User Manual
1502C
Metallic Time-Domain Reflectometer
070-7169-05
This document applies for firmware version 5.04
and above.
www.tektronix.com
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WARRANTY
Tektronix warrants that the products that it manufactures and sells will be free from defects in materials and
workmanship for a period of one (1) year from the date of shipment. If a product proves defective during this
warranty period, Tektronix, at its option, either will repair the defective product without charge for parts and labor,
or will provide a replacement in exchange for the defective product.
In order to obtain service under this warranty, Customer must notify Tektronix of the defect before the expiration
of the warranty period and make suitable arrangements for the performance of service. Customer shall be
responsible for packaging and shipping the defective product to the service center designated by Tektronix, with
shipping charges prepaid. Tektronix shall pay for the return of the product to Customer if the shipment is to a
location within the country in which the Tektronix service center is located. Customer shall be responsible for
paying all shipping charges, duties, taxes, and any other charges for products returned to any other locations.
This warranty shall not apply to any defect, failure or damage caused by improper use or improper or inadequate
maintenance and care. Tektronix shall not be obligated to furnish service under this warranty a) to repair damage
resulting from attempts by personnel other than Tektronix representatives to install, repair or service the product;
b) to repair damage resulting from improper use or connection to incompatible equipment; c) to repair any
damage or malfunction caused by the use of non-Tektronix supplies; or d) to service a product that has been
modified or integrated with other products when the effect of such modification or integration increases the time
or difficulty of servicing the product.
THIS WARRANTY IS GIVEN BY TEKTRONIX IN LIEU OF ANY OTHER WARRANTIES, EXPRESS
OR IMPLIED. TEKTRONIX AND ITS VENDORS DISCLAIM ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. TEKTRONIX’
RESPONSIBILITY TO REPAIR OR REPLACE DEFECTIVE PRODUCTS IS THE SOLE AND
EXCLUSIVE REMEDY PROVIDED TO THE CUSTOMER FOR BREACH OF THIS WARRANTY.
TEKTRONIX AND ITS VENDORS WILL NOT BE LIABLE FOR ANY INDIRECT, SPECIAL,
INCIDENTAL, OR CONSEQUENTIAL DAMAGES IRRESPECTIVE OF WHETHER TEKTRONIX OR
THE VENDOR HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES.
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Contacting Tektronix
Phone
1-800-833-9200*
Address
Tektronix, Inc.
Department or name (if known)
14200 SW Karl Braun Drive
P.O. Box 500
Beaverton, OR 97077
USA
Web site
www.tektronix.com
Sales support
Service support
Technical support
1-800-833-9200, select option 1*
1-800-833-9200, select option 2*
Email: [email protected]
1-800-833-9200, select option 3*
1-503-627-2400
6:00 a.m. – 5:00 p.m. Pacific time
*
This phone number is toll free in North America. After office hours, please
leave a voice mail message.
Outside North America, contact a Tektronix sales office or distributor; see
the Tektronix web site for a list of offices.
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Table of Contents
General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Installation and Repacking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
vii
viii
Safety Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
xi
Operating Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Preparing to Use the 1502C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Front-Panel Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Menu Selections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Test Preparations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cable Test Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Additional Features (Menu Selected) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–1
1–1
1–5
1–6
1–7
1–8
1–12
1–14
1–29
Operator Tutorial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
What is the Tektronix 1502C? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
How Does It Do It? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
You, the Operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Menus and Help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Getting Started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Waveform Up Close . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A Longer Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ohms-at-Cursor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Set Ref (Delta Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VIEW INPUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
STORE and VIEW STORE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VIEW DIFF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Menu-Accessed Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TDR Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2–1
2–1
2–1
2–1
2–1
2–2
2–5
2–7
2–8
2–11
2–13
2–17
2–18
2–20
2–21
2–26
Options and Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Option 04: YT-1 Chart Recorder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Option 05: Metric Default . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Option 07: YT-1S Chart Recorder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Cord Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Test data record Option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Option DE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3–1
3–1
3–1
3–1
3–1
3–2
3–2
3–2
Appendix A: Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Environmental Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Certifications and Compliances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Physical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A–1
A–1
A–3
A–4
A–5
Appendix B: Operator Performance Checks . . . . . . . . . . . . . . . . . . . .
B–1
Appendix C: Operator Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . .
Error Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C–1
C–3
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Table of Contents
Appendix D: Application Note . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pulse Echo Testing of Electrical Transmission Lines
D–1
Using the Tektronix Time-Domain Reflectometry Slide Rule . . . . . . . . . . .
Terms and Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VSWR vs. Percent Reflected Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Return Loss (dB) vs. Percent Reflected Voltage . . . . . . . . . . . . . . . . . . . . . . . . .
Percent Reflected Voltage vs. Characteristic Line Impedance . . . . . . . . . . . . . .
Percent Reflected Voltage vs. Load Resistance . . . . . . . . . . . . . . . . . . . . . . . . . .
Characteristic Line Impedance or Load Resistance vs. Reflection Amplitude . .
Centimeters vs. Inches or Meters vs. Feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Dielectric Constant vs. Velocity Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Time vs. Short Distances, in Centimeters or Inches (any dielectric) . . . . . . . . . .
Time vs. Long Distances, in Meters or Feet (any dielectric) . . . . . . . . . . . . . . . .
D–1
D–1
D–2
D–2
D–3
D–4
D–6
D–6
D–7
D–8
D–8
D–9
Glossary
Index
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Table of Contents
List of Figures
Figure 1–1: Rear Panel Voltage Selector, Fuse, AC Receptacle . . . . .
1–2
1–3
1–5
1–6
Figure 1–2: Display Showing Low Battery Indication . . . . . . . . . . . . .
Figure 1–3: 1502C Front-Panel Controls . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–4: Display and Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–5: Vp Set at .30, Cursor Beyond Reflected Pulse
(Set Too Low) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–13
Figure 1–6: Vp Set at .99, Cursor Less Than Reflected Pulse
(Set Too High) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–13
Figure 1–7: Vp Set at .66, Cursor at Reflected Pulse
(Set Correctly) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–13
1–14
1–15
1–15
1–16
1–16
1–17
1–18
1–19
1–20
1–20
1–21
1–22
Figure 1–8: 20-ft Cable at 5 ft/div . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–9: Short in the Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–10: Open in the Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–11: 455-ft Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–12: 455-ft Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–13: Reflection Adjusted to One Division in Height . . . . . . .
Figure 1–14: Return Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–15: Ohms-at-Cursor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–16: Display with VIEW INPUT Turned Off . . . . . . . . . . . . .
Figure 1–17: Display of a Stored Waveform . . . . . . . . . . . . . . . . . . . . .
Figure 1–18: Display of a Stored Waveform . . . . . . . . . . . . . . . . . . . . .
Figure 1–19: Waveform Moved to Top Half of Display . . . . . . . . . . . .
Figure 1–20: Current Waveform Centered, Stored Waveform
Above . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–22
Figure 1–21: Current Waveform Center, Stored Waveform Above,
Difference Below . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–23
1–24
1–24
1–25
1–25
1–26
1–27
1–27
1–28
1–29
1–30
Figure 1–22: Waveform of Three-Foot Lead-in Cable . . . . . . . . . . . .
Figure 1–23: Cursor Moved to End of Three-Foot Lead-in Cable . . .
Figure 1–24: Cursor Moved to End of Three-Foot Lead-in Cable . . .
Figure 1–25: Cursor Moved to 0.00 ft . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–26: Incident Pulse at Three Divisions . . . . . . . . . . . . . . . . . .
Figure 1–27: Waveform of Short 75 ohm Cable . . . . . . . . . . . . . . . . . .
Figure 1–28: Waveform Centered and Adjusted Vertically . . . . . . . .
Figure 1–29: Cursor Moved to Desired Position . . . . . . . . . . . . . . . . .
Figure 1–30: Waveform Viewed in Normal Operation . . . . . . . . . . . .
Figure 1–31: Waveform Showing Intermittent Changes . . . . . . . . . . .
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Figure 1–32: Waveform Display with No Outgoing Pulses . . . . . . . . .
1–30
Figure 1–33: A Captured Single Sweep . . . . . . . . . . . . . . . . . . . . . . . . .
1–32
Figure 2–1: Display Showing 3-ft Cable in Start-Up Conditions . . . .
2–3
Figure 2–2: Cursor of Rising Edge of Reflected Pulse . . . . . . . . . . . . .
2–3
Figure 2–3: Waveform with VERT SCALE Increased Showing
an Open . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2–4
2–4
2–5
2–6
Figure 2–4: Waveform with Short . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 2–5: 3-foot Cable with Cursor at Far Left . . . . . . . . . . . . . . . .
Figure 2–6: 3-foot Cable with Cursor at Incident Pulse . . . . . . . . . . .
Figure 2–7: 3-foot Cable with Cursor at Incident Pulse, Vertical
Scale at 25 dB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2–6
2–7
Figure 2–8: Cursor on End of Longer Cable . . . . . . . . . . . . . . . . . . . .
