (high or low) during channel configuration. At other  
times, identifies an alarm condition.  
Indicates that review data is being displayed (used in conjunction with the MIN,  
MAX, and LAST annunciators).  
Indicates that the displayed value is the minimum (maximum) value measured on  
this channel.  
Indicates that the displayed value is the most recent scan measurement taken on  
this channel.  
PRN  
Indicates that the autoprint function is enabled (to send readings to a printer) or the  
memory storage function is on (to store readings in internal memory.) Internal  
memory is available with Hydra Data Logger only.  
F
Bright when memory storage is full, dim when memory storage is nearly full. Hydra  
Data Logger only.  
EXT  
TR  
Indicates that external triggering (on the rear panel) is enabled.  
Indicates that internal triggering (from the monitor alarm) is enabled. Also used with  
EXT when external triggering is enabled.  
REM  
CAL  
Indicates that the instrument is under the remote control of one of the computer  
interfaces.  
Indicates that the instrument’s internal calibration constants have been corrupted.  
CAUTION  
FOR FIRE PROTECTION REPLACE WITH T 1/8A 250V (SLOW) FUSE MODEL: 2620  
2625  
90-264V  
50/60 Hz  
15VA  
IEC 664 INSTALLATIONCATEGORY II  
ALARM OUTPUTS  
DIGITAL I/O  
RS-232C  
IEEE STD-488 PORT  
+ –  
0
1
2
3
TR  
0
1
2
3
4
5
6
7
Σ
+30V  
!
9-16 V  
DC PWR  
SH1, AH1, T5, L4, SR1, RL1, DC1, DT1, PP0, C0, E1  
MEETS 0871 B  
COMPLIES FCC-15B  
TX  
GND  
RX  
DTR  
EXTERNAL BATTERY  
WARNING: If voltages greater than 30V are to be measured, a safety ground must be attached  
to the rear panel ground connector when the instrument is operated from battery power.  
oo06f.eps  
Figure 2-6. Rear View  
2-8  
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Overview  
Operating Modes  
2
Input Channels  
The instrument provides one input (channel 0) on the front panel and 20 inputs (channels  
1 .. 20) through a connector on the rear panel. Channels 0, 1, and 11 can measure a  
maximum of 300V; all other channels can measure a maximum of 150V.  
Caution  
The maximum input that can be applied between any terminal  
of channels 2..10 and 12..20 is 150V dc or ac rms. The  
maximum input that can be applied between any terminal of  
channels 0, 1, and 11 and ground is 300V dc or ac rms. The  
maximum common mode input that can be applied is 300V dc  
or ac rms.  
Operating Modes  
The instrument provides three modes of operation:  
Active Mode  
The instrument is in Active Mode whenever the Monitor and/or Scan functions are  
enabled. Scans are activated by the interval timer, an external trigger, an alarm  
trigger, or a single scan (SINGLE K Q) command. When in Active Mode, the  
MON and/or SCAN annunciators are lighted.  
Configuration Mode  
The instrument is in Configuration Mode whenever settings (channel function, alarm  
values, Mx+B scaling values, scan interval, trigger type, etc.) are being examined or  
changed. When in the Configuration Mode, the SET annunciator is on, along with  
other annunciators indicating the parameter(s) being set.  
Inactive Mode  
The instrument is in Inactive Mode when no measurement functions are enabled and  
no instrument settings are being examined or changed. This is a quiescent state; only  
summary channel information is displayed.  
Turning the Instrument On  
Turn the instrument on by pressing POWER on the lower right of the front panel.  
Initially, the entire display lights while the instrument conducts several internal self tests.  
Note  
You can familiarize yourself with the instrument by holding the display  
fully lit. Press and hold K, then press R ON and wait a moment for  
the instrument to beep. Then release K. The entire display will now stay  
on until you press any button; the power-up sequence then resumes.  
A deviation in mainframe software Version 5.5 will not allow the display to  
remain ON. Versions 5.4 and below will allow the display to remain ON.  
Any error conditions are momentarily displayed during this test sequence. Even in the  
presence of an error, the instrument still attempts to complete the self-test sequence and  
begin normal operation. However, if you encounter an error, note the number and refer  
to Self Test Diagnostics and Error Codes in Chapter 6 for additional information.  
Once the self tests are completed, the instrument enters Inactive or Active Mode,  
depending on the following circumstances:  
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2620A, 2625A  
Users Manual  
Active Mode if this mode was in effect prior to the cycling of power. Scanning,  
monitoring, or combined scanning/monitoring is resumed.  
Inactive Mode if the instrument was in Inactive Mode or Configuration Mode prior  
to cycling of power.  
When in Inactive Mode, the instrument shows configuration information for the  
displayed channel. The channel number appears in the right display, and other  
annunciators are dimly lit to show the present setup for this channel. For example, if the  
channel is set up to measure ke, the "k" and "e" annunciators are dimly lit.  
Alternatively, if this channel has not been set up to measure anything, the "OFF"  
annunciator is lit dimly.  
You can change the channel by pressing G or D.  
Front Panel Display  
Full descriptions of the display annunciators are presented in Table 2-1.  
Reading the Display  
The instrument display uses both alphanumeric characters and fixed annunciators. When  
in Configuration Mode, these features are used to provide user prompting. In Inactive  
Mode, they provide status information. In Active Mode, they provide both status  
information and measurement data.  
Information is presented on the display during both front panel control and computer  
interface control. If the instrument is being controlled through a computer interface, the  
display shows the results of computer-interface initiated actions (even if the front panel  
controls have been disabled.)  
The remainder of Chapter 2 (as well as Chapter 3) relates to front panel control of the  
instrument. Refer to Chapter 4 for additional information about computer interface  
operation.  
Left Display  
The left display has five large numeric characters to show measurement results, "otc"  
when an open thermocouple is detected, or "OL" when a measurement is over range.  
During Configuration Mode, the left display is also used to display the numeric values  
and instrument parameters being chosen.  
Right Display  
The right display has five small alphanumeric characters to show the channel number,  
display prompting information during setups, or to count down the scan interval.  
Specific Annunciators  
The rest of the display is devoted to specific annunciators, combinations of which are  
used to describe the operating mode, the type of measurement being displayed, or the  
type of setup information to be entered. These annunciators are described in Table 2-1  
and shown in Figure 2-5.  
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Overview  
Front Panel Buttons  
2
Front Panel Buttons  
Go ahead and press any front panel button. The instrument always provides an audible  
response to each button press. Valid entries yield a short beep; incorrect entries yield a  
longer beep. Dont worry if you press an inappropriate button and get a long beep; you  
cant damage the instrument. It will discard the button entry and wait for another entry.  
Selecting a Channel  
The channel number appears in the right display. Press G or D to select a channel. You  
can change the channel when in Inactive Mode, when looking at data in the Review  
array, or when the Monitor function is on.  
Using the Buttons  
Table 2-2 presents a summary of the control buttons.  
Special button sequences cause a total instrument Configuration Reset or change the  
temperature units between °C and °F.  
Holding D down while turning the power on causes the instrument to perform a  
Configuration Reset. Hold the button down until the instrument beeps, indicating  
that the action has been taken. All channels will be reset OFF. All alarm and scaling  
values will be reset. Scanning and monitoring will be turned off.  
Holding B down while cycling POWER ON toggles the degree unit used with  
temperature measurements (°C or °F). Again, the instrument will beep and display  
°C or °F when this action is complete.  
Table 2-2. Front Panel Pushbuttons  
F
A
B
Calls up the menu to set the function for the channel.  
Calls up the menu to set alarm limits S and T for the channel.  
Calls up the menu to set scaling on the channel.  
G D J H  
Used to change the channel number and to step through choices in any of the  
setup menus. These arrow buttons have an automatic repeat action when held  
down for more than 1 second.  
G generates a service request when the instrument is under remote control without  
local lockout (REMS).  
E
D
Used to accept a selection just made in any setup menu.  
Used to exit setup menu and return to Inactive Mode, without saving settings you’ve  
selected thus far. Exceptions exist under the following two conditions:  
If you cancel out of the alarm menu part way through defining alarm limit T, any  
just-made entries for alarm limit S will still take effect.  
If you cancel out of the Mx+B menu partway through defining the B value, any  
just-made changes to the M value will still take effect.  
This button also provides a handy way to remove the Totalizer value or Review  
data from the display.  
Q
Turns the Scan function on or off.  
Q triggers a single scan when the instrument is under remote control without  
lockout (REMS).  
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2620A, 2625A  
Users Manual  
Table 2-2. Front Panel Pushbuttons (cont)  
M
Turns the Monitor function on or off.  
I
Allows you to change the scan interval. Scanning becomes continuous when the  
interval is set to 0:00:00.  
U
Enables/disables logging measurements to the printer (Autoprint - RS-232 only) or  
to internal data memory (Memory Storage). Only the Hydra Data Logger provides  
internal Memory Storage.  
N
O
L
Calls up the Review array of MIN, MAX and LAST values to the display.  
Calls up the present Totalizer count to the display.  
(RS-232 only) Prints out the Last values of the Review array (2620A and 2625A) or  
Data Logger memory (2625A only) via the RS-232 interface.  
K
Accesses secondary functions under various keys, as described below. When this  
button is pressed, "SHIFt" appears on the right display, but automatically  
disappears if you have not made a selection within 5 seconds or if you press D.  
LOCAL (K)  
When under remote control without lockout (REMS), this returns control to the front  
panel.  
RATE (K J)  
Allows you to change the scanning speed: "Slo" for highest accuracy, or "FASt" for  
highest throughput.  
CLOCK (K I) Allows you to set the internal day/date clock.  
MODE (K U) Allows you to select the conditions for which scan measurements will be  
automatically printed or logged.  
CLEAR (K  
N)  
This button sequence clears the entire contents of the Review array. Review data  
must be presently shown on the display to clear the array.  
COMM (K L) Allows you to set up a computer interface port.  
ZERO (K O) While the Totalizer count is displayed, resets the Totalizer to 0.  
SINGLE (K  
Q)  
Forces an immediate scan of all defined channels. If a scan is presently in progress,  
this new request is ignored. Once begun, the full scan is completed. Configuration  
changes are not allowed while a scan is in progress.  
TRIGS (K M) Allows you to set up the auxiliary scan trigger mechanisms.  
Setting up a Channel  
Channel set ups are made in Configuration Mode, which must be entered from Inactive  
Mode. If the instrument is in Active Mode, turn the Scan and/or Monitor function off  
before proceeding.  
Follow the steps below to change the channel setup. More detailed instructions for  
setting all instrument parameters are provided in Chapter 3.  
During the following steps, note that some items on the display are brightly lit, and  
others are dimly lit. The bright item is intended to focus your attention on the choice the  
instrument is offering you at that moment.  
Note  
Press D to exit the channel setup menu at any time, leaving the old setup  
unchanged.  
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Overview  
Setting up a Channel  
2
1. Select a channel to set up:  
G D Look for the desired channel number in the right display.  
2. Press the following buttons to change the setup:  
F SET and FUNC come on bright, along with the present setting for measurement  
function.  
G D Cycle through the choices for measurement function.  
E Accept your choice of measurement function.  
For resistance measurements, continue on with steps 3 and 4. For temperature  
measurements, skip to step 5.  
3. For dc volts, ac volts, resistance, or frequency, the instrument now provides a choice  
of measurement ranges. Press the buttons as follows:  
G D Cycle through the choices.  
E Accept your choice.  
For dc volts, ac volts, or frequency, the configuration is now complete for this  
channel. The instrument returns to Inactive Mode.  
4. For resistance measurements, one more step is required to specify 2-terminal (2T) or  
4-terminal (4T) measurements. Since 4-terminal measurements require two  
channels, 4-terminal measurements can be set up on channels 1-10 only. For each 4-  
terminal channel, a corresponding channel (11-20) ten numbers higher is reserved  
for the additional two connections required. Press the buttons as follows:  
G D Choose between two terminals (2T) and four terminals (4T).  
E Accept your choice. The instrument returns to Inactive Mode.  
5. If youve specified temperature measurements, the instrument provides a choice of  
thermocouple types or Platinum RTD. Press the buttons as follows:  
G D Cycle through the thermocouple choices. "Pt" is the RTD choice.  
E Accept your choice.  
If you selected one of the thermocouple types, channel configuration is complete; the  
instrument returns to Inactive Mode.  
6. If you selected "Pt" (for RTD-based measurements), use the following buttons to  
specify 2-terminal (2T) or 4-terminal (4T) measurements and the R0 value.  
Since 4T measurements require two channels, 4-terminal measurements can be set  
up on channels 1-10 only. For each 4T channel, a corresponding channel (11-20) ten  
numbers higher is reserved for the additional two connections required.  
G D Choose between two terminals (2T) and four terminals (4T).  
E Accept your choice.  
Now choose the R0 (ice point) value (preset to 100.00). Use J or H to move  
between digits. Use G or D to select a value for each digit.  
E Accept your choice. Channel configuration is complete; the instrument returns  
to Configuration Mode.  
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2620A, 2625A  
Users Manual  
Note  
Any old alarm status/limits, Review array values, or scaling parameters  
are automatically cleared whenever you change a channels function.  
Setting Alarm Limits and Mx+B Scaling Values  
Alarm limits and Mx+B scaling values are set in a manner very similar to that used for  
the channel function. Begin by pressing either of the following buttons:  
A To begin alarm limits settings for this channel.  
B To begin scaling value settings for this channel.  
The setup sequences are briefly discussed below. Refer to Chapter 3 for more details  
about these and other instrument parameters.  
Alarm Limits  
The menu for setting alarm limits allows you to set up both setpoints (S and T). After  
choosing a setpoint, the following settings must be made:  
The alarm sense HI, LO or OFF.  
The limit value (sign and number).  
The decimal point location.  
The value multiplier (m, x1, k, M).  
Use G, D, H and J to cycle through the selections at each setting. Then press E  
to accept your choice and move on to the next setting.  
For example, to set a high limit of +5.35 for alarm S on channel 7, do the following:  
1. Select channel 7 by pressing G or D.  
2. Press A to begin alarm setting for channel 7. "LIMIT" and S (for alarm limit 1)  
now appear in the display. Press EE to accept that you are setting up alarm  
limit 1.  
3. Use the arrow buttons to select "HI". Then press E.  
4. Now use the arrow buttons again to set "+53500". Press H or J to move between  
digits. Press G or D to select the value for each digit. (Ignore the decimal point).  
Press E to accept these digits.  
5. Use the arrow buttons to select the decimal point position ("+5.3500"). Then press  
E to accept this position.  
6. Next, use the arrow buttons again to select the multiplier ("x1"). Press E to  
accept this multiplier and save alarm limit 1.  
7. Limit S for channel 7 is now set for a high value of +5.35. Continue pressing E  
to step through alarm limit 2 and return to the Inactive Mode. Or, press D to  
immediately return to the Inactive Mode.  
Pressing D while partway through setting limit S undoes any changes entered thus far  
for limit S, returning the instrument to Inactive Mode. Pressing D while partway  
through setting limit T cancels entries made thus far for limit T, but does not affect any  
changes already made to limit "1".  
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Overview  
Setting the Scan Interval  
2
Mx+B Scaling  
The menu for setting Mx+B scaling values takes you through the following steps:  
Set the M value (sign and number).  
Set the decimal point location for the M value.  
Set the multiplier for the M value (m, x1, k, M).  
Set the B value (sign and number).  
Set the decimal point location for the B value.  
Set the multiplier for the B value (m, x1, k, M).  
Use G, D, H and J to cycle through the selections at each step. Then press  
EE to accept your choice and advance to the next step.  
For example, to set an M value of 1.8 and a B value of 32 for channel 7, do the  
following:  
1. Select channel 7 by pressing G or D.  
2. Press B to begin Mx+B scaling setting for channel 7.  
3. Use the arrow buttons to select "+18000". Press H or J to move between digits.  
Press G or D to select the value for each digit. (Ignore the decimal point). Press  
EE to accept these digits.  
4. Use the arrow buttons to select the decimal point position ("+1.8000"). Then press  
E to accept this position.  
5. Next, use the arrow buttons again to select the multiplier ("x1"). Press E to  
accept this multiplier.  
6. Use the arrow buttons to select +00320. Then press EE.  
7. Use the arrow buttons to select the decimal point position ("+0032.0"). Then press  
E to accept this position.  
8. Next, use the arrow buttons again to select the multiplier ("x1").Press E to  
accept this multiplier as the multiplier for the B value.  
Mx+B scaling is now set at 1.8x+32 for channel 7.  
Pressing D while partway through setting the M value undoes all changes entered thus  
far, returning the instrument to Inactive Mode. Pressing D while partway through  
setting the B value cancels entries made thus far for the B value, but does not affect any  
changes already made to the M value.  
Setting the Scan Interval  
Press I to set the scan interval. The latest value appears on the right display. The  
format of the display is H:MM:SS. Use J and H to move between digits. Use G and  
D to select the new value for a digit. Values ranging from 0:00:00 to 9:99:99 are  
allowed. Press E to accept the displayed value.  
Set the interval to 0:00:00 for continuous scanning. If you set the interval to a value  
shorter than the time required to measure all channels, scanning effectively becomes  
continuous.  
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2620A, 2625A  
Users Manual  
Using the Monitor Function  
The Monitor function repeatedly measures the displayed channel. Press M to activate  
the Monitor function. Use G and D to change the monitored channel; undefined  
channels (those set to OFF) are automatically skipped over.  
Since the instrument cannot take measurements on a channel that has not been set up, it  
responds with a long beep if you try to activate the Monitor function on a channel that is  
defined as OFF. Press G or D to find a channel that has been set up, then activate the  
Monitor function. If all channels are defined as OFF, you must first set up one or more  
channels before activating the Monitor function.  
Note  
The Monitor function does not update data in the Review array, an  
Autoprint listing, or data memory (2625A). These values are updated only  
with measurements taken by the Scan function.  
Using the Scan Function  
The Scan function takes measurements at the specified interval on all defined channels.  
Pressing Q to activate the Scan function causes all defined channels to be measured in  
sequence. This cycle repeats at the specified scan interval. When Q is pressed a second  
time, the Scan function is turned off, and the instrument returns to the Inactive Mode.  
Note  
During a scan, a channel set up with autoranging will momentarily slow  
the scanning rate whenever the correct range must be determined. This will  
occur during the initial scan; the instrument remembers the range for  
subsequent scans. Scans then occur at the normal measurement rate. If the  
input signal later changes sufficiently, the scanning rate will again slow  
momentarily while the instrument determines the new range.  
If scanning is deactivated while the instrument is actually taking scan measurements, the  
display changes immediately, but the full scan is still completed. The instrument always  
completes a scan in progress.  
You can also trigger a single scan of all defined channels. Select SINGLE (K Q) to  
scan all the defined channels once.  
Reviewing Channel Data  
The instrument automatically stores minimum, maximum, and last-scanned values for  
each defined channel. These values are stored in the Review array and are updated with  
each set of scan measurements. Measurements taken by the Monitor function are not  
included in the Review array.  
The contents of the Review array can be called up to the display when in Active or  
Inactive Mode by pressing N. The displayed channel must be defined (i.e., not OFF)  
to call up Review array data from Inactive Mode; otherwise, a long beep results.  
You can move around in the Review array using the arrow buttons. The access scheme is  
shown in Table 2-3. Either the Review array or the Totalizer count can be displayed at  
one time; you must deactivate one before activating the other.  
To remove the Review data from the display and restore the previous display, press  
N again, or press D.  
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Overview  
Viewing the Totalizer Count  
2
To clear out the contents of the Review array, press N to call the review data up to  
the display, and then select CLEAR (K N). The entire array is then cleared. All  
array values, including the displayed value, are changed to "-----". If a scan is occurring  
when a review clear is requested, new review values are taken from the next scan. If the  
Scan function is not active, "-----" continues to be shown for all values.  
Alarms are shown with the LAST review values. Refer to Alarm Indications in Chapter 3  
for a description of alarm annunciation.  
Table 2-3. Review Array  
Activate  
Review Points  
Deactivate  
N
H
J
N
or  
20  
LAST  
MIN  
MAX  
G
C
D
0
LAST  
MIN  
MAX  
Viewing the Totalizer Count  
The Totalizer continuously samples the Totalizer input on the rear panel. The present  
count can be called up to the display when in Active or Inactive Mode by pressing O.  
The word "totAL" appears on the right display, and the present Totalizer count appears  
on the left display.  
The maximum count is 65535, after which "OL" is displayed. To reset the Totalizer to  
zero, press O to call the Totalizer value to the display, and then select ZERO (K  
O).  
To remove the Totalizer value from the display and restore the previous display, press  
O again, or press D.  
Note that either the Review array or the Totalizer count can be displayed at one time;  
you must deactivate one before activating the other.  
Using External DC Power  
The instrument can be powered from an external 9 to 16V dc source. Refer to Appendix  
A, Specifications, for additional information about dc power requirements.  
Terminals for positive, negative, and ground connections are provided on the instrument  
rear panel. Figure 2-6 shows connection locations.  
Warning  
If voltages greater than 30V are to be measured, a safety  
ground must be attached to the rear panel ground connector  
when the instrument is operated from battery power.  
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2620A, 2625A  
Users Manual  
Using the Rack Mount Kit  
Use the M00-200-634 Rack Mount Kit to mount the instrument in a standard 19-inch  
rack. First, rotate the two bottom feet on the instrument 180 degrees so that the support  
pads point up. Then install the instrument per the instructions provided with the Rack  
Mount Kit.  
2-18  
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Chapter 3  
Operating the Instrument from the Front  
Panel  
Title  
Page  
Introduction ....................................................................................................... 3-3  
Operating Modes ............................................................................................... 3-3  
Other Displayed Data ........................................................................................ 3-4  
What is the Present Configuration?................................................................... 3-4  
If Power is Interrupted .................................................................................. 3-4  
If the Configuration is Reset......................................................................... 3-4  
Channel Configuration ...................................................................................... 3-4  
Selecting Channel, Function, and Range ...................................................... 3-4  
Setting Alarms............................................................................................... 3-9  
Alarm Limits............................................................................................. 3-9  
Alarm Indications ..................................................................................... 3-10  
Resetting Alarm Conditions ..................................................................... 3-11  
Using the Digital I/O Lines........................................................................... 3-11  
Mx+B Scaling ............................................................................................... 3-12  
Instrument Configuration .................................................................................. 3-14  
Entering and Changing Numeric Values....................................................... 3-14  
Selecting Scan Interval.................................................................................. 3-15  
Selecting the Measurement Rate................................................................... 3-15  
Triggering...................................................................................................... 3-16  
External Triggering....................................................................................... 3-16  
Changing the Temperature Unit.................................................................... 3-16  
Setting Date and Time of Day....................................................................... 3-17  
Measurement Connections ................................................................................ 3-17  
DC Volts, AC Volts, Frequency, and Thermocouples.................................. 3-18  
Resistance and RTD...................................................................................... 3-20  
Totalizing........................................................................................................... 3-22  
General.......................................................................................................... 3-22  
Connections................................................................................................... 3-22  
Review Array..................................................................................................... 3-22  
List Button Functions........................................................................................ 3-23  
Autoprint ........................................................................................................... 3-25  
Memory Storage ................................................................................................ 3-25  
Front Panel Lock out Conditions....................................................................... 3-26  
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2620A, 2625A  
Users Manual  
Front Panel Review Only Function............................................................... 3-26  
Front Panel Monitor Only Function.............................................................. 3-26  
Computer Interface-Initiated Lockouts......................................................... 3-27  
REM Annunciator ............................................................................................. 3-27  
Calibration......................................................................................................... 3-27  
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Operating the Instrument from the Front Panel  
Introduction  
3
Introduction  
Chapter 3 describes how to use the instrument features that were introduced in Chapter  
2. The introductory information in Chapter 2 is designed to give you a feel for the  
instruments controls and display. The information presented here in Chapter 3 adds  
more detail about connecting and operating the instrument.  
Operating Modes  
The instrument has three modes of operation. These modes are summarized as follows:  
Active Mode  
The instrument is in Active Mode whenever the Monitor and/or Scan functions are  
enabled; "MON" and/or "SCAN" annunciators are lighted, as appropriate. Note that  
the Scan function can be activated by the scan interval timer, external trigger, alarm  
trigger, or a single scan command.  
Configuration Mode  
The instrument is in Configuration Mode whenever any of the settings are being  
examined or changed. Examples of Configuration Mode are: channel function  
selection, alarm value setting, Mx+B scaling value setting, scan interval setting, and  
trigger type selection. During Configuration Mode, the "SET" annunciator is on,  
along with other annunciators indicating the parameter being set. Configuration  
Mode is summarized in Figure 3-1.  
Inactive Mode  
The instrument is in Inactive Mode when no measurement functions are enabled and  
no instrument settings are being changed. This is a quiescent mode, from which  
Active or Configuration Mode can be entered. The display presents summary  
information, identifying the channel number (brightly lit, right display) and its  
present function (dimly lit annunciator).  
Configuration Mode  
Start from Inactive Mode. For full configuration sequence descriptions, refer to the appropriate  
description in Section 3 or 4. Exit any configuration sequence early (and discard changes) by pressing  
C.  
F
A
B
I
K
Define a measurement function for this channel.  
Set alarm parameters for a defined channel.  
Set scaling and offset parameters for this defined channel.  
Set time interval between scans.  
M
TRIGS  
Select scan triggering type.  
K
K
I
CLOCK  
Set date and time.  
J
RATE  
Select measurement rate.  
K
K
U
L
Select autoprint/memory storage.  
Set computer interface parameters.  
COMM  
Figure 3-1. Configuration Mode  
3-3  
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2620A, 2625A  
Users Manual  
Other Displayed Data  
An array of "MIN", "MAX", and "LAST" values for each channel is updated whenever  
scan measurements are taken. This Review array can be displayed from Active or  
Inactive (but not Configuration) Mode by pressing N.  
The constantly updated Totalizer count can also be displayed (Active or Inactive Mode  
only) by pressing O.  
Note that either the Review array or the Totalizer count can be displayed at one time;  
you must deactivate one before activating the other. Deactivate the Review array by  
pressing N a second time. Deactivate the Totalizer display by pressing O a second  
time. Pressing C also deactivates either function.  
What is the Present Configuration?  
If Power is Interrupted  
All configuration settings (function, range, scan interval, etc.) are stored in nonvolatile  
memory. If power is interrupted (R pressed off or due to power loss), these settings  
are retained. When turned on, the instrument first executes a self test, then resumes the  
state it was in prior to interruption of power. This feature is handy for applications where  
power may be inadvertently lost; the instrument automatically resumes taking  
measurements, as originally configured, once power is restored.  
If the Configuration is Reset  
You can perform a Configuration Reset in either of two ways:  
From the front panel, press and hold when cycling POWER ON.  
Through the computer interface, send the *RST command.  
Refer to Table 3-1 for the configuration reset settings.  
Channel Configuration  
Configuration Mode involves selecting an entry from a list of choices (and may involve  
setting number values.) Measurements are not taken when the instrument is in  
Configuration Mode. Configuration Mode is discussed throughout this chapter; it is used  
whenever a parameter for a channel or for the whole instrument needs to be set.  
Selecting Channel, Function, and Range  
Steps necessary for setting each type of measurement function are shown in the  
following tables:  
DC Voltage Measurement (Table 3-2)  
AC Voltage Measurement (Table 3-2)  
Resistance Measurement (Table 3-3)  
Frequency Measurement (Table 3-4)  
Temperature Measurement Using Thermocouples (Table 3-5)  
Temperature Measurement Using RTDs (Table 3-6)  
Additional channel configuration steps (alarms, scaling, etc) are discussed later in this  
chapter.  
3-4  
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Operating the Instrument from the Front Panel  
Channel Configuration  
3
Table 3-1. Configuration Reset Settings  
Perform a Configuration Reset to restore these conditions by pressing and holding C while cycling  
POWER ON.  
Channels 0 - 20:  
OFF.  
Slow.  
Measurement rate:  
Scaling (M):  
(B):  
1 (all channels)  
0 (all channels)  
Alarm parameters:  
Limit-1 and Limit-2 OFF.  
All limit values 0.  
Alarm assignments:  
Channels 0-3 assigned to outputs 0-3 respectively.  
Channels 4-20 assigned to digital I/O lines 4-7, as follows  
(appropriate channels are OR’ed to drive each I/O line):  
DIGITAL I/O LINE  
ASSIGNED TO  
CHANNELS  
4
4
5
5
6
7
6
7
8
9
10  
14  
18  
11  
15  
19  
12  
16  
20  
13  
17  
Scan interval time:  
0:00:00 (continuous)  
cleared for all channels.  
set high (non-alarm)  
Review values (MIN, MAX, LAST):  
Digital I/O lines:  
Totalizer:  
0, with debounce disabled.  
OFF.  
Autoprint:  
Memory Storage (2625A only):  
RTD R0 parameter:  
OFF, empty  
100.00 (all channels)  
enabled.  
Open Thermocouple Detection (OTC):  
Note  
During a scan, a channel set up with autoranging will momentarily slow  
the scanning rate whenever the correct range must be determined. This will  
occur during the initial scan, with the instrument remembering the range  
for subsequent scans. Scans then occur at the normal measurement rate. If  
the input signal later changes sufficiently, the scanning rate will again  
slow momentarily while the instrument determines the new range.  
AC voltage measurements can be made over a wide range of frequencies. The  
instruments true rms converter insures accuracy for both sine wave and non-sine wave  
signals. Refer to Chapter 5 for additional information about true rms measurements.  
Resistance measurements can be made to determine either resistance or the value of  
another directly related parameter. Slide wire potentiometers, thermistors, and other  
sensors with variable resistance outputs are often used to indicate temperature, position,  
and other physical parameters. The instrument measures resistance by passing a current  
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2620A, 2625A  
Users Manual  
through both a known resistance and the sensed resistance. The resulting voltages are  
measured and appropriate conversions are applied to the measurement, yielding a  
displayed output in ohms.  
Frequency is measured by counting cycles for a known time period. The measurement  
represents the frequency observed during the sampling time. The instrument can measure  
a wide range of frequency inputs. Test applications might include measuring line voltage  
sine wave signals or measuring the output of a voltage-to-frequency converter used in a  
servo system.  
Thermocouple temperature measurements can be made using linearizations for the  
following nine standard thermocouples: J, K, E, T, N, R, S, B, C. You specify what type  
of thermocouple is connected to the channel. The reference temperature sensor is built  
into the Input Module. The instrument applies compensation automatically for  
thermocouple channels. Open thermocouple detection is indicated by "otc" in the left  
display. The thermocouples are further described in Table 3-14.  
Table 3-2. DC Voltage, AC Voltage  
Function  
(DC or AC)  
Range  
(Note)  
Channel  
PRESS  
THESE  
BUTTONS:  
TO  
SELECT  
FROM  
THESE  
CHOICES:  
0
1
.
OFF  
V DC  
V AC  
Auto  
(Completes  
Selection  
and returns  
to Inactive  
Mode)  
300.00 mV  
3.0000V  
30.000V  
150.00*V  
.
Hz  
20  
°C or °F  
* 300.00 CH 0, 1, and 11  
Note: Determine the highest ac or dc voltage value anticipated for this channel. Then select a range  
large enough to accommodate this value. If the highest voltage cannot be anticipated, select “Auto”.  
3-6  
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Operating the Instrument from the Front Panel  
Channel Configuration  
3
Table 3-3. Resistance  
Range  
(Note 1)  
Channel  
Function  
Terminals  
PRESS  
THESE  
BUTTONS:  
TO  
SELECT  
FROM  
THESE  
CHOICES:  
0
1
.
OFF  
V DC  
V AC  
Hz  
°C or °F  
Auto  
300.00 Ω  
2T  
4T  
(Completes  
Selection  
and returns  
to Inactive  
Mode)  
3.0000 kΩ  
30.000 kΩ  
300.00 kΩ  
3.0000 MΩ  
10.000 MΩ  
.
20  
Note 1. Determine the highest resistance value anticipated for this channel. Then select a range large  
enough to accommodate this value. If the highest resistance cannot be anticipated, select “Auto”.  
Note 2. "4T" allowed on channels 1 through 10 only. For each 4T channel, an additional channel (10  
channels higher) is reserved to provide the third and fourth terminals. Channels 11 through 20 are  
available for this purpose. Any channel so reserved cannot be used for other definitions.  
Table 3-4. Frequency  
Function  
Range  
(Note)  
Channel  
PRESS  
THESE  
BUTTONS:  
TO  
SELECT  
FROM  
THESE  
CHOICES:  
0
OFF  
Auto  
900.00 Hz  
9.0000 kHz  
90.000 kHz  
900.00 kHz  
1.0000 MHz  
(Completes  
Selection  
and returns  
to Inactive  
Mode)  
V DC  
V AC  
Hz  
°C or °F  
1
.
.
20  
Note: Determine the highest frequency anticipated for this channel. Then select a range large enough to  
accommodate this value. If the highest frequency cannot be anticipated, select "Auto". "Auto" does not  
cause any delays for frequency measurements.  
3-7  
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2620A, 2625A  
Users Manual  
Table 3-5. Thermocouple Temperature  
Function  
Range  
(Note)  
Channel  
PRESS  
THESE  
BUTTONS:  
TO  
SELECT  
FROM  
THESE  
CHOICES:  
OFF  
V DC  
V AC  
Hz  
°C or °F  
J
K
E
T
N
R
S
b
1
.
.
(Completes  
Selection and  
returns to  
Inactive Mode)  
20  
C
Pt  
Note: The nine thermocouple choices and related temperature measurement ranges are:  
"J"  
Type J (-210 to 760 °C)  
"K"  
"E"  
"T"  
"N"  
"R"  
"S"  
"b"  
"C"  
Type K (-270 to 1372 °C)  
Type E (-270 to 1000 °C)  
Type T (-270 to 400 °C)  
Type N (-270 to 1300 °C)  
Type R (0 to 1767 °C)  
Type S (0 to 1767 °C)  
Type B (0 to 1820 °C)  
Type C (0 to 2316 °C)*  
(Tungsten - 5% Rhenium vs. Tungsten - 26% Rhenium)  
"Pt" selects RTD temperature measurement (DIN/IEC 751). See Table 3-6.  
* Hoskins Engineering Co.  
3-8  
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Operating the Instrument from the Front Panel  
Channel Configuration  
3
Table 3-6. RTD Temperature  
R0  
(Ice Point)  
(Note 3)  
Type  
(Note 1)  
Terminals  
(Note 2)  
Channel  
Function  
PRESS  
THESE  
BUTTONS:  
TO  
SELECT  
FROM  
THESE  
CHOICES:  
0
1
.
OFF  
V DC  
V AC  
Hz  
°C or °F  
J
K
E
T
N
R
S
b
2T  
4T  
100.00 Completes  
selection  
and returns  
to Inactive  
Mode  
.
20  
C
Pt  
Note 1. Pt selects RTD temperature measurement (DIN/IEC 751). See Table 3-5 for J, K, E, T, N, R, S, b,  
and C thermocouple selections.  
Note 2. 4T not available on channels 0 and 11 through 20.  
Note 3. R0 default is 100.00. A unique R0 value can be set for each channel.  
Note  
Temperature units can be displayed in degrees Celsius (ºC) or Fahrenheit  
(ºF). To switch this setting between ºC and ºF, start with the instrument  
powered off, then press and hold B while pressing POWER ON. The  
setting can also be changed through the Computer Interface with the  
TEMP_CONFIG command (refer to Chapter 4.)  
RTD temperature measurement uses a resistance-temperature detector (RTD). RTDs,  
while usually larger and more expensive than thermocouples, are frequently used where  
accuracy, stability, and repeatability are important. The resistance of an RTD varies  
directly with the sensor temperature. Passing a current through this resistance generates a  
proportional voltage that can be accurately translated into a temperature reading. The  
instrument supports the DIN/IEC 751 RTD type.  
Setting Alarms  
Alarm Limits  
Note  
If you press A for a channel that is OFF, an error beep will result.  
Therefore, for a new channel, use F to define the channel's measurement  
function before selecting A.  
Two alarm limits (S and T) can be defined for each analog input channel. An alarm  
occurs when the measured value on the channel moves above the HI value or below the  
LO value. With the desired channel already selected from Inactive Mode, verify or  
change these limits using the procedure shown in Table 3-7. If necessary, refer to  
"Entering and Changing Numeric Values" for a more detailed description of the number  
changing technique used here.  
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2620A, 2625A  
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Alarm evaluation is not carried out for a channel if:  
The limit sense is changed to "OFF". Alarm checking and the alarm limit values are  
re-enabled by setting limit sense to "HI" or "LO".  
An open thermocouple has been detected on that channel (thermocouple temperature  
function only).  
Table 3-7. Alarm Selection  
Channel  
Alarm  
PRESS  
Complete Alarm  
THESE  
Parameters (Below)  
BUTTONS:  
TO  
0
SELECT  
FROM  
THESE  
CHOICES:  
1
.
.
S or T  
20  
Alarm Parameters  
Alarm  
Sign,  
Value  
Decimal  
Point  
Multiplier (Note 2)  
Limit  
(Note 1)  
Position  
PRESS  
THESE  
BUTTONS:  
TO  
SELECT  
FROM  
THESE  
CHOICES:  
OFF  
HI  
LO  
±0000  
0.0000  
00.000  
000.00  
0000.0  
m
x1  
k
M
Note 1. Alarm limit can be cycled through HI, LO, and OFF without resetting the alarm value.  
