3M Microscope Magnifier 900AST User Manual

Advanced Systems  
Tester 900AST Series  
Coaxial Wire Testing  
Technical Tip  
December 2005  
78-8135-6156-6-A  
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3MAdvanced Systems Tester 900AST Series  
Keypad  
The 900AST tester keypad has twelve yellow and  
red “Control Keys” and nine blue “Function Keys”.  
Additional blue keys on the keypad are reserved for  
future expansion and have no designation or current  
function.  
Control Keys  
Use the red and yellow keys to control and setup the  
900AST tester and its functions.  
Use the [Return] key to return to a previous  
step in a function.  
Use the [Contrast] key to adjust the contrast  
or to turn the backlight on or off.  
Use the [Save] key for storing TDR traces.  
Use the [On/Off] key to turn the 900AST  
power on or off (also see “Power Down  
Timeout”).  
Use the [Tab] key to select between  
different options.  
Use the [Setup] key to change the setup of a  
function.  
Use the [Help] key to get context sensitive  
help with any screen or function.  
Use the [Enter] key to accept changes or  
move to the next step in a function. To  
insert a space to the left of the cursor press  
enter.  
Use the [Up] and [Down] keys to  
scroll to different menu options  
or insert/delete characters when  
editing.  
Use the [Left] and [Right] keys to  
select different options or move the  
TDR cursor  
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3MAdvanced Systems Tester 900AST Series  
Contrast and Backlighting  
Note: Use of backlight decreases available battery  
capacity.  
Press the  
key to display the contrast screen.  
Use the  
the  
and keys to adjust the contrast. Press  
key again to turn the backlight on or off.  
key to return to previous screen.  
Use the  
Function Keys  
Use the blue keys to select the different tests in the  
900AST tester. The blue keys become number or  
letter keys when editing.  
Use the [Voltage] key to measure DC or AC  
voltage.  
Use the [Load] key to measure the current  
through a simulated load lamp.  
Use the [Resistance] key to measure  
resistance and access the ‘Soak Test’ and  
‘Contact Resistance’ functions.  
Use the [Toolbox] key to access: Self  
Calibration, Stored Results, Special  
Resistance, and the Ohms to Distance  
Calculator  
Use the [Capacitance] key to measure the  
capacitance of a component or circuit.  
Use the [Tone] key to send interrupted tone  
for circuit identification.  
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3MAdvanced Systems Tester 900AST Series  
Use the [RFL] key to find the distance to a  
resistance fault between two conductors or a  
conductor and ground.  
This key is used for editing only.  
Use the [TDR] key to activate the Time  
Domain Reflectometer.  
Use the [Auto] key to activate automatic  
TDR trace analysis.  
CAUTION  
The 900AST tester is a tool for troubleshooting wiring  
problems. It is not designed for troubleshooting electronic  
circuits or instrumentation. The ohms, soak, contact  
resistance, special resistance and RFL functions  
generate a current limited (< 1 mA) 80V stimulus.  
TDR and Auto TDR functions generate high-energy  
electromagnetic pulses. Unexpected measurement  
results and/or damage are possible if applied to  
electronic circuits.  
Circuit testing should be performed by personnel trained  
in electrical safety practices and in accordance with  
applicable safety standards.  
Connecting to Coaxial Wires for Testing  
Ensure that electrical power has been removed and  
components disconnected from the wiring to be  
tested before beginning wiring tests.  
Note: For best operation, use the special coaxial  
TDR test leads supplied with your 900AST  
tester to perform coaxial wire TDR  
measurements.  
The TDR test cable has a standard male BNC  
connector on the end. Plug the opposite end of the  
TDR test leads plug into the Red/Black and/or Blue/  
Yellow test jacks on the 900AST tester (one or more  
cables may be used depending on the desired TDR  
mode.)  
Connect the end of the TDR test cable to the coaxial  
wire to be tested. Use a BNC adapter (if needed) to  
connect to the coaxial circuit under test.  