Figure 2–9: Scrolling Down the Cable . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 2–10: Ohms-at-Cursor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 2–11: Ohms-at-Cursor Near Beginning of Cable . . . . . . . . . . .
Figure 2–12: Ohms-at-Cursor Beyond Reflected Pulse . . . . . . . . . . . .
Figure 2–13: Ohms-at-Cursor Beyond Reflected Pulse . . . . . . . . . . . .
Figure 2–14: Noise on the Waveform . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 2–15: Noise Reduced . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 2–16: Noise Reduced to Minimum . . . . . . . . . . . . . . . . . . . . . . .
Figure 2–17: Incident and Reflected Pulses with Cursor at 0.00 ft . .
Figure 2–18: Cursor at 3.000 ft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 2–19: New Zero Set at End of Test Cable . . . . . . . . . . . . . . . . .
2–8
2–9
2–9
2–10
2–10
2–11
2–12
2–12
2–13
2–14
2–14
Figure 2–20: Display with 3-ft Cable and NOISE FILTER turned to
VERT SET REF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2–15
Figure 2–21: VERT SCALE adjusted to Make Pulse Two Divisions
High . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2–16
2–17
2–17
2–18
2–19
2–19
2–20
2–21
2–22
2–22
2–24
2–25
Figure 2–22: Display with VIEW INPUT Turned Off . . . . . . . . . . . . .
Figure 2–23: Display with VIEW INPUT Turned On . . . . . . . . . . . . .
Figure 2–24: Waveform Moved to Upper Portion of the Display . . . .
Figure 2–25: Waveform with Cable Shorted . . . . . . . . . . . . . . . . . . . .
Figure 2–26: Waveform with Both Current and Stored Waveforms .
Figure 2–27: Stored, Current, and Difference Waveforms . . . . . . . . .
Figure 2–28: Display with VIEW STORE and VIEW DIFF Disabled
Figure 2–29: Short and Open Viewed via Max Hold . . . . . . . . . . . . . .
Figure 2–30: Waveform Strobed Down Display in Max Hold . . . . . .
Figure 2–31: Display with Pulse Turned Off . . . . . . . . . . . . . . . . . . . .
Figure 2–32: Test Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Table of Contents
Figure 2–33: Captured Single Sweep of Shorted Test Cable . . . . . . . .
2–25
B–2
B–3
B–3
B–4
B–4
B–5
B–5
B–6
B–6
B–8
Figure B–1: Start-up Measurement Display . . . . . . . . . . . . . . . . . . . . .
Figure B–2: Measurement Display with 3-foot Cable . . . . . . . . . . . . .
Figure B–3: Cursor at End of 3-foot Cable . . . . . . . . . . . . . . . . . . . . . .
Figure B–4: Cursor at End of 3-foot Cable, Vp Set to .30 . . . . . . . . . .
Figure B–5: Flat-Line Display Out to 50,0000+ Feet . . . . . . . . . . . . . .
Figure B–6: Flat-Line Display at –2.000 ft . . . . . . . . . . . . . . . . . . . . . .
Figure B–7: Waveform Off the Top of the Display . . . . . . . . . . . . . . . .
Figure B–8: Waveform at the Bottom of the Display . . . . . . . . . . . . . .
Figure B–9: Waveform with Gain at 5.00 mr/div . . . . . . . . . . . . . . . . .
Figure B–10: Top of Pulse on Center Graticule . . . . . . . . . . . . . . . . . .
Figure B–11: Rising Edge of Incident Pulse in Left-most Major
Division . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B–8
B–9
B–9
Figure B–12: Waveform Centered, Cursor at 0.000 ft . . . . . . . . . . . . .
Figure B–13: Pulse Centered on Display . . . . . . . . . . . . . . . . . . . . . . . .
Figure B–14: Cursor on Lowest Major Graticule that Rising Edge
crosses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B–10
Figure B–15: Cursor on Highest Major Graticule that Rising Edge
crosses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B–10
Figure B–16: Jitter Apparent on Leading Edge of Incident Pulse . . . B–11
Figure B–17: Jitter Captured Using Max Hold . . . . . . . . . . . . . . . . . . B–11
Figure D–1: Slide Rule of VSWR vs. Percent Reflected Voltage . . . .
D–2
Figure D–2: Slide Rule of Return Loss vs. Percent Reflected
Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
D–3
D–4
D–5
Figure D–3: Slide Rule 50 ohm Source . . . . . . . . . . . . . . . . . . . . . . . . .
Figure D–4: Slide Rule 75 ohm Source . . . . . . . . . . . . . . . . . . . . . . . . .
Figure D–5: Calculating Resistance/Impedance from Waveform
Amplitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
D–6
Figure D–6: English-Metric, Metric-English Conversion Scales . . . .
D–7
Figure D–7: Dielectric Constant and Velocity Factor, Short
Distance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
D–8
Figure D–8: Dielectric Constant and Velocity Factor, Long
Distance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
D–9
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Table of Contents
List of Tables
Table i: Shipping Carton Test Strength . . . . . . . . . . . . . . . . . . . . . . . .
ix
Table 1–1: Fuse and Voltage Ratings . . . . . . . . . . . . . . . . . . . . . . . . . .
1–2
Table 1–2: Vp of Various Dielectric Types . . . . . . . . . . . . . . . . . . . . . .
1–12
Table A–1: Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . .
Table A–2: Environmental Characteristics . . . . . . . . . . . . . . . . . . . . .
Table A–3: Physical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . .
A–1
A–3
A–5
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General Information
Product Description
The Tektronix 1502C Metallic Time-Domain Reflectometer (MTDR) is a
short-range cable tester capable of finding faults in metal cable. Tests can be
made on coaxial, twisted pair, or parallel cable.
The 1502C sends an electrical pulse down the cable and detects any reflections
made by discontinuities. This is known as time-domain reflectometry. The
1502C is sensitive to impedance changes. Problems in the cable will be detected
and displayed as changes in impedance along the cable. These will be displayed
as hills and valleys in the reflected pulse. The 1502C is capable of finding shorts,
opens, defects in the shield, foreign substances in the cable (e.g., water), kinks,
and more. Even though other instruments might show a cable as “good.” the
1502C can show many previously undetected faults.
The waveform may be temporarily stored within the 1502C and recalled or may
be printed using the optional dot matrix strip chart recorder, which installs into
the front-panel Option Port.
Battery Pack
Options
The 1502C may be operated from an AC power source or an internal lead-acid
battery that supply a minimum of five hours operating time (see the Specifica-
tions appendix for specifics).
Options available for the 1502C are explained in the Options and Accessories
chapter of this manual.
Standards, Documents,
and References Used
Terminology used in this manual is in accordance with industry practice.
Abbreviations are in accordance with ANSI Y1.1–19722, with exceptions and
additions explained in parentheses in the text. Graphic symbology is based on
ANSI Y32.2–1975. Logic symbology is based on ANSI Y32.14–1973 and
manufacturer’s data books or sheets. A copy of ANSI standards may be obtained
from the Institute of Electrical and Electronic Engineers, 345 47th Street, New
York, NY 10017.
Changes and History
Information
Changes that involve manual corrections and/or additional data will be incorpo-
rated into the text and that page will show a revision date on the inside bottom
edge. History information is included in any diagrams in gray.
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General Information
Installation and Repacking
Unpacking and Initial
Inspection
Before unpacking the 1502C from its shipping container or carton, inspect for
signs of external damage. If the carton is damaged, notify the carrier. The
shipping carton contains the basic instrument and its standard accessories. Refer
to the replaceable parts list in the Service Manual for a complete listing.
If the contents of the shipping container are incomplete, if there is mechanical
damage or defect, or if the instrument does not meet operational check require-
ments, contact your local Tektronix Field Office or representative. If the shipping
container is damaged, notify the carrier as well as Tektronix.
The instrument was inspected both mechanically and electrically before
shipment. It should be free if mechanical damage and meet or exceed all
electrical specifications. Procedures to check operational performance are in the
Performance Checks appendix. These checks should satisfy the requirements for
most receiving or incoming inspections.
Power Source and Power
Requirements
The 1502C is intended to be operated from a power source that will not apply
more than 250 volts 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 essential for safe operation.
The AC power connector is a three-way polarized plug with the ground (earth)
lead connected directly to the instrument frame to provide electrical shock
protection. If the unit is connected to any other power source, the unit frame
must be connected to earth ground.
Power and voltage requirements are printed on the back panel. The 1502C can be
operated from either 115 VAC or 230 VAC nominal line voltage at 45 Hz to
440 Hz, or a battery pack.
Further information on the 1502C power requirements can be found in the Safety
Summary in this section and in the Operating Instructions chapter.