Note 2. Multiplier definitions (available for each decimal point position):  
m .001  
x1 1.0  
k 1000  
M 1000000  
Alarm Indications  
Generally, the ALARM annunciator is dimly lit whenever the last measurement on any  
channel was found to be in alarm. When the displayed channel is in alarm during review,  
the ALARM annunciator flashes, LIMIT is lit, and additional annunciators show the  
alarm limit as S and/or T and the alarm sense as "HI" or "LO".  
3-10  
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Operating the Instrument from the Front Panel  
Channel Configuration  
3
Alarm annunciation is disabled when the instrument is in Inactive or Configuration  
Mode.  
ALARM annunciation and evaluation follow these rules:  
1. When any channel reading from the latest scan is in alarm (but the presently  
displayed channel is not in alarm or a scan interval countdown is in progress):  
"ALARM" annunciator is dimly lit.  
2. If the presently displayed channel (i.e., the Monitor or the Review array Last  
channel) is in alarm:  
"ALARM" annunciator flashes. S and/or T limit annunciator on brightly. "HI" and/or  
"LO" sense annunciator on brightly. "LIMIT" annunciator on brightly.  
3. If the present channel is in alarm with a value of "OL" displayed:  
"OL" means that a very large positive number is used for alarm evaluation.  
"-OL" means that a very large negative number is used for alarm evaluation.  
4. If the present channel shows a value of "otc":  
Alarm limit checking is no longer occurring for that channel. Alarm status remains  
as it was prior to the "otc" condition.  
5. If no channels are in alarm:  
All alarm-related annunciators ("ALARM", S, T, "HI", "LO", "LIMIT") are off.  
Note  
Alarms encountered during scan measurement can generate a low level on  
an assigned output. If an alarm is encountered and just the monitor  
function is selected without the scan function, the front panel will indicate  
the alarm; but, the alarm output will not change to indicate the alarm. An  
IEEE-488.1 SRQ can also be generated when an alarm condition is set or  
cleared.  
Resetting Alarm Conditions  
When review values are cleared, all alarm status is also removed. This action occurs in  
the following instances:  
A channel function is changed or set to OFF.  
A channel range is changed.  
CLEAR (K N) is selected while Review array data is being examined.  
Configuration Reset occurs (power up C or *RST)  
Changing an alarm definition clears the alarm status for the changed alarm limit.  
Using the Digital I/O Lines  
The rear panel Digital I/O Connector provides eight lines (numbered 0 through 7) that  
are individually usable as inputs or outputs. No preconfiguring for the use of these lines  
is necessary; an input low signifies that the line is an input, and an output low signifies  
that the line is an output. Output low conditions take precedence over input low  
conditions.  
Both alarm limits S and T for channels 0 through 3 are permanently assigned to alarm  
outputs 0 through 3, respectively, on the rear panel Alarm Output Connector.  
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2620A, 2625A  
Users Manual  
At any Configuration Reset (power up C or computer interface *RST), alarm limits on  
channels 4 through 20 are assigned to Digital I/O lines 4 through 7 in the "ORed" pattern  
shown in Table 3-8. These assignments can be changed via the Computer Interface. Each  
limit (S or T) for a channel can be assigned to any one digital output.  
Table 3-8. Initial Alarm Assignments, Digital I/O Lines 4 Through 7  
Digital I/O Line  
4
5
6
7
Assigned to Channels  
4
5
6
7
8
9
10  
14  
18  
11  
15  
19  
12  
16  
20  
13  
17  
(Appropriate channels are OR’ed to drive each I/O line.)  
All Digital I/O lines are set high (non-active) whenever power is cycled. These lines  
remain high until a new scan detects an alarm condition on an assigned limit or until a  
new Computer Interface command is received.  
Note  
Measurements taken with the Monitor function do not affect the digital  
outputs.  
At the completion of a scan, an alarm condition sets the assigned digital output to a logic  
0 (low) state. The digital output returns to a logic 1 (high) state when all assigned alarm  
conditions are cleared. Note that digital outputs for alarms are updated only at the end of  
each scan. This technique prevents unnecessary toggling of the digital lines during a  
scan.  
Mx+B Scaling  
Any analog input channel (0 through 20) can be assigned scaling ("M" and "B") values  
that are applied to subsequent measurements of that channel. Scaling values can be set  
via the front panel or over a computer interface.  
The "M" value is used as a multiplier of the actual reading; the "B" value is then added  
in the same units as the resultant. If no scaling values are specified for a channel, the  
Configuration Reset values of 1 ("M") and 0 ("B") are used, leaving the measurement  
reading unaltered.  
In the Inactive Mode, the "Mx+B" annunciator lights to indicate that an M value other  
than 1 and/or a B value other than 0 has been specified for the displayed channel. When  
a measurement is displayed for a channel so configured, no measurement units ("",  
"V", etc.) are shown.  
Note  
If you press B for a channel that is OFF, an error beep will result.  
Always use F to define the channels measurement function before using  
B to define the scaling values.  
You can familiarize yourself with the Mx+B setup procedure by pressing B. Then  
press E a few times to cycle through the elements of the scaling values. If only  
E is pressed, no changes are introduced. Note that the scaling value element that can  
3-12  
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Operating the Instrument from the Front Panel  
Channel Configuration  
3
be changed at any point is brightly lit (solid for digits, flashing for other annunciators);  
all other elements are dimly lit at this time. Table 3-9 presents a full description of the  
Mx+B configuration sequence.  
If you press C while setting the "M" value (anytime prior to showing the "B" value),  
no changes entered thus far are stored. If you press C while setting the "B" value,  
changes to M are stored and changes to "B" are discarded. In either case, the instrument  
returns to Inactive Mode.  
The final E press shown in Table 3-9 stores all changes and returns the instrument to  
Inactive Mode.  
Note  
Once Mx+B scaling values are defined for a channel, the instrument uses  
the range chosen for the B value as the display range for the resulting  
scaled value. If the result is larger than the display range chosen, an  
overload ("OL") is displayed.  
For example, you could monitor the output of a high-pressure pump by using Mx+B  
scaling to convert the millivolt output of a pressure transducer to PSI. Such a transducer  
might output 0 to 30 mV, corresponding to pressure of 0 to 5000 PSI. The scaling values  
to convert the transducer millivolts to PSI would be M = 166.67 PSI/V and B = 0 PSI,  
calculated as follows:  
Max Display Value  
Min Display Value  
5000  
30  
M =  
=
= 166.67  
Max Transducer Output  
Min Transducer Output  
B = Min Display Value - (M * Min Transducer Output) = 0 - 166.67 * 0 = 0  
When a channel that has had scaling values entered is scanned or monitored, the  
resulting scaled value is displayed without the underlying function annunciation. The  
decimal point location and scale factor for the result is fixed by the "B" value entered. If  
the scaled value is too small to be represented in 5 digits given this scaling, zero is  
displayed. If the scaled value is too large, "OL" (overload) is displayed (even if the  
underlying measurement was on scale.) "OL" is also displayed if the measurement is in  
overload.  
If scanning or monitoring a scaled channel gives unexpected results (like zero or  
overload), make the following checks:  
1. Verify that the values and scale factors of "M" and "B" are set as intended.  
2. Verify that the desired values are the correct values: calculate the result for a few  
measured values using the entered "M" and "B".  
3. Temporarily set "M" to 1 and "B" to 0; verify that the measurements are returning  
values in the expected range. Unexpected measurements could result from a wiring  
error or the wrong range/function being selected.  
3-13  
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2620A, 2625A  
Users Manual  
Table 3-9. Mx+B Selection  
Channe  
l
Sign, M  
Value  
Decimal  
Point  
Multiplier  
(Note 1)  
Position  
PRESS  
THESE  
G
D
G
D
G
D
G
D
BUTTONS:  
B
E
E
E
H
J
H
J
H
J
TO SELECT  
FROM  
THESE  
0
±0000  
0000.0  
000.00  
00.000  
0.0000  
m
x1  
k
(Continue to  
B value  
below)  
1
.
CHOICES:  
M
.
20  
Sign, M  
Value  
Decimal  
Point  
Multiplier  
(Note 1)  
Position  
PRESS  
THESE  
G
D
G
D
G
D
BUTTONS:  
E
E
E
H
J
H
J
H
J
TO SELECT  
FROM  
THESE  
±0000  
0000.0  
000.00  
00.000  
0.0000  
m
x1  
k
CHOICES:  
M
Note 1. Multiplier definitions:  
m .001  
x1 1.0  
k 1000  
M1000000  
Note 2. If your press C while setting the "M" value (anytime prior to showing the "B" value), no changes  
entered thus far are stored. If you press C while setting the "B" value, changes to M are stored and  
changes to "B" are discarded. in either case, the instrument returns to Inactive Mode.  
Instrument Configuration  
Entering and Changing Numeric Values  
Use the arrow buttons to enter or change a numeric value. Use J and H to select the  
digit to change. (The selected digit is brightly lit.) Use G and D to change the value for  
that digit.  
Setting the scan interval provides a good example of entering a numeric value. Press I  
to set the scan interval. Now try pressing J and H a few times to select different digits.  
(The selected digit is always brightly lit.) For any digit, press G or D to change the  
value. Refer to Table 3-10 for details of setting the scan interval.  
3-14  
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Operating the Instrument from the Front Panel  
Instrument Configuration  
3
This number editing technique occurs during Configuration Mode operations whenever  
you are setting a numeric value. Instances of number editing include the following:  
R0 (RTD)Table 3-6  
Alarms Table 3-7  
Mx+B Scaling Table 3-9  
Scan Interval TimeTable 3-10  
Time/Date Table 3-13  
Selecting Scan Interval  
The scan interval is the period between starts of measurement scans. The resolution of  
the scan interval is one second; the maximum scan interval is 9 hours: 99 minutes: 99  
seconds. The format of the scan interval is x:xx:xx; 1:30:45 translates to 1 hour, 30  
minutes and 45 seconds.  
If scan interval of "0:00:00" is specified, continuous scanning will occur when the Scan  
function is activated. If more than a few seconds are required to scan all defined  
channels, a short scan interval (a few seconds) effectively becomes continuous scanning.  
If the Monitor function is turned on when the instrument is continuously scanning, a  
Monitor channel measurement is still taken between each scan.  
Table 3-10 illustrates the button sequence used for setting scan interval. If necessary,  
refer to "Entering and Changing Numeric Values" for a more detailed description of the  
number editing technique used here.  
Table 3-10. Scan Interval  
Hour  
Minute  
Second  
PRESS  
I
J
J
J
J
E
THESE  
BUTTONS:  
G
D
G
D
G
D
G
D
G
D
TO  
CHANGE  
THE  
0:00:00  
0:00:00  
0:00:0  
0
0:00:0  
0
0:00:0  
0
INDICATED  
DIGIT:  
Note: Go backward (from SECOND to MINUTE to HOUR) by pressing H.  
Press E at any time to accept the displayed scan interval and exit scan interval selection. Press C  
at any time to exit interval selection without storing any changes.  
Selecting the Measurement Rate  
The slow measurement rate provides the highest accuracy and resolution. A fast rate can  
be selected, but keep in mind that fast rate provides one less digit of resolution than does  
slow rate. Measurement rate selection is illustrated in Table 3-11.  
3-15  
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2620A, 2625A  
Users Manual  
Table 3-11. Measurement Rate Selection  
Press these buttons:  
RATE(KJ)]  
G
D
E
To select from these  
choices:  
SLO  
FAST  
(Completes selection  
and returns to Inactive  
Mode)  
Triggering  
To set the scan triggering type from the front panel, use the procedure shown in Table 3-  
12.  
Table 3-12. Trigger Type Selection  
Press these buttons:  
TRIGS(KJ)]  
G
D
E
To select from these  
choices:  
OFF  
On  
ALAr  
Note: The three trigger types signify:  
"OFF" External triggering is disabled. Scan trigger is controlled by scan interval.  
"ON" External triggering is enabled. A low input on the rear-panel TR terminal affects scanning as  
follows:  
If the instrument is in Inactive Mode, or just the Monitor Function is on, the low input enables scanning.  
When the signal on the TR terminal returns to high, scanning is disabled.  
If scanning is already enabled, the external trigger initiates a single scan. If a scan is already in progress,  
this request is ignored.  
"ALAr" An alarm condition on the monitor channel automatically triggers a scan. (External triggering is  
disabled.)  
External Triggering  
The external trigger setting offers additional control of scan starts through a separate  
trigger line on the rear panel. Refer to Chapter 5 for an in-depth discussion of external  
triggering.  
Changing the Temperature Unit  
The displayed temperature unit can be degrees Celsius (ºC) or Fahrenheit (ºF). To switch  
this setting, start with the instrument powered off, then press and hold B while  
pressing POWER ON. After the instrument beeps and the new temperature unit is shown  
in the display, release B.  
The units setting can also be changed through the Computer Interface with the  
TEMP_CONFIG command (refer to Chapter 4.)  
3-16  
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Operating the Instrument from the Front Panel  
Measurement Connections  
3
Setting Date and Time of Day  
The instrument features a built-in, battery-maintained clock and calendar. Verify or  
change the settings using the steps shown in Table 3-13. If necessary, refer to "Entering  
and Changing Numeric Values" for a more detailed description of the number changing  
technique used here.  
3-13. Date/Time Selection  
Year  
“YEAR”  
Month.Day  
“Mn.dY”  
Hour.Minut  
e” Hr.nn”  
PRESS  
THESE  
CLOCK G  
(KI D  
G
D
G
D
BUTTONS:  
])  
E
E
E
H
J
H
J
H
J
TO SELECT  
FROM  
00-99  
01-12.01-31  
00-23.00-59  
THESE  
CHOICES:  
Note: The last E press completes clock and calendar setting and returns the instrument to  
Inactive Mode.  
Pressing C during this sequence also returns the instrument to Inactive Mode; all entries to  
this point are discarded, and the clock/calendar settings are left unchanged.  
Measurement Connections  
Warning  
To avoid electric shock:  
When the input module is installed, consider all channels  
with connections as accessible terminals that may be  
hazardous live.  
Disconnect the input module before touching or changing  
external wiring.  
Remove inputs from live voltages before opening the input  
module.  
3-17  
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2620A, 2625A  
Users Manual  
DC Volts, AC Volts, Frequency, and Thermocouples  
Any analog input channel (0 through 20) can be used to measure dc volts, ac volts, or  
frequency. For channel 0, use the two terminals on the front panel. For channels 1  
through 20, use the H (high) and L (low) inputs on the rear panel Input Module.  
Note  
The terminals for channel 0 on the front panel do not support  
thermocouple measurements.  
Front panel channel 0 and Input Module channels 1 and 11 accept a maximum input of  
300V dc or ac rms. All other channels (2 through 10 and 12 through 20) accept a  
maximum of 150V dc or ac rms.  
Use the following procedure for connections to the Input Module:  
1. Remove the Input Module from the rear panel.  
2. Loosen the two large screws on top and open the module.  
3. Connect wires to H (high) and L (low) terminals for each channel.  
4. Thread these wires through the strain-relief pins and out the back of the module.  
Refer to Figure 3-2.  
5. Close the module cover, secure the screws, and put the module back in the  
instrument.  
3-18  
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Operating the Instrument from the Front Panel  
Measurement Connections  
3
L
H
L
H
L
H
H
L
L
L
H
L
H
L
H
L
H
L
H
H
L
L
H
H
L
L
H
H
L
H
H
L
H
L
H
H
L
H
oo08f.eps  
Figure 3-2. Input Module Connections  
3-19  
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2620A, 2625A  
Users Manual  
Resistance and RTD  
For all channels (0 through 20), 2-terminal resistance or RTD measurements are allowed.  
Four-terminal measurements can be made on channels 1 through 10 only. Refer to  
Figure 3-3.  
For each channel configured for 4-terminal measurements (channels 1-10 only), a second  
channel (numbered 10 higher than the first) becomes unavailable for any other type of  
measurement. For example, using channel 7 to make 4-terminal resistance measurements  
requires the use of input terminals for both channels 7 and 17. Channel 17 cannot be  
used to take any other measurements as long as channel 7 remains configured for 4-  
terminal measurements.  
Table 3-14. Thermocouple Ranges  
Positive Lead  
Type Material  
Positive Lead Color  
Negative Lead*  
Material  
Usable Range  
(ANSI)  
WHITE  
(IEC)  
(°C)  
J
Iron  
BLACK  
GREEN  
VIOLET  
BROWN  
Constantan  
Alumel  
-210 to 760  
-270 to 1372  
-270 to 1000  
-270 to 400  
-270 to 1300  
K
Chromel  
Chromel  
Copper  
YELLPW  
PURPLE  
BLUE  
E
T
N
Constantan  
Constantan  
NISIL-  
NOCROSIL  
R
Platinum  
BLACK  
BLACK  
GRAY  
ORANGE  
ORANGE  
Platinum  
(13% Rhodium)  
0 to 1767  
0 to 1767  
0 to 1820  
0 to 2316  
S
Platinum  
Platinum  
(10% Rhodium)  
B
Platinum  
(30% Rhodium)  
Platinum  
(6% Rhodium)  
C**  
Tungsten  
WHITE  
Tungsten  
(26% Rhenium)  
* ANSI negative lead always RED, IEC negative lead always WHITE  
** Hoskins Engineering Co.  
Use the following procedure for resistance or RTD measurement connections to the  
Input Module:  
1. Remove the Input Module from the rear panel.  
2. Loosen the two large screws on top and open the module.  
3. Connect wires to H (high) and L (low) terminals for each channel (channel 7 for 2-  
terminal configuration or channels 7 and 17 for 4-terminal configuration, in this  
example.)  
4. Thread these wires through the strain-relief pins and out the back of the module.  
Refer to Figure 3-2.  
5. Close the module cover, secure the screws, and put the module back in the  
instrument.  
3-20  
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Operating the Instrument from the Front Panel  
Measurement Connections  
3
2-WIRE (2T) CONNECTION  
11 12 13 14 15 16 17 18 19 20  
H L H L H L H L H L H L H L H L H L H L  
SOURCE  
(4-WIRE)  
H L H L H L H L H L H L H L H L H L H L  
SENSE  
(4-WIRE)  
1
2
3
4
5
6
7
8
9
10  
RESISTANCE  
OR  
RTD SOURCE  
USE H AND L TERMINALS FOR ANY CHANNEL.  
• CHANNEL 0 ON FRONT PANEL  
• CHANNELS 1 THROUGH 20 ON REAR  
PANEL INPUT MODULE (CHANNEL 8 SHOWN HERE).  
4-WIRE (4T) CONNECTION  
11 12 13 14 15 16 17 18 19 20  
H L H L H L H L H L H L H L H L H L H L  
SOURCE  
(4-WIRE)  
H L H L H L H L H L H L H L H L H L H L  
SENSE  
(4-WIRE)  
1
2
3
4
5
6
7
8
9
10  
RESISTANCE  
OR  
RTD SOURCE  
USE H AND L TERMINALS FOR TWO CHANNELS ON REAR PANEL INPUT MODULE.  
CONNECTIONS FOR CHANNEL 8 SHOWN HERE WITH CHANNEL 18 PROVIDING  
ADDITIONAL TWO CONNECTIONS.  
FOR EACH 4-WIRE CONNECTION, ONE SENSE CHANNEL (1 THROUGH 10) AND  
ONE SOURCE CHANNEL (SENSE CHANNEL NUMBER +10 = 11 THROUGH 20) ARE USED.  
oo09f.eps  
Figure 3-3. 2-Terminal and 4-Terminal Connections  
3-21  
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2620A, 2625A  
Users Manual  
Totalizing  
General  
Event counting (totalizing) is commonly used on production lines for counting items.  
The instrument counts events by detecting low-to-high voltage transitions; each low-to-  
high transition increments the totalizer value by one. The maximum count is 65535;  
"OL" (for "overload") is displayed when the count exceeds this limit.  
Connections  
The totalizing input is made at the input labeled \Z (sigma) on the rear panel Digital I/O  
Connector (see Figure 3-4). This input accepts a minimum input of 2.0V pk, which  
translates to 1.4V rms for a sinewave or 1V rms for a square wave. If the input is a  
contact-closure type, input debouncing of 300 Hz (1.67 ms) is available. A maximum  
rate of 5 kHz can be accommodated through the totalizing input, but only if the input  
debouncing is disabled. Input debounce settings are available only through the computer  
interface (see Chapter 4.)  
ALARM OUTPUTS  
DIGITAL I/O  
+
9-16 V  
0
1
2
3 TR  
0
1
2
3
4
5
6
7
Σ
+30V  
!
DC PWR  
oo10f.eps  
Figure 3-4. Totalizing Connection  
Review Array  
Readings from every scan are checked for minimum and maximum values. These values,  
along with the last value measured, are stored in the Review array and can be recalled by  
pressing N. To cycle through the three values for the displayed channel, press H or  
J. If no value has been stored, or if the value has just been cleared, the display shows  
dashes ("-----").  
These values are updated by all scans (scan intervals, continuous scans, single scans, or  
scans initiated with an external trigger input.) Measurements taken with the Monitor  
function do not update these values.  
Note that either the Review array or the Totalizer count can be displayed at one time;  
you must deactivate one before activating the other. Press N a second time (or press  
C) to remove Review data from the display.  
Table 3-15 illustrates how to examine the Review array contents.  
3-22  
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Operating the Instrument from the Front Panel  
List Button Functions  
3
Table 3-15. Review Array  
Deactivate  
(Note 3)  
Activate (Note 1)  
Review Points  
N
H
J
N
or  
20  
LAST  
MIN  
MAX  
G
D
C
0
LAST  
MIN  
MAX  
Note 1. Review array can be entered only from a channel that is defined for some type of measurement  
("VDC", "VAC", etc.) Review array cannot be entered from a channel that is OFF.  
Note 2. All review values (MIN, MAX, LAST for all channels) can be cleared (to "-----") by pressing:  
CLEAR K N  
This clearing action can be initiated only while viewing the Review values. Any scan in  
progress is completed before a requested Review clear is carried out.  
Review values are cleared when any channel configuration is changed.  
Review values are not cleared automatically at the start of a new scan.  
Note 3. When returning to Inactive Mode, the instrument returns to the last channel examined in the  
Review array. This may not be the same channel from which you started viewing the Review  
array.  
Note 4. Alarms are shown with the LAST Review values. See Alarm Indications for a description of  
alarm annunciation.  
All review values for all channels are cleared with any of the following actions:  
CLEAR (K N) is selected. This must be done while review data is on the  
display; otherwise, an error beep results.  
Function or number of terminals for any channel is changed.  
Range or thermocouple/RTD type for any channel is changed.  
The M and/or B scaling value for any channel is changed.  
The RTD R0 value for any channel is changed.  
The temperature unit is changed.  
The measurement rate is changed.  
List Button Functions  
If the RS-232 interface is active, you can print out the Last values from the Review array  
(2620A and 2625A) or all values from Data Logger memory (2625A only). This  
procedure is described in Table 3-16.  
In the LASt printout, channels that are defined as OFF are not included. Following is a  
sample LASt printout:  
3-23  
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2620A, 2625A  
Users Manual  
07:41:37 02/09/91  
CH  
1:  
LAST VALUE  
097.32 mVDC  
0.0973 VDC  
00.097 VDC  
000.10 VDC  
MAX VALUE  
MIN VALUE  
098.51 mVDC  
0.0985 VDC  
00.099 VDC  
000.10 VDC  
096.10 mVDC  
0.0961 VDC  
00.096 VDC  
000.10 VDC  
2:  
3:  
4:  
5:  
OL  
OL  
mVAC  
VAC  
OL  
OL  
mVAC  
VAC  
OL  
OL  
mVAC  
VAC  
6:  
7:  
05.511 VAC  
005.51 VAC  
05.582 VAC  
005.58 VAC  
05.414 VAC  
005.41 VAC  
8:  
9:  
OL  
OL  
OHMS  
OL  
OL  
OHMS  
OL  
OL  
OHMS  
10:  
11:  
12:  
13:  
14:  
15:  
16:  
17:  
18:  
19:  
kOHMS  
kOHMS  
kOHMS  
08.276 kOHMS  
008.28 kOHMS  
0.0083 MOHMS  
00.008 MOHMS  
08.374 kOHMS  
008.37 kOHMS  
0.0084 MOHMS  
00.008 MOHMS  
08.231 kOHMS  
008.23 kOHMS  
0.0082 MOHMS  
00.008 MOHMS  
OL  
HZ  
OL  
HZ  
OL  
HZ  
9.7193 kHZ  
09.719 kHZ  
009.72 kHZ  
0.0097 MHZ  
9.7239 kHZ  
09.724 kHZ  
009.72 kHZ  
0.0097 MHZ  
9.6771 kHZ  
09.677 kHZ  
009.68 kHZ  
0.0097 MHZ  
With the Hydra Series II Data Logger (2625A), a sample Store printout of stored values  
for three scans would be as follows:  
07:41:5202/09/91  
5: -3.2345 mMX+B12:123.87 kOHMS17:31.268VAC  
ALM:15DIO:255TOTAL:0  
07:41:5302/09/91  
5: -3.2345 mMX+B12:123.87 kOHMS17:31.268VAC  
ALM:15DIO:255TOTAL:0  
07:41:5402/09/91  
5: -3.2345 mMX+B12:123.87 kOHMS17:31.268VAC  
ALM:15DIO:255TOTAL:0  
The Hydra Series II Data Logger can hold 2047 scans, with each scan containing 21  
channels of data.  
Table 3-16. List Button Operation  
(Note1)  
(Note 2)  
(Note 3)  
Press these buttons:  
L
G
E
D
LASt  
StorE  
To select from these  
choices:  
Note 1. RS-232 computer interface must be active. If the IEEE-488 interface is active, an error results.  
Note 2. "LASt" prints out all values in the Review array. Review array values are not affected. An error  
results if Review array data has been cleared.  
"StorE" prints out logged scan data from the Hydra Data Logger (2620A) memory. Logged data is  
not affected. An error results if there is no logged data.  
Note 3. Press C to abort a printout while it is occurring.  
3-24  
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Operating the Instrument from the Front Panel  
Autoprint  
3
Autoprint  
The front panel setup procedure is summarized in Table 3-17. Begin this procedure by  
selecting MODE (K U). Select the scan data destination ("dESt" in right display) as  
"Print" (left display). For the Hydra Series II Data Logger, a destination of "both" can  
also be selected, allowing for simultaneous printing and storage. (For the Hydra Series II  
Data Acquisition Unit, "Print" is the only possible selection.) Then select the mode  
("MOde" in right display) from "ALL", "ALAr", or "trAnS" (left display).  
With the Autoprint function defined, press U to enable or disable Autoprint. The  
"PRN" annunciator lights when Autoprint is enabled.  
Memory Storage  
Memory Storage is only available with the Hydra Series II Data Logger. Initiate the  
Memory Storage setup by selecting MODE (K U).  
Now refer to Table 3-17. Select the scan data destination ("dESt" in right display) as  
"StorE" for memory storage only or "both" for simultaneous storage and printing. Then  
select the mode ("MOde" in right display) from "ALL", "ALAr", or "trAnS" (left  
display).  
Once the destination and mode have been set, enable Memory Storage by pressing:  
U
The "PRN" annunciator lights to indicate that Memory Storage is enabled.  
Front panel controls allow you to send memory contents over the RS-232 computer  
interface to a printer. Retrieval can also be made through the RS-232 computer interface  
for data storage that has been accomplished either from the front panel or through the  
computer interface.  
Warning  
No data will be saved unless the “prn” annunciator is lit on the  
hydra series ii front panel florescent display.  
For memory clearing, refer to Table 3-18. You can clear scan data memory by holding  
K pressed while momentarily pressing U and answering "YES" in the left display as  
"CLEAr" appears in the right display. The instrument must be in Active or Inactive  
Mode; you cannot clear memory from Configuration Mode.  
The F annunciator is dimly lit when the logging storage is nearly full (more than 1800  
scans have been stored). The F annuciator is brightly lit when the logging storage is full  
(2047 scans). Storing additional scans causes the oldest scans to be overwritten.  
3-25  
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2620A, 2625A  
Users Manual  
Table 3-17. Autoprint/Memory Storage Selection  
Destination  
(“dESt”) (Note  
1)  
Mode (“MOdE”)  
(Note 2)  
Press these  
buttons:P  
MODE  
KU)  
G
D
G
D
E
E
To select from  
these choices:  
Print  
StorE  
both  
ALL  
ALAr  
trAnS  
Note 1.  
“Print”  
Sends data to be printed through the RS-232 interface.  
Sends data to be stored in memory. (Hydra Data Logger only.)  
Sends data to be stored and printed (Hydra Data Logger only.)  
“StorE”  
“both”  
“ALL”  
Note 2.  
Measurements for all defined channels are printed/stored when a scan occurs.  
“ALAr”  
Measurements for all defined channels are printed/stored when a scan occurs  
and at least one channel is in alarm.  
“trAnS”  
Measurements for all defined channels are printed/stored when a scan occurs  
and at least one channel has transitioned into or out of alarm since the last  
scan.  
Table 3-18. Clearing Memory Storage  
To Initiate  
To Confirm  
To Activate  
Hold K, and press U  
“no” to exit without clearing  
G D  
E
“CLEAr” appears in right display  
“YES”  
C to exit without clearing  
Front Panel Lock out Conditions  
Various methods are available to prevent accidental use of the front panel buttons. These  
actions can be initiated from either the front panel or the computer interface.  
Front Panel Review Only Function  
Access the Review Array (press N, REVIEW annunciator comes on)  
Press F and B simultaneously to activate the Review Only function (REM  
annunciator comes dim).  
J, H, G, and D can now be used to view the various elements of the Review Array.  
All other front panel buttons are locked out, yielding a long beep when pressed. Press  
both F and B again to deactivate the Review Only function and return the  
instrument to normal front panel button operation (regular Review Array display.)  
Front Panel Monitor Only Function  
First place the instrument in the Monitor Function (press M, MON annunciator comes  
on). Then press F and B simultaneously to activate the Monitor Only Function  
(REM annunciator comes on).  
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Operating the Instrument from the Front Panel  
REM Annunciator  
3
G and D can now be used to change the monitored channel. All other front panel  
buttons are locked out; a long beep results from their use. Press both F and B again  
to deactivate the Monitor Only function and return the instrument to normal front panel  
button operation (regular Monitor Function on.)  
Computer Interface-Initiated Lockouts  
Front Panel lockout can also be specified over the Computer Interface with the following  
commands.  
REMS (RS-232 only): four front panel buttons remain active (Q, G, K, and  
R).  
RWLS (RS-232 only): only the R button remains active.  
LOCK 1  
J, H, G, and D can now be used to view the various elements of  
the Review Array. All other front panel buttons are locked out, yielding a long beep  
when pressed. Press both F and B again to deactivate the Review Only function  
and return the instrument to normal front panel button operation (regular Review  
Array display.)  
LOCK 2  
G and H can now be used to change the monitored channel. All  
other front panel buttons are locked out; a long beep results from their use.  
Refer to Chapter 4 for additional information on these commands.  
REM Annunciator  
The front panel REM annunciator identifies the status of both computer interface control  
and front panel lockout. REM may be lit due to actions taken from the computer  
interface or the front panel; it can be off, dim, or bright as shown in Table 3-19.  
Table 3-19. REM Annunciation  
Remote  
Lock  
REM Annunciation  
False  
False  
True  
True  
False  
True  
False  
True  
Off  
Dim  
Bright  
Dim  
Calibration  
Refer to Chapter 6 (Maintenance) of this manual for a general discussion of instrument  
calibration. Refer to the Hydra Series II Service Manual (P/N 688868) for complete  
calibration procedures.  
The CAL ENABLE control point is located in the lower-right corner of the display.  
When the instrument is correctly calibrated, this control should be covered with a  
calibration decal; removing the decal voids assurance of correct calibration.  
Note  
Do not press CAL ENABLE unless you have a copy of the Service Manual  
and intend to calibrate the instrument. If you have accidentally activated  
Calibration and wish to exit immediately, press CAL ENABLE (until CAL  
disappears from the display) or turn power OFF.  
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2620A, 2625A  
Users Manual  
3-28  
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Chapter 4  
Using the Computer Interface  
Title  
Page  
Introduction ....................................................................................................... 4-3  
Front Panel and Computer Interface Operations........................................... 4-3  
Types of Computer Interface ........................................................................ 4-3  
Using the RS-232 Computer Interface .............................................................. 4-3  
Setting Communication Parameters (RS-232).............................................. 4-4  
Autoprint and Memory Storage (RS-232)..................................................... 4-5  
Autoprint: Computer Interface Control .................................................... 4-5  
Autoprint: Output Format......................................................................... 4-5  
Memory Storage: Computer Interface Control......................................... 4-6  
Memory Retrieval..................................................................................... 4-6  
Memory Full Operation ............................................................................ 4-7  
Clearing Memory...................................................................................... 4-7  
Cabling the Instrument to a Host or Printer (RS-232) .................................. 4-7  
Installation Test............................................................................................. 4-8  
RS-232 Information....................................................................................... 4-8  
Character Echoing .................................................................................... 4-8  
Character Deletion.................................................................................... 4-8  
Device Clear Using Ctrl C........................................................................ 4-8  
RS-232 Prompts........................................................................................ 4-9  
Sample Program Using the RS-232 Computer Interface .............................. 4-9  
Using the IEEE-488 Interface............................................................................ 4-9  
IEEE-488 Operating Limitations .................................................................. 4-9  
Installing the IEEE-488 Interface.................................................................. 4-9  
Enabling the IEEE-488 Interface .................................................................. 4-12  
Installation Test............................................................................................. 4-13  
General Information (RS-232 and IEEE-488)................................................... 4-13  
How the Instrument Processes Input............................................................. 4-13  
Input Strings.............................................................................................. 4-14  
Input Terminators ..................................................................................... 4-14  
Typical Input Strings ................................................................................ 4-14  
Sending Numeric Values to the Instrument (RS-232 and IEEE-488) ...... 4-16  
Sending Input Strings to the Instrument ................................................... 4-16  
How the Instrument Processes Output.......................................................... 4-16  
Service Requests (IEEE-488 only) and Status Registers.............................. 4-17  
Event Status and Event Status Enable Registers ...................................... 4-19  
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2620A, 2625A  
Users Manual  
Status Byte Register.................................................................................. 4-19  
Reading the Status Byte Register ............................................................. 4-20  
Service Request Enable Register.............................................................. 4-21  
Instrument Event Register ........................................................................ 4-21  
Computer Interface Command Set .................................................................... 4-22  
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Using the Computer Interface  
Introduction  
4
Introduction  
The instrument can be operated from a host via commands sent through the rear panel  
computer interface. The host can be a terminal, controller, PC, or other computer.  
This chapter describes how to set up and operate the instrument via the RS-232 interface  
(standard with Hydra Series II Data Acquisition Unit and Hydra Series II Data Logger)  
or the IEEE-488 computer interface (optional with Hydra Series II Data Acquisition Unit  
only.) The RS-232 interface can also be connected to a serial printer for direct output of  
data in printed format.  
With the IEEE-488 computer interface installed in the Hydra Series II Data Acquisition  
Unit, the instrument is fully programmable for use on the IEEE Standard 488.1 interface  
bus (1987). The instrument is also designed in compliance with supplemental IEEE Std.  
488.2-1987.  
This chapter assumes you are familiar with the basics of data communication, the RS-  
232 interface, and/or the IEEE-488 bus. For an introduction to the IEEE-488 interface,  
request Fluke Application Bulletin AB-36, "IEEE Standard 488-1978 Digital Interface  
for Programmable Instrumentation."  
An annotated sample program, illustrating the use of the RS-232 computer interface, is  
provided at the end of this chapter. Calibration procedures using the computer interface  
are provided in the Hydra Series II Service Manual (P/N 110731).  
Front Panel and Computer Interface Operations  
When the instrument is operated from the front panel, it is said to be under front panel  
control. When the instrument is operated from a host, it is said to be operating under  
computer interface control.  
Most operations that can be performed from the front panel can also be performed over  
the computer interface. Some operations, like setting communications parameters for the  
RS-232 interface and selecting the instrument address for IEEE-488 operations, can only  
be performed from the front panel.  
Types of Computer Interface  
Only one interface can be selected or used at a time.  
The optional IEEE-488 interface is contained on a single printed circuit assembly and  
can be selected if it is installed in the Hydra Series II Data Acquisition Unit. The IEEE-  
488 interface cannot be used with the Hydra Series II Data Logger. Of course, the RS-  
232 interface can be re-selected even if the IEEE-488 interface is installed.  
If you are going to use the RS-232 interface, continue reading. If you are going to use the  
IEEE-488 interface, skip to "USING THE IEEE-488 INTERFACE" later in this chapter.  
Note  
To determine which computer interface is enabled, select COMM (K  
L). If "IEEE" appears on the display, the IEEE-488 interface is enabled.  
Otherwise, if a baud rate appears, the RS-232 interface is enabled.  