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3MAdvanced Systems Tester 900AST Series  
TDR Setup  
The TDR features a setup function that allows you to  
select the type of Coaxial wire to be tested.  
From the TDR Menu, press the  
enter the TDR Setup.  
Setup key to  
Press the  
select key and the  
and  
arrow  
keys to highlight coaxial cable for wire type.  
Use the  
box. Use the  
select key to move to the wire gauge  
and keys to highlight the type  
of coaxial cable to be tested and select ‘minimum  
possible’ or ‘last used’ initial measurement length  
setting.  
Note: The 900AST tester maintains modified Vp  
settings in internal memory. Press the  
key in the TDR Setup screen to restore  
original default Vp settings for all wire types.  
Use the blue numeric keys changes the velocity  
factor for the selected coaxial wire type or use the  
default setting.  
Press the enter key  
proceed.  
to accept changes and  
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3MAdvanced Systems Tester 900AST Series  
TDR Test Modes  
Press the  
mode.  
or  
keys to move to the desired  
Press the  
key to accept the highlighted mode  
and start the measurement.  
Single Trace  
Use the TDR Single Trace mode to test a single  
coaxial wire or circuit.  
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3MAdvanced Systems Tester 900AST Series  
Dual Trace  
Dual Trace is used to compare two coaxial circuits at  
the same time (usually a faulted and a good circuit).  
Connect the TDR test leads to the (Red and Black  
jacks) and connect the second TDR test lead set  
(Blue and Yellow jacks) to the reference circuit.  
This mode is valuable when testing a system with  
multiple coaxial wires serving the same system.  
Memory  
Memory mode is used to compare a circuit under  
test to a stored trace in memory. The first screen in  
memory mode will show a list of the ID numbers for  
all stored TDR traces. Use the  
and  
keys to  
highlight the desired stored result.  
Press the  
key to select the highlighted result and  
display the stored results list for that ID number by  
type (TDR), date and time.  
You can delete individual stored results by pressing  
the  
key.  
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3MAdvanced Systems Tester 900AST Series  
Use the  
stored result. Press the  
and  
keys to highlight the desired  
key to display the stored  
trace on the bottom of the TDR screen and the  
“live” trace on the top. You may move the cursor by  
using the  
and  
keys.  
The control settings for the stored trace can be  
viewed by pressing the  
or  
keys but the  
settings cannot be changed.  
The TDR Memory function includes a Difference  
(‘Diff’) control, accessible from the memory screen  
by pressing the  
Control OFF. Use the  
key. The default is Difference  
and arrow key to turn  
the Difference Control ON. Diff combines the live  
trace with the stored trace to show the difference in  
the two readings.  
Peak  
Use the TDR Peak mode to capture events that  
may be intermittent. The ‘live’ trace is displayed  
continuously. As a new maximum or minimum trace  
is detected, it will replace the previous one on the  
display.  
If the circuit being tested is stable (no intermittent  
faults), then the minimum, maximum and “live”  
traces should appear as a single trace.  
Note: If any of the control values are changed, the  
peak histories will be erased and new values  
will begin to display.  
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3MAdvanced Systems Tester 900AST Series  
Length allows you to set the distance (or span) from  
the left side of the screen to the right side. The left  
side of the screen is at the end of the BNC test lead  
and the right side is the farthest distance that can be  
displayed with the selected length  
Use the  
backward through the TDR controls. Use the  
and keys to change the parameters for the  
or  
keys to move forward or  
control selected.  
Available controls are Length, Filter, VP, Pulse, and  
Gain. Individual controls and their parameters are  
described in the 900AST Series Instruction Manual.  
Move Cursor  
Note: The 900AST tester automatically compensates  
for the length of the special TDR test leads.  
Zero distance is at the end of the test lead  
BNC male connector.  
Always place the cursor to the left side of an event  
to mark its location. Use the  
and  
arrow  
keys to move the cursor across the screen. The  
distance from the 900AST tester to the cursor is  
always shown in the center of the distance bar. The  
left side of the screen is at the end of the test leads,  
and the right side is the farthest distance that can be  
displayed with the selected length.  