Repacking for Shipment
When the 1502C is to be shipped to a Tektronix Service Center for service or
repair, attach a tag showing the name and address of the owner, name of the
individual at your firm who may be contacted, the complete serial number of the
instrument, and a description of the service required. If the original packaging is
unfit for use or is not available, repackage the instrument as follows:
1. Obtain a carton of corrugated cardboard having inside dimensions that are at
least six inches greater than the equipment dimensions to allow for cushion-
ing. The test strength of the shipping carton should be 275 pounds
(102.5 kg). Refer to the following table for test strength requirements:
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General Information
Table i: Shipping Carton Test Strength
Gross Weight (lb)
0 – 10
Carton Test Strength (lb)
200
275
375
500
600
11 – 30
31 – 120
121 – 140
141 – 160
2. Install the front cover on the 1502C and surround the instrument with
polyethylene sheeting to protect the finish.
3. Cushion the instrument on all sides with packing material or urethane foam
between the carton and the sides of the instrument.
4. Seal with shipping tape or an industrial stapler.
If you have any questions, contact your local Tektronix Field Office or represen-
tative.
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General Safety Summary
The safety information in this summary is for operating personnel. Specific
warnings and cautions will be found throughout the manual where they apply,
but might not appear in this summary. For specific service safety information,
see the 1502C Service Manual.
Safety Terms and Symbols
Terms in this manual:
WARNING. Warning statements identify conditions or practices that could result in
injury or loss of life.
CAUTION. Caution statements identify conditions or practices that could result in
damage to this product or other property.
Terms on the Product:
DANGER indicates an injury hazard immediately accessible as you read the
marking.
WARNING indicates an injury hazard not immediately accessible as you read the
marking.
CAUTION indicates a hazard to property including the product.
Symbols in the Manual:
WARNING or CAUTION
Information
Symbols on the Product:
Double
Insulated
DANGER
High Voltage
Protective Ground
(Earth) Terminal
ATTENTION
Refer to
Manual
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General Safety Summary
Power Source
This product is intended to operate from a power source that will not apply more
than 250 volts RMS between the supply conductors or between the supply
conductor and ground. A protective ground connection, by way of the grounding
conductor in the power cord, is essential for safe operation.
Grounding the Product
This product is grounded through the grounding conductor of the power cord. To
avoid electrical shock, plug the power cord into a properly wired receptacle
before connecting to the product input or output terminals. A protective ground
connection by way of the grounding conductor in the power cord is essential for
safe operation.
Danger Arising from Loss
of Ground
Upon loss of the protective-ground connection, all accessible conductive parts
(including knobs and controls that appear to be insulating) can render an electric
shock.
Use the Proper Power
Cord
Use only the power cord and connector specified for this product. Do not use this
instrument without a rated AC line cord.
The standard power cord (161-0288-00) is rated for outdoor use. All other
optional power cords are rated for indoor use only.
Use only a power cord that is in good condition.
Refer cord and connector changes to qualified service personnel.
Use the Proper Fuse
To avoid fire hazard, use only a fuse of the correct type.
Refer fuse replacement to qualified service personnel.
Do Not Operate in
Explosive Atmosphere
To avoid explosion, do not operate this product in an explosive atmosphere
unless it has been specifically certified for such operation.
Do Not Remove Covers or
Panels
To avoid personal injury, do not remove the product covers or panels. Do not
operate the product without the covers and panels properly installed.
Connecting Cables to the
Front-Panel BNC
To avoid possible damage to the front-end circuitry, connection of a cable that is,
or can be, driven by active circuitry should be avoided if the voltage could
exceed 400 V.
Disposal of Batteries
This instrument contains a lead-acid battery. Some states and/or local jurisdic-
tions might require special disposition/recycling of this type of material in
accordance with Hazardous Waste guidelines. Check your local and state
regulations prior to disposing of an old battery.
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General Safety Summary
Tektronix Factory Service will accept 1502C batteries for recycling. If you
choose to return the battery to us for recycling, the battery cases must be intact,
the battery should be packed with the battery terminals insulated against possible
short-circuits, and should be packed in shock-absorbant material.
Tektronix, Inc.
Attn: Service Department
P.O. Box 500
Beaverton, Oregon 97077 U.S.A.
For additional information, phone:1–800–TEK–WIDE
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Operating Instructions
Overview
Handling
The 1502C front panel is protected by a watertight cover, in which the standard
accessories are stored. Secure the front cover by snapping the side latches
outward. If the instrument is inadvertently left on, installing the front cover will
turn off the POWER switch automatically.
The carrying handle rotates 325° and serves as a stand when positioned beneath
the instrument.
Inside the case, at the back of the instrument, is a moisture-absorbing canister
containing silica gel. In extremely wet environments, it might be be necessary to
periodically remove and dry the canister. This procedure is explained in the
1502C Service Manual.
The 1502C can be stored in temperatures ranging from –62° C to +85° C if a
battery is not installed. If a battery is installed and the storage temperature is
below –35° C or above +65° C, the battery pack should be removed and stored
separately (see 1502C Service Manual for instructions on removing the battery).
Battery storage temperature should be between –35° C to +65° C.
Powering the 1502C
In the field, the 1502C can be powered using the internal battery. See Figure 1–1.
For AC operation, check the rear panel for proper voltage setting. The voltage
selector can be seen through the window of the protective cap. If the setting
differs from the voltage available, it can be easily changed. Simply remove the
protective cap and select the proper voltage using a screwdriver.
The 1502C is intended to be operated from a power source that will not apply
more than 250 V 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 essential for safe operation.
The AC power connector is a three-way polarized plug with the ground (earth)
lead connected to the instrument frame to provide electrical shock protection. If
the unit is connected to any other power source, the unit frame must be
connected to an earth ground. See Safety and Installation section.
CAUTION. If you change the voltage selector, you must change the line fuse to the
appropriate value as listed near the fuse holder and in the table below.
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Operating Instructions
REMOVE
CAP TO
REMOVE
CAP TO
SELECT
VOLTAGE
REPLACE
FUSE
Voltage
Selector
Line Fuse
AC Power
Cord Receptacle
Figure 1–1: Rear Panel Voltage Selector, Fuse, AC Receptacle
Table 1–1: Fuse and Voltage Ratings
Fuse Rating
250 V
Voltage Rating
Nominal Range
0.3 AT
115 VAC (90 – 132 VAC)
230 VAC (180 – 250 VAC)
0.15 AT
Care of the Battery Pack
CAUTION. Read these instructions concerning the care of the battery pack. They
contain instructions that reflect on your safety and the performance of the
instrument.
The 1502C can be powered by a rechargeable lead-gel battery pack that is
accessible only by removing the case from the instrument. When AC power is
applied, the battery pack is charged at a rate that is dependent on the battery
charge state.
The battery pack will operate the 1502C for a minimum of eight continuous
hours (including making 30 chart recordings) if the LCD backlight is turned off.
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Operating Instructions
Battery Charging
The battery pack will charge fully in 16 hours when the instrument is connected,
via the power cord, to an AC power source with the instrument turned off. The
instrument may be turned on and operated while the batteries are charging, but
this will increase the charging time. For longest battery life, a full charge is
preferred over a partial charge.
For maximum capacity, the batteries should be charged within a temperature
range of +20° C to +25° C. However, the batteries can be charged within a
temperature range of 0° C to +40° C and operated in temperatures ranging from
–10° C to +55° C.
CAUTION. Do not charge battery pack below 0° C or above +40° C. Do not
discharge battery pack below –10° C or above +55° C. If removing the battery
pack during or after exposure to these extreme conditions, turn the instrument off
and remove the AC power cord.
The battery pack should be stored within a temperature range of –35° C to
+65° C. However, the self-discharge rate will increase as the temperature
increases.
If the instrument is stored with the battery pack installed, the battery pack should
be charged every 90 days. A fully charged battery pack will lose about 12% of its
capacity in three to four months if stored between +20° C and +25° C.
Low Battery
If the battery is low, it will be indicated on the LCD (bat/low). If this is the case,
protective circuitry will shut down the 1502C within minutes. Either switch to
AC power or work very fast. If the instrument is equipped with a chart recorder,
using the recorder will further reduce the battery level, or the added load might
shut down the instrument.
bat/low
0.00 ft
O
N
Low Battery
Indicator
O
F
F
O
F
F
O
F
F
1 avg
500 mr
500 ft
Figure 1–2: Display Showing Low Battery Indication
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Operating Instructions
Protection circuits in the charger prevent deep discharge of the batteries during
instrument operation. The circuits automatically shut down the instrument
whenever battery voltage falls below approximately 10 V. If shutdown occurs,
the batteries should be fully recharged before further use.
NOTE. Turn the POWER switch off after instrument shutdown to prevent
continued discharge of the batteries.
Low Temperature
Operation
When the instrument is stored at temperatures below –10° C, voids might
develop in the liquid crystal display (LCD). These voids should disappear if the
instrument is placed in an ambient temperature ≥ +5° C for 24 hours.
When operating the 1502C in an environment below +10° C, a heater will
activate. The element is built into the LCD module and will heat the display to
permit normal operation. Depending on the surrounding temperature, it might
take up to 15 minutes to completely warm the crystals in the LCD. Once
warmed, the display will operate normally.
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Operating Instructions
Preparing to Use the 1502C
Check the power requirements, remove the front cover, and you are ready to test
cables. The following pages explain the front-panel controls.