Using the RS-232 Computer Interface  
The RS-232 interface allows ASCII, asynchronous, serial communication between the  
instrument and a host, a serial printer, or a terminal.  
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2620A, 2625A  
Users Manual  
Setting Communication Parameters (RS-232)  
Baud rate ("bAUd"), parity ("PAR"), and echo ("Echo") parameters can be set directly  
by the user; number of data bits and number of stop bits cannot be set. Refer to Figure 4-  
1.  
For the instrument and host to communicate via the RS-232 interface, the  
communication parameters of the instrument must match those of the host. RS-232  
communication parameters can be set only from the front panel. If the communication  
parameters of the host and the instrument do not match, proceed as follows to select the  
appropriate baud rate and parity parameters for the instrument (summarized in Table 4-  
1):  
Parity = “E” or “Odd”  
START  
7 Bit Data  
8 Bit Data  
PARITY STOP  
Parity = “No”  
START  
STOP  
oo11f.eps  
Figure 4-1. Data/Stop Bits  
Table 4-1. RS-232 Setup  
Parity  
Baud  
Echo  
(Note)  
Press  
these  
buttons:  
COMM  
(K L)  
G
D
G
E
D
G
D
E
E
To select  
from  
IEEE  
300  
Odd  
E
OFF  
On  
these  
600  
no  
choices:  
1200  
2400  
4800  
9600  
Note: If “IEEE” is selected here (2620A only), the RS-232 setup sequence is exited and the IEEE setup  
sequence is begun. Refer to Table 4-3.  
1. Select COMM (KL).  
2. The baud rate presently selected is now shown in the left display, and "bAUd" is  
shown in the right display. If "IEEE" appears, press Guntil a baud number appears.  
3. Press Gor Dto scroll to the desired baud (9600, 4800, etc., but not "IEEE".) Press  
EEto select the displayed baud rate.  
4. "PAR" appears in the right display. The parity selection ("Odd", "E", or "no") is now  
shown in the left display.  
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Using the Computer Interface  
Using the RS-232 Computer Interface  
4
5. Press Gor Dto scroll to odd, even, or no parity, respectively. Press EEto  
select the displayed parity.  
6. "Echo" now appears in the right display, with "On" or "OFF" appearing on the left  
display.  
When Echo is "On", each character sent to the instrument over the RS-232 interface  
is "echoed" back to the host. If Echo is "OFF", commands are not echoed.  
Press Dor Gto select echo "On" or "OFF". Then press Eto accept the  
displayed setting.  
Autoprint and Memory Storage (RS-232)  
Instrument measurements can be automatically sent to an RS-232 serial printer  
(Autoprint) or to internal Memory Storage. Both the Hydra Series II Data Acquisition  
Unit and the Hydra Series II Data Logger have the Autoprint function; only the Hydra  
Series II Data Logger has internal Memory Storage.  
Note  
During Autoprint operations, consider setting the instrument echo mode to  
"OFF". Although Autoprint does operate when echo mode is "on", the  
"OFF" setting prevents mixing of echoed command characters with  
autoprinted data.  
Autoprint can be controlled from the front panel or over the RS-232 interface. Setting up  
storage into (and retrieving data from) memory in the Hydra Series II Data Logger can  
be controlled either from the front panel or over the RS-232 interface. Refer to Chapter 3  
for front panel operation. The stored data cannot be viewed from the front panel; data  
must be requested through the RS-232 computer interface or listed on a printer.  
Here are some rules to follow when using Autoprint and Memory Storage:  
1. The RS-232 interface must be enabled before Autoprint can be enabled. (RS-232 is  
always enabled on the Hydra Series II Data Logger.)  
2. Since the instrument does not print over the IEEE-488 interface, Autoprint is  
automatically turned off when you enable the IEEE-488 interface (Hydra Series II  
Data Acquisition Unit only.)  
3. If you have selected Memory Storage (Hydra Series II Data Logger only), verify that  
the RS-232 interface is configured correctly before you upload the memory contents  
to a PC or printer.  
Autoprint: Computer Interface Control  
Autoprint can be controlled from the front panel or over the RS-232 interface. Refer to  
Chapter 3 for front panel operation.  
Through the RS-232 interface, the PRINT_TYPE command can be used to set up  
Autoprint, and the PRINT command can be used to enable Autoprint. These commands  
follow a structure paralleling the front panel procedure. PRINT_TYPE selects  
destination (0 for Print Scans, 1 for Store Scans, or 2 for both) and type (0 for ALL, 1 for  
ALAr, or 2 for trAnS.) PRINT sets printing on (1) or off (0).  
Autoprint: Output Format  
The first line of an autoprint printout contains time and date values that identify when  
the scan was started. Time values include Hour:Minute:Seconds, and date values include  
Month/Year/Day. As an example, the following line is a valid start-of-scan time:  
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2620A, 2625A  
Users Manual  
10:33:45 5/11/90  
Lines following the time and date contain measurement data for channels that have been  
set up for this session. The last line of the printout contains the Totalizer count and the  
status of the digital I/O lines.  
Channel data is formatted to fit three readings onto an 80-column line. Each reading  
provides the following information:  
Channel number, followed by a colon and a space (4 characters)  
space or minus sign (1 character)  
Digits and decimal point. Measurements taken at the fast rate use 5 characters (4  
digits plus a decimal point.) Measurements taken at the slow rate use 6 characters (5  
digits plus a decimal point.)  
Space(1 character)  
Measurement multiplier - m for X0.001, space for X1, kfor X1,000, Mfor  
X1,000,000  
Measurement units - VDC, VAC, OHMS, HZ, C, F, Mx+B (4 characters, left  
justified)  
Space(1 character)  
Alarm indication for Limit-1 (H=High, L=Low, R=Return) (1 character); a blank  
space = no alarm limit is used, or alarm inactive.  
Slash (/) used as a separator when either alarm indicator is shown (1 character)  
Alarm indication for Limit-2 (H, L, R); space = no alarm limit is used, or alarm  
inactive.  
Two spaces between channel measurements (2 characters)  
The following example illustrates this format:  
07:42:0102/09/91  
5: -3.2345 mMX+B H/R12:123.87 kOHMS/L17:31.268VAC  
ALM:15DIO:204TOTAL:0  
Memory Storage: Computer Interface Control  
Memory Storage can be controlled from the front panel or over the RS-232 interface.  
Refer to Chapter 3 for front panel operation.  
Through the RS-232 interface, the PRINT_TYPE and PRINT commands can be used to  
set up and enable Memory Storage. PRINT_TYPE selects the destination (0 for printer, 1  
for Memory Storage, and 2 for both) and the mode used to select the scans to store (0 for  
ALL, 1 for ALAr, or 2 for trAnS.) PRINT sets storage on (1) or off (0).  
The PRINT_TYPE? and PRINT? queries can be used to determine present settings for  
the PRINT_TYPE (destination, type) and PRINT commands, respectively.  
Memory Retrieval  
Note  
The LOG? query does not return channel numbers with scan data.  
Therefore, if you add or delete defined channels, you may want to clear the  
memory contents so that subsequent LOG? queries return only data for the  
new set of scanned channels.  
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Using the Computer Interface  
Using the RS-232 Computer Interface  
4
Data for the oldest set of scan readings in Hydra Series II Data Logger memory can be  
retrieved with the LOG? query. Each set of scan readings is cleared from memory when  
read with LOG? The LOG? query returns the following information:  
Date and time at the start of the logged scan. Date and time are returned as integer  
values in the same format as used with the TIME_DATE? query (hours 0-23,  
minutes 0-59, seconds 0-59, month 1-12, day 1-31, year 00-99.)  
Values for the channels measured. This measurement data is returned as a list of  
values in scientific notation format.  
State of the Digital I/O lines and totalize count at the time the channels were  
scanned. The state of the digital I/O lines may reflect evaluation of alarms for this  
set of scan measurements. Alarm outputs and digital I/O values are returned as  
integer values. The Totalizer value is returned as a scientific notation value.  
Data for a specific scan can be retrieved with the LOGGED? <index> query. The  
<index> parameter can be 1 through 2047, signifying the number of the scan. Scan data  
is not removed from memory with this query.  
The number of stored scans can be retrieved with LOG_COUNT?  
Memory Full Operation  
If Data Logger memory is full, two methods of handling additional scan data are  
available. With the LOG_MODE 0 command, older scans are written over by newer  
scans on a first-in, first-out basis. Therefore, the instrument can continue to make scans  
until a certain event occurs, and storage of all data leading up to the event is assured.  
With the LOG_MODE 1 command, new scans are stored only when memory is  
available. All data following a specific event (e.g., an alarm) can thereby be saved.  
Memory can be made available in one of the following two ways:  
LOG? command clears each scan as it is read.  
Memory Clear (Front Panel or LOG_CLR) removes all scans.  
The LOG_MODE setting is non-volatile and cannot be changed from the instrument  
front panel.  
Clearing Memory  
Memory clearing is available with the Hydra Series II Data Logger (2625A) only. With  
the RS-232 interface active, use the LOG_CLR command to clear all stored Data Logger  
memory values. Refer to Chapter 3 for the front panel version of memory clearing.  
Cabling the Instrument to a Host or Printer (RS-232)  
Communications with a host are handled through a DB-9 interface connector on the rear  
panel of the instrument. Pin usage is diagramed on the instruments rear panel and shown  
in Figure 2-6.  
Connect the instrument to the host (or terminal) using a cable appropriate to your  
application. Usually, total cable length should not exceed 50 feet (15 meters). Longer  
cables are permitted if the load capacitance measured at the interface point (including the  
signal terminator) does not exceed 2500 picofarads.  
To connect the instrument to an IBM PC/AT (DB-9 connector), use RS40 and RS41  
cables connected in series, or use any other cable designed for interconnecting two IBM  
PC/ATs. The RS40 and RS41 cables are described in Chapter 1.  
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2620A, 2625A  
Users Manual  
To connect the instrument to a specific brand of RS-232 printer, use the cable that would  
be used to connect that printer to an RS-232 port on an IBM PC/AT (DB-9 connector).  
The RS42 cable is compatible with most serial printers; contact Fluke for printer  
compatibility information.  
Once the cable is connected, turn the instrument back on. You are now ready to operate  
the instrument over the RS-232 interface.  
Installation Test  
The procedure below demonstrates the instrument processing a computer interface  
command and, at the same time, confirms that the instrument has been properly set up  
and cabled for computer interface operations:  
1. Ask for the instrument identification by sending the following query:  
*IDN? <CR>  
2. Verify that the instrument sends either of the following responses:  
FLUKE,2620A,0,Mn.n An.n Dn.n  
=>  
FLUKE,2625A,0,Mn.n An.n Dn.n  
=>  
Mn.n identifies the main software version.  
An.n identifies the A/D software version.  
Dn.n identifies the display software version.  
The RS-232 prompt => means that the command has been executed and the  
instrument is ready to accept another command.  
RS-232 Information  
Character Echoing  
With the RS-232 interface, characters sent to the instrument can be automatically echoed  
back to the host. When Echo is set "On", characters sent to the instrument are echoed  
back to the host. With Echo "OFF", characters are not echoed back. To set the Echo  
parameter, refer to the procedure earlier in this chapter under "Setting Communication  
Parameters (RS-232)".  
Character Deletion  
Characters sent directly from a host to the instrument can be deleted by pressing the  
<DELETE> or <BACKSPACE> key. Backspaces are echoed to the host if Echo is "On".  
Device Clear Using Ctrl C  
CTRL C is the RS-232 equivalent of IEEE-488 DC1 (device clear), causing the output  
sequence:  
=> <CR> carriage return <LF> line feed.  
Use of CTRL C clears the RS-232 input buffer.  
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Using the Computer Interface  
Using the IEEE-488 Interface  
4
RS-232 Prompts  
The instrument parses and executes, in turn, each command received from the host over  
the RS-232 interface. The instrument returns one of the following three response  
prompts to indicate the results of command execution:  
=> No errors; the command was successfully parsed and executed.  
?> The command was not understood. Used when an IEEE-488.2 Command Error or  
Query Error was generated by the command.  
!> The command was successfully parsed but could not be executed for some reason.  
Used when an IEEE-488.2 Execution Error or Device Dependent Error was  
generated for the command. An example of this would be trying to execute a  
calibration command when calibration mode is not enabled.  
Sample Program Using the RS-232 Computer Interface  
Figure 4-2 presents a sample program for controlling the instrument over the RS-232  
interface. This program is written in BASIC and is compatible with IBM PC, PC/AT, or  
equivalent personal computers.  
Using the IEEE-488 Interface  
IEEE-488 Operating Limitations  
The following limitations govern the IEEE-488 interface:  
A maximum of 15 devices can be connected to a single IEEE-488 bus system.  
The maximum length of an IEEE-488 cable used in one IEEE-488 system must be  
the lesser of 20 meters or 2 meters times the number of devices in the system.  
With an IEEE-488 interface installed and active, the instrument (2620A/05 or Hydra  
Series II with 2620A-05K) supports the IEEE-488 capabilities shown in Table 4-2.  
Installing the IEEE-488 Interface  
The following instructions pertain to the 2620A/05 Data Acquisition Unit or a Hydra  
Series II Data Acquisition Unit equipped with a 2620A-05K IEEE-488 kit. A standard  
IEEE-488 cable attaches to the instrument rear panel. The following cables are available  
from Fluke: Y8021 (1-meter), Y8022 (2-meter), and Y8023 (4-meter).  
Select COMM (KL) to check the interface setting. If "IEEE" is displayed, the  
IEEE-488 interface is already installed and selected. If a numeric baud rate appears in  
the left display, the RS-232 interface is selected; press Dso that "IEEE" is displayed,  
then press EE, select the address, and press EEagain.  
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2620A, 2625A  
Users Manual  
10 ’ EXAMPLE.BAS  
Hydra program to scan VDC, VAC, OHMS, FREQ, or TEMP  
20 ’  
30 ’  
- initialize RS232 communication and set up Hydra  
- display and record measurement data in "TESTDATA.PRN"  
40 ’ Hydra must be set up for RS232, 9600 baud, no parity (from front panel)  
50 KEY OFF  
60 ’ Open communications port 9600 baud, no parity, 8 bit data,  
70 ’ ignor Clear to Send, Data Set Ready, Carrier Detect  
80 OPEN "COM1:9600,N,8,,cs,ds,cd" FOR RANDOM AS #1  
90 IF ERRORCODE <> 0 THEN PRINT "ERROR - Could not open com1:" : END  
100 ’  
110 OPEN "testdata.prn" FOR OUTPUT AS #2  
’Open data file  
120 IF ERRORCODE <> 0 THEN PRINT "ERROR - Could not open data file" : END  
130 ’  
140 PRINT #1, "ECHO 0"  
150 ’  
’Turn off command echo  
160 NUMBEROFCHANS = 0  
170 WHILE (NUMBEROFCHANS < 1) OR (NUMBEROFCHANS > 20)  
180 INPUT "Enter number of channels (1-20): ", NUMBEROFCHANS  
190 WEND  
200 PRINT "(Wait...)"  
210 FOR I = (NUMBEROFCHANS + 1) TO 20  
’ Turn unused channels off  
220  
230  
PRINT #1, "FUNC" + STR$(I) + ",OFF"  
GOSUB 800  
240 NEXT I  
250 ’  
260 CLS  
270 LOCATE 2,25 : PRINT "Sample Program for Hydra"  
275 PRINT #1, "*IDN?" : GOSUB 800 : LINE INPUT #1, RESULT$  
276 LOCATE 3,20 : PRINT RESULT$;  
280 ’  
290 WHILE (1)  
300 ’ Print banner line at bottom of screen  
310  
320  
330 ’  
340  
350  
360  
370  
LOCATE 25,1  
PRINT "1 = VDC 2 = VAC 3 = OHMS 4 = FREQ 5 = TEMP 6 = QUIT";  
FUNC$ = "0"  
WHILE (FUNC$ < "1") OR (FUNC$ > "6")  
LOCATE 23,1 : INPUT "  
Selection: ", FUNC$  
WEND  
380 ’ Exit and clean up if "Quit"  
390  
If FUNC$ = "6" THEN CLOSE 1, 2 : CLS : KEY ON : END  
400 ’  
410 ’ Set up later part of command string to Hydra (function and range)  
420  
IF FUNC$ = "1" THEN CMD$ = "VDC, 1"  
IF FUNC$ = "2" THEN CMD$ = "VAC, 1"  
IF FUNC$ = "3" THEN CMD$ = "OHMS, 1, 2"  
IF FUNC$ = "4" THEN CMD$ = "FREQ, 1"  
IF FUNC$ = "5" THEN CMD$ = "TEMP, K"  
430  
440  
450  
460  
470 ’  
480 ’ Set up Hydra  
485  
490  
LOCATE 23,1 : PRINT "Programming... ";  
FOR I = 1 TO NUMBEROFCHANS ’ Program channels  
Figure 4-2. Sample Program  
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Using the Computer Interface  
Using the IEEE-488 Interface  
4
500  
510  
PRINT #1, "FUNC " + STR$(I) + "," + CMD$  
GOSUB 800  
520 NEXT I  
530 ’  
540 LOCATE 23,1  
550 PRINT "Measuring " + CMD$ + "  
560 ’  
" ’ Print to screen  
’ Scan 3 times  
570 FOR I = 1 TO 3  
580  
590  
595  
597  
598  
600  
610  
612  
620  
640  
650  
660  
670  
680  
PRINT #1, "*TRG"  
GOSUB 800  
’ Start a single  
’ Get prompt  
PRINT #1, "SCAN_TIME? : GOSUB 800 ’ Get scan time stamp  
LINE INPUT #1, RESULTS$  
PRINT #2, RESULT$  
’ save time stamp in data file  
FOR J = 1 TO NUMBEROFCHANS ’ Request scan data  
PRINT #1, "LAST? " + STR$(J) ’ Request channel data  
GOSUB 800  
’ Get prompt  
’ Get channel result  
INPUT #1, RESULT$  
LOCATE J+3, 25 : PRINT "Chan " + STR$(J) + ": ";  
PRINT RESULT$ ’ Print results to screen  
PRINT #2, RESULT$ + ",";  
NEXT J  
’ Print results to file  
PRINT #2, ""  
690 NEXT I  
700 WEND  
710 ’  
720 ’ Subroutine: response  
730 ’ Checks prompt for errors  
740 ’ The possible command responses are:  
750 ’  
760 ’  
770 ’  
780 ’  
"=> (CR) (LF)" (command successful)  
"?> (CR) (LF)" (command syntax error)  
"!> (CR) (LF)" (Command execution error)  
800 PROMPT$ = INPUT$(4, #1)  
’ Get prompt  
’ Command successful  
810 IF INSTR(1, PROMPT$, "=>" <> 0 THEN RETURN  
820 IF INSTR(1, PROMPT$, "?>" <> 0 THEN PRINT "Command Syntax Error!!"  
830 IF INSTR(1, PROMPT$, "!>" <> 0 THEN PRINT "Command Execution Error!!"  
840 PRINT "Program execution halted due to communication errors."  
850 END  
Figure 4-2. Sample Program (cont)  
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2620A, 2625A  
Users Manual  
Table 4-2. IEEE-488.1 Capabilities  
Capability  
SH1 and AH1  
Description  
Read and write bus handshaking, including hold off.  
T5  
Basic talker with serial poll and without talk only mode. Serial poll is used to  
return the instrument status byte to the controller.  
TE0  
L4  
No extended talker.  
Basic listener without listen only mode. Listen only mode is only useful for an  
IEEE-488 device like a printer.  
LE0  
SR1  
No extended listener.  
Service request interface; allows SRQs (service requests). The SRQ function  
allows the instrument to notify the controller when an operation is complete.  
RL1  
Remote local capability with local lock out. Usually the instrument front panel  
will not be operational while the instrument is in use by the IEEE-488 interface.  
Remote local capability enables the front panel. Local lock out disables the  
front panel.  
PP0  
DC1  
No parallel poll capability. Parallel poll is rarely used in the industry. It was  
intended as a fast way to get a status bit from several devices, but failed in  
gaining acceptance.  
Device clear capability. This allows the instrument to be initialized to a known  
state. The IEEE-488.2 standard describes exactly what this known state is.  
C0  
E1  
Not a controller.  
Open Collector Outputs  
Enabling the IEEE-488 Interface  
The IEEE-488 interface can be enabled only from the front panel, using the following  
procedure. This procedure is also summarized in Table 4-3.  
Table 4-3. IEEE-488 Setup  
Baud  
Address  
Press these  
buttons:  
COMM  
(K L)  
G
G
E
E
D
D
To select  
from these  
choices:  
IEEE  
300  
600  
0
1
1200  
2400  
4800  
9600  
30  
1. Select COMM (KL).  
The left display shows "IEEE" or an RS-232 baud rate, and "bAUd" appears in the  
right display. Proceed with the following steps.  
If "IEEE" is shown in the left display, the IEEE-488 interface is already enabled.  
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Using the Computer Interface  
General Information (RS-232 and IEEE-488)  
4
2. Press Dto scroll to "IEEE"; then press Eto enable the IEEE-488 interface and  
disable the RS-232 interface. "IEEE" will not appear in the left display if the IEEE-  
488 interface is not installed.  
3. The instrument must now be assigned an address ("0" to "30", inclusive). If you  
want to make a change, scroll to the desired address with the Gand Dbuttons.  
Then press Eto select the displayed address. The address remains selected until  
it is changed.  
Note  
Pressing Cat any point returns the instrument to the Inactive Mode,  
leaving the original interface selection unchanged. If RS-232 was active,  
the instrument returns to RS-232, with all parameters unchanged.  
Installation Test  
The procedure below demonstrates how the instrument processes a computer interface  
command and, at the same time, confirms that the instrument has been properly set up  
and cabled for IEEE-488 operations:  
Note  
This is a program as entered from a Fluke 1722A Instrument Controller  
using Fluke BASIC commands. Syntax may vary with the host computer  
and language.  
Enter the following at the host:  
INIT PORT 0 <CR>  
CLEAR PORT 0 <CR>  
PRINT @ <address of instrument>, "*IDN?" <CR>  
INPUT LINE @ <address of instrument>, A$ <CR>  
PRINT A$ <CR>  
1. Verify that the instrument sends the following identification response:  
FLUKE,2620A,0,Mn.n An.n Dn.n  
Mn.n identifies the main software version.  
An.n identifies the A/D software version.  
Dn.n identifies the display software version.  
If the instrument does not respond to the test procedure as indicated, make the following  
checks:  
1. Check all cable connections.  
2. Check that the interface has been properly enabled and addressed.  
General Information (RS-232 and IEEE-488)  
How the Instrument Processes Input  
The following paragraphs summarize how the instrument processes input that is received  
from a host (or stand-alone terminal).  
Note  
In this manual "input" means a string sent to the instrument from a host.  
"Output" means a string sent from the instrument to the host.  
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2620A, 2625A  
Users Manual  
Input Strings  
The instrument processes and executes valid input strings sent by the host. A valid input  
string is one or more syntactically correct commands, separated by semicolons (;),  
followed by an input terminator. ASCII and IEEE-488 bus codes are provided in  
Appendix B.  
The instrument stores received input in a 350-byte input buffer.  
Note  
Input strings received over the RS-232 interface are not executed or  
checked for proper syntax until an input terminator is received. If the RS-  
232 input buffer becomes full, a Device Dependent Error prompt is  
returned, and the input string is ignored.  
The instrument accepts alphabetic characters in either upper- or lower-case. If a  
command cannot be understood (i.e, the equivalent of an IEEE-488 "Command Error"),  
the command and the rest of the command line are ignored.  
Input Terminators  
An input terminator is a character or command (IEEE-488.1), sent by the host, that  
identifies the end of a string of one or more commands.  
When an input terminator is received (RS-232 applications), the instrument executes all  
commands entered since the last terminator was received, on a first-in, first-out basis. (In  
IEEE-488 applications, commands are not delayed until receipt of an input terminator;  
commands are executed as they are received.)  
As input characters are processed and commands executed, space is made available in  
the input buffer for new characters. In RS-232 applications, if a communications error  
(e.g., parity, framing, overrun) is detected or the input buffer fills, a device-dependent  
error is generated. If the input buffer is full, new characters are ignored as the instrument  
waits for a termination character.  
If, on the other hand, the input buffer becomes full when the IEEE-488 interface is used,  
the instrument stops accepting characters until there is room in the buffer. Characters in  
the input buffer cannot be overwritten with the IEEE-488 interface.  
The following are valid terminators for the RS-232 interface:  
LF (Line Feed)  
CR (Carriage Return)  
CR LF  
LF CR  
The following are valid terminators for the IEEE-488 interface:  
EOI (End or Identity) on any character  
LF (Line Feed)  
In some instances, a terminator is automatically transmitted by the host at the end of the  
command string (i.e., the instruments input string). For example, in Fluke BASIC, the  
PRINT statement finishes with a CR LF pair.  
Typical Input Strings  
Example strings that could be sent to the instrument over either IEEE-488 interface are  
shown in Figure 4-3.  
4-14  
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Using the Computer Interface  
General Information (RS-232 and IEEE-488)  
4
FUNC 1, OHMS, 3, 2  
Select ohms function for channel 1  
Select 30-kilohm range  
Select 2-wire (2T) connections  
FUNC 12, TEMP, K  
Select temperature measurement for channel 12  
Select K-type thermocouple input  
FUNC 1, TEMP, PT, 2; RTD_R0 12, 101.22  
Select temperature measurement for channel 1  
Select RTD (DIN/IEC 751)  
Select 2-wire (2T) connections  
Set new R0 value for channel 12  
INTVL 0, 10, 0; SCAN 1; LAST?  
Set interval between scan starts to 10 minutes  
Start scanning  
Return measured values for all scanned channels  
oo13f.eps  
Figure 4-3. Typical Input Strings  
4-15  
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2620A, 2625A  
Users Manual  
Sending Numeric Values to the Instrument (RS-232 and IEEE-488)  
Numeric values can be sent to the instrument as integers, real numbers, or real numbers  
with exponents, as shown in the following examples:  
EXAMPLE  
EXPLANATION  
+12345  
123.45  
-1.2345E2  
Sends the signed integer “+12345”  
Sends the real number “123.45”  
Sends -1.2345 x 102  
Sending Input Strings to the Instrument  
Observe the following rules when you construct strings to be sent to the instrument over  
the computer interface:  
RULE 1: READ THE INSTRUMENT’S OUTPUT BUFFER ONLY ONCE FOR  
EACH QUERY COMMAND.  
This rule applies to the IEEE-488 interface only. The instrument’s output buffer is  
cleared after it has been read. This prevents previously read data from being read a  
second time by mistake. If you attempt to read the instrument’s output buffer twice  
the instrument generates a query error.  
RULE 2: READ QUERY RESPONSES BEFORE SENDING ANOTHER INPUT  
STRING.  
This rule applies to the IEEE-488 interface only. Output data remains available in  
the output buffer until it is read by the host or until the next input string is received  
by the instrument. This means the instrument’s output buffer must be read by the  
host before, rather than after, the next input string is sent to the instrument.  
Otherwise, unread data in the buffer is overwritten.  
RULE 3: THE INSTRUMENT EXECUTES EACH COMMAND COMPLETELY,  
IN THE ORDER RECEIVED, BEFORE MOVING ON TO THE NEXT  
COMMAND.  
If an input string contains a trigger, enter the commands from left to right, as follows:  
1. Commands to configure the instrument (if any).  
2. The trigger command (*TRG).  
3. Queries to read the result of a triggered measurement (LAST?), or to reconfigure the  
instrument (if any).  
4. The terminator.  
How the Instrument Processes Output  
The instrument outputs an alphanumeric string in response to any query from the host.  
(Query commands are easily identified because they all end with “?”.) An output string  
is terminated by a Carriage Return and Line Feed (<CR> <LF>) for RS-232 applications  
or a Line Feed with End or Identity (<LF> <EOI>) for IEEE-488 applications.  
After sending the instrument a command string via the RS-232 interface, wait for the  
instrument to return a prompt before sending another command string. (A command  
string can consist of 1 or more syntactically correct commands.) If you do not do so, a  
device-dependent command error is generated, and the second string is discarded.  
If the instrument is used in an IEEE-488 bus system, the output data is not actually sent  
onto the bus until the host addresses the instrument as a talker. When the output buffer is  
4-16  
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Using the Computer Interface  
General Information (RS-232 and IEEE-488)  
4
loaded, the Message Available (MAV) bit in the Status Byte Register is set true. (For  
more information, see "Status Byte Register" later in this chapter.)  
Numeric output from the instrument is returned as shown in the following examples:  
Integer Values Examples  
3
0
In response to RANGE? query, range is 3 for the selected function.  
In response to ALARMS? query, there are no alarms on this channel.  
Scientific Notation Values  
+1.2345E+6  
Measured value of 1.2345 X 106  
+12.345E+6 OHM Measured value of 12.345 X 106 ohms (format 2)  
+1E+9  
-1E+9  
+9E+9  
Positive overload (“OL” appears on the display).  
Negative overload (“-OL” appears on the display).  
Open thermocouple indication (“otc” appears on the display).  
Service Requests (IEEE-488 only) and Status Registers  
Service requests let an instrument on the IEEE-488 bus get the attention of the host.  
Service requests are sent over the service request (SRQ) line.  
Note  
If the instruments is in the remote state without front panel lockout (i.e.,  
REMS), a service request can be sent from the front panel by pressing (up  
button picture).  
If more than one instrument on the bus is capable of sending service requests, the host  
can determine which instrument made the request by taking a "serial poll". Each  
instrument on the bus responds to the poll by sending the contents of its Status Byte  
Register (STB). If an instrument on the bus has made a service request, the request  
service bit (RQS, bit 6) of its Status Byte Register (STB) will be set to 1, identifying it as  
an instrument that requested service.  
The contents of the Status Byte Register (STB) are defined by the Service Request  
Enable Register (SRE), Event Status Register (ESR), Event Status Enable Register  
(ESE), and the output buffer. These status registers are discussed in the following  
paragraphs. Figure 4-4 shows the relationship of these registers.  
4-17  
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U
2
ers  
a
Instrument  
Event Register  
Read Using IER?  
Standard  
6
2
7
5 4 3  
1
0
6
2
7
5 4 3  
1
0
Event Status Register  
Read Using *ESR?  
&
&
&
&
&
&
&
&
&
&
&
2
&
2
&
1
&
1
Queue  
Not-Empty  
&
0
&
0
Standard  
Event Status Enable  
Register  
Instrument  
Event Enable  
Register  
6
7
5 4 3  
6
7
5 4 3  
Read Using *ESE?  
Write to Using *ESE  
Read Using IEE?  
Write Using IEE  
Output Queue  
Read by Serial Poll  
Status Byte Register  
Read Using *STB?  
RQS  
Service  
Request  
Generation  
IEB  
MAV  
ESB  
6
2
7
3
1
MSS  
&
&
&
&
&
2
&
1
&
0
Service Request  
Enable Register  
Read Using *SRE?  
Write to Using *SRE  
7
5 4 3  
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Using the Computer Interface  
General Information (RS-232 and IEEE-488)  
4
Table 4-4. Status Byte Register  
Bit  
Name  
IEB  
Description  
0
Instrument Event Bit. When any bit in the Instrument Event Register is set and  
the corresponding mask bit(s) in the Instrument Event Enable register is set,  
this Instrument Event Bit in the Status Byte will be set.  
When read, the Instrument Event Bit is recomputed based on the new value  
from the Instrument Event Register and its mask, the Instrument Event Enable  
Register.  
1,2,3  
not used  
MAV  
4
5
6
7
Message Available  
ESB  
Event Status Bit  
RQS/MSS  
not used  
Request Service/Master Summary Status  
Event Status and Event Status Enable Registers  
The Event Status Register (ESR) records specified events in specific bits. (See Figure 4-  
4 and Table 4-5). When a bit in the ESR is set (i.e., 1), the event that corresponds to that  
bit has occurred since the register was last read or cleared. For example, if bit 3 (DDE) is  
set to 1, a device-dependent error has occurred.  
The Event Status Enable Register (ESE) is a mask register that allows the host to enable  
or disable (mask) each bit in the ESR. When a bit in the ESE is 1, the corresponding bit  
in the ESR is enabled. When any enabled bit in the ESR changes from 0 to 1, the ESB bit  
in the Status Byte Register also goes to 1. When the ESR is read (using the *ESR?  
query) or cleared (using the *CLS command), the ESB bit in the Status Byte Register  
returns to 0.  
Status Byte Register  
The Status Byte Register (STB) is a binary-encoded register that contains eight bits.  
Note that the Service Request Enable Register (SRE) uses bits 1 through 5 and bit 7 to  
set bit 6, the request service (RQS) bit, as enabled by the SRE. When the RQS bit is set  
true (1), the instrument sets the SRQ line true (1), which generates a service request. The  
eight bits of the Status Byte Register (as read by the *STB? query) are described in  
Table 4-4.  
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2620A, 2625A  
Users Manual  
Table 4-5. Event Status Register  
Description  
Bit  
Name  
OPC  
0
Operation Complete. Set true (1) upon execution of the *OPC command,  
indicating that the instrument has completed all selected pending operations.  
1
2
not used  
QYE  
Always set to 0.  
Query Error. Generated true (1) by the INTERRUPTED or UNTERMINATED  
message exchange state transitions. (See IEEE-488.2.) Sets the QYE bit of the  
Event Status Register. Under RS-232, this causes the "?>" prompt to be  
returned.  
3
4
DDE  
EXE  
Device Dependent Error. Generated true (1) by overflows of the RS-232 input  
buffer or by calibration errors. Sets the DDE bit of the Event Status Register.  
Under RS-232, this causes the "!>" prompt to be returned.  
Execution Error. Generated true (1) by parameters out of bounds or by a valid  
command that could not be processed due to an internal condition (such as  
calibration commands being received when calibration is not enabled). Sets the  
EXE bit of the Event Status Register. Under RS-232, this causes the "!>"  
prompt to be returned.  
5
CME  
Generated true (1) by syntax errors, including: unrecognized command,  
incorrect command sequences, and GET messages inside a <program  
message>. Sets the CME bit of the Event Status Register. Under RS-232, this  
causes the "?>" prompt to be returned.  
6
7
not used  
PON  
Always set to 0.  
Always set to 0 Power On. Set true (1) after an off-to-on transition has occurred  
in the instrument’s power supply.  
Reading the Status Byte Register  
The host can read the Status Byte Register by taking a serial poll or by sending the  
instrument a *STB? query. The value of the status byte is not affected by the *STB?  
query.  
Note  
Changes to the status or enable registers are evaluated immediately.  
Therefore, an adequate change in cause or enabling criteria will change  
the status byte.  
When the Status Byte Register is read, an integer is returned. This integer is the decimal  
equivalent of an 8-bit binary number. For example, 48 is the decimal equivalent of the  
binary 00110000, meaning that bit 4 (MAV) and bit 5 (ESB) are set to "1". Bit 4  
contributes integer 16, and bit 5 contributes integer 32.  
If the status byte is read by serial poll, bit 6 is returned as a request service (RQS); if it is  
read with an *STB? query, bit 6 is returned as Master Summary Status (MSS).  
EXAMPLE EXPLANATION  
*STB?  
Reads the Status Byte Register. Assume that "32" is returned. Converting 32  
to the binary 00100000 indicates that bit 5 (ESB) is set to 1. To determine  
the event status, you would have to read the Event Status Register in the  
same manner, using the *ESR? query.  
4-20  
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Using the Computer Interface  
General Information (RS-232 and IEEE-488)  
4
Service Request Enable Register  
The Service Request Enable Register (SRE) is an 8-bit register that enables or disables  
(i.e., masks) corresponding summary messages in the Status Byte Register (STB). The  
instrument can be programmed to make a service request on errors or when output is  
available. Conditions that trigger a service request are specified by writing a binary-  
weighted value to the Service Request Enable Register, using the *SRE command.  
EXAMPLE EXPLANATION  
*SRE  
16Enables the generation of an SRQ when bit 4 (MAV) in the Status Byte  
Register (STB) is set to 1.  
16 is the decimal equivalent of 00010000 binary. This means that bit 4 in the  
Service Request Enable Register (SRE, which corresponds to the MAV bit  
in the Status ByteRegister) is 1, and all other bits are 0.  
*SRE 48 Enables the generation of an SRQ when bits 4 or 5 (MAV or ESB) in the  
Status Byte Register are set to 1. The binary equivalent of 48 is 00110000,  
indicating that bits 4 and 5 are set to 1.  
If any bit in the SRE is set to 1 and the matching bit(s) in the STB become 1, the RQS bit  
(bit 6) in the Status Byte Register (STB) is set and a service request can be generated.  
Use the *SRE? query to read the Service Request Enable Register. The instrument  
returns a binary-weighted integer that represents the enabled bits in the register. (The  
value of bit 6 will always be zero.) Convert the returned value to binary to determine the  
status of register bits.  
EXAMPLE EXPLANATION  
*SRE?  
Reads the value of the SRE Register. Assume "4" is returned. Converting 4  
to the binary 00000100 indicates that bit 2 in the SRE is set to 1.  