TDR Save for Coaxial Wiring Comparison  
Approximately 200 TDR screenshots can be saved.  
You can save only the active “Single Trace” TDR  
screen.  
Select the TDR control parameters so the screen  
displays the trace as desired.  
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3MAdvanced Systems Tester 900AST Series  
Press the  
key.  
The 900AST tester will display the Save Results  
screen as follows:  
Use the blue keys to enter an alphanumeric ID. The  
ID may have up to twelve digits. Whether a number  
or letter is entered depends on how many times the  
key is pressed. As an example, if the Ohms key is  
pressed once, the number “3” will be displayed. If  
the same key is pressed twice, the letter “d” will be  
displayed.  
Use the  
arrow to position the cursor under the  
first space and enter the first character, and then  
use the  
space.  
arrow to move the cursor under the next  
cursor  
Insert the next character and use the  
again to position the cursor to the next position.  
Continue entering numbers or letters in this manner  
until all have been entered.  
Use  
To delete a character, press the  
Use to add a ‘dash’ in a record name.  
to insert a space to the left of the cursor.  
key.  
Once the ID has been entered, press the  
save the current TDR trace information.  
key to  
Event Recognition  
Events are the “dips” and “peaks” seen on the screen  
caused by faults or changes (such as an open circuit  
or short) on the conductor or pair. Connectors  
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3MAdvanced Systems Tester 900AST Series  
generally cause small upward peaks due to a change  
in impedance. To determine if an upward event is an  
impedance change or a main event fault you may go  
to the other end of the coaxial cable and disconnect  
it. Next, take a jumper and short the inner conductor  
to the outer shield. If you see a large downward  
deflection in the trace the small peak is impedance  
change. Conversely, if you can’t see the short or  
downward deflection you have an open circuit in the  
cable.  
Target Contact  
The first peak or dip on the screen is usually the  
“target contact” which occurs at the point where  
the 900AST tester connects to the circuit under test.  
Since impedances of the different types of coaxial  
conductors vary significantly, the initial event caused  
by the 100-ohm TDR launch circuit contacting  
the target can usually be ignored. Remember that  
distance zero (0”) begins at the end of the test leads  
for the TDR function. Should the dip after the initial  
peak move significantly below the line you may have  
a short at the shield termination point on the end  
of the cable. Move to the other end of the coaxial  
conductor and connect the tester leaving the first end  
open. The end of the trace should produce an upward  
deflection at the end of the cable. A downward  
deflection may indicate a short.  
Open Circuit  
Any open circuit will show up as a peak on the  
screen. A complete open will be the tallest peak you  
will see. You cannot see events past a complete open.  
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3MAdvanced Systems Tester 900AST Series  
Short Circuit  
A short circuit (or zero-Ohm resistance fault) will  
show up as the lowest dip on the screen. You cannot  
see events past a short circuit  
Branch Circuit  
The beginning of the branch circuit will look like  
a small dip and the end of the branch will look like  
an open (upward peak). Use the 900AST tester  
Resistance function to measure the resistance of  
the conductors. If the resistance is high, you may  
suspect a branch circuit.  
Resistance Faults on Coaxial Cable  
A resistance fault will show as a dip on screen. The  
lower the value of resistance (or the closer to a zero-  
ohm short), the lower the dip. Use the resistance  
function to check the coaxial cable for a resistive  
fault. Use the Soak test function to determine if the  
resistive fault is caused by moisture, corrosion or if  
it is purely resistive.  
Soak Test  
Use the Soak Test function to continuously measure  
the insulation resistance of a coaxial conductor inner  
conductor to shield.  
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3MAdvanced Systems Tester 900AST Series  
Connect the 900AST test leads to the coaxial  
conductor under test.  
Press the  
key to access the Soak test from the  
Resistance screen.  
Use the  
key to save the active resistance to the  
“Snap Shot” area.  
Rising resistance in the active box typically indicates  
moisture while falling resistance indicates corrosion.  