8
7
9
METALLIC TDR
CABLE TESTER
Tektronix
1502C
POSITION
POSITION
MENU
ac
0.00 ft
10
VIEW
O
N
INPUT
11
12
13
VIEW
O
F
F
STORE
VIEW
DIFF
O
F
F
STORE
O
F
F
1 avg
0.2 ft
500 mr
DO NOT APPLY
EXT VOLTAGE
NOISE FILTER
VERT SCALE
DIST/DIV
Vp
.04
.03
.5
.4
.05
.06
.07
.08
.09
.6
.7
.3
POWER
.02
.01
.8
HORZ
(PULL ON)
.9
SET REF
VERT
.00
1
2
3
4
5
6
Figure 1–3: 1502C Front-Panel Controls
CAUTION. Do not connect live circuits to the CABLE connector. Voltages
exceeding 5 volts can damage the pulser or sampler circuits.
Bleed the test cable of any residual static charge before attaching it to the
instrument. To bleed the cable, connect the standard 50 W terminator and standard
female-to-female BNC connector together, then temporarily attach both to the
cable. Remove the connectors before attaching the cable to the instrument.
When testing receiving antenna cables, avoid close proximity to transmitters.
Voltages may appear on the cable if a nearby transmitter is in use, resulting in
damage to the instrument. Before testing, be sure that there are no RF voltages
present, or disconnect the cable at both ends.
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Operating Instructions
Display
Power
Type
Front-Panel to Cursor
Distance Window
Waveform
Cursor
ac
0.00 ft
View Input
Indicator
O
N
Grid
View Store
Indicator
O
F
F
View Difference
Indicator
O
F
F
Store
Indicator
O
F
F
1 avg
500 mr
0.2 ft
Selected
Noise Filter
Selected
Vertical Scale Distance per
Division
Selected
Figure 1–4: Display and Indicators
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Operating Instructions
Front-Panel Controls
1. CABLE: A female BNC connector for attaching a cable to the 1502C for
testing.
2. NOISE FILTER: If the displayed waveform is noisy, the apparent noise can
be reduced by using noise averaging. Averaging settings are between 1 and
128. The time for averaging is directly proportional to the averaging setting
chosen. A setting of 128 might take the instrument up to 35 seconds to
acquire and display a waveform. The first two positions on the NOISE
FILTER control are used for setting the vertical and horizontal reference
points. The selected value or function is displayed above the control on the
LCD.
NOISE FILTER
HORZ
VERT
SET REF
3. VERT SCALE: This control sets the vertical sensitivity, displayed in mr
per division, or the vertical gain, displayed in dB. Although the instrument
defaults to millirho, you may choose the preferred mode from the Setup
Menu. The selected value is displayed above the control on the LCD.
VERT SCALE
4. DIST/DIV: Determines the number of feet (or meters) per division across
the display. The minimum setting is 0.1 ft/div (0.025 meters) and the
maximum setting is 200 ft/div (50 meters). The selected value is displayed
above the control on the LCD.
DIST/DIV
A standard instrument defaults to ft/div. A metric instrument (Option 05)
defaults to m/div, but either may be changed temporarily from the menu. The
default can be changed by changing an internal jumper (see 1502C Service
Manual and always refer such changes to qualified service personnel).
5. Vp: The two Velocity of Propagation controls are set according to the
propagation velocity factor of the cable being tested. For example, solid
polyethylene commonly has a Vp of 0.66. Solid polytetraflourethylene
(Teflon ) is approximately 0.70. Air is 0.99. The controls are decaded: the
left control is the first digit and the right control is the second digit. For
example, with a Vp of 0.30, the first knob would be set to .3 and the second
knob to .00.
Vp
.4
.5
.04 .05
.03
.7 .02
.8
.3
.6
.9
.06
.07
.08
.09
.01
.00
6. POWER: Pull for power ON and push in for power OFF. When the front
POWER
(PULL ON)
cover is installed, this switch is automatically pushed OFF.
n
o
n
o
7.
8.
POSITION: This is a continuously rotating control that positions the
POSITION
POSITION
displayed waveform vertically, up or down the LCD.
POSITION: This is a continuously rotating control that moves a
vertical cursor completely across the LCD graticule. In addition, the
waveform is also moved when the cursor reaches the extreme right or left
side of the display. A readout (seven digits maximum) is displayed in the
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Operating Instructions
upper right corner of the LCD, showing the distance from the front panel
BNC to the current cursor location.
9. MENU: This pushbutton provides access to the menus and selects items
MENU
chosen from the menus.
10. VIEW INPUT: When pushed momentarily, this button toggles the display
of the waveform acquired at the CABLE connector. This function is useful to
stop displaying a current waveform to avoid confusion when looking at a
stored waveform. This function defaults to ON when the instrument is
powered up.
VIEW
INPUT
11. VIEW STORE: When pushed momentarily, this button toggles the display
VIEW
STORE
of the stored waveform.
12. VIEW DIFF: When pushed momentarily, this button toggles the display of
the current waveform minus the stored waveform and shows the difference
between them.
VIEW
DIFF
13. STORE: When pushed momentarily, the waveform currently displayed will
be stored in the instrument memory. If a waveform is already stored, pushing
this button will erase it. The settings of the stored waveform are available
from the first level menu under View Stored Waveform Settings.
STORE
Menu Selections
There are several layers of menu, as explained below.
Main Menu
The Main Menu is entered by pushing the MENU button on the front panel.
1. Return to Normal Operations puts the instrument into normal operation
mode.
2. Help with Instrument Controls explains the operation of each control.
When a control or switch is adjusted or pushed, a brief explanation appears
on the LCD.
3. Cable Information has these choices:
a. Help with Cables gives a brief explanation of cable parameters.
b. Velocity of Propagation Values displays a table of common dielectrics
and their Vp values. These are nominal values. The manufacturer’s listed
specifications should be used whenever possible.
c. Impedance Values displays impedances of common cables. In some
cases, these values have been rounded off. Manufacturer’s specifications
should be checked for precise values.
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Operating Instructions
d. Finding Unknown Vp Values describes a procedure for finding an
unknown Vp.
4. Setup Menu controls the manner in which the instrument obtains and
displays its test results.
a. Acquisition Control Menu has these choices:
i. Max Hold Is: On/Off. Turn Max Hold on by pushing MENU then
STORE. In this mode, waveforms are accumulated on the display. Max
Hold can be deactivated by pushing STORE or the mode exited by
using the Setup Menu.
ii. Pulse Is: On/Off. Turns the pulse generator off so the 1502C does not
send out pulses.
iii. Single Sweep Is: On/Off. This function is much like a still camera; it
will acquire one waveform and hold it.
b. Ohms-at-Cursor is: On/Off. When activated, the impedance at thee
point of the cursor is displayed beneath the distance window on the
display.
c. Vertical Scale Is: dB/mr. This offers you a choice as to how the vertical
gain of the instrument is displayed. You may choose decibels or millirho.
When powered down, the instrument will default to millirho when
powered back up.
d. Distance/Div Is: ft/m. Offers you a choice of how the horizontal scale is
displayed. You may choose from feet per division or meters per division.
When powered up, the instrument will default to feet unless the internal
jumper has been moved to the meters position. Instructions on changing
this default are contained in the 1502C Service Manual.
e. Light Is: On/Off. This control turns the electroluminescent backlight
behind the LCD on or off.
5. Diagnostics Menu lists an extensive selection of diagnostics to test the
operation of the instrument.
NOTE. The Diagnostics Menu is intended for instrument repair and calibration.
Proper instrument setup is important for correct diagnostics results. Refer to the
1502C Service Manual for more information on diagnostics.
a. Service Diagnostics Menu has these choices:
i. Sampling Efficiency Diagnostic displays a continuous efficiency
diagnostic of the sampling circuits.
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Operating Instructions
ii. Noise Diagnostic measures the internal RMS noise levels of the
instrument.
iii. Offset/Gain Diagnostic reports out-of-tolerance steps in the program-
mable gain stage. This can help a service technician to quickly isolate
the cause of waveform distortion problems.
iv. RAM/ROM Diagnostics Menu performs tests on the RAM (Random
Access Memory) and the ROM (Read Only Memory).
v. Timebase Is: Normal - Auto Correction / Diagnostic - No
Correction. When in Normal - Auto Correction, the instrument
compensates for variations in temperature and voltage. This condition
might not be desirable while calibrating the instrument. While in
Diagnostic - No Correction, the circuits will not correct for these
variations.
b. Front Panel Diagnostics aids in testing the front panel.
c. LCD Diagnostics Menu has these choices:
i. LCD Alignment Diagnostic generates a dot pattern of every other
pixel on the LCD. These pixels can be alternated to test the LCD.
ii. Response Time Diagnostic generates alternate squares of dark and
light, reversing their order. This tests the response time of the LCD and
can give an indication of the effectiveness of the LCD heater in a cold
environment.
iii. LCD Drive Test Diagnostic generates a moving vertical bar pattern
across the LCD.
iv. Contrast Adjust allows you to adjust the contrast of the LCD. It
generates an alternating four-pixel pattern. The nominal contrast is set
internally. When in Contrast Adjust mode, VERT SCALE is used as the
contrast adjustment control. This value ranges from 0 to 255 units and
is used by the processor to evaluate and correct circuit variations caused
by temperature changes in the environment. When the diagnostic menu
is exited, the LCD contrast returns to that set by internal adjust.
d. Chart Diagnostics Menu offers various tests for the optional chart
recorder.
i. LCD Chart allows adjusting the number of dots per segment and the
number of prints (strikes) per segment.
ii. Head Alignment Chart generates a pattern to allow mechanical
alignment of the optional chart recorder.