Instrument Event Register  
The Instrument Event Register (IER) is used in conjunction with the Instrument Event  
Enable Register (IEE) to determine the conditions under which the Instrument Event Bit  
of the Status Byte Register is set. Bits used in the Instrument Event Register are  
described in Table 4-6. Whenever the Instrument Event Register is read, the instrument  
bits are cleared.  
4-21  
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2620A, 2625A  
Users Manual  
Table 4-6. Instrument Event Register (IER)  
Note  
Whenever the Instrument Event Register is read, the condition bits are cleared.  
This register is used in conjunction with the Instrument Event Enable Register to determine the conditions  
under which the Instrument Event Bit of the Status Byte is set.  
Bit  
Name  
ALT  
Description  
0
1
Alarm Limit Transition. Set high (1) when any measurement value has  
transitioned into or out of alarm. Alarms are defined through the front panel or  
the computer interface (ALARM_LIMIT). This bit is cleared when alarms or  
review values are cleared.  
TOB  
Totalize Overflow. Set high (1) when the Totalizer overflows (>65,535). This  
bit is cleared when the Totalizer is zeroed from the front panel or set to some  
other non-overflow value (<65,535) with the computer interface TOTAL  
command.  
2
3
OTC  
CCB  
Open Thermocouple. Set high (1) when open thermocouple checking is  
enabled and any thermocouple channel is measured with a source  
impedance greater than 1 to 4 kilohms.  
Calibration Corrupted. Set high (1) when the instrument calibration data is  
corrupted. When a calibration data check shows a corruption of calibration  
data, the calibration alarm bit remains set in the Instrument Status Register  
until the instrument is recalibrated.  
4
CNC  
Configuration Corrupted. The instrument configuration stored in NVRAM has  
been found to be corrupted. The RAM CRC is no longer valid.  
5,6  
7
not used  
SCB  
Scan Complete. Set high (1) when a measurement scan has been completed.  
Computer Interface Command Set  
Generally, RS-232 and IEEE-488 commands are identical. A few exceptions apply only  
when the RS-232 interface is active.  
See Table 4-7 for a summary of computer interface commands and queries. A detailed  
description of each command or query can be found in Table 4-8. (alphabetically  
arranged.)  
Note  
Computer interface command descriptions use angle brackets (< >) to  
denote a parameter that must be supplied by the user or a string that is  
returned by the instrument.  
4-22  
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Using the Computer Interface  
Computer Interface Command Set  
4
Table 4-7. Command and Query Summary  
Alarms  
ALARMS?  
Active Alarms Query  
ALARM_ASSOC  
Associate Alarm Output  
Alarm Association Query  
Clear Alarm Association  
Set Alarm Output Level  
Alarm Output State Query  
Set Alarm Limit  
ALARM_ASSOC?  
ALARM_ASSOC_CLR  
ALARM_DO_LEVEL  
ALARM_DO_LEVELS?  
ALARM_LIMIT  
ALARM_LIMIT?  
Alarm Limit Assignments Query  
Digital I/O  
DIO_LEVELS?  
DO_LEVEL  
Function and Range  
FUNC  
Digital I/O State Query  
Set Digital Output Level  
Channel Function Definition  
Channel Function Query  
RTD Ice Point (R0)  
FUNC?  
RTD_R0  
RTD_R0?  
RTD Ice-Point (R0) Query  
Channel Range Query  
RANGE?  
IEEE Common Commands (includes Status Registers)  
*CLS  
*ESE  
*ESE?  
*ESR?  
*IDN?  
*OPC  
*OPC?  
*RST  
*SRE  
*SRE?  
*STB?  
*TRG  
*TST?  
*WAI  
Clear Status  
Event Status Enable  
Event Status Enable Query  
Event Status Register Query  
Identification Query  
Operation Complete  
Operation Complete Query  
Reset  
Service Request Enable  
Service Request Enable Query  
Read Status Byte Query  
Trigger  
Self Test Query  
Wait-to-continue  
IEE  
Instrument Event Enable  
Instrument Event Enable Query  
Instrument Event Register Query  
IEE?  
IER?  
4-23  
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2620A, 2625A  
Users Manual  
Table 4-7. Command and Query Summary (cont)  
Lock  
LOCK  
LOCK?  
Lock/unlock front panel control keys  
Returns instrument front panel lock status  
Measurement Rate  
RATE  
Select Measurement Rate  
Measurement Rate Query  
RATE?  
Measurement Values  
LAST?  
Channel’s Last Scan Value  
Channel’s Maximum Value  
Channel’s Minimum Value  
Next Scan’s Values  
MAX?  
MIN?  
NEXT?  
Monitor  
MON  
Enable/Disable Monitoring  
Monitor Channel Number  
Monitor Channel Value  
MON_CHAN?  
MON_VAL?  
Mx+B Scaling  
SCALE_MB  
SCALE_MB?  
Set Mx+B Scaling Values  
Mx+B Scaling Values Query  
RS-232 Commands (includes Autoprint)  
LOG?  
Retrieve Logged Data Query  
LOG_CLR  
LOG_COUNT?  
LOG_MODE  
LOG_MODE?  
LOGGED?  
LOG_BIN?  
PRINT  
Clear Logged Scans  
Logged Scan Count Query  
Action when Internal Memory is Full  
Action when Internal Memory is Full Query  
Retrieve Scanned Data Query  
Binary Upload of Logged Data  
Data Logging Enable/Disable  
Data Logging Query  
PRINT?  
PRINT_TYPE  
PRINT_TYPE?  
LOCS  
Set Data Logging Type  
Data Logging Type Query  
Local without Lockout  
LWLS  
Local with Lockout  
REMS  
Remote without Lockout  
Remote with Lockout  
RWLS  
ECHO  
Enable/disable echoing  
4-24  
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Using the Computer Interface  
Computer Interface Command Set  
4
Table 4-7. Command and Query Summary (cont)  
Response Format  
FORMAT  
Response Format  
FORMAT?  
Review Array  
REVIEW_CLR  
Scan  
Query Response Format  
Clear Review Values  
INTVL  
Set Scan Interval  
INTVL?  
Scan Interval Query  
Enable/Disable Scanning  
Return Scan Status  
Time of Scan  
SCAN  
SCAN?  
SCAN_TIME?  
Temperature Unit  
TEMP_CONFIG  
TEMP_CONFIG?  
Time/Date  
DATE  
Temperature Configuration  
Temperature Configuration Query  
Set Date  
TIME  
Set the instrument clock.  
Retrieve Time and Date  
TIME_DATE?  
Totalizer  
TOTAL  
Set Totalizer Count  
TOTAL?  
Totalizer Value Query  
Set Totalizing Debounce  
Totalizer Debounce Query  
TOTAL_DBNC  
TOTAL_DBNC?  
Triggering  
TRIGGER  
TRIGGER?  
Select Trigger Type  
Trigger Type Query  
4-25  
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2620A, 2625A  
Users Manual  
Table 4-8. Command and Query Reference  
*CLS  
Clear Status  
Clears all event registers summarized in the status byte, except for  
Message Available, which is cleared only if *CLS is the first message in  
the queue.  
*ESE  
Event Status Enable  
Sets the Event Status Enable Register to the given value.  
*ESE <value>  
<value>  
=
(0 .. 255)  
This is a mask for the Event Status Register and is the first step in  
determining which Events may issue an SRQ. The mask selects which  
events may set the Instrument Event Bit of the Status Byte. If the value is  
not in the range 0 to 255, an Execution Error is generated.  
*ESE?  
*ESR?  
*IDN?  
Event Status Enable Query  
Returns an integer representing the present value of the Event Status  
Enable Register.  
Event Status Register Query  
First returns an integer representing the value of the Event Status Register,  
then clears the register.  
Identification Query  
Returns the instrument identification code.  
The identification code consists of four descriptive fields separated by  
commas. Note that commas are reserved as field separators and cannot be  
used within the fields.  
FIELD  
DESCRIPTION  
1
2
3
4
Manufacturer’s name (FLUKE).  
Instrument model number (2620A or 2625A).  
0
Firmware revision levels.  
As an example, for main software version M2.41, display software version  
D1.3, A/D software version A3.7, the response would be:  
FLUKE,2620A,0,M2.41 A3.7 D1.3  
Operation Complete  
*OPC  
Causes the instrument to generate an Operation Complete when parsed.  
Operation Complete Query  
*OPC?  
Causes the instrument to place an ASCII 1 in the output queue when  
parsed.  
*RST  
Reset  
Performs a Configuration Reset (equals front panel power-up CANCEL. The  
computer interface parameters (RS-232 and IEEE-488) are not changed.  
Also, the Status Byte and Event Status Registers are not changed, and  
calibration data is retained.  
4-26  
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Using the Computer Interface  
Computer Interface Command Set  
4
Table 4-8. Command and Query Reference (cont)  
*SRE  
Service Request Enable  
Sets the Service Request Enable Register to the given value.  
*SRE <value>  
<value> = (0 .. 255)  
If the value is greater than 255, a Command Error is generated. The  
value of bit 6 is ignored, since it is not used by the Service Request  
Enable Register.  
*SRE?  
*STB?  
*TRG  
Service Request Enable Query  
Returns the integer value of the Service Request Enable Register, with  
bit 6 set to 0.  
Read Status Byte Query  
Returns the integer value of the Status Byte, with bit 6 as the master  
summary bit. Note that a serial poll returns bit 6 as the RQS message.  
Trigger  
When parsed, this command causes the instrument to request a Single  
Scan. If a scan is already in progress when this command is parsed, an  
additional scan is not executed.  
*TST?  
Self Test Query  
Causes an internal self test to be run, returning the result as an integer  
(representing the binary encoded value.) The self test does not require  
any local operator interaction and returns the instrument to the power-up  
state. The binary coding is:  
Bit  
Binary Value  
Error  
0
1
1
2
ROM test failed (bad CRS)  
External RAM test failed  
2
4
Internal RAM test failed  
3
8
Display selft test failed  
4
5
6
7
8
9
10  
11  
12  
16  
32  
64  
128  
256  
512  
1024  
2048  
4096  
Display bad or not installed  
Instrument configuration corrupted.  
EEPROM instrument configuration bad  
EEPROM calibration data bad  
A/D bad or not installed  
A/D ROM test failed  
A/D RAM test failed  
A/D self test failed  
Memory RAM test failed (2625A only).  
*WAI  
Wait-to-continue  
This command is accepted by Hydra, but has no effect. *WAI is required  
by the IEEE-488.2 standard, but is non-operational in Hydra.  
4-27  
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2620A, 2625A  
Users Manual  
Table 4-8. Command and Query Reference (cont)  
ALARMS?  
Active Alarms Query  
Returns alarm status for the indicated channel(s). The value returned  
represents data from the most recent scan. The most recent scan is the  
scan in progress or, if scanning is not in progress, the last completed  
scan.  
ALARMS? <channel>  
<channel> = (0 .. 20)  
If the channel specification field is left blank, values for all defined  
channels are returned (values for channels defined as OFF are not  
included.) An Execution Error results if a request is made for a channel  
defined as OFF, the channel specified is invalid, no scan measurements  
have been made, or review values have been cleared.  
Data is returned as comma-separated integer values, indicating which  
limits were in alarm when last scanned. The returned values are  
interpreted as follows:  
0
1
2
3
neither limit is in alarm and/or alarm(s) not defined  
Limit "1" in alarm  
Limit "2" in alarm  
Limit "1" and Limit "2" in alarm  
If measurements are not active, the last known value is returned. The  
value 0 is returned for measured channels that do not have alarms  
defined.  
For alarm status of all defined channels (no channel specification made),  
undefined (OFF) channels are not included. For each defined channel,  
an integer value (0, 1, 2, or 3) is returned. Commas separate integers for  
different channels, and no blank spaces are included. For example, if  
channel 1 has no alarm, channel 12 has Limit "2" in alarm, channel 13  
has Limit "1" and Limit "2" in alarm, and channel 14 has Limit "1" in  
alarm, the return is "0,2,3,1".  
ALARM_ASSOC  
Associate Alarm Output  
For the indicated channel and alarm limit, associate the given digital  
output line.  
ALARM_ASSOC <channel>,<limit_num>,<DO_line>  
<channel>  
= (4 .. 20)  
<limit_num> = 1 2  
<DO_line> = (0 .. 7)  
Any other values or use of an invalid channel cause an Execution Error  
to be generated. If an association already exists for the specified channel  
and limit, executing this command revises the association. When  
switching alarm associations, the output being left (switched away from)  
is set to a high (non-alarm) state. To set multiple channels to a single  
DO_line, issue this command for each association to be made.  
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4
Table 4-8. Command and Query Reference (cont)  
ALARM_ASSOC?  
Alarm Association Query  
Returns alarm output associations for the indicated channel and alarm  
limit.  
ALARM_ASSOC? <channel>,<limit_num>  
<channel> = (4 .. 20)  
<limit_num> = 1 2  
Returns the digital output line number associated with the indicated  
alarm limit. An Execution Error is generated if no output is associated  
with this alarm limit, if invalid channel numbers are used, or if limits other  
than 1 or 2 are used.  
ALARM_ASSOC_CLR  
ALARM_DO_LEVEL  
ALARM_DO_LEVELS?  
Clear Alarm Association  
Clear the digital output association for the indicated channel and alarm  
limit.  
ALARM_ASSOC_CLR <channel>,<limit_num>  
<channel>  
= (4 .. 20)  
<limit_num> = 1 2  
When the association is cleared, the output pin is left in a high (non-  
alarm) state. If the alarm limit specified is not 1 or 2, or if the channel is  
invalid, an Execution Error is generated.  
Set Alarm Output Level  
Set or clear the indicated alarm digital output.  
ALARM_DO_LEVEL <DO_line>,<DO_state>  
<DO_line> = (0 .. 3)  
<DO_state> = 1 (high) 0 (low)  
Alarm outputs 0-3 correspond to channels 0-3, respectively. If the digital  
output line requested is not in the range 0 through 3, an Execution Error  
is generated. If the DO_state specified is not 1 (high) or 0 (low), an  
Execution Error is generated.  
Alarm Output State Query  
Returns digital output levels for the four alarm digital outputs.  
Returns an integer value representing the state of each of the digital I/O  
lines. The low order four bits are the status of the alarm digital outputs; 0  
indicates line is low (in alarm), and 1 indicates line is high (not in alarm).  
These lowest four bits correspond to alarm digital outputs 0 through 3,  
which are permanently associated to channels 0 through 3, respectively.  
A value of 15 indicates that all alarm outputs are in the non-alarm (high)  
state.  
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Users Manual  
Table 4-8. Command and Query Reference (cont)  
ALARM_LIMIT  
Set Alarm Limit  
Store alarm limit information for the indicated channel and limit. The  
fields to be given (in order) are:  
ALARM_LIMIT <channel>,<limit_num>,<sense>,<value>  
<channel>  
= (0 .. 20)  
<limit_num> = 1 2  
<sense>  
<value>  
= HI LO OFF  
= Signed numeric quantity  
A Command Error is generated if a value is supplied when the sense is  
OFF. An Execution Error is generated under any of the following  
circumstances:  
<value> is outside the range +/-9999.9 Mega (E+6).  
<channel>, <limit_num>, or <sense> are not specified from the given list.  
A <channel> that is defined as OFF is specified.  
Note that old alarm settings for a channel are lost when the function for  
that channel is changed.  
ALARM_LIMIT?  
Alarm Limit Assignments Query  
Return alarm limit data for specified channel and limit.  
ALARM_LIMIT? <channel>,<limit_num>  
<channel>  
= (0 .. 20)  
<limit_num> = 1 2  
Returns HI, LO, or OFF, indicating the sense of that limit. For HI or LO  
limits, the value is returned in scientific notation format with five digits of  
resolution. If the channel specified is invalid, or the requested limit is not  
1 or 2, an Execution Error is generated.  
Remember that old alarm settings for a channel are lost when  
the function for that channel is changed.  
Set Date  
DATE  
Set instrument calendar values.  
DATE <month>,<date>,<year>  
<month> = (1 .. 12)  
<date> = (1 .. 31)  
<year> = (00 .. 99)  
Invalid values generate an Execution Error.  
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4
Table 4-8. Command and Query Reference (cont)  
DIO_LEVELS?  
Digital I/O State Query  
Returns digital input and output levels for the eight configurable digital  
I/O lines.  
Returns an integer value representing the actual states of the digital I/O  
lines. The low-order eight bits are used to indicate the status of each  
configurable I/O line (0 indicates low; 1 indicates high.) Bits 0 through 7  
correspond to I/O lines 0 through 7. The highest possible integer value is  
255, indicating that all eight digital I/O lines are set high.  
NOTE  
The digital I/O line levels returned by the DIO_LEVELS? query may not  
match the levels set with the DO_LEVEL command. Lines that were set  
to 1 (high) may have been externally driven low. The DIO_LEVELS?  
query causes the actual state of the lines to be read.  
DO_LEVEL  
Set Digital Output Level  
Set or clear the indicated digital output.  
DO_LEVEL <DO_line>,<DO_state>  
<DO_line>  
<DO_state>  
=
=
(0 .. 7)  
1 0  
If the digital output line requested is not in the range 0 through 7, an  
Execution Error is generated. If the DO_state specified is not 1 (high) or  
0 (low), an Execution Error is generated. Low is the active alarm state. At  
power up, all digital outputs are set high.  
ECHO  
Enable/Disable RS-232 Echo Mode (RS-232 only)  
ECHO <1 0>  
1 = Turn RS-232 echoing on.  
0 = Turn RS-232 echoing off.  
If the IEEE-488 interface is selected, use of ECHO results in an  
execution error.  
FORMAT  
Response Format  
Set the output format type.  
FORMAT <f_type>  
<f_type> =  
1 2  
The default is 1, which is IEEE-488.2 compatible. Since no measurement  
units are allowed in IEEE, an alternative (2) is provided. When format 2 is  
in effect the responses are no longer IEEE-488.2 compatible. The  
primary use for format 2 is with RS-232, as it provides a means of  
recording the units with the measurement value. Any parameter other  
than 1 or 2 causes an Execution Error to be generated. The units strings  
used are as follows:  
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Users Manual  
Table 4-8. Command and Query Reference (cont)  
MEASUREMENT  
Scaled “MX+B”  
Volts DC  
Volts AC  
Resistance  
UNITS STRING  
“VDC”  
“VAC”  
“OHMS”  
“Hz”  
Frequency  
Temperature  
Temperature  
“C”  
“F”  
FORMAT?  
Query Response Format  
Returns the format presently in use:  
The default. IEEE-488.2-compatible. No measurement units are allowed.  
Responses are RS-232-compatible, allowing a means of recording the  
units with the measurement value.  
FUNC  
Channel Function Definition  
Define the measurement function and range for the indicated channel.  
Attempting to use the FUNC command when measurements are active  
results in an Execution Error.  
Note  
Successful execution of the FUNC command clears any alarm limits and  
scaling values for this channel. Therefore, you must define a channel’s  
function before setting alarm limits and/or scaling values for that channel.  
Also, the FUNC command clears all values in the Review array. FUNC  
<channel>,<OFF>  
FUNC <channel>,<VAC VDC FREQ>,<range>  
FUNC <channel>,<OHMS>,<range>,<terminals>  
FUNC <channel>,<TEMP>,<thermocouple type>  
FUNC <channel>,<TEMP>,<PT>,<terminals>  
<channel> = (0 .. 20)  
If the channel number is invalid, an Execution Error is generated.  
<function> = VAC VDC OHMS FREQ TEMP OFF  
If the function is OFF, any additional supplied parameters generate a  
Command Error.  
<range> = AUTO (1 .. 6) (Thermocouple/RTD_type)  
Ranges for VAC, VDC, OHMS, and FREQ are listed in the following  
table. Enter AUTO to select autoranging. Use of any other values causes  
an Execution Error.  
RANGE  
VOLTAGE  
300 mV  
3 V  
30 V  
150/300 V  
Error  
OHMS  
300  
3kΩ  
30 kΩ  
300 kΩ  
3 MΩ  
10 MΩ  
FREQUENCY  
900 Hz  
9 kHz  
90 kHz  
900 kHz  
1 Mhz  
1
2
3
4
5
6
Error  
Error  
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4
Table 4-8. Command and Query Reference (cont)  
For temperature functions, the "range" is a thermocouple type (J, K, E, T,  
N, R, S, B, C) or DIN/IEC 751 RTD (PT).  
Use of any other value causes an Execution Error.  
<terminals> = 2 (2-terminal)  
4 (4-terminal)  
Specification of terminals is necessary when the function type is OHMS  
or when an RTD temperature measurement is being defined. When this  
field is called for, a value must be supplied, or a Command Error is  
generated. Defining a 4-terminal channel (1 through 10) automatically  
sets the additional channel (11 through 20) to OFF.  
If a value is supplied in this field when it is not necessary, a Command  
Error is generated. An Execution Error is generated if values other than 2  
or 4 are used.  
FUNC?  
Channel Function Query  
Return the function for the indicated channel.  
FUNC? <channel>  
<channel> = (0 .. 20)  
If the channel indicated is invalid, an Execution Error is generated. For  
valid channels, two or three comma-separated data fields are returned.  
One of the following function definitions is returned in the first data field:  
TEMP, VAC, VDC, OHMS, FREQ, OFF  
For a 4-terminal configuration, two channels are used. For the lower  
channel, the instrument responds to FUNC? with OHMS or TEMP in the  
first field. For the upper channel (lower channel +10), the instrument  
responds with OFF in the first field.  
The second data field indicates the range when a function has been  
chosen. If the channel is set up to autorange, AUTO is returned. If the  
function is TEMP, the thermocouple/RTD_type is returned in this field. If  
the function is OFF, there is no range data returned.  
If the type is OHMS or RTD-temperature, a third field is included to  
indicate the number of terminals used. See the Channel Function  
Definition (FUNC) command for a definition of the data returned for the  
range and number-of-terminals fields.  
IEE  
Instrument Event Enable  
Sets the Instrument Event Enable Register to the given value.  
IEE <value>  
<value> = (0 .. 255)  
This is a mask for the Instrument Event Register and is the first step in  
determining which conditions may issue an SRQ. The mask selects  
which conditions may set the Instrument Event Bit of the Status Byte. If  
the value is not in the range 0 to 255, an Execution Error is generated.  
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2620A, 2625A  
Users Manual  
Table 4-8. Command and Query Reference (cont)  
IEE?  
Instrument Event Enable Query  
Returns the present value of the Instrument Event Enable Register as an  
integer.  
IER?  
Instrument Event Register Query  
Returns the value of the Instrument Event Register as an integer, then  
clears all bits.  
INTVL  
Set Scan Interval  
Set scan interval time.  
INTVL <hours>,<minutes>,<seconds>  
<hours>  
= (0 .. 9)  
<minutes> = (0 .. 99)  
<seconds> = (0 .. 99)  
An Execution Error is generated if values outside the specified ranges  
are used or if measurements are active.  
INTVL?  
LAST?  
Scan Interval Query  
Return scan interval time. Returns three values: hours, minutes, and  
seconds.  
Channel’s Last Scan Value  
Returns value(s) for channels measured in the most recent scan. The  
value returned represents data from the most recent scan. The most  
recent scan is the scan in progress or, if scanning is not in progress, the  
last completed scan.  
LAST? <channel>  
<channel> = (0 .. 20)  
Returns measurement values for either the indicated channel or all  
defined channels. If the channel specification field is left blank, values for  
all defined channels are returned (values for channels defined as OFF  
are not included.) An Execution Error results if a request is made for a  
channel defined as OFF, the channel specified is invalid, the channel  
specified has been set up but not yet measured, or Review array values  
have been cleared.  
The response is a signed number with decimal point and exponent. For  
slow scanning rate, 5 digits are returned (+/-XX.XXXE+/-X); for fast  
scanning rate, 4 digits are returned (+/-XX.XXE+/-X). The range setting  
determines placement of the decimal point.  
For values of all defined channels (no channel specification made),  
undefined (OFF) channels are not included. For each defined channel, a  
separate signed number with decimal point and exponent is returned.  
Commas separate numbers for different channels, and no blank spaces  
are included.  
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4
Table 4-8. Command and Query Reference (cont)  
LOCK  
Lock the instrument front panel so that only use of the arrow keys and  
the simultaneous use of Fand Bare recognized. The following  
LOCK commands are recognized:  
Unlock  
Lock and begin review. If the instrument is not in review, a review is  
begun (even if there are no defined channels.)  
Monitor lock. If the instrument is not already in monitor, an Execution  
Error is generated.  
The three LOCK states are non-volatile. If power is interrupted, the  
instrument retains the last LOCK setting.  
LOCK?  
LOCS  
Retrieve instrument front panel lock status.  
0, 1, or 2 is returned, identifying the state set with the LOCK command.  
Local without Lockout (RS-232 only)  
Enter the IEEE-488.1 local without front panel lockout (LOCS) state. All  
front panel buttons are enabled, and the REM annunciator is not lit. This  
is the state assumed by the instrument at power-up reset.  
If this command is used with the IEEE-488 interface, an Execution Error  
is generated.  
LOG?  
Retrieve Logged Data Query (RS-232 only)  
Return the oldest logged scan values for all configured channels and  
remove them from storage. This query is valid during scanning. The  
remaining count of stored scans (LOG_COUNT?) is decremented by 1.  
Channels defined as OFF are not included. If there are no (more) logged  
scans or if the instrument is a Hydra Data Acquisition Unit, an Execution  
Error is generated.  
The response includes the following information:  
Date and time at the start of the logged scan.  
Date and time are returned as integer values. For example, returned  
values of "20,32,44,5,18,90" signify May 18, 1990 20:32:44.  
Values for the channels measured.  
The measurement data is returned as a list of scientific notation values,  
separated by commas. For example, "+3.4567E-3,-4.9876E+6" are valid  
measurement values. If the fast measurement rate is used, the values  
have one less digit of resolution ("+3.457E-3, -4.988E+6").  
If you are using the RS-232 interface format 2, valid data responses  
would include: +894.45E+3 OHM,-9.1234E-3 C.  
State of the Digital I/O lines and totalize count at the end of the scan.  
Two values are returned. The first is an integer in the range 0 through 15,  
identifying the four alarm output states. The second is an integer in the  
range 0 through 255, identifying digital I/O line states.  
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2620A, 2625A  
Users Manual  
Table 4-8. Command and Query Reference (cont)  
The Totalizer count is returned as a scientific notation value in the range  
0 through 65535 (00.000E+3 through 65.535E+3). If the Totalizer has  
overflowed, a value of 1E+9 is returned.  
An Execution Error is generated if this query is used with the IEEE-488  
interface.  
The following example shows the type of data received in response to  
LOG?. The first line shows time and date. The second line shows  
measurement values. The third line shows alarm outputs state, DIO  
state, and totalizer value. Note that the actual response combines all this  
information on one line; three lines are shown here for presentation  
clarity.  
16,15,30,10,3,90,  
-034.53E-3,+09.433E+0,+09.433E+0,+09.434E+0,+09.434E+0,  
15,255,+00.000E+3  
LOGGED?  
Retrieve specified scan data from memory (RS-232 only)  
LOGGED? <index>  
<index>  
=
(1 .. 2047)  
Scan data is not removed from memory with this query. Use of <index>  
values outside the range causes an Execution Error. Use of <index>  
values within the range and have no data stored will also cause an  
Execution Error. An Execution Error is generated if the instrument is a  
Hydra Data Acquisition Unit.  
Scan data is returned in the same format as for the LOG? query.  
Binary Upload of Logged Data (RS-232 only)  
LOG_BIN?  
For quick upload of logged data from a 2625A. See Appendix E. An  
Execution Error is generated if the instrument is a Hydra Data Acquisition  
Unit, or <index> is out of range or invalid.  
LOG_BIN? <index>  
LOG_CLR  
Clear Logged Scans (RS-232 only)  
Clear all stored scan data. An Execution Error is generated if the  
instrument is a Hydra Data Acquisition Unit.  
LOG_COUNT?  
Logged Scan Count Query (RS-232 only)  
Return the number of stored scans. Returns an integer value  
representing the number of scans presently stored in memory. The  
maximum value that can be returned is 2047; 0 indicates that there are  
no stored scans. An Execution Error is generated if the instrument is a  
Hydra Data Acquisition Unit.  
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4
Table 4-8. Command and Query Reference (cont)  
LOG_MODE  
Determines treatment of new scan data when memory is full (RS-232  
only)  
LOG_MODE <mode>  
0 Wrap around. When memory is full, oldest scans are discarded to  
make room for new scans. This is the default mode.  
1 Discard new scans. New scans are stored only when memory  
becomes available. (See LOG? and LOG_CLR.)  
The LOG_MODE setting is non-volatile and cannot be changed from the  
instrument front panel. An Execution Error is generated if the instrument  
is a Hydra Data Acquisition Unit.  
LOG_MODE?  
Query treatment of new scan data when memory is full (RS-232 only)  
0 or 1 is returned, signifying the mode set with the LOG_MODE  
command. An Execution Error is generated if the instrument is a Hydra  
Data Acquisition Unit  
LWLS  
MAX?  
Local with Lockout (RS-232 only)  
Enter the IEEE-488.1 local with front panel lockout (LWLS) state. All front  
panel buttons are disabled. The REM annunciator is not lit.  
Channel’s Maximum Value  
Returns maximum value(s) for channels measured in the most recent  
scan. The value returned represents data from the most recent scan. The  
most recent scan is the scan in progress or, if scanning is not in  
progress, the last completed scan.  
MAX?  
<channel>  
<channel> = (0 .. 20)  
Leave the channel specification field blank if values for all defined  
channels are desired. An Execution Error results if a request is made for  
a channel defined as OFF, the channel specified is invalid, the channel  
specified has been set up but not yet measured, or Review array values  
have been cleared. The response is a signed number with decimal point  
and exponent. For slow scanning rate, 5 digits are returned (+/-  
XX.XXXE+/-X); for fast scanning rate, 4 digits are returned (+/-XX.XXE+/-  
X). The range setting determines placement of the decimal point.  
For maximum values of all defined channels (no channel specification  
made), undefined (OFF) channels are not included. For each defined  
channel, a separate signed number with decimal point and exponent is  
returned. Commas separate numbers for different channels, and no  
blank spaces are included.  
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Users Manual  
Table 4-8. Command and Query Reference (cont)  
MIN?  
Channel’s Minimum Value  
Returns minimum value(s) for channels measured in the most recent  
scan. The value returned represents data from the most recent scan. The  
most recent scan is the scan in progress or, if scanning is not in  
progress, the last completed scan.  
MIN? <channel>  
<channel> = (0 .. 20)  
If the channel specification field is left blank, values for all defined  
channels are returned. Channels defined as OFF are not included. An  
Execution Error results if a request is made for a channel defined as  
OFF, the channel specified is invalid, the channel specified has been set  
up but not yet measured, or Review array values have been cleared.  
The response is a signed number with decimal point and exponent. For  
slow scanning rate, 5 digits are returned (+/-XX.XXXE+/-X); for fast  
scanning rate, 4 digits are returned (+/-XX.XXE+/-X). The range setting  
determines placement of the decimal point.  
For minimum values of all defined channels (no channel specification  
made), undefined (OFF) channels are not included. For each defined  
channel, a separate signed number with decimal point and exponent is  
returned. Commas separate numbers for different channels, and no  
blank spaces are included.  
MON  
Enable/Disable Monitoring  
This command performs the same function as Mon the front panel.  
MON 1,<channel> Enables monitoring of given channel (if monitoring  
is disabled). Changes monitored channel (if monitoring is already  
enabled).  
MON 0  
Disables monitoring.  
The <channel> parameter can be 0 through 20. A command error is  
generated if no <channel> parameter is given when enabling monitoring.  
If the channel to be monitored is invalid or defined as OFF, or if values  
other than 0 or 1 are given, an Execution Error is generated.  
The MON and SCAN commands work in conjunction with the front panel  
controls. The Monitor and Scan functions can be enabled or disabled  
from either the front panel or the computer interface. The most recently  
specified monitor channel (from front panel or computer interface)  
becomes the one channel monitored.  
Front panel Qand Mbuttons work only when the lockout state is  
LOCS.  
MON_CHAN?  
MON_VAL?  
Monitor Channel Number  
This query asks for the number of the presently defined monitor channel.  
If monitoring is not active, an Execution Error is generated.  
Monitor Channel Value  
This query asks for a measurement on the monitor channel. If monitoring  
is not active, an Execution Error results.  
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4
Table 4-8. Command and Query Reference (cont)  
NEXT?  
Next Scan’s Values  
The NEXT? query returns data values for the next scan to complete. If a  
scan is in progress when the NEXT? query is processed, the data values  
returned are from the scan in progress. If a scan is not presently in  
progress, the NEXT? query waits for data to become available. When  
scanning is occurring, use the NEXT? query to return data from each scan.  
NEXT? returns comma-separated information for the date and  
time at the start of the next measurement scan, the values for channels  
measured, the state of the Digital I/O lines, and the totalize count.  
The time and date are returned in the following order: Hours (0-23), Minutes  
(0-59), Seconds (0-59), Month (1-12), Date (1-31), Year (0-99)  
Measurement data is returned as a list of scientific notation values. For an  
overload (OL), "1E+9" is returned. If an open thermocouple is detected,  
"9E+9" is returned.  
Alarm output and digital I/O values are returned as integer values. The  
Totalizer value is returned as a scientific notation value.  
Channels defined as OFF are not included. If all channels are defined as  
OFF, an Execution Error is generated.  
PRINT  
Data Logging Enable/Disable (RS-232 only)  
Turn data logging on or off.  
PRINT <state>  
<state> = 1 (on) 0 (off)  
An Execution Error is generated if any other value is used or if this  
command is used with the IEEE-488 interface.  
PRINT?  
Data Logging Query (RS-232 only)  
Return the status of data logging. Returns 0 (OFF) or 1 (ON).  
An Execution Error is generated if this query is used with the IEEE-488  
interface.  
PRINT_TYPE  
Set Data Logging Type (RS-232 only)  
Enable internal Memory Storage or Autoprint and set the type of scan data  
logged.  
PRINT_TYPE <destination>,<type>  
<destination> = 0 (PRINT SCANS)  
1 (STORE SCANS)  
2 (BOTH)  
<type> =  
0 (ALL)  
1 (channel in ALARM)  
2 (channel had alarm TRANSition)  
An Execution Error is generated if any other value is used, if this command  
is used with a 2620A and you attempt to select STORE SCANS or BOTH.  
The Hydra Data Logger can hold 2047 scans, with each scan containing 21  
channels of data. Refer to "List Button Functions" in Section 3 for an  
example of some printed scans.  
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Users Manual  
Table 4-8. Command and Query Reference (cont)  
PRINT_TYPE?  
Data Logging Type Query (RS-232 only)  
Return the Autoprint or internal Memory Storage type and the type of  
scan data logged. Returns 0 (AUTOPRINT), 1 (STORE), OR 2 (BOTH),  
and 0 (ALL), 1 (ALARM), or 2 (TRANS). For example, "1,0" could be  
returned, signifying that all scan data is sent to internal Memory Storage.  
An Execution Error is generated if this query is used with the IEEE-488  
interface.  
RANGE?  
Channel Range Query  
Returns the range used for the most recent scan involving this channel.  
The most recent scan is the scan in progress or, if scanning is not in  
progress, the last completed scan.  
This is the range presently in use for channels set up to autorange. Note  
that measurements on the monitor channel do not affect the response to  
this command.  
RANGE? <channel>  
<channel> = (0 .. 20)  
If the channel specification field is left blank, values for all defined  
channels are returned. Channels defined as OFF are not included. An  
Execution Error results if a request is made for a channel defined as  
OFF, the channel specified is invalid, or if the channel has been set up  
but not measured. The range value returned is the measurement range  
and is not affected by Mx+B scaling. Temperature functions  
(thermocouple and RTD) have only one range, which is considered fixed  
(1).  
For each defined channel, an integer value (1-6) is returned. Commas  
separate integers for different channels, and no blank spaces are  
included. For example, if channel 1 last used the 30V range during a  
scan measurement, channel 11 used the 3 Mrange, channel 12 used  
the 900 Hz range, and channel 13 measured a thermocouple, the  
response is "3,5,1,1". Refer to the FUNC description for range  
definitions.  
RATE  
Select Measurement Rate  
Specify the measurement rate. Successful execution of this command  
clears all values in the Review array.  
RATE <rate>  
<rate> = 0 (slow) 1 (fast)  
An Execution Error is generated if the argument is not 0 or 1 or if  
measurements are active.  
RATE?  
Measurement Rate Query  
Return measurement rate for the instrument.  
Returns 0 (SLOW) or 1 (FAST).  
4-40  
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Using the Computer Interface  
Computer Interface Command Set  
4
Table 4-8. Command and Query Reference (cont)  
REMS  
Remote without Lockout (RS-232 only)  
Enter the IEEE-488.1 remote without front panel lockout (REMS) state.  
The REM annunciator is lit, and only the following three front panel  
buttons are now active (with special REMS functionality):  
Qtriggers a single scan.  
Ggenerates a service request.  
Kreturns the instrument to normal front panel control.  
If this command is used with the IEEE-488 interface, an Execution Error  
is generated.  