Auto TDR for Coaxial Fault Detection  
Use the Auto TDR function to have the 900AST  
tester analyze and interpret a TDR coaxial cable  
trace.  
The Auto TDR function imports the coaxial  
configuration selected in the TDR function using the  
Setup key.  
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3MAdvanced Systems Tester 900AST Series  
To change the coaxial configuration go to the TDR  
function and press the Setup key.  
Use the  
and  
keys and the Blue numeric  
keys to enter the length of cable to analyze. Enter a  
length longer than the cable being tested but as close  
as possible to the total length of the cable.  
When the correct information is displayed on the  
Auto TDR screen, press the  
key to start the  
analysis. The 900AST performs tests to determine  
if the cable is shorted, open circuited, or has a  
resistance fault.  
Note: Auto TDR operates from a captured trace.  
The trace is not ‘live’ as in the standard TDR  
mode.  
Auto TDR Resistive Faults  
Note: Resistance faults are very difficult to detect  
using TDR techniques. If a resistance fault  
is detected, the 900AST tester prompts you  
to consider using the RFL (Resistance Fault  
Locate) function as shown below.  
Auto TDR Trace Analysis  
If the Auto TDR detects an open circuit, the cursor  
is positioned at the location of the open circuit and  
OPEN is displayed below the trace. If the Auto  
TDR detects a short circuit or low resistance fault,  
the cursor is positioned at the location of the short  
circuit and SHORT is displayed below the trace.  
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3MAdvanced Systems Tester 900AST Series  
In this case the low impedance anomaly at 24  
inches is detected but not classified. The Auto TDR  
displays ‘????’ below the trace.  
Restoring the Aircraft After Testing/  
Troubleshooting  
Disconnect the 900AST TDR test cable from the  
aircraft wiring. Also, remove any adapters (if  
used). Ensure the other end of the coaxial cable is  
reconnected. Reinstall the line replaceable unit or  
component that was removed to accomplish testing  
or troubleshooting and perform all applicable  
maintenance manual procedures and operational  
checks.  
Care and Maintenance  
Please see the 900AST Series Instruction Manual for  
care and maintenance information.  
16  
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3MAdvanced Systems Tester 900AST Series  
This is the EU symbol for equipment that is covered  
under the Waste from Electrical and Electronic  
Equipment (WEEE) directive per CENELEC  
Specification 5041. It indicates that certain products  
should not be discarded in the trash, but rather  
should be recycled. This applies to all electronic  
pluggable and battery powered products.  
3M is a trademark of 3M Company.  
Important Notice  
All statements, technical information, and recommendations  
related to 3M’s products are based on information believed to  
be reliable, but the accuracy or completeness is not guaranteed.  
Before using this product, you must evaluate it and determine if  
it is suitable for your intended application. You assume all risks  
and liability associated with such use. Any statements related to  
the product which are not contained in 3M’s current publications,  
or any contrary statements contained on your purchase order  
shall have no force or effect unless expressly agreed upon, in  
writing, by an authorized officer of 3M.  
Warranty; Limited Remedy; Limited Liability.  
This product will be free from defects in material and manu-  
facture for a period of one (1) year from the time of pur-  
chase. 3M MAKES NO OTHER WARRANTIES INCLUDING,  
BUT NOT LIMITED TO, ANY IMPLIED WARRANTY OF  
MERCHANTABILITY OR FITNESS FOR A PARTICULAR  
PURPOSE. If this product is defective within the warranty period  
stated above, your exclusive remedy shall be, at 3M’s option, to  
replace or repair the 3M product or refund the purchase price of  
the 3M product. Except where prohibited by law, 3M will not  
be liable for any indirect, special, incidental or consequen-  
tial loss or damage arising from this 3M product, regardless  
of the legal theory asserted.  
Aerospace and Aircraft Maintenance Division  
Transportation Business  
3M Center, Building 220-9W-14  
St. Paul, MN 55144-1000  
1-800-364-3577 or 651-737-6501  
© 3M 2005  
78-8135-6156-6-A  
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