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Operating Instructions
6. View Stored Waveform Settings displays the instrument settings for the
stored waveform.
7. Option Port Menu contains three items. Two items allow configuration of
the option port for communicating with devices other than the optional chart
recorder and one item test the option port.
a. Option Port Diagnostic creates a repeating pattern of signals at the
option port to allow service technicians to verify that all signals are
present and working correctly.
b. Set Option Port Timing allows adjustment of the data rate used to
communicate with external devices. The timing rate between bytes can
be set from about 0.05 to 12.8 milliseconds.
c. Option Port Debugging Is Off/On. Off is quiet, On is verbose. This
chooses how detailed the error message reporting will be when
communicating with an external device.
It is possible to connect the instrument to a computer through a parallel
interface with a unique software driver. Because different computers vary
widely in processing speed, the instrument must be able to adapt to differing
data rates while communicating with those computers. With user-developed
software drivers, the ability to obtain detailed error messages during the
development can be very useful. For more information, contact your
Tektronix Customer Service representatives. They have information
describing the option port hardware and software protocol and custom
development methods available.
The SP-232, a serial interface product, also allows for connection of the
1502C to other instrumentation, including computers, via the option port.
SP-232 is an RS-232C-compatible interface. For more information, contact
your Tektronix Customer Service Representative. They can provide you with
additional details on the hardware and software protocol.
8. Display Contrast (Software Version 5.02 and above)
a. Press the MENU button firmly once. If the display is very light or very
dark, you might not be able to see a change in the contrast.
b. Turn the VERTICAL SCALE knob slowly clockwise to darken the
display or counterclockwise to lighten the display. If you turn the knob
far enough, the contrast will wrap from the darkest to lightest value.
c. When the screen is clearly readable, press the MENU button again to
return to normal measurement operation. The new contrast value will
remain in effect until the instrument is turned off.
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Operating Instructions
Test Preparations
The Importance of Vp
(Velocity of Propagation)
Vp is the speed of a signal down the cable given as a percentage of the speed of
light in free space. It is sometimes expressed as a whole number (e.g., 66) or a
percentage (e.g., 66%). On the 1502C, it is the percentage expressed as a decimal
number (e.g., 66% = .66). If you do not know the velocity of propagation, you
can get a general idea from the following table, or use the Help with Cables
section of the Cable Information menu. You can also find the Vp with the
procedure that follows using a cable sample.
NOTE. If you do not know the Vp of your cable, it will not prevent you from
finding a fault in your cable. However, if the Vp is set wrong, the distance
readings will be affected.
All Vp settings should be set for the cable under test, not the supplied jumper
cable.
Table 1–2: Vp of Various Dielectric Types
Dielectric
Probable Vp
Jelly Filled
.64
.66
.70
.72
.78
.84
.98
Polyethylene (PIC, PE, or SPE)
PTFE (Teflon R) or TFE
Pulp Insulation
Foam or Cellular PE (FPE)
Semi-solid PE (SSPE)
Air (helical spacers)
Finding an Unknown Vp
1. Obtain a known length of cable of the exact type you wish to test. Attach the
cable to the CABLE connector on the front panel.
2. Pull POWER on.
3. Turn the DIST/DIV to an appropriate setting (e.g., if trying to find the Vp of
a three-foot cable, turn the DIST/DIV to 1 ft/div).
4. Turn the
POSITION control until the distance reading is the same as the
known length of this cable.
5. Turn the Vp controls until the cursor is resting on the rising portion of the
reflected pulse. The Vp controls of the instrument are now set to the Vp of
the cable.
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Operating Instructions
The following three illustrations show settings too low, too high, and correct for
a sample three-foot cable.
ac
3.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 1–5: Vp Set at .30, Cursor Beyond Reflected Pulse (Set Too Low)
ac
3.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 1–6: Vp Set at .99, Cursor Less Than Reflected Pulse (Set Too High)
ac
3.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 1–7: Vp Set at .66, Cursor at Reflected Pulse (Set Correctly)
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Operating Instructions
Cable Test Procedure
Distance to the Fault
Be sure to read the previous paragraphs on Vp.
1. Set the 1502C controls:
POWER
On
CABLE
Cable to BNC
1 avg
500 mr
(see below)
(per cable)
NOISE FILTER
VERT SCALE
DIST/DIV
Vp
2. If you know approximately how long the cable is, set the DIST/DIV
appropriately (e.g., 20-ft cable would occupy four divisions on the LCD if
5 ft/div was used). The entire cable should be displayed.
ac
0.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 1–8: 20-ft Cable at 5 ft/div
If the cable length is unknown, set DIST/DIV to 200 ft/div and continue to
decrease the setting until the reflected pulse is visible. Depending on the cable
length and the amount of pulse energy absorbed by the cable, it might be
necessary to increase the VERT SCALE to provide more gain to see the reflected
pulse.
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Operating Instructions
ac
20.000 ft
O
N
O
F
F
Short
O
F
F
O
F
F
Figure 1–9: Short in the Cable
When the entire cable is displayed, you can tell if there is an open or a short.
Essentially, a large downward pulse indicates a short (see Figure 1–9), while a
large upward pulse indicates an open (see Figure 1–10). Less catastrophic faults
can be seen as smaller reflections. Bends and kinks, frays, water, and interweav-
ing all have distinctive signatures.
ac
20.000 ft
O
N
Open
O
F
F
O
F
F
O
F
F
Figure 1–10: Open in the Cable
3. To find the distance to the fault or end of the cable, turn the
POSITION
control until the cursor rests on the leading edge of the rising or falling
reflected pulse (see Figure 1–10). Read the distance in the distance window
in the upper right corner of the display.
A more thorough inspection might be required. This example uses a longer
cable:
4. When inspecting a 452-foot cable, a setting of 50 ft/div allows a relatively
fast inspection. If needed, turn VERT SCALE to increase the gain. The
higher the gain, the smaller the faults that can be detected. If noise increases,
increase the NOISE FILTER setting.
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Operating Instructions
ac
452.000 ft
O
N
Open
O
F
F
O
F
F
O
F
F
Figure 1–11: 455-ft Cable
5. Change DIST/DIV to 20 ft/div. The entire cable can now be inspected in
detail on the LCD. Turn the POSITION control so the cursor travels to
the far right side of the LCD. Keep turning and the cable will be “dragged”
across the display.
ac
452.000 ft
O
N
O
F
F
Short
O
F
F
O
F
F
Figure 1–12: 455-ft Cable
A “rise” or “fall” is a signature of an impedance mismatch (fault). A dramatic
rise in the pulse indicates and open. A dramatic lowering of the pulse indicates a
short. Variations, such as inductive and capacitive effects on the cable, will
appear as bumps and dips in the waveform. Capacitive faults appear as a
lowering of the pulse (e.g., water in the cable). Inductive faults appear as a rising
of the pulse (e.g., fray). Whenever an abnormality is found, set the cursor at the
beginning of the fault and read the distance to the fault on the distance window
of the LCD.
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Operating Instructions
Reflection Coefficient
Measurements
The reflection coefficient is a measure of the impedance change at a point in the
cable. It is the ratio of the signal reflected back from a point, divided by the
signal going into that point. It is designated by the Greek letter r and is written
in this manual as rho. The 1502C measures the reflection coefficient in millirho
(thousandths of a rho).
To measure a reflection, adjust VERT SCALE to make the reflection one
division high. Read the reflection coefficient directly off the display above the
VERT SCALE control. For reflections that are greater than 500 mr/div, adjust
VERT SCALE for a reflection that is two divisions high and multiply the VERT
SCALE reading by two.
ac
0.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 1–13: Reflection Adjusted to One Division in Height
In an ideal transmission system with no changes in impedance, there will be no
reflections, so rho is equal to zero. A good cable that is terminated in its
characteristic impedance is close to ideal and will appear as a flat line on the
1502C display.
Small impedance changes, like those from a connector, might have reflections
from 10 to 100 mr. If rho is positive, it indicates an impedance higher than that
of the cable before the reflection. It will show as an upward shift or bump on the
waveform. If rho is negative, it indicates an impedance lower than that of the
cable prior to the reflection. It will show as a downward shift or dip on the
waveform.
If the cable has an open or short, all the energy sent out by the 1502C will be
reflected. This is a reflection coefficient of rho = 1, or +1000 mr for the open
and –1000 mr for the short.