REVIEW_CLR  
Clear Review Values  
Clear all minimum, maximum, and last values (all channels) in the  
Review array. (It is not possible to selectively clear individual entries in  
the Review array.) The Review clearing operation is carried out only at  
the completion of any scan in progress.  
Clearing the Review array also clears all alarm status.  
RTD Ice Point (R0)  
RTD_R0  
For the indicated channel, store the numeric data as RTD R0. Successful  
execution of this command clears all Review array values (all channels.)  
RTD_R0 <channel>,<R0>  
<channel> = (0 .. 20)  
<R0>  
0 <= R0 <= 999.99  
An Execution Error is generated if the R0 value supplied is not within the  
indicated range, the channel specified is invalid, the channel is defined  
as OFF, or measurements are active.  
RTD_R0?  
RTD Ice-Point (R0) Query  
Return RTD R0 (ice-point resistance) value for the indicated channel.  
RTD_R0? <channel>  
<channel> = (0 .. 20)  
If the channel number is invalid, an Execution Error is generated. If a  
channel is defined OFF, or if no change has been made to R0 for a  
channel, the value "100.00" is returned.  
4-41  
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Users Manual  
Table 4-8. Command and Query Reference (cont)  
RWLS  
Remote with Lockout (RS-232 only)  
Enter the IEEE-488.1 remote with front panel lockout (RWLS) state. All  
front panel buttons are disabled, and the REM annunciator is lit.  
If this command is used with the IEEE-488 interface, an Execution Error  
is generated.  
SCALE_MB  
Set Mx+B Scaling Values  
Set the M and B scaling values for the indicated channel, and display the  
results of the Mx+B calculation in the indicated display range. Successful  
execution of this command clears all  
values in the Review array (all channels.)  
SCALE_MB <channel>,<M_value>,<B_value>,<disp_range>  
<channel> = (0 .. 20)  
<M_value> = signed numeric quantity  
<B_value> = signed numeric quan<disp_range> = (16)  
<disp_range> = (1 .. 16)  
CODE DISPLAY  
OFFSET  
MAX OFFSET CODE DISPLAY  
MAX  
VALUE  
VALUE  
1
2
3
4
5
6
7
8
0.0000 m  
00.000 m  
000.00 m  
0000.0 m  
0.0000 x1  
00.000 x1  
000.00 x1  
0000.0 x1  
0.01  
0.1  
1.0  
9
0.0000 k  
00.000 k  
000.00 k  
0000.0 k  
0.0000 M  
00.000 M  
000.00 M  
0000.0 M  
1.0E4  
1.0E5  
1.0E6  
1.0E6  
1.0E7  
1.0E8  
1.0E9  
1.0E10  
10  
11  
12  
13  
14  
15  
16  
1.0  
10.0  
100.0  
1000.0  
1000.0  
When M=1 and B=0, Mx+B scaling is effectively nonexistent. The values  
for M and B must be in the span +/-9999.9 Mega (E+6).  
An Execution Error is generated for any of the following:  
Invalid entries for channel number, M or B values, or display range code  
are used.  
The range required by the B value is larger than allowed by the display  
range code.  
The channel is defined as OFF.  
Measurements are active.  
Mx+B scaling values for a channel are automatically reset to 1 (M) and 0  
(B) when the function for that channel is changed.  
4-42  
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Using the Computer Interface  
Computer Interface Command Set  
4
Table 4-8. Command and Query Reference (cont)  
SCALE_MB?  
Mx+B Scaling Values Query  
Return the M and B scaling values for the indicated channel.  
SCALE_MB? <channel>  
<channel> = (0 .. 20)  
If the channel number given is invalid, an Execution Error is generated.  
Remember that Mx+B scaling values are automatically reset to 1 (M) and  
0 (B) when the function for that channel is changed.  
This command returns three values. The first two are the M and B values  
for the channel indicated, even when M=1 and B=0 or the function is  
defined as OFF. These first two values are returned in M and B order  
and in scientific notation format with five digits of resolution. The third  
value returned indicates the Mx+B resultant display range.  
SCAN  
Enable/Disable Scanning  
This command performs the same function as Qon the front panel.  
SCAN 1  
SCAN 0  
Enable scanning.  
Disable scanning (any scan in progress is completed first.)  
If there are no configured channels (all are defined as OFF) or values  
other than 0 or 1 are given, an Execution Error is generated.  
The MON and SCAN commands work in conjunction with the front panel  
controls. The Monitor and Scan functions can be enabled or disabled  
from either the front panel or the computer interface. The most recently  
specified monitor channel (from front panel or computer interface)  
becomes the one channel monitored.  
Front panel Qand Mbuttons work only when the lockout state is  
LOCS.  
SCAN?  
Return scan status. If a scan is in progress, a "1" is returned at the end of  
the scan. (A response delay may occur if SCAN? is sent early in a scan.)  
This feature allows synchronization for other commands that would not  
be recognized if received during a scan. For example, SCAN?;*TRG  
could be used to trigger a new scan after completion of the current scan.  
Otherwise, a *TRG command sent while a scan is in progress would be  
discarded. If a scan is not in progress, a "0" is returned immediately.  
SCAN_TIME?  
Time of Scan  
Returns values indicating the time and date at start of last scan. Uses the  
same format and order as the TIME_DATE? query. The data is returned  
in the following order: Hours (0-23), Minutes (0-59), Seconds (0-59),  
Month (1-12), Date (1-31), Year (0-99). Setting of time does not include  
seconds, but retrieval of time does.  
TEMP_CONFIG  
Temperature Configuration  
Set temperature configuration using the given value. Successful  
execution of this command clears all Review array  
values (all channels.)  
TEMP_CONFIG <value>  
<value> = encoded bit fields  
4-43  
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Users Manual  
Table 4-8. Command and Query Reference (cont)  
Use the lowest two bits of the value given as individual flags to specify  
the temperature configuration. Therefore, the value given must be in the  
range from 0 through 3 or an Execution Error is generated. These  
settings affect every channel; they cannot be set for each channel  
individually. If this command is attempted when measurements are  
active, an Execution Error results.  
Bit Number  
0
Value  
Meaning  
0
1
°C  
°F  
1
0
1
Disable open thermocouple detection  
Enable open thermocouple detection  
TEMP_CONFIG?  
Temperature Configuration Query  
Response to this query corresponds to settings made with the  
TEMP_CONFIG command, as follows:  
Bit Number  
0
Value  
Meaning  
0
1
°C  
°F  
1
0
1
Disable open thermocouple detection  
Enable open thermocouple detection  
TIME  
Set the instrument clock.  
TIME <hours>,<minutes>  
<hours> = (0 .. 23) (24-hour scale, 18:00 = 6:00 pm).  
<minutes> = (0 .. 59)  
Invalid values generate an Execution Error. Seconds are automatically  
set to 00 with the TIME command.  
TIME_DATE?  
Retrieve Time and Date  
Returns comma-separated integer values for time, date, and year as  
maintained by the instrument clock. These returned values use the TIME  
and DATE command integer formats as follows:  
hours  
minutes  
seconds  
month  
day  
0-23  
0-59  
0-59  
1-12  
1-31  
00-99  
year  
Seconds are returned, but cannot be set other than to 00.  
4-44  
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Using the Computer Interface  
Computer Interface Command Set  
4
Table 4-8. Command and Query Reference (cont)  
TOTAL  
Set Totalizer Count  
Give the Totalizer count a new initial value.  
TOTAL <t_value>  
<t_value> = (0 .. 65535)  
If the value is not in the range 0 through 65,535, an Execution Error is  
generated.  
Clear the Totalizer count by setting the Totalizer to zero (0).  
Totalizer Value Query  
TOTAL?  
Returns the value of the present Totalizer count. Format of the value is  
+00.000E+3. When the Totalizer has overflowed, the value returned is  
+001.00E+9.  
TOTAL_DBNC  
Set Totalizing Debounce  
Set totalizing input debounce state.  
TOTAL_DBNC <dbnc_state>  
<dbnc_state> = 1 (on)  
0
(off)  
Use of any other value causes an Execution Error to be generated. At  
initial power up, totalize debounce is disabled (0).  
TOTAL_DBNC?  
TRIGGER  
Totalizer Debounce Query  
Returns the totalizing input’s debounce state as an integer. When  
disabled, the response is 0, indicating debounce is not in use. When  
enabled, the response is 1, indicating debounce is being used.  
Select Trigger Type  
Select the type of scan triggering.  
TRIGGER <trig_type>  
<trig_type> = 0 (off)  
1
(on)  
2
(alarm)  
Off (0) signifies that external triggering is disabled. Only normal scan  
interval triggering can be used. If the scan interval is 0, continuous  
scanning results. On (1) means that external triggering is enabled. An  
acceptable low input on the External Trigger input (TR terminal on the rear  
panel) then affects scanning as follows:  
If the instrument is in Inactive Mode or Monitor Mode, the low input  
enables scanning. When the TR input returns to high, scanning is  
disabled.  
If scanning is already enabled, the external trigger requests a single scan.  
This request is ignored if a scan is presently in progress.  
Alarm (2) signifies that an alarm condition on the monitor channel triggers  
a single scan. When the scan is completed, the Monitor function is  
resumed. This cycle repeats as long as the alarm condition is encountered  
on the monitor channel. The external trigger input is disabled. The *TRG  
and GET commands can still be used.  
If the type given is not one of the listed values, an Execution Error is  
generated.  
4-45  
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Users Manual  
Table 4-8. Command and Query Reference (cont)  
TRIGGER?  
Trigger Type Query  
Returns an integer representing the present trigger type:  
0
1
2
(off)  
(on)  
(alarm)  
4-46  
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Chapter 5  
Additional Considerations  
Title  
Page  
Introduction ....................................................................................................... 5-3  
Measurement Rate............................................................................................. 5-3  
Advanced Trigger Mechanisms......................................................................... 5-3  
Front Panel Trigger Control.......................................................................... 5-3  
Computer Interface Trigger Control ............................................................. 5-3  
Both External and Monitor Alarms Disabled (Type 0) ................................ 5-4  
External Trigger Enabled (Type 1)............................................................... 5-4  
Monitor Alarm Enabled (Type 2) ................................................................. 5-6  
Thermal Voltages .............................................................................................. 5-6  
When Measuring Resistance or Temperature (RTD)........................................ 5-6  
True RMS Measurements.................................................................................. 5-8  
Effects of Internal Noise in AC Measurements ............................................ 5-8  
Waveform Comparison (True RMS vs Average Responding) ..................... 5-8  
Making Mixed Measurements........................................................................... 5-9  
Using Shielded Wiring...................................................................................... 5-11  
General Rule ................................................................................................. 5-11  
Alternate Suggestions ................................................................................... 5-11  
Non-Isolated Sensor Configuration .......................................................... 5-11  
Isolated and Shielded Sensor Configuration ............................................ 5-11  
In More Detail............................................................................................... 5-12  
5-1  
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5-2  
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Additional Considerations  
Introduction  
5
Introduction  
Chapter 5 discusses some topics that will help you use the instrument more effectively.  
These considerations assume that you are familiar with the basic operation of the  
instrument and have some basic understanding of electronics.  
Measurement Rate  
The two measurement rates provide a choice of maximum accuracy and noise rejection  
(slow rate) or maximum throughput (fast rate). The selected rate applies to all channels  
on the instrument. Therefore, your rate selection will be based on overall consideration  
of the speed and accuracy you need.  
Exact measurement rates vary somewhat by type of measurement. Refer to Appendix A,  
Specifications for complete measurement rate information.  
Advanced Trigger Mechanisms  
Normally, the built-in scan interval timer controls when scan measurements are taken.  
However, two additional mechanisms are available for activating scans:  
1. An external trigger signal, connected at the rear panel "TR" input.  
2. An alarm condition on the Monitor channel.  
Note  
These two additional trigger mechanisms are mutually exclusive.  
The External Trigger input and Monitor-Alarm trigger can be enabled from the front  
panel or through computer interface commands  
Front Panel Trigger Control  
To access the trigger controls from the front panel, select TRIGS (K M). Then press  
G or Gto cycle through the choices for trigger types:  
OFF Both External and Monitor-Alarm triggers are disabled.  
On  
The External Trigger input is enabled.  
ALAr The Monitor-Alarm trigger is enabled.  
Press EEonce youve selected the desired trigger type. Note that internal scan  
interval triggering is not affected by this selection and remains available.  
Computer Interface Trigger Control  
Select a scan trigger type over the computer interface by sending the command:  
TRIGGER<type>  
where <type> is:  
0
1
2
Both External and Monitor-Alarm triggers are disabled.  
The External Trigger input is enabled.  
The Monitor-Alarm trigger is enabled.  
If one of these types is not specified, an Execution Error is generated.  
5-3  
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2620A, 2625A  
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Verify the trigger type over the computer interface by sending the query:  
TRIGGER?  
Single scans can be triggered via the RS-232 interface or the IEEE-488 interface by  
sending the *TRG command. Note that the IEEE-488 interface GET command can be  
used only when the IEEE-488 interface is enabled.  
Note  
If the instrument is in the remote state without front panel lockout (i.e.,  
REMS), a *TRG can be generated from the front panel by pressing Q.  
Both External and Monitor Alarms Disabled (Type 0)  
External trigger input is disabled (Front Panel OFF, Computer Interface TRIGGER=0).  
The *TRG and GET commands can still be used, and only normal scan interval  
triggering can be used. If the scan interval is 0:00:00, continuous scanning results. Also,  
a small scan interval (specifying a time less than that required by the instrument to  
complete a full scan) effectively becomes continuous scanning. The number of channels  
in the scan and the types of measurement determine the time necessary to complete one  
scan.  
External Trigger Enabled (Type 1)  
This corresponds to the Front Panel ON or Computer Interface TRIGGER=1 setting.  
When External Trigger is enabled, a low signal on the rear panel TR terminal affects  
scanning as follows:  
If the scan function has already been activated, the trigger signal causes a single set  
of scan measurements to be taken. This feature is convenient in cases where you  
want to collect normal scheduled scans, as well as scan measurements in response to  
some abnormal situation. When the condition arises, a trigger signal can be sent to  
the instrument, causing it to take an extra set of scan measurements.  
If scan measurements are occurring when the trigger requesting a single scan arrives,  
this request for another scan is ignored. (This stipulation applies whether the scan in  
progress was initiated by the scan interval timer, a command over the computer  
interface, or from a previous external-trigger signal.)  
If the instrument is in Inactive Mode, or just the Monitor function is selected, the  
low trigger signal enables interval scanning. Scans are executed at the specified scan  
interval. (If the scan interval is 0, continuous scanning results; a small scan interval  
time effectively becomes continuous scanning.) When the TR input returns high,  
interval scanning is disabled. This feature is handy in cases where you want to begin  
normal scheduled scans after the system under test has reached some particular  
operating condition. When that condition arises, a trigger signal can be sent to the  
instrument, causing it to begin interval scanning.  
If the instrument is in Configuration Mode, all external trigger signals are ignored.  
The instrument must be in Inactive Mode or Active Mode before any external trigger  
signal will be recognized.  
The external trigger accepts a contact closure or logic low signal; the input is non-  
isolated and TTL compatible. Note that scanning is enabled on the falling edge of the  
trigger signal. This trigger signal must be held low for a minimum of 5 microseconds; it  
must also have previously been unasserted (high) for at least 100 milliseconds. Refer to  
Figure 5-1. Signal level constraints are as follows:  
High 2.0V min., 7.0V max.  
Low -0.6V min., 0.8V max  
5-4  
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Additional Considerations  
Advanced Trigger Mechanisms  
5
ALARM OUTPUTS  
DIGITAL I/O  
+ –  
0
1
2
3 TR  
0
1
2
3
4
5
6
7
Σ
+30V  
!
9-16 V  
DC PWR  
7.0V  
HIGH  
VALID EXTERNAL  
TRIGGERS  
SCAN  
TIME  
SCAN  
HIGH  
100 mS  
2.0V  
0.8V  
IGNORED  
(SCAN IN  
PROGRESS)  
LOW  
0
FALLING  
EDGE  
–0.6V  
HELD 5 µS  
oo15f.eps  
Figure 5-1. External Trigger Timing  
5-5  
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Monitor Alarm Enabled (Type 2)  
This corresponds to the Front Panel ALAr or Computer Interface TRIGGER=2 setting.  
When the Monitor Alarm trigger is enabled and the Monitor function is on, a scan is  
triggered if the monitor measurement is found to be in alarm. After this scan occurs, a  
monitor measurement is again made. If the monitor measurement is still in alarm,  
another scan is triggered. This pattern continues as long as the monitor channel remains  
in alarm.  
Monitor alarm trigger can be used when interval scanning is enabled. This feature is  
convenient when you want to take normal scheduled scans and also use the monitor  
function as a "watchdog" on a particular channel. Whenever an alarm condition arises on  
that monitored channel, the instrument automatically takes additional scan  
measurements.  
If you change the Monitor function to a different channel while the Monitor-alarm  
trigger is in use, measurements on the new monitor channel are used to trigger scans  
when the monitor measurement is in alarm. When monitor and scanning are both  
enabled, at least one monitor channel measurement is taken after every set of scan  
measurements - even in the case of continuous scanning.  
Thermal Voltages  
Thermal voltages are the thermovoltaic potentials that appear at the junction between  
dissimilar metals. Thermal voltages, which can easily exceed 1 uV, typically arise where  
wires are attached to binding posts.  
With low-level dc voltage and thermocouple temperature measurements, these thermal  
voltages can be an additional source of measurement error.  
Thermal voltages can also cause problems in the low ohms ranges. Some low value  
resistors are constructed with dissimilar metals. Just handling such resistors can cause  
thermal voltages large enough to introduce measurement errors.  
On Hydra Series II, the rear panel Input Module (channels 1 through 20) contains an  
isothermal block to minimize thermal voltage errors. The front connector pair (channel  
0), which does not attach directly to this block, is more susceptible to thermal voltage  
errors. Use the following techniques to reduce the effect of thermal voltages:  
1. Use similar metals for connections wherever possible (e.g., copper-to-copper, gold-  
to-gold, etc.).  
2. Use tight connections.  
3. Use clean connections (especially free of grease and dirt).  
4. Use caution when handling the measurement source.  
5. Wait for all measurement connections to reach thermal equilibrium. (Thermal  
voltages are generated only where there is a temperature gradient.)  
When Measuring Resistance or Temperature (RTD)  
The instrument can measure a resistance with two or four terminal connections.  
Advantages for each configuration are discussed below:  
2-Terminal Configuration  
The instrument measures resistance in a 2-terminal configuration using a resistance  
ratio (sometimes called ratio-ohms) technique. Using only the high (H) and low (L)  
terminals for one channel, 2-terminal resistance measurements are simple to set up  
and yield good results for many measurement conditions. However, if lead wire and  
internal relay resistances are significant in relation to the resistances being measured,  
the 4-terminal configuration should be used. (Internal relay resistances are noted in  
Appendix A, Specifications.) A 2-terminal configuration is illustrated in Figure 5-2.  
The full-scale voltage for each resistance range is shown in Table 5-1. The Ve (or  
H) input test lead is positive with respect to the COM (or L) lead.  
5-6  
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Additional Considerations  
When Measuring Resistance or Temperature (Rtd)  
5
2-WIRE (2T) CONNECTION  
11 12 13 14 15 16 17 18 19 20  
H L H L H L H L H L H L H L H L H L H L  
SOURCE  
(4-WIRE)  
H L H L H L H L H L H L H L H L H L H L  
SENSE  
(4-WIRE)  
1
2
3
4
5
6
7
8
9
10  
RESISTANCE  
OR  
RTD SOURCE  
USE H AND L TERMINALS FOR ANY CHANNEL.  
• CHANNEL 0 ON FRONT PANEL  
• CHANNELS 1 THROUGH 20 ON REAR  
PANEL INPUT MODULE (CHANNEL 8 SHOWN HERE).  
4-WIRE (4T) CONNECTION  
11 12 13 14 15 16 17 18 19 20  
H L H L H L H L H L H L H L H L H L H L  
SOURCE  
(4-WIRE)  
H L H L H L H L H L H L H L H L H L H L  
SENSE  
(4-WIRE)  
1
2
3
4
5
6
7
8
9
10  
RESISTANCE  
OR  
RTD SOURCE  
USE H AND L TERMINALS FOR TWO CHANNELS ON REAR PANEL INPUT MODULE.  
CONNECTIONS FOR CHANNEL 8 SHOWN HERE WITH CHANNEL 18 PROVIDING  
ADDITIONAL TWO CONNECTIONS.  
FOR EACH 4-WIRE CONNECTION, ONE SENSE CHANNEL (1 THROUGH 10) AND  
ONE SOURCE CHANNEL (SENSE CHANNEL NUMBER +10 = 11 THROUGH 20) ARE USED.  
oo16f.eps  
Figure 5-2. 2T and 4T-Connections  
5-7  
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Table 5-1. Ohms Test Voltage  
Typical Full Scale Voltage  
Range  
300.00  
3.0000 kΩ  
30.000 kΩ  
300.00 kΩ  
3.0000 MΩ  
0.22  
0.25  
0.29  
0.68  
2.25  
2.72  
10.000 MΩ  
4-Terminal Configuration  
In 4-terminal configuration, the instrument uses a second pair of leads to  
automatically eliminate measurement-lead and internal-relay resistance errors.  
With measurement lead and internal relay resistances eliminated, this configuration  
yields the most accurate readings.  
Four-terminal measurements are allowed on channels 1 through 10 only. However,  
two pairs of high (H) and low (L) terminals are needed for this type of measurement.  
The first pair is provided by the selected channel (any of channels 1 through 10). The  
second pair is provided by the channel 10 numbers higher. For example, channels 2  
and 12 (or 7 and 17) could provide the two pairs of terminals. This second channel  
provides the necessary two additional terminals, and is therefore not available for  
any other use until the first channel is changed to a function other than 4-terminal  
OHMS or RTD.  
A 4-terminal configuration is illustrated in Figure 5-2.  
True RMS Measurements  
The instrument measures the true rms value of ac voltages. In physical terms, the rms  
(root-mean-square) value of a waveform is the equivalent dc value that causes the same  
amount of heat to be dissipated in a resistor. True rms measurement greatly simplifies  
the analysis of complex ac signals. Since the rms value is the dc equivalent of the  
original waveform, it provides a reliable basis for comparing dissimilar waveforms.  
Effects of Internal Noise in AC Measurements  
With the input shorted and the instrument set for ac volts (VAC) measurement, internal  
amplifier noise causes a typical display reading of approximately 0.50 mV. Since the  
instrument is a true rms responding measurement device, this noise contributes  
minimally to the reading at the specified floor of each range. When the rms value of the  
two signals (internal noise and range floor) is calculated, the effect of the noise is shown  
as:  
total rms digits =  
0.502 +15.002 = 15.008  
The display will read 15.01. At the 28.00 mV input level on the 300.00 mV range in the  
slow rate, the display will read 28.00 with no observable error.  
Waveform Comparison (True RMS vs Average Responding)  
Figure 5-3 illustrates the relationship between ac and dc components for common  
waveforms and compares readings for true-rms measurements (such as with the  
instrument) and average-responding measurements. For example, consider the first  
waveform, a 1.41421V (zero-to-peak) sine wave. Both the instrument and rms-calibrated  
5-8  
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Additional Considerations  
Making Mixed Measurements  
5
average-responding measurement devices display the correct rms reading of 1.0000V  
(the dc component equals 0). However, consider the 2V (peak-to-peak) square wave.  
Both types of measurement correctly display the dc component (0V), but the instrument  
also correctly measures the ac component (1.0000V). The average-responding device  
measures 1.111V, which amounts to an 11% error.  
Average-responding measurement devices have been in use for a long time; you may  
have accumulated test or reference data based on such instruments. The conversion  
factors in Figure 5-3 can aid in converting between the two measurement methods.  
Making Mixed Measurements  
With multiple channels, Hydra Series II allows mixing of measurement types. But the  
possibility of the ac signal on one channel affecting measurements on other channels  
must be considered. This effect is known as cross talk.  
The ac volts signal could be either a voltage that is to be measured on another channel  
(which is known as a normal mode signal) or an ac voltage signal on another channel  
that is present between the channel inputs and earth ground (which is known as a  
common mode signal). A common mode signal could occur, for example, if an  
unshielded thermocouple were to be used to measure the metal case temperature of an ac  
power line diode.  
AC voltage cross talk can affect the various measurement types differently. It can cause  
other ac voltage measurements to read too high. DC and resistance (OHMS)  
measurements could either shift or read noisy. Frequency measurements could be noisy,  
or, in the extreme case, the cross talk frequency could actually become the measured  
signal.  
Cross talk can occur at numerous places: in the device or process being monitored, in the  
wiring to the Hydra Series II instrument, or within the Hydra Series II instrument itself.  
Fortunately, precautions can be taken to provide error-free measurements by minimizing  
the effects of cross talk. Use the following guidelines to minimize cross talk between ac  
volts signal inputs and other sensitive channels:  
Keep any input wiring carrying ac volts signals physically separate from other  
sensitive channels input wiring.  
Avoid connecting inputs with ac volts signals adjacent to sensitive channel inputs.  
(Leave unconnected channels between the inputs, if possible).  
5-9  
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2620A, 2625A  
Users Manual  
PEAK VOLTAGES  
MEASURED VOLTAGES  
AC COMPONENT ONLY  
DC AND AC  
TOTAL RMS  
AC-COUPLED  
INPUT  
WAVEFORM  
DC  
TRUE RMS =  
ac2 + dc2  
COMPONENT  
ONLY  
PK-PK  
2.828  
0-PK  
RMS CAL*  
HYDRA  
SINE  
1.414  
PK  
0
1.000  
PK-PK  
1.000  
0.000  
0.900  
1.000  
1.000  
1.000  
RECTIFIED SINE  
(FULL WAVE)  
1.414  
2.000  
1.414  
2.000  
0.421  
0.779  
PK  
0.436  
PK-PK  
0
RECTIFIED SINE  
(HALF WAVE)  
PK  
0.771  
1.000  
PK-PK  
0.636  
0.000  
0.707  
0
SQUARE  
PK  
2.000  
1.414  
2.000  
1.000  
1.414  
1.111  
0.785  
0
PK-PK  
1.000  
1.000  
RECTIFIED  
SQUARE  
PK-PK  
0.707  
PK  
0
RECTANGULAR  
PULSE  
2.000  
PK  
4.442 K2  
PK-PK  
X
0
2K  
Y
2D  
D = X/Y  
K = D-D2  
2
D
TRIANGLE  
SAWTOOTH  
3.464  
1.732  
PK  
0.962  
1.000  
0
PK-PK  
0.000  
1.000  
*
RMS CAL IS THE DISPLAYED VALUE FOR AVERAGE RESPONDING INSTRUMENTS THAT ARE CALIBRATED  
TO DISPLAY RMS FOR SINE WAVES  
oo17f.eps  
Figure 5-3. Comparison of Common Waveforms  
5-10  
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Additional Considerations  
Using Shielded Wiring  
5
Avoid connecting inputs with ac volts signals to any channel 10 numbers away from  
a sensitive channel (i.e. 4-terminal input channels.)  
Avoid tying L (low) or (especially) H (high) inputs of a sensitive channel to earth  
(chassis) ground. This is very important in resistance measurements.  
Avoid high source impedances on sensitive channels, or minimize the capacitance of  
the sensitive channel to earth (chassis) ground for high impedance inputs.  
Whenever high ohms measurements (> 10 k) must be made accurately, avoid  
connecting any inputs carrying ac volts signals to the Hydra Series II instrument.  
Note  
If frequencies other than 50 or 60 Hz must be present on other channels  
while measuring resistance, temperature, or dc voltage, frequencies of 40  
Hz + multiples of 80 Hz (40, 120, 200, etc.) up to 2 kHz should be avoided.  
Otherwise, frequencies at intervals of 5 Hz will generally contribute no  
more error to a resistance measurement than frequencies of 50 or 60 Hz.  
It is not necessary to follow all of these guidelines. In fact, for most applications,  
adhering to just one of these guidelines will provide satisfactory results. Refer to  
Appendix D for detailed information about cross talk.  
Using Shielded Wiring  
Shielded wires and sensors, such as sheathed thermocouples, are often used in noisy  
environments to reduce measurement errors. When you are connecting these sensors to a  
measuring instrument, the proper connection of the shield depends on the entire  
measurement system and environment.  
General Rule  
Connect the shield to L (low) at the input terminals for each Hydra Series II channel.  
Alternate Suggestions  
In specific instances, following the General Rule may not result in the optimum noise  
rejection; it may be necessary to try alternate configurations and check for improved  
performance.  
Non-Isolated Sensor Configuration  
If non-isolated sensors are used, (e.g. a thermocouple probe where the sensor and its  
shield are electrically connected), try leaving the shield disconnected (open) at the  
2620A-100 Input Module.  
Isolated and Shielded Sensor Configuration  
WWarning  
The following suggestions rely on the shield being kept  
electrically isolated from the sensor h (high) and l (low)wiring,  
except where specifically stated otherwise  
If isolated and shielded sensors are used with the instrument, (e.g., an isolated  
thermocouple probe where the thermocouple junction is electrically isolated from  
shield), two additional configurations to try are:  
5-11  
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2620A, 2625A  
Users Manual  
1. Connect the shield to L (low) at the 2620A-100 Input Module, and try connecting the  
sensor shield to a quiet earth ground at or very near the measurement sensor end  
(and at only one place), or  
2. Connect the shield to L (low) at the Input Module, and try connecting the shield to  
earth ground (only) as close to the rear of the instrument as possible. Isolated and  
shielded sensors will likely result in the best instrument measurement performance  
possible in a noisy environment.  
In More Detail  
If a low noise configuration is required, adhering to the following two rules minimizes  
measurement errors and noise when using shielded sensors and wiring:  
1. Connect the shield so that it and the L (low) terminal are at the same or very nearly  
the same voltage, and  
2. Connect the shield so that common-mode voltages will not cause current to flow  
through the L (or H) source resistance(s).  
One key to applying these rules is to note that very high, but finite impedances exist  
between H (high) and L (low), between H and earth ground, and between L and earth  
ground inside the instrument.  
5-12  
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Chapter 6  
Maintenance  
Title  
Page  
Introduction ....................................................................................................... 6-3  
Cleaning............................................................................................................. 6-3  
Line Fuse ........................................................................................................... 6-3  
Self-Test Diagnostics and Error Codes ............................................................. 6-3  
Performance Tests............................................................................................. 6-4  
Accuracy Verification Test........................................................................... 6-7  
Channel Integrity Test................................................................................... 6-7  
Thermocouple Measurement Range Accuracy Test ..................................... 6-9  
4-Terminal Resistance Test........................................................................... 6-10  
Thermocouple Temperature Accuracy Test.................................................. 6-11  
Open Thermocouple Response Test ............................................................. 6-13  
RTD Temperature Accuracy Test................................................................. 6-14  
RTD Temperature Accuracy Test (Using Decade Resistance Source).... 6-14  
RTD Temperature Accuracy Test (Using DIN/IEC 751)......................... 6-15  
Digital Input/Output Verification Tests........................................................ 6-15  
Digital Output Test ................................................................................... 6-16  
Digital Input Test...................................................................................... 6-16  
Totalizer Test............................................................................................ 6-17  
Totalizer Sensitivity Test.......................................................................... 6-18  
Dedicated Alarm Output Test ....................................................................... 6-19  
External Trigger Input Test........................................................................... 6-21  
Calibration......................................................................................................... 6-21  
Variations in the Display................................................................................... 6-22  
Service............................................................................................................... 6-22  
6-1  
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2620A, 2625A  
Users Manual  
6-2  
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Maintenance  
Introduction  
6
Introduction  
This chapter describes basic maintenance that the instrument user can perform. Do not  
attempt any maintenance not described in this chapter. For additional maintenance,  
service, and calibration procedures, qualified service personnel can refer to the Hydra  
Series II Service Manual (P/N 688868).  
Cleaning  
Warning  
To avoid electrical shock or damage to the instrument, never  
get water inside the case. to avoid damaging the instrument’s  
housing, never apply solvents to the instrument.  
For cleaning, wipe the instrument with a cloth that is lightly dampened with water or  
mild detergent. Do not use aromatic hydrocarbons, chlorinated solvents, or methanol-  
based fluids.  
Line Fuse  
The instrument uses a T 125 mA, 250V (Slow blow) line fuse in series with the power  
supply. To replace this fuse (located on the rear panel), unplug the line cord and remove  
the fuse holder with the fuse as shown in Figure 6-1. The instrument is shipped with a  
replacement fuse that is loosely secured in the fuse holder.  
Self-Test Diagnostics and Error Codes  
When the instrument is powered up, the entire display lights.  
Note  
To hold the display fully lit, press and hold K, then press R ON and  
wait a moment for the instrument to beep. Then release K. The entire  
display will now stay on until you press any button; the power-up sequence  
then resumes.  
Self-test diagnostics are performed each time the instrument is powered up. Any errors  
encountered during this initial 4-second period are displayed momentarily. Even in the  
presence of an error, the instrument still attempts to complete the self-test routine and  
begin normal operation.  
An error indicates that a malfunction has occurred and maintenance is required. If you  
encounter an error, note the number or letter and consult Table 6-1. See if the instrument  
repeats the error. If the problem persists and you intend to repair the instrument yourself,  
refer to the Service Manual. Otherwise, package the instrument securely (using the  
original container if available.) Then forward the package, postage paid, to the nearest  
Fluke Service Center. Include a brief description of the problem. Fluke assumes no  
responsibility for damage in transit.  
6-3  
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2620A, 2625A  
Users Manual  
Power-Line Cord Connector  
To Remove,  
Squeeze and  
Slide Out  
+
0
1
2
3
9-16 V  
DC PWR  
DIGITAL I/O  
3
T
R
+30V  
0
1
2
!
Complies with the limit for a class B computing device  
pursuant to Subpart J of4Part 155 of FC6C Rul7es  
MEETS 0871 B  
Σ
Line Fuse  
(T 125 mA, 250V,  
Slow Blow)  
Fuse Holder  
(Spare Fuse Provided)  
oo18f.eps  
Figure 6-1. Replacing the Line Fuse  
Performance Tests  
When received, the 2620A/2625A Hydra Series II instrument is calibrated and in  
operating condition. The following Performance Verification Procedures are provided  
for acceptance testing upon initial receipt or to verify correct operation at any time. All  
tests may be performed in sequence to verify overall operation, or the tests may be run  
independently.  
If the instrument fails any of these performance tests, calibration adjustment and/or  
repair is needed. To perform these tests, you will need a Fluke 5700A Multifunction  
Calibrator or equipment meeting the minimum specifications given in Table 6-2.  
6-4  
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Maintenance  
Performance Tests  
6
Table 6-1. Power-Up Error Codes  
Description  
Error  
1
2
3
4
5
6
7
8
9
A
b
C
ROM checksum error  
External RAM test failed  
Internal RAM test failed  
Display power-up test failure  
Display not responding  
Instrument configuration corrupted  
EEPROM instrument configuration corrupted  
EEPROM calibration data corrupted  
A/D not responding  
A/D ROM test failure  
A/D RAM test failure  
A/D self test failure  
Each of the measurements listed in the following steps assume the instrument is being  
tested after a 1/2 hour warm up, in an environment with an ambient temperature of 18 to  
28 degrees C, and a relative humidity of less than 70%.  
Note  
All measurements listed in the performance test tables are made in the slow  
reading rate unless otherwise noted.  
Warning  
The 2620A/2625A instrument contains high voltages that can be  
dangerous or fatal. Only qualified personnel should attempt to  
service the instrument. Turn off the Hydra Series II and remove  
all power sources before performing the following procedures.  
6-5  
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2620A, 2625A  
Users Manual  
Table 6-2. Recommended Test Equipment  
Minimum Specification  
Instrument Type  
Recommended  
Model  
Multifunction Calibrator  
DC Voltage:  
Fluke 5700A  
Range: 90 mV to 300V dc  
Accuracy: .005%  
AC Voltage:  
Frequency  
1 kHz  
Voltage  
Accuracy  
0.05%  
29 mV to 300V  
15 mV to 300V  
100 kHz  
Frequency:  
10 kHz  
1.25%  
1V rms  
.0125%  
Decade Resistance  
Source  
General Resistance  
Inc. Model RDS 66A  
Ohms  
Accuracy  
290Ω  
2.9 kΩ  
29 kΩ  
0.0125%  
0.0125%  
0.0125%  
0.0125%  
0.0125%  
290 kΩ  
2.9 MΩ  
Note  
The 5700A Calibrator can be used for 0.05%  
accuracy (rated) on the 3.0 k, 30 k, and 3.0  
Mranges. The 5700A can be used for 0.06%  
accuracy on the 300range.  