Long cables have enough loss to affect the size of reflections. In the 1502C, this
loss will usually be apparent as an upward ramping of the waveform along the
length of the cable. In some cases, the reflection coefficient measurement can be
corrected for this loss. This correction can be made using a procedure very
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Operating Instructions
similar to the Vertical Compensation for Higher Impedance Cable procedure (see
the VERT SET REF section).
Return Loss
Measurements
Return loss is another was of measuring impedance changes in a cable. Mathe-
matically, return loss is related to rho by the formula:
Return Loss (in dB) = –20 * log (base ten) of Absolute Value of Rho (Vref/Vinc)
The 1502C can be made to display in dB instead of mr/div through the menu:
1. Press MENU.
2. Select Setup Menu.
3. Press MENU again.
4. Select Vertical Scale is: Millirho.
5. Press MENU again. This should change is to Vertical Scale is: Decibels.
6. Press MENU twice to return to normal operation.
To measure return loss with the 1502C, adjust the height of the reflected pulse to
be two divisions high and read the dB return loss directly off the LCD. The
incident pulse is set to be two divisions high at zero dB automatically when the
instrument is turned on.
ac
0.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 1–14: Return Loss
A large return loss means that most of the pulse energy was lost instead of being
returned as a reflection. The lost energy might have been sent down the cable or
absorbed by a terminator or load on the cable. A terminator matched to the cable
would absorb most of the pulse, so its return loss would be large. An open or
short would reflect all the energy, so its return loss would be zero.
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Operating Instructions
Ohms-at-Cursor
The 1502C can compute and display what impedance mismatch would cause a
reflection as high (or low) as the point at the cursor. This measurement is useful
for evaluating the first impedance mismatch (first reflection) or small impedance
changes along the cable (e.g., connectors, splices).
This function can be selected in the Setup Menu. Once it is enabled, the
impedance value will be displayed under the distance in the distance window.
ac
2.800 ft
50 W
Ohms-at-Cursor
Readout
O
N
O
F
F
O
F
F
O
F
F
Figure 1–15: Ohms-at-Cursor
The accuracy of the difference measurement in impedance between two points
near each other is much better than the absolute accuracy of any single point
measurement. For example, a cable might vary from 51.3 W to 58.4 W across a
connector, the 7.1 W difference is accurate to about 2%. The 51.3 W measure-
ment by itself is only specified to be accurate to 10%.
The series resistance of the cable to the point at the cursor affects the accuracy of
the impedance measurement directly. In a cable with no large impedance
changes, the series resistance is added to the reading. For example, the near end
of a long 50 W coaxial cable might read 51.5 W, but increase to 57.5 W several
hundred feet along the cable. The 6 W difference is due to the series resistance of
the cable, not to a change in the actual impedance of the cable.
Another limitation to the ohms-at-cursor function is that energy is lost going
both directions through a fault. This will cause readings of points farther down
the cable to be less accurate than points nearer to the instrument.
In general, it is not wise to try to make absolute measurements past faults
because the larger the fault, the less accurate those measurements will be.
Although they do not appear as faults, resistive pads (often used to match cable
impedances) also affect measurements this way.
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Operating Instructions
Using VIEW INPUT
When pushed, the VIEW INPUT button displays the input at the front panel
CABLE connector. When VIEW INPUT is turned off and no other buttons are
pushed, the display will not have a waveform on it (see Figure 1–16). The
default condition when the instrument is powered up is to have VIEW INPUT
on.
ac
0.000 ft
O
F
F
O
F
F
O
F
F
O
F
F
Figure 1–16: Display with VIEW INPUT Turned Off
How to Store the
Waveform
When pushed, the STORE button puts the current waveform being displayed into
memory. If already stored, pushing STORE again will erase the stored wave-
form.
The front panel control settings and the menu-accessed settings are also stored.
They are accessed under View Stored Waveform Settings in the first level of the
menu.
ac
3.000 ft
O
N
O
F
F
O
F
F
O
N
Figure 1–17: Display of a Stored Waveform
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Operating Instructions
Using VIEW STORE
The VIEW STORE button, when pushed on, displays the waveform stored in the
memory as a dotted line. If there is no waveform in memory, a message appears
on the LCD informing you of this.
ac
3.000 ft
O
F
F
O
N
O
F
F
O
N
Figure 1–18: Display of a Stored Waveform
Using VIEW DIFF
When pushed on, the VIEW DIFF button displays the difference between the
current waveform and the stored waveform as a dotted line. If no waveform has
been stored, a message will appear. The difference waveform is made by
subtracting each point in the stored waveform from each point in the current
waveform.
NOTE. If the two waveforms are identical (e.g., if STORE is pushed and VIEW
DIFF is immediately pushed) the difference would be zero. Therefore you would
see the difference waveform as a straight line.
The VIEW DIFF waveform will move up and down with the current input as you
n
o
move the POSITION control. Any of the waveforms may be turned on or off
independently. You might want to turn off some waveforms if the display
becomes too busy or confusing.
NOTE. Because the stored waveform is not affected by changes in the instrument
controls, care should be taken with current waveform settings or the results
could be misleading.
One method to minimize the overlapping of the waveforms in VIEW DIFF is:
1. Move the waveform to be stored into the top half of the display.
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Operating Instructions
ac
3.000 ft
O
N
O
F
F
O
F
F
O
N
Figure 1–19: Waveform Moved to Top Half of Display
2. Push STORE to capture the waveform. Remember, once it is stored, this
waveform cannot be moved on the display.
3. Move the current waveform (the one you want to compare against the stored
waveform) to the center of the display.
4. Push VIEW STORE and the stored waveform will appear above the current
waveform.
ac
3.000 ft
O
N
O
N
O
F
F
O
N
Figure 1–20: Current Waveform Centered, Stored Waveform Above
5. Push VIEW DIFF and the difference waveform will appear below the current
waveform.
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Operating Instructions
Stored
Waveform
VIEW STORE
ac
3.000 ft
O
N
Current
Waveform
VIEW INPUT
O
N
O
N
O
Difference
N
VIEW DIFF
Figure 1–21: Current Waveform Center, Stored Waveform Above, Difference Below
Notice the VIEW INPUT waveform is solid, VIEW DIFF is dotted, and VIEW
STORE is dot-dash.
There are many situations where the VIEW DIFF function can be useful. One
common situation is to store the waveform of a suspect cable, repair the cable,
then compare the two waveforms after the repair. During repairs, the VIEW
INPUT, VIEW DIFF, and VIEW STORE waveforms can be used to judge the
effectiveness of the repairs. The optional chart recorder can be used to make a
chart of the three waveforms to document the repair.
Another valuable use for the VIEW DIFF function is for verifying cable integrity
before and after servicing or periodic maintenance that requires moving or
disconnecting the cable.
The VIEW DIFF function is useful when you want to see any changes in the
cable. In some systems, there might be several reflections coming back from
each branch of the network. It might become necessary to disconnect branch
lines from the cable under test to determine whether a waveform represents a
physical fault or is simply an echo from one of the branches. The STORE and
VIEW DIFF functions allow you to see and compare the network with and
without branches.
Two important things to be observed when using the VIEW DIFF function:
H
If you change either the VERT SCALE or DIST/DIV, you will no longer be
comparing features that are the same distance apart or of the same magnitude
on the display. It is possible to save a feature (e.g., a connector or tap) at one
distance down the cable and compare it to a similar feature at a different
n
distance by moving the
POSITION and POSITION controls.
o
H
When this is done, great care should be taken to make sure the vertical and
horizontal scales are identical for the two waveforms being compared. If
either the stored or current waveform is clipped at the top or bottom of the
display, the difference waveform will be affected.
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Operating Instructions
Using Horizontal Set
Reference
HORZ SET REF (D mode) allows you to offset the distance reading. For
example, a lead-in cable to a switching network is three feet long and you desire
to start the measurement after the end of the lead-in cable. HORZ SET REF
makes it simple.
ac
0.000 ft
O
N
O
F
F
O
F
F
End of
3-ft cable
O
F
F
Figure 1–22: Waveform of Three-Foot Lead-in Cable
1. Turn the NOISE FILTER control to HORZ SET REF. The noise readout on
the LCD will show: set D.
2. Turn the
POSITION control to set the cursor where you want to start the
distance reading. This will be the new zero reference point. For a three-foot
lead-in cable, the cursor should be set at 3.00 ft.
ac
3.000 ft
O
N
O
F
F
O
F
F
move cursor to reference and Press STORE
O
F
F
Figure 1–23: Cursor Moved to End of Three-Foot Lead-in Cable
3. Push STORE.
4. Turn the NOISE FILTER control to 1 avg. The instrument is now in HORZ
SET REF, or delta mode. The distance window should now read 0.00 ft. As
the cursor is scrolled down the cable, the distance reading will now be from
the new zero reference point.
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Operating Instructions
ac
0.000 ft D
O
N
O
F
F
O
F
F
O
F
F
Figure 1–24: Cursor Moved to End of Three-Foot Lead-in Cable
NOTE. Vp changes will affect where the reference is set on the cable. Be sure to
set the Vp first, then set the delta to the desired location.
5. To exit HORZ SET REF, use the following procedure:
a. Turn the NOISE FILTER control to HORZ SET REF.
b. Turn DIST/DIV to .1 ft/div. If the distance reading is extremely high,
you might want to use a higher setting initially, then turn to .1 ft/div for
the next adjustment.
c. Turn the
POSITION control until the distance window reads 0.00 ft.
ac
0.000 ft
O
N
O
F
F
O
F
F
move cursor to reference and Press STORE
O
F
F
Figure 1–25: Cursor Moved to 0.00 ft
d. Push STORE.
e. Turn NOISE FILTER to desired setting.
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Operating Instructions
Using Vertical Set
VERT SET REF works similar to HORZ SET REF except that it sets a reference
for gain (pulse height) instead of distance. This feature allows zeroing the dB
scale at whatever pulse height is desired.
Reference
1. Turn NOISE FILTER fully counterclockwise. “Set Ref” will appear in the
noise averaging area of the LCD.
2. Adjust the incident pulse to the desired height (e.g., four divisions). It might
n
o
be necessary to adjust POSITION.
ac
0.000 ft
O
N
O
F
F
O
F
F
set vertical scale and press STORE
O
F
F
Figure 1–26: Incident Pulse at Three Divisions
3. Push STORE.
4. Return NOISE FILTER to the desired setting. Notice that the vertical scale
now reads 500 mr/div.
NOTE. The millirho vertical scale will not be in calibration after arbitrarily
adjusting the pulse height.
The millirho scale is the reciprocal of the number of divisions high the pulse has
been set. For example, 1 pulse divided by 3 divisions equals 0.25 mr equals
250 mr/div.
Vertical Compensation for
Higher Impedance Cable
When testing cables other than 50W, this procedure allows reflection measure-
ments in millirho.
1. Attach a short sample of the given cable (75 W in this example) to the
instrument.
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ac
19.200 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 1–27: Waveform of Short 75 ohm Cable
2. Adjust the
POSITION control to position the reflected pulse at center
screen.
3. Turn NOISE FILTER to VERT SET REF.
4. Adjust VERT SCALE so the reflected pulse (from open at far end of cable
sample) is two divisions high.
ac
19.200 ft
O
N
O
F
F
O
F
F
set vertical scale and press STORE
O
F
F
Figure 1–28: Waveform Centered and Adjusted Vertically
5. Press STORE.
6. Return NOISE FILTER to the desired setting.
7. Adjust the
POSITION control to the desired position on the waveform to
measure loss.
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Operating Instructions
ac
1.840 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 1–29: Cursor Moved to Desired Position
The instrument is now set to measure reflections in millirho relative to the
sample cable impedance.
To measure reflections on a 50 W cable, the VERT SET REF must be reset.
8. To exit VERT SET REF, use the following procedure:
a. Turn NOISE FILTER to VERT SET REF.
b. Adjust VERT SCALE to obtain an incident pulse height of two
divisions.
c. Push STORE.
d. Turn NOISE FILTER to desire filter setting.
The instrument can be turned off and back on to default to the two division pulse
height.
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Operating Instructions
Additional Features (Menu Selected)
Max Hold
The 1502C will capture and store waveforms on an ongoing basis. This is useful
when the cable or wire is subjected to intermittent or periodic conditions. The
1502C will monitor the line and display any fluctuations on the LCD.
1. Attach the cable to the 1502C front-panel CABLE connector.
2. Push MENU to access the main menu.
3. Scroll to Setup Menu and push MENU again.
4. Scroll to Acquisition Control Menu and push MENU again.
5. Scroll to Max Hold is: Off and push MENU again. This line will change to
Max Hold is: On. The monitoring function is now ready to activate.
6. Repeatedly push MENU until the instrument returns to normal operation.
ac
0.000 ft
O
N
O
F
F
Figure 1–30: Waveform Viewed in Normal Operation
7. When you are ready to monitor this cable for intermittents, push STORE.
The 1502C will now capture any changes in the cable.
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Operating Instructions
ac
0.000 ft
O
N
Captured
changes
O
N
Figure 1–31: Waveform Showing Intermittent Changes
8. To exit monitor mode, push STORE again.
9. To exit Max Hold, access the Acquisition Control Menu again, turn off Max
Hold, and push MENU repeatedly until the instrument returns to normal
operation.
Pulse On/Off
This feature puts the 1502C in a “listening mode” by turning off the pulse
generator.
1. Attach a cable to the 1502C front-panel CABLE connector.
2. Push MENU to access the Main Menu.
3. Scroll to Setup Menu and push MENU again.
4. Scroll to Acquisition Control Menu and push MENU again.
5. Scroll to Pulse is: On and push MENU again. This will change to Pulse is:
Off.
ac
0.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 1–32: Waveform Display with No Outgoing Pulses
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Operating Instructions
6. Repeatedly press MENU until the instrument returns to normal operation.
CAUTION. This function is used mostly for troubleshooting by qualified techni-
cians. It is not recommended that you use the 1502C as a stand-alone monitor-
ing device. The input circuitry is very sensitive and can be easily damaged by
even moderate level signals.
NOTE. In this mode, the 1502C is acting as a detector only. Any pulses detected
will not originate from the instrument, so any distance readings will be invalid.
If you are listening to a local area network, for example, it is possible to detect
traffic, but not possible to measure the distance to its origin.
Pulse is: Off can be used in conjunction with Max Hold is: On.
7. To exit Pulse is: Off, access the Acquisition Control Menu again, turn the
pulse back on, then repeatedly push MENU until the instrument returns to
normal operation.
Single Sweep
The single sweep function will acquire one waveform only and display it.
1. Attach a cable to the 1502C front-panel CABLE connector.
2. Push MENU to access the Main Menu.
3. Scroll to Setup Menu and push MENU again.
4. Scroll to Acquisition Control Menu and push MENU again.
5. Scroll to Single Sweep is: Off and push MENU again. This will change to
Single Sweep is: On.
6. Repeatedly press MENU until the instrument returns to normal operation.
7. When you are ready to begin a sweep, push VIEW INPUT. A sweep will
also be initiated when you change any of the front-panel controls. This
allows you to observe front panel changes without exiting the Single Sweep
mode.
As in normal operation, averaged waveforms will take longer to acquire.
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Operating Instructions
ac
0.000 ft
O
F
F
O
F
F
O
F
F
O
F
F
Figure 1–33: A Captured Single Sweep
8. To exit Single Sweep is: On, access the Acquisition Control Menu again, turn
the Single Sweep back off, then repeatedly push MENU until the instrument
returns to normal operation.
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Operator Tutorial
This chapter will show, step by step, the features and uses of the 1502C.
What is the Tektronix 1502C?
The Tektronix 1502C Metallic Time-Domain Reflectometer is a short range
metallic cable tester capable of finding faults in metal cable. Tests can be made
on coaxial cable, twisted pair, or parallel cable.
How Does It Do It?
The 1502C sends an electrical pulse down the cable and receives reflections back
made by any discontinuities. This is known as time-domain reflectometry. The
1502C is sensitive to impedance changes. Problems in the cable will be detected
and displayed as changes in impedance along the cable. These will be displayed
as hills and valleys in the reflected pulse. The 1502C is capable of finding shorts,
opens, defects in the shield, foreign substances in the cable (e.g., water), kinks,
and more. Even though other instruments might show a cable as good, the
1502C can show many previously hidden faults.
You, the Operator
The 1502C is a highly accurate cable tester. It is easy to use and will provide
fast, accurate measurements. Because of electrical and environmental differences
in cables and their applications, each waveform will likely differ. The best way
to learn these differences is experience with the instrument. You are the 1502C’s
most important feature.
Experiment with different cables in known conditions and see how they
compare. Subject cables to situations you might find in your application and
learn the effects. We have included some examples of cable faults in this manual
to help you gain familiarity. With practice, you will quickly become familiar
with even the most subtle differences in waveforms, thereby increasing the value
of the 1502C in locating problems.
Menus and Help
The 1502C is equipped with various help screens. Simply press MENU for
assistance. The instrument will prompt you. More information on MENU is
located in the Operating Instructions chapter of this manual.
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Getting Started
Let’s start by inspecting a cable. For the next few examples, we will use the
3-foot precision test cable provided with the 1502C (Tektronix part number
012–1350–00).
1. Pull on the POWER switch. The instrument will initialize, give instructions
for accessing the menu, and enter normal operation mode.
2. Set the 1502C front-panel controls to:
CABLE
Attach 3-ft cable
NOISE FILTER
VERT SCALE
DIST/DIV
Vp
1 avg
500 mr (default)
1 ft/div (0.25 m if using metric)
.66
NOTE. Vp (velocity of propagation) of the test cable is important for making
accurate distance measurements. If you do not know the Vp factor of a cable,
distance readings will be directly affected. You can get a general idea from the
table on page 1–12 or find the Vp with a sample piece of cable using the
procedure on page 1–12, or use the Cable Information Menu. If it is impossible
to obtain the Vp of the cable, the instrument will still show cable faults, but the
distance readings might be erroneous. The test cable used in this tutorial has a
Vp of .66.