Mercury Thermometer  
Thermocouple Probe  
0.02 degrees Celsius resolution  
Type K  
Princo ASTM-56C  
Fluke P-20K  
Room Temperature  
Oil/Water Bath  
Thermos bottle and cap  
Multimeter  
Measures +5V dc  
Fluke 77  
Signal Generator  
Sinewave, 0.5 to 1V rms 10 Hz to 5 kHz  
Alternate Equipment List  
Fluke 6011A  
(Minimum specifications are the same as in the Standard Equipment List)  
Instrument Type Recommended Model  
DC Voltage Calibrator  
Fluke 5440B  
DMM Calibrator  
Fluke 5100B (for AC Volts only)  
Philips PM5193 or Fluke 6011A  
Function/Signal Generator  
6-6  
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Maintenance  
Performance Tests  
6
Accuracy Verification Test  
1. Power up the instrument and allow it to temperature stabilize for 1/2 hour.  
2. Connect a cable from the Output VA HI and LO connectors of the 5700A to the VΩ  
and COM connectors on the front panel of the Hydra Series II Instrument. Select the  
channel 0 function and range on the Hydra Series II and the input level from the  
5700A using the values listed in Table 6-3. Press the MON (monitor) button to  
measure and display the measurement value for channel 0. The display should read  
between the minimum and maximum values listed in the table.  
Channel Integrity Test  
Assure the Accuracy Verification Test for channel 0 meets minimum acceptable levels  
before performing this test.  
1. Switch OFF power to the instrument and disconnect all high voltage inputs.  
2. Remove the Input Module from the rear of the instrument. Open the Input Module  
and connect a pair of test leads to the H (high) and L (low) terminals of channel 1.  
Install the Input Module back into the instrument.  
3. Connect the ends of the test leads together to apply a short (0 ohms).  
4. Reconnect power and switch the instrument ON.  
5. For channel 1, select the 2-terminal ohms function and 300 ohms range on the Hydra  
Series II Instrument. Press MON and ensure the display reads a resistance of less  
than or equal to 4.0 ohms. (This test assumes that lead wire resistances are less than  
0.1e.)  
6. Open the ends of the test leads and ensure that the display reads "OL" (overload).  
7. Press MON. This will stop the measurement.  
8. Connect a cable from the Output VA HI and LO of the 5700A to the Input Module  
test leads (observe proper polarity).  
9. Select the VDC function and 300 volt range on the Hydra Series II and apply first  
0V dc then 290V dc input from the 5700A. Ensure the display reads between the  
minimum and maximum values as shown in Table 6-3 for the 0 and 290V dc input  
levels.  
Note  
Channels 0, 1, and 11 can accommodate a maximum input of 300V dc or  
ac. However, the maximum input for all other channels can only be 150V  
dc or ac.  
10. With the exception of the selected voltage range and input voltage from the 5700A,  
repeat steps 1 through 9 for each remaining Input Module channel (2 through 20).  
Channels 2 through 10 and 12 through 20 should be configured for the 150V dc  
range and an input voltage of 150 volts.  
6-7  
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2620A, 2625A  
Users Manual  
Table 6-3. Performance Tests (Voltage, Resistance, and Frequency)  
Display Accuracy  
(1 year, 18-28°C)  
Function  
Range  
Input Level  
Frequency  
MIN  
MAX  
300 mV  
300 mV  
300 mV  
3V  
0V  
150 mV  
290 mV  
2.9V  
-0.02  
149.94  
289.91  
2.8991  
-2.9009  
28.991  
149.94  
289.91  
0.02  
DC Volts  
--  
150.06  
290.09  
2.9009  
-2.8991  
29.009  
150.06  
290.09  
---  
---  
---  
---  
---  
---  
---  
-3V  
-2.9V  
29V  
30V  
150V  
300V  
150V  
290V  
Note  
Voltages greater than 150V can only be applied to channels 0,1, and 11.  
300 mV  
300 mV  
300 mV  
3V  
19.71  
18.50  
20.29  
21.50  
20 mV  
20 mV  
290 mV  
290 mV  
2.9V  
1 kHz  
100 kHz  
1 kHz  
289.28  
275.00  
2.8937  
28.931  
149.54  
289.34  
290.72  
305.00  
2.9063  
29.069  
150.46  
290.66  
100 kHz  
1 kHz  
3V  
30V  
29V  
1 kHz  
150V  
300V  
150V  
1 kHz  
290V  
1 kHz  
Note  
Voltages greater than 150V can only be applied to channels 0, 1, and 11. The rear Input Module must be  
installed when measuring ac volts on channel 0.  
Note  
For 2-terminal measurements, the resistance accuracy given in this table applies to Channel 0 and makes  
allowance for up to 0.05 ohm of lead wire resistance. You must add any additional lead wire resistance  
present in your set up to the resistance values given in this table.  
Resistance  
Using inputs in decades of 3:  
300 Ω  
short  
0.00  
0.09  
300 Ω  
short  
299.90  
0.0000  
2.9989  
29.990  
299.88  
2.9979  
300.15  
0.0003  
3.0011  
30.010  
300.12  
3.0021  
3 kΩ  
3 kΩ  
30 kΩ  
300 kΩ  
3 MΩ  
30 kΩ  
300 kΩ  
3 MΩ  
6-8  
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Maintenance  
Performance Tests  
6
Table 6-3. Performance Tests (Voltage, Resistance, and Frequency) (cont)  
Using inputs in decades of 1.9:  
300 Ω  
short  
0.00  
0.09  
190 Ω  
short  
189.93  
0.0000  
1.8992  
18.992  
189.91  
1.8983  
190.12  
0.0003  
1.9008  
19.008  
190.09  
1.9017  
3 kΩ  
1.9 kΩ  
19 kΩ  
190 kΩ  
1.9 MΩ  
30 kΩ  
300 kΩ  
3 MΩ  
Using inputs in decades of 1:  
300 Ω  
short  
0.00  
0.09  
100 Ω  
short  
99. 95  
0.0000  
0. 9995  
9. 995  
99. 94  
0. 9990  
9. 979  
100.10  
0.0003  
1.0006  
10.005  
100.06  
1.0010  
10.021  
3 kΩ  
3 kΩ  
1 kΩ  
30 kΩ  
300 kΩ  
3 MΩ  
10 M*  
10 kΩ  
100 kΩ  
1 mΩ  
10 MΩ  
*Optional test point if standards available.  
Note  
All channels (0 through 20) can accommodate 2-terminal resistance measurements. Channel 0, with only  
two connections, cannot be used for 4-terminal measurements. Four-terminal resistance measurements  
can be defined for channels 1 through 10 only. Channels 11 through 20 are used, as required, for 4-  
terminal to provide the additional two connections. For example, a 4-terminal set up on channel 1 uses  
channels 1 and 11, each channel providing two connections.  
Frequency  
90 kHz  
10 kHz/2V p-p  
9.994  
10.006  
Thermocouple Measurement Range Accuracy Test  
Assure the Accuracy Verification Test for channel 0 meets minimum acceptable levels  
before performing this test.  
Thermocouple temperature measurements are accomplished using Hydra Series IIs  
internal 100 mV and 1V dc ranges. (The ranges are not configurable by the operator.)  
This procedure will provide the means to test these ranges.  
To test the 100 mV and 1V dc ranges requires computer interfacing with a host (terminal  
or computer). The host must send commands to select these ranges. These ranges cannot  
be selected from the front panel of Hydra Series II.  
1. Ensure that communication parameters ( i.e., transmission mode, baud rate, parity,  
and echo mode) on the Hydra Series II and the host are properly configured to send  
and receive serial data. Refer to Chapter 4.  
2. Power up Hydra Series II and allow it to temperature stabilize for 1/2 hour.  
6-9  
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2620A, 2625A  
Users Manual  
3. Connect a cable from the Output VA HI and LO connectors of the 5700A to the VΩ  
and COM connectors on the front panel of the Hydra Series II Instrument.  
4. Set the 5700A to output 0V dc  
5. Using either a terminal or a computer running a terminal emulation program as the  
selected host, send the following commands to Hydra Series II:  
FUNC 0,VDC,I100MV <CR>  
MON 1,0 <CR>  
MON_VAL? <CR>  
The returned value for channel 0 should be 0 mV ±0.006 mV.  
Set the 5700A to output 90 mV DC. Send the following command:MON_VAL?  
<CR>  
The value returned should now be 90 mV ±0.028 mV (between 89.972 and 90.028  
mV).  
6. Change Hydra Series II's channel 0 function to the internal 1V dc range by  
redefining channel 0. Send the following commands:  
MON 0 <CR>  
FUNC 0,VDC,I1V <CR>  
Set the 5700A to output 0.9V dc. Send the following commands:  
MON 1,0 <CR>  
MON_VAL? <CR>  
The value returned should be 900 mV ±0.21 mV (899.79 to 900.21 mV).  
4-Terminal Resistance Test  
Assure Channel 0's Accuracy Verification Test for DC Volts and Resistance meets  
minimum acceptable levels.  
1. Switch OFF power to the instrument and disconnect all high voltage inputs.  
2. Remove the Input Module from the rear of the instrument. Open the Input Module  
and connect a pair of test leads (keep as short as possible) to the H (high) and L  
(low) terminals of channel 1 and a second pair of test leads to the H and L terminals  
of channel 11. Install the Input Module back into the instrument.  
3. Observing polarity connect channel 1's test leads to the Sense HI and LO terminals  
of the 5700A and channel 11's test leads to the Output HI and LO terminals of the  
5700A. Connect as shown in Figure 6-2.  
4. Switch the instrument ON.  
5. Select the 4-terminal OHMS function, AUTO range, for channel 1 on the Hydra  
Series II Instrument.  
6. Set the 5700A to output the resistance values listed in Table 6-3 (Use decades of  
1.9).  
7. On Hydra Series II press MON and ensure the display reads between the minimum  
and maximum values shown on Table 6-3.  
8. The 4-terminal Resistance Test is complete. However if you desire to perform this  
test on Input Module channels (2 through 10) repeat steps 1 through 7 substituting in  
the appropriate channel number.  
6-10  
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Maintenance  
Performance Tests  
6
Note  
4-terminal connections are made using pairs of channels. 4-terminal  
measurements can only be made on channels 1 through 10. The  
accompanying pairs are channels 11 through 20.  
Thermocouple Temperature Accuracy Test  
Assure the Thermocouple Measurement Range Accuracy Test meets minimum  
acceptable levels before performing this test.  
1. Switch OFF power to the instrument and disconnect all high voltage inputs.  
2. Remove the Input Module from the rear of the instrument. Open the Input Module  
and connect a K-type thermocouple to the H (high) and L (low) terminals of channel  
1. Install the Input Module back into the instrument.  
Note  
If other than a K type thermocouple is used, be sure that the instrument is  
set up for the type of thermocouple used.  
3. Reconnect power and switch the instrument ON.  
4. Insert the thermocouple and a mercury thermometer in a room temperature bath.  
Allow 20 minutes for thermal stabilization.  
5. Select the temperature and K-type thermocouple function for channel 1. Press MON.  
6. The value displayed should be the temperature of the room temperature bath as  
measured by the mercury thermometer (within tolerances given in Table 6-4, plus  
any sensor inaccuracies.)  
7. The Thermocouple Temperature Accuracy Test is complete. However if you desire  
to perform this test on any other Input Module channel (2 through 20) repeat steps 1  
through 6 substituting in the appropriate channel number.  
6-11  
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2620A, 2625A  
Users Manual  
11 12 13 14 15 16 17 18 19 20  
H L H L H L H L H L H L H L H L H L H L  
SOURCE  
(4-WIRE)  
HYDRA  
INPUT  
MODULE  
H L H L H L H L H L H L H L H L H L H L  
SENSE  
(4-WIRE)  
1
2
3
4
5
6
7
8
9
10  
5700A  
OUTPUT  
SENSE  
VA  
V
WIDEBAND  
HI  
HI  
LO  
HI  
LO  
AUX  
ARD  
GROUND  
CURRENT  
NC  
NC  
2-WIRE  
COMP  
OFF  
: ON  
: OFF  
EX SNS  
EX GRD  
SENSE  
SOURCE  
UUT  
5700A  
SOURCE  
SENSE  
oo19f.eps  
Figure 6-2. 4-Terminal Connections to 5700A  
6-12  
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Maintenance  
Performance Tests  
6
4-WIRE (4T) CONNECTION  
11 12 13 14 15 16 17 18 19 20  
H L H L H L H L H L H L H L H L H L H L  
SOURCE  
(4-WIRE)  
HYDRA  
INPUT  
MODULE  
H L H L H L H L H L H L H L H L H L H L  
SENSE  
(4-WIRE)  
1
2
3
4
5
6
7
8
9
10  
DECADE  
RESISTANCE  
BOX  
oo20f.eps  
Figure 6-3. 4-Terminal Connections to Decade Resistance Box  
Table 6-4. Performance Tests for Thermocouple Temperature Function (IPTS-68/ITS-90)  
Thermocouple Type  
Thermocouple Accuracy Specifications 1 Year  
@ 18-28 Degrees C  
J
K
N
E
T
±0.40°C  
±0.44°C  
±0.53°C  
±0.38°C  
±0.45°C  
Open Thermocouple Response Test  
1. Switch OFF power to the instrument and disconnect all high voltage inputs.  
2. Remove the Input Module from the rear of the instrument. Open the Input Module  
and connect test leads to the H (high) and L (low) terminals of channel 1. Install the  
Input Module back into the instrument.  
3. Reconnect power and switch the instrument ON.  
4. Connect the test leads from the Input Module to an 820 ohm resistor.  
5. Select the temperature and K-type thermocouple function for channel 1. Press MON.  
6. The value displayed should approximate the ambient temperature.  
7. Replace the 820 ohm resistor with a 4 kilohm resistor to simulate a high resistance or  
open thermocouple.  
8. Verify a reading of "otc".  
9. The Open Thermocouple Response Test is complete. However if you desire to  
perform this test on any other Input Module channel (2 through 20) repeat steps 1  
through 8 substituting in the appropriate channel number.  
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2620A, 2625A  
Users Manual  
RTD Temperature Accuracy Test  
The following two RTD Temperature Accuracy Tests are different in that one uses a  
Decade Resistance Source and the other uses an RTD. Only one of the tests need to be  
performed to assure operation.  
RTD Temperature Accuracy Test (Using Decade Resistance Source)  
Assure Channel 0s Accuracy Verification Test for DC Volts and 300 Ohm Resistance  
Range meets minimum acceptable levels.  
1. Switch OFF power to the instrument and disconnect all high voltage inputs.  
2. Remove the Input Module from the rear of the instrument. Open the Input Module  
and connect a pair of test leads (keep as short as possible) to the H (high) and L  
(low) terminals of channel 1. For 4-terminal performance testing, connect a second  
pair of test leads to the H (high) and L (low) terminals of channel 11. Install the  
Input Module back into the instrument.  
3. Connect channel 1s test leads to the Output HI and LO terminals of the Decade  
Resistance Source. For 4-terminal performance testing, also connect channel 11s  
test leads to the Output HI and LO terminals of the Decade Resistance Source.  
Connect as shown in Figure 6-3.  
Note  
4-terminal connections are made using pairs of channels. 4-terminal  
measurements can only be made on channels 1 through 10. The  
accompanying pairs are channels 11 through 20.  
4. Switch the instrument ON.  
5. Select the 4-terminal RTD temperature function, RTD type PT, for channel 1 on the  
Hydra Series II Instrument. Press MON and ensure the display reads between the  
minimum and maximum values shown on Table 6-5.  
6. The RTD Temperature Accuracy test is complete. However if you desire to perform  
this test on Input Module channels (2 through 10) repeat steps 1 through 5  
substituting in the appropriate channel number.  
Note  
The only type of temperature measurement that can be made on channel 0  
is 2-terminal RTD. Channels 11 through 20 will support only 2-terminal  
RTDs.  
Table 6-5. Performance Tests for RTD Temperature Function (Resistance)  
(DIN/IEC 751 Amendment 1) (IPTS-68)  
DECADE RESISTANCE  
SOURCE  
TEMPERATURE SIMULATED  
TEMPERATURE ACCURACY  
1 YEAR @ 18-28°C  
°C  
100 e  
200 e  
300 e  
0
± 0.12°C  
± 0.22°C  
± 0.37°C  
266.42  
558.00  
These figures assume that RTD R0 is set to 100.00 ohms for each channel.  
Accuracy given is for 4-wire measurements only. For 2-wire measurements, degrade the accuracy  
specifications by 5.2 °C per ohm of single lead wire resistance. For 2-wire measurements, degrade the  
accuracy by an additional 11°C (channels 1 .. 20) or 0.05°C (channel 0).  
6-14  
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Maintenance  
Performance Tests  
6
RTD Temperature Accuracy Test (Using DIN/IEC 751)  
1. Switch OFF power to the instrument and disconnect all other high voltage inputs.  
2. Remove the Input Module from the rear of the instrument. Open the Input Module  
and connect a Platinum RTD, conforming to the European Standards IEC 751 (DIN  
43760).  
2-terminal RTD: Connect the RTDs excitation leads to the H (high) and L (low)  
terminals of channel 1.  
4-terminal RTD: Connect the RTDs excitation leads (one red and one black wire) to  
the H (high) and L (low) terminals of channel 1. Connect the RTDs second pair of  
red and black leads to the H and L leads of channel 11 (refer to Figure 6-3 for proper  
connection). Install the Input Module back into the instrument.  
Note  
4-terminal connections are made using pairs of channels. 4-terminal  
measurements can only be made on channels 1 through 10. Their  
accompanying pairs are channels 11 through 20.  
3. Switch the instrument ON.  
4. Insert the RTD probe and a mercury thermometer in a room temperature bath. Allow  
20 minutes for thermal stabilization.  
5. Dependent on the type connection made in step 2, select either the 2-Terminal or 4-  
Terminal RTD temperature function, RTD type PT (DIN IEC 751), for channel 1 on  
the Hydra Series II Instrument. Press M and ensure the display reads the  
temperature of the room temperature bath (within tolerances shown in Table 6-6) as  
measured by the mercury thermometer.  
Table 6-6. Performance Tests for RTD Temperature Function (DIN/IEC 751 Amendment 1)(IPTS-68)  
TEMPERATURE ACCURACY SPECIFICATIONS  
RTD TYPE  
1 YEAR @ 18-28 DEGREES C  
2-wire (channel 0)  
2-wire (channels 1-20)  
4-wire  
-0.54°C to + 0.59°C  
-0.54°C to 11.54°C  
+/-0.54°C  
Assumes RTD R0 is set to 100.00 ohms for each channel  
6. The RTD Temperature Accuracy test is complete. However if you desire to perform  
this test on any other channel (0 or 2 through 20) repeat steps 1 through 5  
substituting in the appropriate channel number.  
Note  
The only type of temperature measurement that can be made on channel 0  
is 2-terminal RTD. Channels 11 through 20 will support only 2-terminal  
RTDs.  
Digital Input/Output Verification Tests  
Digital Input/Output verification testing requires computer interfacing with a host  
(terminal or computer). The host must send commands to the instrument to control the  
digital lines for this test. Refer to Chapter 4 for a description of configuring and  
operating the instrument.  
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2620A, 2625A  
Users Manual  
Digital Output Test  
1. Ensure that communication parameters (i.e., transmission mode, baud rate, parity,  
and echo mode) on the Hydra Series II and the host are properly configured to send  
and receive serial data. Refer to Chapter 4.  
2. Switch OFF power to the instrument and disconnect all high voltage inputs.  
3. Remove the Digital I/O ten terminal connector from the rear of the instrument and  
all external connections to it. Connect short wires (to be used as test leads) to the  
ground (J) and 0 through 7 terminals. Leave the other wire ends unconnected at this  
time. Reinstall the connector.  
4. Switch power ON to both Hydra Series II and the host. Verify that Hydra Series II is  
not scanning. If Hydra Series II is scanning, press SCAN to turn scanning off, then  
cycle power off-on again.  
5. Using a digital multimeter (DMM), verify that all digital outputs (0-7) are in the  
OFF or HIGH state. This is done by connecting the low or common of the  
multimeter to the ground test lead and the high of the multimeter to the digital output  
and verifying a voltage greater than +3.8V dc.  
6. Using either a terminal or a computer running a terminal emulation program, set up  
Hydra Series II to turn Digital Outputs ON (LOW state). In sequence send the  
following commands to Hydra Series II and measure that the correct Digital Output  
line transitioned LOW measures less than +0.8V dc.  
DO_LEVEL 0,0 <CR>  
Assure output 0 measures a LOW state.  
DO_LEVEL 1,0 <CR>  
Assure output 1 measures a LOW state.  
DO_LEVEL 2,0 <CR>  
Assure output 2 measures a LOW state.  
Repeat the command for all eight outputs.  
7. Set up Hydra Series II to turn Digital Outputs OFF (HIGH state).  
In sequence send the following commands to Hydra Series II and measure that the  
correct Digital Output line transitioned HIGH measures greater than +3.8V dc.  
DO_LEVEL 0,1 <CR>  
Assure output 0 measures a HIGH state.  
DO_LEVEL 1,1 <<CR>>  
Assure output 1 measures a HIGH state.  
Repeat the command for all eight outputs.  
Digital Input Test  
1. Perform the DIGITAL OUTPUT TEST steps 1 through 5.  
2. Using either a terminal or a computer running a terminal emulation program, set up  
Hydra Series II to read the Digital Input lines.  
Send the following command to Hydra Series II:  
DIO_LEVELS? <CR>  
6-16  
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Maintenance  
Performance Tests  
6
Verify that the returned value as shown on the Host screen = 255.  
Note  
The number returned is the decimal equivalent of the Digital Input binary  
word (inputs 0 through 7s status). See Table 6-7 to determine if the  
number returned corresponds to the bits jumpered to ground in this test.  
3. Jumper input 0 to ground by connecting the ground test lead to input 0s test lead.  
Then send the following command to Hydra Series II:  
DIO_LEVELS? <CR>  
Verify that the returned value as shown on the Host screen = 254.  
4. Disconnect input 0 from ground then jumper input 1 to ground.  
Send the command: DIO_LEVELS? <CR>  
Verify the returned value is 253.  
5. Repeat step 4 for each input and verify the correct returned value (See Table 6-7).  
Table 6-7. Digital Input Values  
TERMINAL GROUNDED  
STATE OF DIGITAL INPUTS  
inputs 0-7, all HIGH  
DECIMAL VALUE  
none  
255  
254  
253  
251  
247  
239  
223  
191  
127  
0
1
2
3
4
5
6
7
inputs 1-7 HIGH, input 0 LOW  
inputs 0,2-7 HIGH, input 1 LOW  
inputs 0-1 and 3-7 HIGH, input 2 LOW  
inputs 0-2 and 4-7 HIGH, input 3 LOW  
inputs 0-3 and 5-7 HIGH, input 4 LOW  
inputs 0-4 and 6-7 HIGH, input 5 LOW  
inputs 0-5 and 7 HIGH, input 6 LOW  
inputs 0-6 HIGH, input 7 LOW  
Totalizer Test  
This totalizer verification test requires toggling the Digital Output line 0 and using it as  
the Total input. The test requires computer interfacing with a host (terminal or  
computer). The host must send commands to the 2620A/2625A instrument to control the  
digital line for this test. Refer to Chapter 4 for a description of configuring and operating  
the Hydra Series II instrument.  
1. Ensure that communication parameters (i.e., transmission mode, baud rate, parity,  
and echo mode) on the Hydra Series II and the host are properly configured to send  
and receive serial data. Refer to Chapter 4.  
2. Switch OFF power to the instrument and disconnect all high voltage inputs.  
3. Remove the Digital I/O ten terminal connector from the rear of the instrument and  
all external connections to it. Connect short wires (to be used as test leads) to the 0  
terminal and the Total () terminal. Leave other ends of wires unconnected at this  
time. Reinstall the connector.  
4. Switch ON power to both Hydra Series II and the host.  
6-17  
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2620A, 2625A  
Users Manual  
5. Press the TOTAL button on the front panel of Hydra Series II.  
Assure Hydra Series II displays a 0 value.  
6. Jumper output 0 to the Total () input by connecting the () terminal test lead to  
output 0s test lead.  
7. Using either a terminal or a computer running a terminal emulation program, set up  
Hydra Series II to toggle (turn ON and OFF) Digital Output 0.  
In sequence send the following commands to Hydra Series II and assure Hydra  
Series IImeasures and displays the correct total value:  
DO_LEVEL 0,0 <CR>  
DO_LEVEL 0,1 <CR>  
Assure Hydra Series II displays a totalizer count of 1.  
8. Again in sequence send the commands:  
DO_LEVEL 0,0 <CR>  
DO_LEVEL 0,1 <CR>  
A totalizer count of 2 should now be displayed.  
9. Repeat step 8 for each incremental totalizing count.  
10. Set the Hydra Series IIs totalized count to a value near full range (65535) and test  
for overload.  
Send the following commands to Hydra Series II:  
TOTAL 65534 <CR>  
DO_LEVEL 0,0 <CR>  
DO_LEVEL 0,1 <CR>  
A totalizer count of 65535 should be displayed.  
11. Send:  
DO_LEVEL 0,0 <CR>  
DO_LEVEL 0,1 <CR>  
Hydra Series IIs display should now read "OL". This indicates that the counter has  
been overrun.  
Totalizer Sensitivity Test  
1. Perform the Totalizer Test and assure it is operational.  
2. Remove the jumper connecting the () terminal test lead to output 0s test lead.  
3. Assure Hydra Series II is still in the total measuring mode. If not press the TOTAL  
button. Reset the totalizer count shown on the display by pressing Hydra Series IIs  
front panel SHIFT button followed by ZERO (total) button.  
Hydra Series IIs display should now show a value of 0.  
4. Connect the output of the signal generator to the () and ground J terminals.  
5. Program the signal generator to output a 1.5V rms sine signal at 10 Hz.  
6-18  
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Maintenance  
Performance Tests  
6
Hydra Series IIs display should now show the totalizing value incrementing at a 10  
count per second rate.  
Dedicated Alarm Output Test  
The Dedicated Alarm Output Test verifies that Alarm Outputs 0 through 3 are  
functioning properly. Because this test is dependent on voltage readings the Accuracy  
Verification Test for channel 0 and the Channel Integrity Test for channels 1 through 3  
should be performed if voltage readings are suspect.  
1. Switch OFF power to the instrument and disconnect all high voltage inputs.  
2. Remove the Alarm Output eight terminal connector module from the rear of Hydra  
Series II and all external connections to it. Connect short wires (to be used as test  
leads) to the ground (J) and 0 through 3 terminals. Leave other ends of wires  
unconnected at this time. Reinstall the connector.  
3. Remove the Input Module from the rear of Hydra Series II. Open the Input Module  
and jumper the H (high) terminal of channels 1, 2, and 3 together. Connect a test  
lead to the H of channel 1. Also jumper the L (low) terminals of channel 1, 2, and 3  
together. Connect a second test lead to the L of channel 1. Install the Input Module  
back into Hydra Series II. Refer to Figure 6-4.  
4. Switch power ON.  
5. Using a digital multimeter (DMM), verify that alarm outputs 0 through 3 are in the  
OFF or HIGH state. Perform this test by connecting the low or common of the  
multimeter to the ground test lead and the high of the multimeter to the alarm output.  
Verify a voltage greater than +3.8V dc.  
6. Connect a cable from the Output VA HI and LO connectors of the 5700A to the VΩ  
and COM connectors on the front panel of Hydra Series II. Then jumper Hydra  
Series IIs Vterminal to the H (high) test lead of the Input Module and the COM  
terminal to the L (low) test lead (See Input Connection diagram).  
7. On Hydra Series II, select the VDC function, 3V range, and assign a HI alarm limit  
of +1.0000 for channels 0 through 3. Set up all other channels (4-20) to the OFF  
function. Select a scan interval of 5 seconds.  
8. Set the 5700A to output +0.9900 volts.  
9. Press Hydra Series IIs SCAN button. Hydra Series II should scan channels 0  
through 3 every 5 seconds.  
10. Using a digital multimeter, again verify that alarm outputs 0 through 3 are in the  
OFF or HIGH state.  
11. Set the 5700A to output +1.1000 volts. Verify that the alarm outputs 0 through 3 are  
in the ON or LOW state (measure less than +0.8V dc).  
6-19  
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2620A, 2625A  
Users Manual  
ALARM OUTPUTS  
DIGITAL I/O  
ALARM  
OUTPUT  
CONNECTOR  
+ –  
9-16 V  
0
1
2
3 TR  
0
1
2
3
4
5
6
7
Σ
+30V  
!
DC PWR  
0
1 2 3 GND  
11 12 13 14 15 16 17 18 19 20  
H L H L H L H L H L H L H L H L H L H L  
SOURCE  
(4-WIRE)  
INPUT  
MODULE  
H L H L H L H L H L H L H L H L H L H L  
SENSE  
(4-WIRE)  
1
2
3
4
5
6
7
8
9
10  
5700A  
HYDRA  
FRONT PANEL  
OUTPUT  
SENSE  
V
V A  
WIDEBAND  
HI  
HI  
REVIEW  
LAST  
LO  
LO  
COM  
V
HI  
FUNC  
ALRM  
300V  
MAX  
AUX  
CURRENT  
GUARD GROUND  
Mx+B  
(USE STACKED  
BANANA JACKS)  
oo21f.eps  
Figure 6-4. Dedicated Alarms Output Test  
6-20  
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Maintenance  
Calibration  
6
External Trigger Input Test  
The External Trigger Input Test verifies that the rear panel trigger input of Hydra Series  
II is functioning properly.  
1. Switch OFF power to the instrument and disconnect all high voltage inputs.  
2. Remove the Alarm Output eight terminal connector module from the rear of Hydra  
Series II and all external connections to it. Connect short wires (to be used as test  
leads) to the ground (J) and TR terminals. Leave other ends of wires unconnected at  
this time. Reinstall the connector. Refer to Figure 6-5.  
ALARM OUTPUTS  
DIGITAL I/O  
+ –  
9-16 V  
0
1
2
3 TR  
0  
1  
2  
3  
4  
5  
6  
7  
Σ
+30V  
!
DC PWR  
oo22f.eps  
Figure 6-5. External Trigger Test  
3. Switch power ON.  
4. On Hydra Series II, select the VDC function, 30V range for channels 0 through 5.  
Select a scan interval of 30 seconds.  
5. Select trigger ON to enable the external trigger input. Press the SHIFT and  
MON(TRIGS) buttons (the display shows TRIG), then press either the up or down  
arrow buttons to display ON. Press ENTER.  
6. Press Hydra Series IIs SCAN button. Hydra Series II should scan channels 0  
through 5 once every 30 seconds.  
7. During the interval when scanning is not occurring, connect (short) the test leads of  
the TR and ground Alarm Output terminals.  
Ensure the connection causes a single scan to occur.  
8. Disconnect (open) the TR and ground connection.  
Ensure the scan continues to execute at its specified interval.  
Calibration  
Note  
Refer to the Fluke Hydra Series II Service Manual (P/N 688868) for  
calibration procedures. The instrument must be stabilized in an  
environment with ambient temperature of 22 to 24ºC and relative humidity  
of less than 70% and have been turned on for at least 1/2 hour prior to  
calibration.  
The instrument features closed-case calibration controlled over the Computer Interface.  
Using known reference sources, closed-case calibration has many advantages. There are  
6-21  
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2620A, 2625A  
Users Manual  
no parts to disassemble, no mechanical adjustments to make, and the instrument can be  
calibrated by an automated instrumentation system.  
The instrument should normally be calibrated on a regular cycle, typically every 90 days  
or 1 year. The chosen calibration cycle depends on the accuracy specification you wish  
to maintain. The instrument should also be calibrated if it fails the performance test or  
has undergone repair.  
Note  
Do not press CAL ENABLE unless you have a copy of the Service Manual  
and intend to calibrate the instrument. If you have activated calibration  
and wish to exit calibration, press CAL ENABLE until CAL disappears  
from the display (or press power OFF).  
Refer to the Hydra Series II Service Manual for the essential calibration procedures.  
Variations in the Display  
Note  
This feature is not available with instruments having Main Firmware  
version 5.5.  
Under normal operation, the display presents various combinations of brightly and dimly  
lit annunciators and digits. However, you may encounter other, random irregularities  
across different areas of the display under the following circumstances:  
After prolonged periods of displaying the same information.  
If the display has not been used for a prolonged period.  
This phenomenon can be cleared by activating the entire display and leaving it on  
overnight (or at least for several hours). Use the following procedure to keep the display  
fully lit:  
1. With power OFF, press and hold SHIFT, then press power ON.  
2. Wait a moment for the instrument to beep, then release SHIFT. The entire display  
will now stay on until you are ready to deactivate it.  
3. At the end of the activation period, press any button on the front panel; the  
instrument resumes the mode in effect prior to the power interruption (Active or  
Inactive.)  
Service  
If the instrument fails, check that operating instructions presented earlier in this manual  
are being followed. If the problem cannot be remedied, forward the instrument, postage  
paid, to the nearest Fluke Service Center. Be sure to pack the instrument securely; use  
the original container if available. Include a brief description of the problem. Fluke  
assumes NO responsibility for damage in transit.  
To locate an authorized service center, visit us on the World Wide Web: www.fluke.com  
or call Fluke using any of the phone numbers listed below.  
1-800-44-FLUKE (1-800-443-5853) in U.S.A. and Canada  
+31 402-678-200 in Europe  
+81-3-3434-0181 Japan  
+65-*-276-6196 Singapore  
+1-425-356-5500 in other countries  
6-22  
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Appendices  
Appendix  
Title  
Page  
A
B
C
D
E
F
Specifications....................................................................................................... A-1  
ASCII & IEEE-488 Bus Codes............................................................................ B-1  
IEEE-488.2 Devise Documentation Requirements.............................................. C-1  
Making Mixed Measurements ............................................................................. D-1  
Binary Upload of Logged Data (LOG_BIN?) (2625A only)............................... E-1  
RS-232 Cabling.................................................................................................... F-1  
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Appendix A  
Specifications  
Introduction  
The instrument specifications presented here are applicable within the conditions listed  
in the Environmental chapter.  
The specifications state total instrument accuracy following calibration, including:  
A/D errors  
Linearization conformity  
Initial calibration errors  
Isothermality errors  
Relay thermal emfs  
Reference junction conformity  
Temperature coefficients  
Humidity errors  
Sensor inaccuracies are not included in the accuracy figures.  
Accuracies at Ambient Temperatures Other Than Specified  
To determine typical accuracies at temperatures intermediate to those listed in the  
specification tables, linearly interpolate between the applicable 0ºC to 60ºC and 18ºC to  
28ºC accuracy specifications.  
Response Times  
Refer to Typical Scanning Rate and Maximum Autoranging Time later in this Appendix.  
A-1  
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2620A/2625A  
Users Manual  
DC Voltage Inputs  
Range  
Resolution  
Slow  
Fast  
300 mV  
3 V  
10 µV  
0.1 mV  
1 mV  
0.1 mV  
1 mV  
30 V  
10 mV  
0.1 V  
300 V  
10 mV  
Accuracy ± (% ± V)  
1 Year, Fast  
Range  
18°C to 28°C  
1 Year, Slow  
0°C to 60°C  
90 Days, Slow  
1 Year, Slow  
1 Year, Fast  
300 mV  
3V  
0.018% + 20 µV  
0.019% + 0.2 mV  
0.019% + 2 mV  
0.019% + 20 mV  
0.023% + 20 µV  
0.024% + 0.2 mV  
0.024% + 2 mV  
0.024% + 20 mV  
0.040% + 0.2 mV  
0.041% + 2 mV  
0.041% + 20 mV  
0.041% + 0.2V  
0.067% + 20 µV  
0.065% + 0.2 mV  
0.086% + 2 mV  
0.087% + 20 mV  
0.084% + 0.2 mV  
0.082% + 2 mV  
0.103% + 20 mV  
0.104% + 0.2V  
30V  
150/300V  
Input Impedance  
100 Me minimum in parallel with 150 pF maximum for all ranges 3V and below 10 Me  
in parallel with 100 pF maximum for the 30V and 300V ranges  
Normal Mode Rejection  
53 dB minimum at 60 Hz ±0.1%, slow rate  
47 dB minimum at 50 Hz ±0.1%, slow rate  
Common Mode Rejection  
120 dB minimum at dc, 1 ke imbalance, slow rate  
120 dB minimum at 50 or 60 Hz ±0.1%, 1 ke imbalance, slow rate  
Maximum Input  
300V dc or ac rms on any range for channels 0,1, and 11  
150V dc or ac rms for channels 2 to 10 and 12 to 20  
Cross-Talk Rejection  
Refer to Appendix D  
A-2  
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Appendices  
Specifications  
A
Thermocouple Inputs  
Temperature Measurements - Accuracy (Thermocouples) (IPTS-68)  
Thermocouple  
Accuracy (±°C)*  
18°C to 28°C  
0°C TO 60°C  
1 Year 1 Year  
Type  
Temperatur  
e (C°)  
90 Days  
Slow  
1 Year  
Slow  
1 Year  
Fast  
Slow  
Fast  
-100 to -30  
-30 to 150  
0.43  
0.38  
0.43  
0.52  
0.43  
0.60  
0.98  
0.62  
0.52  
0.46  
0.66  
0.45  
0.38  
0.39  
0.49  
0.68  
0.45  
0.36  
0.83  
0.80  
0.93  
0.87  
0.83  
1.08  
1.07  
0.73  
0.79  
0.75  
0.63  
0.71  
1.12  
1.96  
0.44  
0.40  
0.47  
0.53  
0.45  
0.67  
1.08  
0.63  
0.54  
0.48  
0.73  
0.46  
0.39  
0.43  
0.55  
0.69  
0.46  
0.38  
0.85  
0.82  
1.02  
0.89  
0.89  
1.17  
1.09  
0.76  
0.85  
0.77  
0.65  
0.76  
1.25  
2.18  
0.91  
0.81  
0.92  
1.13  
0.94  
1.37  
1.96  
1.43  
1.21  
1.07  
1.47  
0.91  
0.77  
0.82  
1.04  
1.49  
0.95  
0.78  
2.47  
2.31  
2.51  
2.60  
2.35  
2.90  
3.50  
2.24  
2.32  
1.94  
1.63  
1.82  
2.86  
4.71  
0.55  
0.58  
0.87  
0.65  
0.63  
1.27  
1.94  
0.74  
0.66  
0.68  
1.40  
0.58  
0.62  
0.80  
1.10  
0.82  
0.59  
0.61  
1.03  
1.16  
1.80  
1.27  
1.47  
2.00  
1.24  
1.17  
1.39  
0.89  
0.98  
1.30  
2.39  
4.15  
1.09  
1.02  
1.36  
1.31  
1.17  
2.02  
2.88  
1.60  
1.38  
1.27  
2.18  
1.09  
0.99  
1.22  
1.63  
1.71  
1.13  
1.01  
2.66  
2.54  
3.31  
2.79  
2.94  
3.76  
3.66  
2.56  
2.87  
2.12  
1.94  
2.39  
4.05  
6.76  
J
150 to 760  
-100 to -25  
-25 to 120  
K
120 to 1000  
1000 to 1372  
-100 to -25  
-25 to 120  
N
E
120 to 410  
410 to 1300  
-100 to 25  
-25 to 350  
350 to 650  
650 to 1000  
-150 to 0  
T
R
S
B
0 to 120  
120 to 400  
250 to 400  
400 to 1000  
1000 to 1767  
250 to 1000  
1000 to 1400  
1400 to 1767  
600 to 1200  
1200 to 1550  
1550 to 1820  
0 to 150  
150 to 650  
650 to 1000  
1000 to 1800  
1800 to 2316  
C
*Sensor inaccuracies are not included  
A-3  
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2620A/2625A  
Users Manual  
Temperature Measurements - Accuracy (Thermocouples) (ITS-90)  
Thermocouple  
Accuracy (±°C)*  
18°C to 28°C  
1 Year  
0°C to 60°C  
1 Year  
Type  
(°C)  
Temperatur  
e
90 Days  
Slow  
1 Year  
Fast  
1 Year  
Fast  
Slow  
Slow  
(°C)  
-100 to -30  
-30 to 150  
0.44  
0.41  
0.48  
0.53  
0.46  
0.79  
1.32  
0.63  
0.53  
0.45  
0.88  
0.46  
0.39  
0.47  
0.63  
0.68  
0.45  
0.37  
0.86  
0.90  
1.49  
1.00  
1.22  
1.66  
1.18  
1.14  
1.33  
0.74  
0.69  
0.89  
1.72  
2.60  
0.45  
0.43  
0.53  
0.54  
0.48  
0.85  
1.42  
0.64  
0.54  
0.48  
0.95  
0.47  
0.42  
0.51  
0.70  
0.69  
0.46  
0.39  
0.88  
0.94  
1.58  
1.05  
1.29  
1.76  
1.19  
1.19  
1.39  
0.76  
0.73  
0.95  
1.85  
2.82  
0.92  
0.83  
0.98  
1.14  
0.96  
1.55  
2.30  
1.44  
1.21  
1.05  
1.70  
0.92  
0.77  
0.90  
1.18  
1.49  
0.95  
0.80  
2.49  
2.28  
3.12  
2.68  
2.74  
3.54  
3.61  
2.57  
2.86  
1.93  
1.66  
2.00  
3.46  
5.35  
0.57  
0.61  
0.92  
0.66  
0.66  
1.45  
2.29  
0.75  
0.66  
0.73  
1.63  
0.59  
0.65  
0.88  
1.24  
0.82  
0.59  
0.61  
1.03  
1.34  
2.39  
1.47  
1.86  
2.61  
1.35  
1.60  
1.93  
0.89  
1.08  
1.48  
2.99  
4.80  
1.10  
1.06  
1.42  
1.33  
1.19  
2.20  
3.23  
1.61  
1.39  
1.30  
2.41  
1.10  
1.02  
1.30  
1.77  
1.71  
1.13  
1.02  
2.68  
2.63  
3.95  
2.93  
3.33  
4.43  
3.77  
2.99  
3.41  
2.11  
2.04  
2.57  
4.65  
7.40  
J
150 to 760  
-100 to -25  
-25 to 120  
K
120 to 1000  
1000 to 1372  
-100 to -25  
-25 to 120  
N
E
120 to 410  
410 to 1300  
-100 to -25  
-25 to 350  
350 to 650  
650 to 1000  
-150 to 0  
T
R
S
B
0 to 120  
120 to 400  
250 to 400  
400 to 1000  
1000 to 1767  
250 to 1000  
1000 to 1400  
1400 to 1767  
600 to 1200  
1200 to 1550  
1550 to 1820  
0 to 150  
150 to 650  
650 to 1000  
1000 to 1800  
1800 to 2316  
C
* Sensor inaccuracies are not included.  
A-4  
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Appendices  
Specifications  
A
Input Impedance  
100 Mminimum in parallel with 150 pF maximum  
Common Mode and Normal Mode Rejection  
See Specifications, DC Voltage Inputs  
Cross-Talk Rejection  
Refer to Appendix D  
Open Thermocouple Detect  
Small ac signal injection and detection scheme before each measurement detects greater  
than 1 to 4 kas open. Performed on each channel unless defeated by computer  
command.  
RTD Inputs  
Type  
DIN/IEC 751, 100e Platinum (385)  
IEC 751, Amendment 1, 100 e Platinum (IPTS-68)  
RTD  
4 Wire Accuracy* (±°C)  
18°C to 28°C  
Temperature  
(°C)  
Resolution  
Slow Fast  
0°C to 60°C  
90 Day  
Slow  
1 Year  
Slow  
1 Year  
Fast  
1 Year  
1 Year  
Fast  
Slow  
0.07  
0.13  
0.17  
0.24  
0.37  
-200.00  
0.00  
0.02  
0.02  
0.02  
0.02  
0.02  
0.1  
0.1  
0.1  
0.1  
0.1  
0.06  
0.09  
0.10  
0.14  
0.19  
0.06  
0.09  
0.11  
0.14  
0.20  
0.48  
0.55  
0.58  
0.65  
0.76  
0.49  
0.59  
0.64  
0.75  
0.93  
100.00  
300.00  
600.00  
* Sensor inaccuracies are not included  
IEC 751, Amendment 1, 100 e Platinum (ITS-90)  
RTD  
Temperature  
(°C)  
4 Wire Accuracy* (±°C)  
Resolution  
18°C to 28°C  
0°C to 60°C  
Slow  
Fast  
90 Day  
Slow  
1 Year  
Slow  
1 Year  
Fast  
1 Year  
1 Year  
Fast  
Slow  
0.07  
0.13  
0.19  
0.28  
0.48  
-200.00  
0.00  
0.02  
0.02  
0.02  
0.02  
0.02  
0.1  
0.1  
0.1  
0.1  
0.1  
0.06  
0.09  
0.13  
0.17  
0.30  
0.06  
0.09  
0.13  
0.18  
0.31  
0.48  
0.55  
0.60  
0.69  
0.87  
0.49  
0.59  
0.67  
0.79  
1.04  
100.00  
300.00  
600.00  
* Sensor inaccuracies are not included  
A-5  
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2620A/2625A  
Users Manual  
IEC 751, Amendment 2, 100 e Platinum (ITS-90)  
RTD  
4 Wire Accuracy* (±°C)  
Temperature  
(°C)  
Resolution  
18°C to 28°C  
0°C to 60°C  
Slow  
Fast  
90 Day  
Slow  
1 Year  
Slow  
1 Year  
Fast  
1 Year  
1 Year  
Fast  
Slow  
0.13  
0.13  
0.18  
0.34  
0.73  
-200.00  
0.00  
0.02  
0.02  
0.02  
0.02  
0.02  
0.1  
0.1  
0.1  
0.1  
0.1  
0.13  
0.09  
0.12  
0.23  
0.55  
0.13  
0.09  
0.12  
0.24  
0.56  
0.54  
0.55  
0.59  
0.74  
1.12  
0.55  
0.59  
0.66  
0.85  
1.29  
100.00  
300.00  
600.00  
* Sensor inaccuracies are not included  
2-Wire Accuracy  
For 2-wire sensors with R = 100: degrade accuracy by 5.0ºC per lead-ohm, plus  
degrade accuracy an addit0ional 11ºC for channels 1 to 20 and 0.05ºC for channel 0.  
Maximum Current Through Sensor  
1 mA  
Typical Full Scale Voltage  
0.22 V  
Maximum Open Circuit Voltage  
3.2 V  
Maximum Sensor Temperature  
600ºC nominal  
999.99ºF max displayed  
Cross-talk Rejection  
Refer to Appendix D.  
AC Voltage Inputs  
Range  
Resolution  
Minimum Input For  
Rated Accuracy  
Slow  
Fast  
300 mV  
3 V  
10 µV  
100 µV  
1 mV  
100 µV  
1 mV  
20 mV  
200 mV  
2 V  
30 V  
10 mV  
100 mV  
300 V  
10 mV  
20 V  
A-6  
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Appendices  
Specifications  
A
1 Year Accuracy ±(% ± V)  
18°C to 28°C 0°C to 60°C  
Slow Fast  
Range  
Frequency  
Fast  
Slow  
20 Hz - 50 Hz  
1.43% + 0.25 mV 1.43% + 0.4 mV  
0.30% + 0.25 mV 0.30% + 0.4 mV  
0.16% + 0.25 mV 0.16% + 0.4 mV  
0.37% + 0.25 mV 0.37% + 0.4 mV  
1.54% + 0.25 mV 1.54% + 0.4 mV  
0.41% + 0.25 mV 0.41% + 0.4 mV  
0.27% + 0.25 mV 0.27% + 0.4 mV  
0.68% + 0.25 mV 0.68% + 0.4 mV  
50 Hz - 100 Hz  
100 Hz - 10 kHz  
10 kHz - 20 kHz  
20 kHz - 50 kHz  
300 mV  
1.9% + 0.30 mV  
1.9% + 0.5 mV  
5.0% + 1.0 mV  
1.42% + 4 mV  
0.29% + 4 mV  
0.13% + 4 mV  
0.22% + 4 mV  
0.6% + 5 mV  
1.0% + 10 mV  
1.43% + 40 mV  
0.29% + 40 mV  
0.15% + 40 mV  
0.22% + 40 mV  
0.9% + 50 mV  
2.0% + 100 mV  
1.42% + 0.4V  
0.29% + 0.4V  
0.14% + 0.4V  
0.22% + 0.4V  
0.9% + 0.5V  
3.0% + 0.30 mV  
7.0% + 0.50 mV  
1.53% + 2.5 mV  
0.40% + 2.5 mV  
0.24% + 2.5 mV  
0.35% + 2.5 mV  
0.9% + 3.0 mV  
1.4% + 5.0 mV  
1.58% + 25 mV  
0.45% + 25 mV  
0.30% + 25 mV  
0.40% + 25 mV  
1.1% + 30 mV  
2.2% + 50 mV  
1.57% + 0.25V  
0.44% + 0.25V  
0.29% + 0.25V  
0.38% + 0.25V  
1.0% + 0.30V  
3.0% + 0.5 mV  
7.0% + 1.0 mV  
1.53% + 4 mV  
0.40% + 4 mV  
0.24% + 4 mV  
0.35% + 4 mV  
0.9% + 5 mV  
1.4% + 10 mV  
1.58% + 40 mV  
0.45% + 40 mV  
0.30% + 40 mV  
0.40% + 40 mV  
1.1% + 50 mV  
2.2% + 100 mV  
1.57% + 0.4V  
0.44% + 0.4V  
0.29% + 0.4V  
0.38% + 0.4V  
1.0% + 0.5V  
50 kHz - 100 kHz 5.0% + 0.50 mV  
20 Hz - 50 Hz  
1.42% + 2.5 mV  
0.29% + 2.5 mV  
0.13% + 2.5 mV  
0.22% + 2.5 mV  
0.6% + 3.0 mV  
50 Hz - 100 Hz  
100 Hz - 10 kHz  
10 kHz - 20 kHz  
20 kHz - 50 kHz  
3V  
50 kHz - 100 kHz 1.0% + 5.0 mV  
20 Hz - 50 Hz  
1.43% + 25 mV  
0.29% + 25 mV  
0.15% + 25 mV  
0.22% + 25 mV  
0.9% + 30 mV  
50 Hz - 100 Hz  
100 Hz - 10 kHz  
10 kHz - 20 kHz  
20 kHz - 50 kHz  
30V  
50 kHz - 100 kHz 2.0% + 50 mV  
20 Hz - 50 Hz  
1.42% + 0.25V  
0.29% + 0.25V  
0.14% + 0.25V  
0.22% + 0.25V  
0.9% + 0.30V  
50 Hz - 100 Hz  
100 Hz - 10 kHz  
10 kHz - 20 kHz  
20 kHz - 50 kHz  
300V  
50 kHz - 100 kHz 2.5% + 0.50V  
2.5% + 1.0V  
2.6% + 0.50V  
2.6% + 1.0V  
A-7  
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2620A/2625A  
Users Manual  
Frequency  
20 Hz - 50 Hz  
Maximum Input at Upper Frequency  
300 V rms  
300 V rms  
200 V rms  
100 V rms  
40 V rms  
20 V rms  
50 Hz - 100 Hz  
100 Hz - 10 kHz  
10 kHz - 20 kHz  
20 kHz - 50 kHz  
50 kHz - 100 kHz  
Input Impedance  
1 Min parallel with 100 pF maximum Maximum  
Maximum Crest Factor  
3.0  
2.0 for rated accuracy  
Crest Factor Error  
Non-sinusoidal input signals with crest factors between 2 and 3 and pulse widths 100 µs  
and longer add 0.2% to the accuracy specifications.  
Common Mode Rejection  
80 dB minimum at 50 or 60 Hz ± 0.1%, 1 kimbalance, slow rate  
Maximum AC Input  
300V rms or 424V peak on channels 0, 1, and 11  
150V rms or 212V peak on channels 2 to 10 and 12 to 20  
Voltage ratings between channels must not be exceeded  
2 x 106 Volt-Hertz product on any range, normal mode input  
1 x 10 6 Volt-Hertz product on any range, common mode input  
DC Component Error  
SCAN and first MONitor measurements will be incorrect if the dc signal component  
exceeds 60 counts in slow rate or 10 counts in fast rate. To measure ac with a dc  
component present, MONitor the input and wait 5 seconds before recording the  
measurement.  
Cross-Talk Rejection  
Refer to Appendix D.  
A-8  
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Appendices  
Specifications  
A
Ohms Inputs  
Maximum  
Current  
Typical Full  
Maximum Open  
Range  
Resolution  
Through  
Unknown  
Scale Voltage  
Circuit Voltage  
Slow  
Fast  
300 Ω  
3 kΩ  
10 mΩ  
0.1 Ω  
1 Ω  
0.1 Ω  
1 Ω  
0.22 V  
0.25V  
0.29 V  
0.68 V  
2.25 V  
2.72 V  
1 mA  
110 µA  
13 µA  
3.2V  
1.5 V  
1.5 V  
3.2 V  
3.2 V  
3.2 V  
30 kΩ  
300 kΩ  
3 MΩ  
10 Ω  
100 Ω  
1 kΩ  
10 Ω  
100 Ω  
1 kΩ  
3.2 .µA  
3.2 µA  
3.2 µA  
10 MΩ  
10 kΩ  
4-Wire Accuracy ±(%±)  
Range  
18°C to 28°C  
0°C to 60°C  
90 Days, Slow  
0.013% + 20 mΩ  
0.015% + 0.2 Ω  
0.013% + 2 Ω  
1 Year, Slow  
0.014% + 20 mΩ  
0.016% + 0.2 Ω  
0.014% + 2 Ω  
1 Year, Fast  
0.014% + 0.2 Ω  
0.016% + 2 Ω  
1 Year, Slow  
0.031% + 20 mΩ  
0.039% + 0.2 Ω  
0.039% + 2 Ω  
1 Year, Fast  
0.031% + 0.2 Ω  
0.039% + 2 Ω  
300 Ω  
3 kΩ  
30 kΩ  
300 kΩ  
3 MΩ  
0.014% + 20 Ω  
0.021% + 200 Ω  
0.063% + 2 kΩ  
0.709% + 20 kΩ  
0.039% + 20 Ω  
0.050% + 200 Ω  
0.231% + 2 kΩ  
0.923% + 20 kΩ  
0.020% + 20 Ω  
0.059% + 200 Ω  
0.168% + 2 kΩ  
0.021% + 20 Ω  
0.063% + 200 Ω  
0.169% + 2 kΩ  
0.050% + 20 Ω  
0.231% + 200 Ω  
0.573% + 2 kΩ  
10 MΩ  
2-Wire Accuracy  
Add 4.0to accuracy specifications for channels 1 to 20, and add 20 mfor channel 0.  
Lead wire resistances are not included.  
Input Protection  
300V dc or ac rms on all ranges  
Cross-Talk Rejection  
Refer to Appendix D.  
A-9  
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2620A/2625A  
Users Manual  
Frequency Inputs  
Frequency Range  
15 Hz to greater than 1 Mhz  
Range  
Resolution  
Accuracy + (% ± Hz)  
Slow  
0.01 Hz  
0.1 Hz  
1 Hz  
Fast  
Slow  
Fast  
15 Hz - 900 Hz  
9 kHz  
0.1 Hz  
1 Hz  
0.05% + 0.02 Hz  
0.05% + 0.1 Hz  
0.05% + 1 Hz  
0.05% + 0.2 Hz  
0.05% + 1 Hz  
0.05% + 10 Hz  
0.05% + 100 Hz  
0.05% + 1 kHz  
90 kHz  
10 Hz  
100 Hz  
1 kHz  
900 kHz  
1 MHz  
10 Hz  
100 Hz  
0.05% + 10 Hz  
0.05% + 100 Hz  
Sensitivity  
Frequency  
15 Hz - 100 kHz  
Level (Sine Wave)  
100 mV rms  
150 mV rms  
2 V rms  
100 kHz - 300 kHz  
300 kHz - 1 MHz  
Above 1 MHz  
Not specified  
Maximum AC Input  
300V rms or 424V peak on channels 0, 1, and 11  
150V rms or 212V peak on channels 2 to 10 and 12 to 20  
Voltage ratings between channels must not be exceeded  
2 x 106 Volt-Hertz product on any range, normal mode input  
1 x 106 Volt-Hertz product on any range, common mode input  
Cross-Talk Rejection  
Refer to Appendix D.  
A-10  
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Appendices  
Specifications  
A
Typical Scanning Rate  
See table below. The measurement conditions are: averaged rate over 20 scans;  
continuous scanning; alarm limits and Mx+B scanning set on all channels; logging data  
to internal memory; and RS-232 communications set at 9600 baud. Measurements were  
taken with short-circuit inputs on all channels, except frequency, which was taken with  
5V at 15 Hz on all channels.  
CHANNELS  
FUNCTION  
RANGE  
SLOW  
10  
FAST  
10  
1
20  
1
20  
VDC  
300 mV  
3V  
1.8  
1.8  
1.8  
1.8  
1.8  
1.0  
1.7  
1.1  
1.1  
1.1  
1.1  
1.0  
1.7  
1.7  
1.7  
1.2  
1.1  
1.1  
1.7  
0.5  
3.9  
3.9  
3.9  
3.9  
3.6  
3.3  
3.1  
1.5  
1.5  
1.5  
1.5  
1.5  
3.1  
3.1  
3.1  
1.8  
1.6  
1.6  
3.1  
0.6  
4.1  
4.1  
4.1  
4.1  
3.9  
3.8  
3.2  
1.6  
1.6  
1.6  
1.6  
1.5  
3.2  
3.2  
3.2  
1.8  
1.7  
1.6  
3.2  
0.6  
2.5  
2.5  
2.5  
2.5  
2.4  
2.1  
2.1  
1.3  
1.3  
1.3  
1.3  
1.3  
2.1  
2.1  
2.1  
1.8  
1.8  
1.7  
2.1  
0.6  
13.2  
13.2  
13.2  
13.2  
11.3  
10.9  
6.0  
18.3  
18.4  
18.2  
18.1  
14.1  
15.2  
6.7  
30V  
150/300V  
AUTO  
J (TC)  
PT (RTD)  
300 mV  
3V  
TEMPERATURE  
VAC  
2.5  
2.6  
2.5  
2.6  
30V  
2.5  
2.6  
150/300V  
AUTO  
300Ω  
2.5  
2.6  
2.4  
2.5  
OHMS  
6.0  
6.7  
3 kΩ  
6.0  
6.7  
30 kΩ  
300 kΩ  
3 MΩ  
6.0  
6.7  
4.1  
4.4  
3.9  
4.2  
10 MΩ  
AUTO  
ANY  
3.8  
4.0  
6.0  
6.7  
FREQUENCY  
0.7  
0.7  
A-11  
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2620A/2625A  
Users Manual  
Maximum Autoranging Time  
(Seconds per Channel)  
Function  
Range Change  
Slow  
Fast  
VDC  
150 V  
VAC  
300 mV  
300 mV  
300 mV  
300 mV  
300 Ω  
---------------------------->  
---------------------------->  
---------------------------->  
---------------------------->  
---------------------------->  
---------------------------->  
150 V  
0.26  
0.25  
0.19  
4.50  
1.08  
1.30  
0.75  
0.19  
150V  
4.12  
0.59  
150 V  
Ohms  
10.0 MΩ  
1.38  
10.0 MΩ  
1.81  
300 Ω  
Totalizing Input  
Input Voltage  
30V maximum  
4V minimum  
2V peak minimum signal  
Isolation  
None  
dc-coupled  
Threshold  
1.4V  
Hysteresis  
500 mV  
Input Debouncing  
None or 1.66 ms  
Rate  
0 to 5 kHz with debouncing off  
Maximum Count  
65,535  
Digital Inputs  
Input Voltage  
30V maximum  
-4V minimum  
A-12  
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Appendices  
Specifications  
A
Isolation  
none  
dc-coupled  
Threshold  
1.4V  
Hysteresis  
500 mV  
Trigger Input  
Input Voltages  
contact closure and TTL compatible  
“high” =2.0V min, 7.0V max  
“low” = -0.6V min, 0.8V max  
Isolation  
None  
dc-coupled  
Minimum Pulse Width  
5 µs  
Maximum Frequency  
5 Hz  
Specified Conditions  
The instrument must be in the quiescent state, with no interval scans in process, no  
commands in the queue, no RS-232 or IEEE interface activity, and no front panel  
activity if the latency and repeatability performance is to be achieved. For addition  
information, refer to Chapter 5.  
Maximum Latency  
Latency is measured from the edge of the trigger input to the start of the first channel  
measurement for the Specified Conditions (above).  
480 ms for fast rate, scanning DCV, ACV, ohms, and frequency only  
550 ms for fast rate, scanning any thermocouple or 100 mV dc channels  
440 ms for slow rate, scanning DCV, ACV, ohms, and frequency only  
890 ms for slow rate, scanning any thermocouple or 100 mV dc channels  
Repeatability  
3 ms for the Specified Conditions (above)  
A-13  
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2620A/2625A  
Users Manual  
Digital and Alarm Outputs  
Output Logic Levels  
Logical “zero”:  
Logical “one”:  
0.8V max for an Iout of -1.0 mA (1LSTTL load)  
3.8V min for an Iout of 0.05 mA (1LSTTL load)  
For non-TTL loads: 1.8V max for an Iout or -20 mA  
Logical “zero”:  
Isolation  
none  
3.25 max for an Iout of -50 mA  
Real-Time Clock and Calendar  
Accuracy  
Within 1 minute per month for 0°C to 50°C range  
Battery Life  
10 years minimum for Operating Temperature range  
Environmental  
Warmup Time  
1 hour to rated specifications  
15 minutes when relative humidity is kept below the rated maximum minus 20% (e.g.  
below 70% for a 90% maximum rating).  
Operating Temperature  
0°C to 60°C  
Storage Temperature  
-40°C to +75°C  
Instrument storage at temperature extremes may necessitate adding up to  
0.008% to the dc and ac voltage accuracy specifications. Alternatively, any resulting  
shift can be compensated for by recalibrating the instrument.  
Relative Humidity (Non-Condensing)  
90% maximum for 0°C to 28°C  
75% maximum for 28°C to 35°C  
50% maximum for 35°C to 50°C  
35% maximum for 50°C to 60°C  
(Except 70% maximum for 0°C to 35°C, 30% maximum for 40°C to 50°C, and 20%  
maximum for 50°C to 60°C, for the 300 ke, 3 Me, and 10 Me ranges.)  
A-14  
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Appendices  
Specifications  
A
Altitude  
Operating: 2,000 m maximum  
Non-operating: 12,200 m maximum  
Vibration  
0.7 g at 15 Hz  
1.3 g at 25 Hz  
3 g at 55 Hz  
Shock  
30 g half sine per Mil-T-28800  
Bench handling per Mil-T-28800  
General  
Channel Capacity  
21 Analog Inputs  
4 Alarm Outputs  
8 Digital I/O (inputs/outputs)  
Measurement Speed  
Slow rate: 4 readings/second nominal  
Fast rate: 17 readings/second nominal  
1.5 readings/second nominal for ACV and high-inputs  
For additional information, refer to Typical Scanning Rated and Maximum Autoranging  
Time.  
Memory Life  
10 years minimum over Operating Temperature range  
Stores: real-time clock, set-up configuration, and measurement data  
Common Mode Voltage  
300V dc or ac rms maximum from any analog input (channel) to earth provided that  
channel to channel maximum voltage ratings are observed.  
Voltage Ratings  
Channels 0,1, and 11 are rated at 300V dc or ac rms maximum from a channel terminal  
to earth and from a channel terminal to any other channel terminal.  
Channels 2 to 10 and 12 to 20 are rated at 150V dc or ac rms maximum from a channel  
terminal to any other channel terminal within channels 2 to 10 and 12 to 20.  
IEC Overvoltage Category II.  
Size  
9.3 cm high, 21.6 cm wide, 31.2 cm deep  
Weight  
Net, 2.95 kg  
Shipping, 4.0 kg  
A-15  
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2620A/2625A  
Users Manual  
Power  
90V to 264V ac (no switching required), 50 and 60 Hz, 10 VA maximum  
9V dc to 16V dc, 10W maximum  
If both sources are applied simultaneously, ac is used if it exceeds approximately 8.3  
times dc.  
Automatic switchover occurs between ac and dc without interruption.  
(At 120V ac the equivalent dc voltage is ~14.5V).  
Standards  
IEC 1010-1, ANSI/ISA S82.01-1994, CSA-C22.2 No.1010.1-92, and EN61010-1:1993.  
Complies with EN 50081-1, EN 50082-1, Vfg. 243/1991 and FCC-15B at the Class B  
level, when shielded cables are used.  
RS-232-C  
Connector:  
9 pin male (DB-9P)  
TX, RX, DTR, GND  
Signals:  
Modem Control:  
Baud rates:  
Data format:  
bit  
Flow control:  
Echo:  
full duplex  
300, 600, 1200, 2400, 4800, and 9600  
8 data bits, no parity bit, one stop bit, or 7 data bits, one parity  
(odd or even), one stop bit  
XON/XOFF  
on/off  
2625A Data Storage  
Stores 2047 scans  
Each scan includes:  
Time stamp  
Readings for all defined analog input channels  
Status of the eight digital I/O  
Totalizer count  
Memory is battery-backed  
Memory life: 5 years minimum at 25°C  
2620A Options  
IEEE-488 (Option -05k)  
Capability codes: SH1, AH1, T5, L4, SR1, RL1, PP0, DC1, DT1, E1, TE0, LE0, and C0  
Complies with IEEE-488.1 standard.  
A-16  
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Appendix B  
ASCII & IEEE-488 Bus Codes  
B-1  
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2620A/2625A  
Users Manual  
ASCII &  
BUS CODES  
B7  
27  
26  
25  
24  
0
0
0
0
0
0
0
0
B6  
0
0
0
0
1
1
1
1
B5  
0
0
1
1
0
0
1
1
B4  
0
1
0
1
0
1
0
1
BITS  
NUMBERS  
SYMBOLS  
48  
CONTROL  
UPPER CASE  
LOWER CASE  
B3 B2 B1 B0  
0NUL0  
SP20  
0
@
P
112 p  
16  
10 32  
30  
64  
40 80  
50  
96  
60  
70  
0 0 0 0  
0
NUL  
DLE  
17  
SPACE MLA0  
MLA16  
31  
@
MTA0  
P
MTA16  
51  
MSA0  
P
MSA16  
71  
33  
21 49  
65  
41 81  
97  
61 113  
1
1
11  
0 0 0 1  
0 0 1 0  
0 0 1 1  
0 1 0 0  
!
"
#
$
1
A
B
C
D
Q
a
b
c
q
SOH GTL DC1  
!
MLA1  
1
MLA17  
32  
A
MTA1  
Q
MTA17  
52  
a
MSA1  
q
MSA17  
72  
2
2
3
4
18  
12 34  
22 50  
66  
42 82  
98  
62 114  
2
R
r
STX  
3
DC2  
19  
"
MLA2  
2
MLA18  
33  
B
67  
MTA2  
R
MTA18  
53  
b
99  
MSA2  
r
MSA18  
73  
13 35  
23 51  
43 83  
63 115  
3
S
s
ETX  
4
DC3  
20  
#
36  
MLA3  
24  
3
52  
MLA19  
34  
C
68  
MTA3  
44  
S
84  
MTA19  
54  
c
MSA3  
s
MSA19  
74  
14  
100 d  
t
64 116  
4
T
d
MSA4  
t
MSA20  
DCL  
15  
MLA4  
25  
MLA20  
35  
MTA4  
45  
MTA20  
55  
EOT  
5
SDC DC4  
21  
$
4
D
T
69  
37  
53  
101  
65  
5
85  
75  
117 u  
E
%
5
U
e
0 1 0 1  
0 1 1 0  
MTA5  
46  
MLA5  
26  
MLA21  
36  
E
%
5
MTA21  
56  
e
MSA5  
ENQ  
6
PPC NAK  
PPU  
16  
U
u
MSA21  
6
22  
86  
102  
66 118  
76  
38  
70  
54  
V
&
F
f
v
6
ACK  
SYN  
23  
&
MLA6  
27  
6
55  
MTA22  
57  
F
71  
MTA6  
47  
V
87  
f
MSA6  
67  
v
MSA22  
77  
MLA22  
37  
17  
18  
7 BEL7  
'
7
G
W
103 g  
119 w  
39  
0 1 1 1  
ETB  
24  
'
40  
7
MLA23  
G
MTA23  
58  
g
MSA7  
w MSA23  
BEL  
8
MLA7  
28  
MTA7  
48  
W
(
H
104 h  
x
38 72  
88  
68 120  
78  
BS 8  
56  
X
8
1 0 0 0  
1 0 0 1  
(
41  
BS  
GET CAN SPE  
8
H
MTA8  
X
MTA24  
59  
h
105  
MSA8  
x
MSA24  
79  
MLA8  
29  
MLA24  
39  
49 89  
9
9
25  
19  
69 121  
57  
73  
)
Y
I
i
j
HT  
9
y
)
42  
MLA9  
2A  
9
I
Y
MTA25  
5A  
HT  
10  
TCT  
A
MLA25  
3A  
MTA9  
4A  
i
MSA9  
y
MSA25  
7A  
EM  
26  
SPD  
1A  
58  
90  
74  
106  
6A 122  
*
+
,
:
LF  
J
Z
z
1 0 1 0  
1 0 1 1  
1 1 0 0  
1 1 0 1  
1 1 1 0  
LF  
11  
*
43  
MLA10  
:
MTA26  
5B  
SUB  
27  
MLA26  
3B  
J
MTA10  
4B  
Z
j
MSA10  
z
MSA26  
7B  
1B  
1C  
1D  
1E  
2B 59  
107  
6B 123  
B
C
75  
91  
;
K
[
k
{
VT  
FF  
13 CR D  
ESC  
;
ESC  
28  
+
44  
MLA11  
MLA27  
3C  
J
MTA27  
5C  
k
MSA11  
{
MSA27  
7C  
VT  
12  
MTA11  
4C  
[
2C 60  
76  
92  
108  
6C 124  
<
L
\
|
MSA12  
:
<
FF  
FS  
29  
,
45  
MLA12  
MLA28  
3D  
L
MTA12  
MTA28  
5D  
:
MSA28  
7D  
\
|
61  
62  
2D  
4D 93  
M
N
109 m 6D  
}
125  
77  
]
-
CR  
GS  
30  
-
MLA13  
2E  
MLA29  
3E  
M
MTA29  
5E  
MTA13  
]
m
MSA13  
6E  
}
MSA29  
7E  
4E  
14 SO E  
>
110 n  
78  
94  
126  
46  
.
~
^
SO  
RS  
31  
.
MLA14  
2F  
>
N
MTA14  
4F  
MTA30  
n
MSA14  
MLA30  
3F  
~
127  
MSA30  
^
95  
5F  
15  
F
1F 47  
63  
6F  
/
?
O
111 o  
79  
7F  
_
1 1 1 1  
SI  
~
RUB-  
~
_
/
MLA15  
?
SI  
US  
UNL  
O
MTA15  
o
MSA15 OUT  
UNT  
MSA31  
23 22 21 20  
LISTEN  
TALK  
ADDRESSES  
SECONDARY ADDRESSES  
OR COMMANDS  
ADDRESSED UNIVERSAL  
COMMANDS COMMANDS  
ADDRESSES  
hex  
1722A DISPLAY  
KEYdecimal  
38  
26  
&
&
MLA6  
ASCII  
oo25f.eps  
B-2  
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Appendix C  
IEEE-488.2 Devise Documentation  
Requirements  
Introduction  
Section 4.9 of the IEEE Standard 488.2-1987 states: "All devices shall supply  
information to the user about how the device has implemented this standard." (In this  
context, "device" means the Fluke 2620A Hydra Series II Data Acquisition Unit. The  
Fluke Hydra Series II Data Logger cannot be equipped for IEEE-488 operation.) The  
information in Appendix C is provided in compliance with this requirement.  
Implementation of IEEE Standard 488.2-1987  
Items 1-23 below correspond to the specific items of information required by Section  
4.9, "Device Documentation Requirements", of the Standard. The information supplied  
by Fluke in response is italicized. (Throughout Appendix C, the word "Section" refers to  
the section[s] in the Standard, not this manual.)  
1. A list of IEEE 488.2 Interface Function subsets implemented, Section 5.  
IEEE-488.1 interface functions implemented in the Fluke Data  
Acquisition Unit are listed under "IEEE-488" capability codes in  
Appendix A.  
2. A description of device behavior when the address is set outside the range 0-30,  
Section 5.2.  
It is not possible to set the Fluke Data Acquisition Unit address outside the  
specified range.  
3. A description of when a user initiated address change is recognized by the device.  
An address change is recognized when set via the IEEE setup menu,  
which is entered by pressing COMM ([sft] [lst]). This address will be  
used until it is changed. The address change is recognized after ENTER is  
pressed to accept the address shown on the display.  
4. A description of the device setting at power-on, Section 5.12. Any commands which  
modify the power-on settings shall also be included.  
The initial power-up device setting is:  
Channels 0 - 20:OFF.  
C-1  
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2620A/2625A  
Users Manual  
Measurement rate: Slow.  
Scaling (M):1 (all channels)  
Offset (B): 0 (all channels)  
Alarm parameters: Limit-1 and Limit-2 OFF. All limit values 0.  
Alarm assignments: Channels 0-3 assigned to outputs 0-3,respectively.  
Channels 4-20 assigned to digital  
I/O lines 4-7, as shown in Table 3-8.  
Scan interval time: 0:00:00 (continuous)  
Review values (MIN, MAX, LAST) cleared for all channels.  
Digital I/O lines: high (non-alarm)  
Totalizer: 0, with debounce disabled.  
Autoprint/Memory Storage: OFF.  
RTD R0 parameter: 100.00 (all channels)  
Open Thermocouple Detection (OTC) enabled.  
5. A description of message exchange options:  
The size and behavior of the input buffer.  
The input buffer size is 350 bytes. If the input buffer fills, the IEEE-488.1  
bus will be held off until there is room in the buffer for a new byte.  
Which queries return more than one <RESPONSE MESSAGE UNIT>, Section  
6.4.3.  
The following queries always return more than one <RESPONSE  
MESSAGE UNIT>:  
LOG?, NEXT?, INTVL?, TIME_DATE?, PRINT_TYPE?, *IDN?, SCAN_TIME?,  
SCALE_MB?  
The following queries may return more than one <RESPONSE MESSAGE  
UNIT>:  
FUNC?, MIN?, MAX?, LAST?, ALARMS?, RANGE?,ALARM_LIMIT?  
Which queries generate a response when parsed, Section 6.4.5.4.  
All queries generate a response when parsed.  
Which queries generate a response when read, Section 6.4.5.4.  
No queries generate a response when read by the controller.  
Which commands are coupled, Section 6.4.5.3.  
No commands are coupled.  
6. A list of functional elements used in constructing device-specific commands.  
Whether <compound command program header> elements are used must also be  
included, Section 7.1.1 and 7.3.3.  
Device-specific commands used:  
<PROGRAM MESSAGE>  
<PROGRAM MESSAGE TERMINATOR>  
C-2  
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IEEE-488.2 Devise Documentation Requirements  
Appendices C  
<PROGRAM MESSAGE UNIT>  
<PROGRAM MESSAGE UNIT SEPARATOR>  
<COMMAND MESSAGE UNIT>  
<QUERY MESSAGE UNIT>  
<COMMAND PROGRAM HEADER>  
<QUERY PROGRAM HEADER>  
<PROGRAM DATA>  
<CHARACTER PROGRAM DATA>  
<DECIMAL NUMERIC PROGRAM DATA>  
7. A description of any buffer size limitations related to block data, Section 7.7.6.5.  
No block data is used.  
8. A list of <PROGRAM DATA> elements which may appear within an <expression>  
as well as the maximum sub-expression nesting depth. Any additional syntax  
restrictions which the device may place on the <expression> shall also be included.  
No sub-expressions are used. The only <PROGRAM DATA> functional  
elements used are <CHARACTER PROGRAM DATA> AND <DECIMAL  
NUMERIC PROGRAM DATA>.  
9. A description of the response syntax for every query, Section 8.  
<NR1 NUMERIC RESPONSE DATA> is returned for:  
*ESE?, *ESR?, *OPC?, *SRE?, *STB?, *TST?, IEE?, IER?, RATE?,RANGE?,  
INTVL?, TEMP_CONFIG?, MON_CHAN?, FORMAT?,  
ALARMS?,ALARM_ASSOC?, ALARM_DO_LEVELS?, TOTAL_DBNC?,  
TIME_DATE?, TRIGGER?,EEREG?, SCAN_TIME?, LOG_COUNT?,  
DIO_LEVELS?  
<NR3 NUMERIC RESPONSE DATA> is returned for:  
MON_VAL?, TOTAL?, RTD_R0?, MIN?, MAX?, LAST?  
<CHARACTER RESPONSE DATA> is returned for:  
*IDN?, FUNC?  
The following queries return data in two formats:  
ALARM_LIMIT?  
Sense (HI, LO, OFF) in <CHARACTER RESPONSE DATA>Value (if HI or LO) in  
<NR3 NUMERIC RESPONSE DATA>  
SCALE_MB?  
M and B values in <NR3 NUMERIC RESPONSE DATA>Resultant display range in  
<NR1 NUMERIC RESPONSE DATA>  
NEXT?, LOG?  
Time, date, and digital I/O values in <NR1 NUMERIC RESPONSE  
DATA>Measurement data and Totalizer in <NR3 NUMERIC RESPONSE DATA>  
10. A description of any device-to-device message transfer traffic which does not follow  
the rules for <RESPONSE MESSAGE> elements, Section 8.1.  
C-3  
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2620A/2625A  
Users Manual  
There are no device-to-device messages.  
11. The size of any block data responses, Section 8.7.9.4.  
There are no block data responses.  
12. A list of common commands and queries which are implemented, Section 10.  
*CLS, *ESE, *ESE?, *ESR?, *IDN?, *OPC, *OPC?, *RST, *SRE, *SRE?, *STB?,  
*TRG, *TST?, *WAI  
13. A description of the state of the device after successful completion of the Calibration  
query, Section 10.2.  
The *CAL? command not implemented (an optional command).  
14. The maximum length of the block used to define the trigger macro, if *DDT is  
implemented, Section 10.4.  
*DDT is not implemented.  
15. The maximum length of macro labels, the maximum length of the block used to  
define a macro, and how recursion is handled during macro expansion, if the macro  
commands are implemented, Section 10.7.  
Macros are not implemented.  
16. A description of the response to the identification common query, *IDN?, Section  
10.14.  
The *IDN? query returns:  
FLUKE,2620A,0,M2.41 A3.7 D1.3  
The version number of the main software is "M2.41", "A3.7" is the version number of  
the analog sub-system software, and "D1.3" is the version number of the display sub-  
system software.  
17. The size of the protected user data storage area, *PUD, Section 10.27.  
*PUD not implemented. There is no protected user data storage area.  
18. The size of the resource description, if the *RDT command or *RDT? query are  
implemented, Sections 10.30 and 10.31.  
The *RDT and *RDT? commands are not implemented.  
19. A description of the states affected by *RST (Section 10.32), *LRN? (Section  
10.17), *RCL (Section 10.29), and *SAV (Section 10.33).  
*RST restores the device to the state assumed at initial power-up, except for those  
items specifically forbidden by the *RST command definition. The initial power-up  
state is defined under item "4.", above.  
*LRN?, *RCL, and *SAV are not implemented.  
20. A description of the scope of the self-test performed by the *TST? query, Section  
10.38.  
* TST? performs the tests listed under "*TST?" in Table 4-8 of the Users Manual. The  
device reverts to the power-up state after performing these tests.  
21. A description of additional status data structures used in the devices status reporting,  
Section 11.  
The Instrument Event Enable (IEE) register and the Instrument Event Register (IER)  
are described in Figure 4-4.  
C-4  
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IEEE-488.2 Devise Documentation Requirements  
Appendices C  
22. For each command, a statement describing whether is overlapped or sequential.  
All commands are sequential; none are overlapped.  
23. For each command, the device documentation shall specify the functional criteria  
that are met when an operation complete message is generated in response to that  
command, Section 12.8.3.  
Operation complete is generated when the command is parsed.  
C-5  
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2620A/2625A  
Users Manual  
C-6  
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Appendix D  
Making Mixed Measurements  
Introduction  
This appendix augments the discussion of ac signal effects on other channels (cross talk)  
found in Chapter 5 ("Making Mixed Measurements"). Effects on each measurement  
function are discussed below. These numbers should only be considered as references.  
Since cross talk can be introduced into a measurement system in many places, each setup  
must be considered individually.  
The effect of cross talk could be much better than shown for "Typical"; in extreme cases,  
the effect could be worse than the "Worst Case" numbers. In general, the "Worst Case"  
information assumes that none of the guidelines for minimizing cross talk (Chapter 5)  
have been followed; the "Typical" information assumes that the guidelines have been  
followed where reasonable.  
These numbers assume that input L (low) is tied to earth ground; refer to "Using  
Shielded Wiring" in Chapter 5. For dc volts and thermocouple temperature  
measurements, a source impedance of 1 k in series with the H (high) input is assumed  
(except where otherwise noted.)  
Signal Cross Talk in a DC Voltage Channel  
VDC(error)  
DCV Error Ratio (CTRR) =  
VACrms  
Worst case  
Typical  
50, 60 Hz, ±0.1%:  
Other Frequencies:  
1.1 × 10-7  
3.8 × 10-6  
2.0 × 10-8  
8.6 × 10-7  
For example, to find the typical effect of a 300V ac signal at 60 Hz on another channel  
for the 300 mV range, you would calculate: 300 × 2.0 × 10-8 = 0.01 mV.  
D-1  
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2620A/2625A  
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AC Signal Cross Talk Into an AC Voltage Channel  
VACrms(error)  
ACV Error Ratio =  
Range  
VACrms(crosstalk) × Frequency(crosstalk)  
Ratio (worst case)  
Ratio (typical)  
×
×
×
×
v × Hz  
v × Hz  
v × Hz  
v × Hz  
v × Hz  
30.000 V 1.2 × 10-6  
2.6 × 10-7  
v × Hz  
150.00/300.00 1.2 × 10-5  
3.4 × 10-6  
v × Hz  
v × Hz  
For example, to find the typical effect of a 60 Hz, 220V ac signal on another channel for  
the 300 mV range, you would calculate: 220 X 60 X 1.4 X 10-8 = 0.18 mV.  
AC Signal Cross Talk Into an Ohms Channel  
AC Frequency = 50, 60 Hz, ±0.1%  
Ohms(error)  
OHMS Error Ratio1 =  
VACrms(crosstalk)  
Range  
Ratio (worst case)  
3.0000 ke  
Ratio (typical)  
×
2.4 ×  
×
30.000ke 3.1 × 10-  
Vrms  
Vrms  
4
-5  
Vrms  
Vrms  
8.4 × 10  
Vrms  
kOhms  
Vrms  
kOhms  
300.00 ke  
3.0000 Me  
10.000 Me  
5.6 × 10-3  
3.8 × 10-4  
1.4 × 10-3  
3.7 × 10-3  
Vrms  
MOhms  
Vrms  
MOhms  
3.8 × 10-5  
Vrms  
MOhms  
Vrms  
MOhms  
Vrms  
4.3 ×  
For example, to find the typical effect of a 60 Hz, 100V ac signal on another channel for  
the 30 krange, you would calculate: 100 X 8.4 X 10-5 = 0.008 k.  
AC Signal Cross Talk Into a Frequency Channel  
Frequency measurements are unaffected by cross talk as long as the voltage-frequency  
product is kept below the following limits:  
Worst Case  
Typical  
V x Hz Product Limit  
3.7 × 104 (V × Hz)  
1.0 × 106 (V × Hz)  
These values assume no more than 1000 pf of capacitance between either end of the resistor (HI and LOW ) and  
earth ground.  
D-2  
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Making Mixed Measurements  
Appendices D  
AC Signal Crosstalk Into a Temperature Channel  
Frequency = 50, 60 Hz  
°C(error)  
TEMPERATURE Error Ratio =  
VACrms(crosstalk)  
Types J, K, E, T, N:  
Worst case  
Typical  
°C  
Vrms  
°C  
Vrms  
2.7 ×10-3  
5.0 ×10-4  
°C  
Vrms  
°C  
Vrms  
Types R, S, B, C:  
Type PT (RTD):  
1.1 ×10-2  
8.6 ×10-5  
2.0 ×10-3  
°C  
Vrms  
No Effect  
D-3  
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2620A/2625A  
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D-4  
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Appendix E  
Binary Upload of Logged Data  
(LOG_BIN?) (2625A only)  
Introduction  
The LOG_BIN? <index> query can be used to quickly upload logged data from a 2625A.  
The response is a single ASCII string, which encodes the raw binary data stored at the  
specified <index> position. The logged data is also retained in the 2625A.  
The measurement data returned from the 2625A is in the (binary) IEEE single-precision  
floating point format. Making use of this data can be difficult and is very machine  
dependent. A working example, using the C programming language on an IBM PC, is  
provided in this appendix. This example uses a pre-computed LOG_BIN?response  
string, and checks that the conversion process works as expected.  
Two steps are required in adapting the LOG_BIN? response string for use with your  
computer.  
First, you must decode the ASCII string into binary data.  
For example, one possible LOG_BIN? response string is:  
LOG_BIN? 1  
42@Y40BA00oo000007o0001oP000?h000  
=>  
This ASCII string represents the following binary (hex) data:  
10 24 29 10 04 91 00 0f ff  
00 00 00 00 7f c0 00 00 7f  
80 00 00 3f 80 00 00 00 00  
Second, you must convert this binary data into valid floating point numbers for your  
underlying computer architecture.  
Decoding the ASCII String  
The ASCII response string contains six bits of raw data for each ASCII character, offset  
from ASCII 0(0x30 hex, 48 decimal). Therefore, the conversion process subtracts 48  
from the integer value of each character, then shifts it into place. Each set of four ASCII  
characters form three bytes of raw data. The number of bytes of raw data depends on the  
number of channels for the scan. The following C code converts a LOG_BIN? response  
string into a byte array:  
E-1  
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2620A/2625A  
Users Manual  
/*  
-* decode(): Decode LOG_BIN? response string into raw byte stream  
**  
** Decoding is done on multiples of four input bytes:  
**  
**  
543210  
543210  
543210  
543210  
(bit number in ASCII bytes)  
**  
+--------+--------+--------+--------+  
| src[0] | src[1] | src[2] | src[3] |  
+--------+--------+--------+--------+  
**  
ASCII string input  
**  
**  
765432  
/
107654  
321076  
543210  
(bit number in raw bytes)  
**  
/
/
/
**  
/
/
**  
|
|
|
|
|
/
/
/
**  
/
**  
|
|
|
/
**  
/
**  
|
**  
76543210 76543210 76543210  
+--------+--------+--------+  
| dst[0] | dst[1] | dst[2] |  
+--------+--------+--------+  
(bit number in raw bytes)  
Raw data output  
**  
**  
**  
**  
** Inputs:  
**  
**  
**  
**  
**  
**  
**  
dst  
Destination for binary data (must have enough space  
allocated; the maximum needed is 6 timestamp bytes + 3  
bytes for temp units, measurement rate, and digital I/O  
+ 4 bytes/float * 22 floating point values = 97 bytes).  
src  
Source ASCII string (null terminated)  
** Outputs:  
**  
**  
dst  
Set to binary data, based on ASCII string  
** Returns:  
**  
*/  
Number of bytes placed in destination buffer  
int  
decode(dst, src)  
unsigned char *dst;  
char *src;  
{
/* src to dst xlate */  
static struct nibtab_s {  
int lindex;  
int lmask;  
int lshift;  
int rindex;  
int rmask;  
int rshift;  
} nibtab[3] = {  
/* left  
right */  
0, 0x3f, 2,  
1, 0x0f, 4,  
2, 0x03, 6,  
1, 0x30, 4,  
2, 0x3c, 2,  
3, 0x3f, 0,  
/* dst[0] from src[0] and src[1] */  
/* dst[1] from src[1] and src[2] */  
/* dst[2] from src[2] and src[3] */  
};  
auto unsigned char n;  
auto struct nibtab_s *t;  
auto unsigned char tmpsrc[4];  
auto int dst_bytes;  
/* Number of bytes created */  
dst_bytes = 0;  
/* Process src in chunks of four */  
while (*src) {  
/* Copy source, filing "holes" at end with zeros */  
for (n = 0; n < 4; n++) {  
if (*src)  
tmpsrc[n] = *src++ - ’0’;  
else  
tmpsrc[n] = 0;  
}
/* Mung source into destination */  
for (t = nibtab; t < &nibtab[3]; t++) {  
*dst = (tmpsrc[t->lindex] & t->lmask) << t->lshift;  
*dst |= (tmpsrc[t->rindex] & t->rmask) >> t->rshift;  
dst++;  
dst_bytes++;  
}
}
return (dst_bytes);  
}
Figure E-1. ASCII String Decoding  
E-2  
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Appendices  
Binary Upload of Logged Data (LOG_BIN?) (2625A only)  
E
The raw data output array contains the information listed below. Note that the number of  
floating point values is equal to the number of channels in use, plus one. (The totalizer  
count is always present in the data, and is stored as a floating point number.)  
Time stamp (BCD format)  
byte0: hours  
byte1: minutes  
byte2: seconds  
byte3: month  
byte4: date  
byte5: year  
Temperature units, measurement rate, and I/O  
byte6: temperature units and rate (0x10 bit means degrees Fahrenheit, else  
Centigrade; 0x01 bit means fast rate, else slow rate)  
byte7: Alarm outputs  
byte8: Digital I/O  
Totalizer value as 32-bit single-precision IEEE floating point number stored using  
the byte ordering shown below. The format of this number is explained under  
"Floating Point Conversion".  
byte 9: MMSB of float  
byte 10: MLSB of float  
byte 11: LMSB of float  
byte 12: LLSB of float  
Measurement data; only defined channels are included (exactly like LOG?query);  
same floating point format, but with a wider range of values. NaN (Not a Number) is  
used to indicate open thermocouple, and plus or minus Inf (infinity) to indicate  
overload. The bit values for NaN and Inf are explained in the next section.  
byte 13: MMSB of float  
byte 14: MLSB of float  
byte 15: LMSB of float  
byte 16: LLSB of float  
bytes 17-20: Second measurement result, if any  
bytes 21-24: Third measurement result, if any  
..........  
Since the ASCII decoding (explained above) creates data multiples of three in length, it  
is possible that there will be one or two unused bytes at the end of the decoded byte  
stream.  
Floating Point Conversion  
ANSI/IEEE Std 754-1985, "IEEE Standard for Binary Floating-Point Arithmetic,"  
describes the single-precision floating point format used to return measurement data.  
This standard defines the format for single-precision floating point as:  
X = (-1) s 2(e-127) x 1.m  
where  
s = sign  
e = exponent  
m = mantissa  
E-3  
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2620A/2625A  
Users Manual  
The floating point format used is 32-bit with a 1-bit sign, 8-bit exponent, and 24-bit  
mantissa with the most significant bit hidden under the LSB of the exponent. The  
number is formatted as shown in Table F-1.  
Table E-1. Floating Point Format  
sign 1 bit  
high byte (MMSB)  
exponent 8 bits  
hi-mid byte (MLSB)  
mantissa 23 bits (plus one hidden bit)  
low mid byte (LMSB) low byte (LLSB)  
For all other measurement queries, Hydra Series II returns the string "+9E+9" for open  
thermocouple (OTC) measurement values. However, for the LOG_BIN?query, NaN (not  
a number) is returned instead. The IEEE floating point standard defines NaN as a  
positive, maximum exponent number with non-zero mantissa bits. Hydra Series II sets  
just the most significant mantissa bit, so the raw binary byte stream value is 7f c0 00 00  
(hex).  
For all other measurement queries, Hydra Series II usually returns ±1e9 for overload  
(OL) measurement values. However, for the LOG_BIN? query, Hydra Series II returns  
Inf (infinity) instead. The IEEE floating point standard defines Inf as a positive or  
negative maximum exponent number with a zero mantissa. Hydra Series II returns +Inf  
as the byte stream 7f 80 00 00 (hex) and -Inf as ff 80 00 00 (hex).  
The C code in Figure F-2 converts raw data into a useful format for the Intel x86 (IBM  
PC) architecture. The BCD time stamp is converted to integers, and floating point  
numbers created for the totalizer and measurement values.  
Example  
Figure F-3 is a short example that uses the routines in Figures F-1 and F-2 to decode a  
fixed (pre-computed) LOG_BIN? response string.  
When compiled and run on an Intel architecture computer, the program should print  
"Conversion worked".  
Although this example is useful for educational purposes, it is not very efficient. If  
desired, the decoding and conversion processes can be combined into a single, fast  
algorithm.  
E-4  
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Appendices  
Binary Upload of Logged Data (LOG_BIN?) (2625A only)  
E
/* Import globals from main program */  
extern int timestamp[];  
extern int misc[];  
extern float values[];  
/*  
-* convert(): Convert a LOG_BIN? array of binary data into useful data  
**  
** Converts BCD values to integer, raw floating point values into float  
** values usable under the Intel x86 (IBM PC) architecture.  
**  
** Inputs:  
**  
**  
**  
src  
length  
Array of binary data, from LOG_BIN? query  
Number of bytes in src array  
** Outputs:  
**  
**  
**  
**  
*/  
timestamp[]  
Set to decimal timestamp values  
misc[]  
Set to temp units, rate, and digital I/O values  
Set to floating point values found in binary data  
(must be room for a maximum of 22 floats)  
values[]  
void  
convert(src, length)  
unsigned char *src;  
int length;  
{
unsigned char *m;  
int n;  
/* Convert timestamp from BCD to decimal */  
for (n=0; n < 6; n++, src++) {  
/* Binary Coded Decimal (BCD) format, packs the upper nibble as the  
*/  
*/  
*/  
/* tens digit, the lower nibble as the ones digit. Convert this  
/* into an integer number.  
timestamp[n] = (10 * (*src >> 4) + (*src & 0x0f));  
}
/* Save temperature units, measurement rate, and digital I/O values */  
for (n=0; n < 3; n++) {  
misc[n] = *src++;  
}
/* Convert raw measurement data into floating point */  
m = (unsigned char *)values;  
for (length -= 9; length > 3; length -= 4) {  
#ifdef sun  
/* SunOS architecture (also works for Motorola CPUs) */  
*m++ = src[0];  
*m++ = src[1];  
*m++ = src[2];  
*m++ = src[3];  
#else  
/* Assume Intel x86 architecture */  
*m++ = src[3];  
*m++ = src[2];  
*m++ = src[1];  
*m++ = src[0];  
#endif  
src += 4;  
}
}
Figure E-2. Floating Point Conversion  
E-5  
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2620A/2625A  
Users Manual  
/* Globals convert() uses for destination */  
int timestamp[6];  
int misc[3];  
float values[22];  
/* Scan timestamp */  
/* Temperature units, measurement rate, digital I/O */  
/* Measurement values */  
extern int isnan();  
extern int isinf();  
/* Floating point value is NaN (not a number) */  
/* Floating point value is Inf (infinity) */  
/*  
-* main(): LOG_BIN? query response example program  
**  
** Converts a hard-coded LOG_BIN? response string into usable data.  
*/  
main()  
{
extern int decode();  
/* ASCII to binary decoding */  
/* Convert Hydra binary to usable types */  
extern void convert();  
/* Canned response for three channels: channel 1 is OTC, channel 5 is */  
/* OL and channel 10 is 1.0; remaining encoded data described below  
/* (note that you can not determine the channel number, measurement  
*/  
*/  
/* units, or measurement range, from this string; you must keep track */  
/* of that elsewhere)  
char *log_bin_response = "42@Y40BA00oo000007o0001oP000?h000";  
*/  
/* Place to temporarily store raw data; 100 bytes is more than enough */  
/* for any LOG_BIN? response string  
unsigned char raw_data[100];  
*/  
/* Decode string into raw data, then convert raw data into usable data */  
convert(raw_data, decode(raw_data, log_bin_response));  
/* Above global variables now usable; check example LOG_BIN? data */  
/* against expected values  
*/  
if ((timestamp[0] == 10) &&  
(timestamp[1] == 24) &&  
(timestamp[2] == 29) &&  
(timestamp[3] == 10) &&  
(timestamp[4] == 4) &&  
(timestamp[5] == 91) &&  
/* Hours  
/* Minutes  
/* Seconds  
/* Month  
/* Day  
*/  
*/  
*/  
*/  
*/  
*/  
/* Year  
(misc[0]  
(misc[1]  
(misc[2]  
(values[0]  
== 0) &&  
/* Temp units and rate */  
== 15) &&  
== 255) &&  
== 0.0) &&  
/* Alarm outputs  
/* Digital I/O  
*/  
*/  
*/  
*/  
*/  
*/  
/* Totalizer  
isnan(values[1]) &&  
isinf(values[2]) &&  
/* Channel 1 data  
/* Channel 5 data  
/* Channel 10 data  
(values[3]  
== 1.0)) {  
printf("Conversion worked\n");  
}
else {  
printf("ERROR: conversion did not succeed!\n");  
}
exit(0);  
}
/* If your math library supplies alternatives to isnan() or isinf(), */  
/* use them instead!  
*/  
int  
isnan(f)  
float f;  
{
/* This is not portable, or completely accurate (since NaN mantissa  
*/  
/* must only be non-zero, and the sign bit can be set), but this works */  
/* for NaN values returned by Hydra  
*/  
/* Compiler was free to promote to double */  
float ff = f;  
return ((*(unsigned long *)&ff) == 0x7fc00000L);  
}
int  
isinf(f)  
float f;  
{
/* Again, this is not portable, but this time it is accurate */  
/* Compiler was free to promote to double */  
float ff = f;  
return ((*(unsigned long *)&ff) == 0x7f800000L) ||  
((*(unsigned long *)&ff) == 0xff800000L);  
}
Figure E-3. Example  
E-6  
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Appendix F  
RS-232 Cabling  
Introduction  
This appendix details the RS-232 cabling between the instrument and a PC, instrument  
controller (Fluke 17XXA series), printer, or modem. All connections can be made using  
the Fluke RS-series of cables (see Options and Accessories in Chapter 1). RS-232 cables  
should not exceed 50 feet (15 meters) although longer cables are permitted if the load  
capacitance measured at a connection point (including signal terminator) does not  
exceed 2500 picofarads. The Fluke RS cables are 6 feet (1.83 meters) in length.  
Connections  
Figure G-1 summarizes the cable requirements for all typical RS-232 connections;  
Figure G2 through G6 summarize instrument cabling diagrams; Figure G7 shows the pin  
arrangement for DB-9 and DB-25 connectors. There are two wiring schemes (modem  
and null-modem), two types of connectors (DB-9 and DB-25), two cable end conditions  
(male and female), and two equipment configurations (Data Terminal Equipment [DTE]  
and Data Communications Equipment [DCE]). Because of variations in RS-232  
connectors, it is not possible to identify all possible configurations. In this application,  
“null-modem” refers to a reversing of the following lines; receive (RX) and transmit  
(TX), data terminal ready (DTR) and data set ready (DSR), and request to send (RTS)  
and clear to send (CTS). Not all interfaces use all lines. Check the documentation for the  
equipment you are interfacing with the instrument.  
Cables  
The Fluke RS-series of RS-232 cables are in the following standard configurations:  
RS40 - Null modem with DB-9/female and DB-25/female connectors  
RS41 - Modem with DB-9/female and DB-25/male connectors  
RS42 - Null modem with DB-9/female and DB-25/male connectors  
RS43 - Null modem with DB-9/female and DB-9/female connectors  
Cables from other sources may be used, or cables can be fabricated based on the figures  
in this appendix. The RS40 and RS42 cables are identical, except for the DB-25  
connectors (female and male, respectively). Some interfaces allow a selection of cables.  
F-1  
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2620A/2625A  
Users Manual  
For example, connection to a serial-to-parallel converter (when using a printer with a  
parallel input) may be as a DTE (cable RS42) or DCE (cable RS40).  
GENERIC  
(NULL MODEM)  
PC  
(DTE)  
HYDRA  
(DTE)  
RS43  
(DB-9/MALE)  
(DB-9/MALE)  
PC  
(DTE)  
HYDRA  
(DTE)  
RS40  
(DB-25/MALE)  
(DB-9/MALE)  
MODEM  
(DCE)  
(DB-25/FEMALE)  
HYDRA  
(DTE)  
(DB-9/MALE)  
RS41  
(MODEM)  
PRINTER  
(DTE)  
(DB-25/FEMALE)  
HYDRA  
(DTE)  
(DB-9/MALE)  
RS42  
RS42  
SERIAL-TO-PARALLEL  
(DTE)  
HYDRA  
(DTE)  
PRINTER  
PRINTER  
(DB-25/FEMALE)  
(DB-9/MALE)  
SERIAL-TO-PARALLEL  
(DCE)  
(DB-25/FEMALE)  
HYDRA  
(DTE)  
(DB-9/MALE)  
RS41  
(MODEM)  
KEY  
DTE – DATA TERMINAL EQUIPMENT  
DCE – DATA COMMUNICATIONS EQUIPMENT  
MALE  
FEMALE  
oo71f.eps  
Figure F-1. Summary of RS-232 Connections  
F-2  
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Appendices  
RS-232 Cabling  
F
RS43 CABLE  
(NULL MODEM)  
HYDRA  
PC  
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
DCD  
Rx  
Rx  
Tx  
Tx  
DTR  
GND  
DSR  
RTS  
CTS  
DTR  
GND  
DSR  
RTS  
CTS  
RI  
RS-232C  
DB-9  
DB-9  
COM  
KEY  
PINS  
DCD – DATA CARRIER DETECT  
Rx – RECEIVE  
FEMALE  
MALE  
Tx – TRANSMIT  
DTR – DATA TERMINAL READY  
GND – GROUND  
DSR – DATA SET READY  
RTS – REQUEST TO SEND  
CTS – CLEAR TO SEND  
RI – RING INDICATOR  
oo73f.eps  
Figure F-2. Hydra (DB-9) to PC (DB-9) RS-232 Connection (Generic)  
F-3  
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2620A/2625A  
Users Manual  
RS40 CABLE  
(OR EQUAL)  
PC  
1
2
Tx  
3
Rx  
4
RTS  
CTS  
DSR  
GND  
DCD  
5
6
7
HYDRA  
8
1
2
3
4
5
6
7
8
9
9
Rx  
Tx  
10  
11  
12  
13  
14  
15  
16  
17  
18  
19  
20  
21  
22  
23  
24  
25  
DTR  
GND  
DSR  
RTS  
CTS  
RS-232C  
DB-9  
DTR  
RI  
KEY  
PINS  
FEMALE  
Tx – TRANSMIT  
Rx – RECEIVE  
MALE  
RTS – REQUEST TO SEND  
CTS – CLEAR TO SEND  
DSR – DATA SET READY  
GND – GROUND  
DCD – DATA CARRIER DETECT  
DTR – DATA TERMINAL READY  
RI – RING INDICATOR  
DB-25  
COM  
oo74f.eps  
Figure F-3. Hydra (DB-9) to PC (DB-25) RS-232 Connection  
F-4  
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Appendices  
RS-232 Cabling  
F
RS41 CABLE  
(OR EQUAL)  
MODEM  
1
2
Tx  
3
Rx  
4
RTS  
CTS  
DSR  
GND  
DCD  
5
6
7
HYDRA  
8
1
2
3
4
5
6
7
8
9
9
Rx  
Tx  
10  
11  
12  
13  
14  
15  
16  
17  
18  
19  
20  
21  
22  
23  
24  
25  
DTR  
GND  
DSR  
RTS  
CTS  
RS-232C  
DB-9  
DTR  
RI  
KEY  
PINS  
FEMALE  
Tx – TRANSMIT  
Rx – RECEIVE  
MALE  
RTS – REQUEST TO SEND  
CTS – CLEAR TO SEND  
DSR – DATA SET READY  
GND – GROUND  
DB-25  
DCD – DATA CARRIER DETECT  
DTR – DATA TERMINAL READY  
RI – RING INDICATOR  
oo07f.eps  
Figure F-4. Hydra (DB-9) to Modem (DB-25) RS-232 Connection  
F-5  
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2620A/2625A  
Users Manual  
RS42 CABLE  
(OR EQUAL)  
PRINTER  
1
2
Tx  
Rx  
3
4
RTS  
5
CTS  
DSR  
GND  
DCD  
6
7
HYDRA  
8
1
2
3
4
5
6
7
8
9
9
Rx  
Tx  
10  
11  
12  
13  
14  
15  
16  
17  
18  
19  
20  
21  
22  
23  
24  
25  
DTR  
GND  
DSR  
RTS  
CTS  
RS-232C  
DB-9  
DTR  
RI  
KEY  
PINS  
FEMALE  
Tx – TRANSMIT  
Rx – RECEIVE  
MALE  
RTS – REQUEST TO SEND  
CTS – CLEAR TO SEND  
DSR – DATA SET READY  
GND – GROUND  
DB-25  
DCD – DATA CARRIER DETECT  
DTR – DATA TERMINAL READY  
RI – RING INDICATOR  
oo76f.eps  
Figure F-5. Hydra (DB-9) to Printer (DB-25) RS-232 Connection  
F-6  
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Appendices  
RS-232 Cabling  
F
6
7
8
9
6
5
SOLDER  
SIDE  
CONNECTOR  
SIDE  
1
2
3
4
5
MALE  
FEMALE  
9
8
7
CONNECTOR  
SIDE  
SOLDER  
SIDE  
5
4
3
2
1
DB-9  
CONNECTOR  
13 12 11 10  
9
8
7
6
4
3
2
1
SOLDER  
SIDE  
CONNECTOR  
SIDE  
25 24 23 22 21 20 19 18 17 16 15 14  
MALE  
FEMALE  
1
2
3
4
5
6
7
8
9
10 11  
13  
12  
CONNECTOR  
SIDE  
SOLDER  
SIDE  
14 15 16 17 18 19 20 21 22 23 24 25  
DB-25  
CONNECTOR  
oo77f.eps  
Figure F-6. RS-232 DB9 and DB-25 Connectors  
F-7  
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2620A/2625A  
Users Manual  
F-8  
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Hydra Configuration Record  
SET-UP NAME_________________________________________ DATE_________________________  
SCAN RATE:  
q Slow  
q Fast  
TEMPERATURE UNITS q °C q°F  
COMMUNICATION I/F q RS-232-C  
SCAN INTERVAL:_______ :_______: _______  
Baud Rate _______________________  
OUTPUT:  
q Printer  
q Memory  
Parity q Even  
Echo q On  
q IEEE-488  
Address__________________  
q
Odd  
Off  
q None  
q
Mode: q All Data  
q Alarm Data  
q Alarm Transition Data  
TRIGGERS:  
q Off q External  
q Monitor Alarm Ch# ____ Totalizer Debounce q On q Off  
Chan  
Input Name  
Type  
Range  
LIM 1  
Alarm  
LIM 2  
Alarm  
M
B
Output  
Output  
0
0
0
1
1
1
2
2
2
3
3
3
4
4
4
5
5
5
6
6
6
7
7
7
8
8
8
9
9
9
10  
11  
12  
13  
14  
15  
16  
17  
18  
19  
20  
10  
11  
12  
13  
14  
15  
16  
17  
18  
19  
20  
10  
11  
12  
13  
14  
15  
16  
17  
18  
19  
20  
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Index  
Channel integrity test, 6-7  
Character deletion, 4-8  
Character echoing, 4-8  
Cleaning, 6-3  
—2—  
2-wire accuracy, A-6, A-9  
Clearing memory, 4-7  
Common mode rejection, A-8  
Computer interface trigger control, 5-3  
Computer interface-initiated lockouts, 3-27  
Connections, 3-22  
—4—  
4-terminal resistance test, 6-10  
—A—  
Cross-talk rejection, A-6  
AC signal cross talk in a dc voltage channel, D-1  
AC signal cross talk into a frequency  
—D—  
DC volts, ac volts, frequency, and  
thermocouples, 3-18  
AC signal cross talk into an ac voltage  
channel, D-2  
Decoding the ascii string, E-1  
Dedicated alarm output test, 6-19  
Device clear using ctrl c, 4-8  
Digital input test, 6-16  
Digital input/output verification tests, 6-15  
Digital output test, 6-16  
AC signal cross talk into an ohms channel, D-2  
AC signal crosstalk into a temperature  
channel, D-3  
Accuracy verification test, 6-7  
Advanced trigger mechanisms, 5-3  
Alarm indications, 3-10  
Alarm limits, 3-9  
Autoprint, 3-25  
—E—  
computer interface control, 4-5  
output format, 4-5  
Autoprint and memory storage (RS-232), 4-5  
Enabling the IEEE-488 interface, 4-12  
Entering and changing numeric values, 3-14  
External trigger enabled (type 1), 5-4  
External trigger input test, 6-21  
External triggering, 3-16  
—B—  
Both external and monitor alarms disabled  
—F—  
Floating point conversion, E-3  
Front panel and computer interface  
—C—  
Cabling the instrument to a host or printer  
Front panel lock out conditions, 3-26  
Front panel monitor only function, 3-26  
Front panel review only function, 3-26  
Calibration, 3-27, 6-21  
Changing the temperature unit, 3-16  
Channel configuration, 3-4  
1
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2620A/2625A  
Users Manual  
Front panel trigger control, 5-3  
—R—  
Rate, A-12  
—G—  
REM annunciator, 3-27  
Resetting alarm conditions, 3-11  
Resistance, 3-7  
Resistance and RTD, 3-20  
Review array, 3-22  
General, 3-22  
General information (RS-232 and  
RS-232 information, 4-8  
RS-232 prompts, 4-9  
—H—  
How the instrument processes input, 4-13  
RTD temperature accuracy test, 6-14  
RTD temperature accuracy test (using decade  
resistance source), 6-14  
RTD temperature accuracy test (using DIN/IEC  
—I—  
IEEE-488 operating limitations, 4-9  
If power is interrupted, 3-4  
If the configuration is reset, 3-4  
Implementation of IEEE standard  
—S—  
Sample program using the RS-232 computer  
Input debouncing, A-12  
Input protection, A-9  
Input strings, 4-14  
Input terminators, 4-14  
Installing the IEEE-488 interface, 4-9  
Instrument configuration, 3-14  
Isolation, A-12  
Selecting the measurement rate, 3-15  
Self-test diagnostics and error codes, 6-3  
Sending numeric values to the instrument (RS-232  
and IEEE-488), 4-16  
Setting alarms, 3-9  
Setting communication parameters (RS-232), 4-4  
Setting date and time of day, 3-17  
—L—  
—T—  
Line fuse, 6-3  
Thermocouple measurement range accuracy test,  
List button functions, 3-23  
Thermocouple temperature accuracy test, 6-11  
Threshold, A-12  
Totalizer sensitivity test, 6-18  
Totalizing input, A-12  
Triggering, 3-16  
—M—  
Maximum autoranging time, A-12  
Measurement connections, 3-18  
Measurement rate, 5-3  
Memory full operation, 4-7  
Types of computer interface, 4-3  
Typical input strings, 4-14  
Memory storage, 3-25  
computer interface control, 4-6  
Mx+B scaling, 3-12  
—U—  
Using the IEEE-488 Interface, 4-9  
Using the RS-232 computer interface, 4-3  
—O—  
Operating modes, 3-3  
Other displayed data, 3-4  
—V—  
—P—  
Variations in the display, 6-22  
Performance tests, 6-4  
—W—  
What is the present configuration?, 3-4  
2
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