VERT SCALE will already be set to 500 mr (default). The cursor will be near
the leading edge of the incident pulse (at the point on the waveform representing
the front panel). Other information displayed includes the type of power used (ac
or bat) and the distance window in the upper right corner of the LCD displays
the distance from the front panel to the cursor (0.000 ft in this case). This data
will be displayed when the instrument is turned on. Switch status and other
instrument functions are also displayed (see Figure 1–4 on page 1–6 for
descriptions).
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ac
0.000 ft
O
N
O
F
F
Figure 2–1: Display Showing 3-ft Cable in Start-Up Conditions
3. The rising pulse on the left is the test pulse (incident pulse) leaving the
instrument. The rising reflected pulse on the right displays the echo coming
back. Turn the
POSITION control clockwise until the cursor rests on the
rising edge of the reflected pulse.
ac
3.000 ft
O
N
Reflected
Pulse
O
F
F
Incident
Pulse
O
F
F
O
F
F
Figure 2–2: Cursor of Rising Edge of Reflected Pulse
The upper right corner should read 3.000 ft. Note that the reflected pulse
rises. This is the classic signature of an open cable, a point of higher
impedance.
4. Adjust the VERT SCALE control. This will increase the height of the pulse.
For accurate measurements, the pulse should occupy most of the display.
Note that the LCD shows the VERT SCALE setting in mr. For now, set this
control to 354 mr/div.
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ac
3.000 ft
O
N
Open
O
F
F
O
F
F
O
F
F
Figure 2–3: Waveform with VERT SCALE Increased Showing an Open
n
5. The POSITION control moves the waveform up and down the display.
o
Adjust this for best viewing.
6. Short the end of the cable with an electrical clip or other suitable device. See
the pulse take a dive? That is the classic signature of a short, a point of lower
impedance.
ac
3.000 ft
O
N
O
F
F
Short
O
F
F
O
F
F
Figure 2–4: Waveform with Short
The distance window still reads 3.000 ft. If the short is not directly across the
conductors of the BNC (e.g., needle nose pliers) the downward edge of the
waveform might be slightly past the cursor, indicating the length of the
shorting device (e.g., jumper wire).
7. Remove the short.
With a little practice, you will be able to identify many kinds of cable faults.
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The Waveform Up Close
It helps to know what makes up a pulse. Here is the waveform anatomy using the
3-foot test cable as an example:
1. Turn the
POSITION control counterclockwise until the distance window
reads –2.000 ft. The cursor will be on the far left side of the display and the
reflected pulse will be near center.
2. Set the 1502C front-panel controls:
CABLE
3-ft test cable, no short
NOISE FILTER
VERT SCALE
DIST/DIV
Vp
1 avg
500 mr
1 ft (0.25 m)
.66
3. The first (left) step is the incident pulse, as sent from the pulse generator (see
Figure 2–5). The second step is the reflected pulse, as it bounces back from
the end of the cable. The reflected pulse and the time between pulses
provides the information needed for calculating the distance between faults
or the end of the cable.
ac
–2.000 ft
O
N
Reflected
Pulse
O
F
F
Incident
Pulse
O
F
F
O
F
F
Figure 2–5: 3-foot Cable with Cursor at Far Left
4. Adjust the
POSITION control so the cursor is at the beginning of the rise
of the incident pulse. Note the distance window reads approximately
–0.520 ft. This is the distance from the front panel BNC connector to the
pulse generator circuit board inside the instrument (where the test pulse in
generated).
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ac
–0.520 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 2–6: 3-foot Cable with Cursor at Incident Pulse
5. Adjust the VERT SCALE control to approximately 25 mr. Adjust the
n
o
POSITION control to keep the middle portion of the pulse on the display.
The bumps following the incident pulse are the aberrations from the internal
circuitry and reflections between the open end of the cable and the front
panel.
ac
–0.520 ft
O
N
Front-panel
Connector
O
F
F
O
F
F
O
F
F
Figure 2–7: 3-foot Cable with Cursor at Incident Pulse, Vertical Scale at 25 dB
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A Longer Cable
Longer cables might not fit in the display. Let’s demonstrate that with a longer
cable.
Obtain a known length of 50 W cable. For this example, we are using a coaxial
cable approximately 452 feet long. Your cable length will probably differ, but the
following test procedure remains fundamentally correct for any cable length up
to 2,000 feet.
1. Set the 1502C front-panel controls:
CABLE
available longer cable
1 avg
500 mr
50 ft (25 m)
appropriate setting for your cable
NOISE FILTER
VERT SCALE
DIST/DIV
Vp
2. With these settings, we can view the entire cable. By placing the cursor at
the rise of the reflected pulse, we can see this particular cable is 452.000 ft.
ac
452.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 2–8: Cursor on End of Longer Cable
3. By decreasing the DIST/DIV control, the cable can be more closely
inspected at the point of the cursor. Decrease the DIST/DIV to 10 ft/div. This
has expanded the cable across the display.
4. Turn the
POSITION control counterclockwise. Note that the distance
window changes as you scroll down the cable. In reality, you are electrically
inspecting the cable, foot by foot.
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ac
362.800 ft
Cursor
O
N
O
F
F
Cable Scrolling
in this direction
O
F
F
O
F
F
Figure 2–9: Scrolling Down the Cable
NOTE. When testing a long cable, it is helpful to set DIST/DIV to a higher setting
when scrolling to either end of the cable. For example, if testing a 1,500-ft cable,
it would be very tiring to scroll the entire length from end to end at 1 ft/div.
Ohms-at-Cursor
Using the long cable as an example, we can find the impedance at the cursor.
1. Set the 1502C front-panel controls:
CABLE
available longer cable
1 avg
500 mr
50 ft (25 m)
.66 (or whatever your cable is)
NOISE FILTER
VERT SCALE
DIST/DIV
Vp
2. Press MENU.
3. Scroll to Setup Menu and press MENU again.
4. Scroll to Ohms at Cursor is: Off and press Menu. This line will then change
to Ohms at Cursor is: On.
5. Press MENU repeatedly until the instrument returns to normal operation
mode.
6. Turn the
POSITION control to set the cursor near the end of the cable as
illustrated (see Figure 2–10).
In our example, you see the distance reading is 408.000 feet and the
ohms-at-cursor is 59.5 W. The ohms-at-cursor tells you that the loss in the
cable results in an impedance measurement of 59.5 W. You may then assume
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50 W impedance plus 9.5 W series resistance. You can check this by putting a
known reference on the end of the cable and measuring its impedance with
ohms-at-cursor. The difference between the actual reading and the expected
reference reading is the series resistance.
ac
408.000 ft
59.5 W
Ohms-at-Cursor
Readout
O
N
O
F
F
O
F
F
O
F
F
Figure 2–10: Ohms-at-Cursor
7. Turn the POSITION control to set the cursor near the beginning of the
cable. In this example, the ohms-at-cursor reading is 50.9 W at 17.880 feet.
There is less loss at the beginning of the cable because there is less series
resistance.
ac
17.880 ft
50.9 W
O
N
O
F
F
O
F
F
O
F
F
Figure 2–11: Ohms-at-Cursor Near Beginning of Cable
8. Turn the
POSITION control clockwise to set the cursor past the reflected
pulse. Note that the ohms-at-cursor reading is ≥1 kW.
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ac
578.000 ft
>=1 K W
O
N
O
F
F
O
F
F
O
F
F
Figure 2–12: Ohms-at-Cursor Beyond Reflected Pulse
9. Turn the
POSITION control to move the cursor to the far left side of the
display (–2.000 ft). Note that the ohms-at-cursor reading is now < 1 W.
–2.000 ft
ac
< 1 W
O
N
O
F
F
O
F
F
O
F
F
Figure 2–13: Ohms-at-Cursor Beyond Reflected Pulse
If the cursor is placed too near a fault, the reflection will not have stabilized,
which will make the ohms-at-cursor reading misleading. This is especially true
very near the instrument where some aberrations are still significant. See the
Ohms-at-Cursor section of the Operating Instructions chapter for more on the
limitations of this feature.
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Noise
On a longer cable, “grass” might appear on the displayed waveform. This is
primarily caused by the cable acting as an antenna, picking up nearby electrical
noise.
1. Set the 1502C front-panel controls:
CABLE
3-ft cable
1 avg
500 mr
1 ft (0.25 m)
.66
NOISE FILTER
VERT SCALE
DIST/DIV
Vp
POSITION
40.000 ft
2. Attach the 50 W terminator to the end of the test cable using the female-to-
female BNC adaptor (both of these items are supplied with the instrument).
n
3. Increase VERT SCALE to 1.00 mr. Use the POSITION control to keep
o
the waveform on the display. As the VERT SCALE setting increases, there
will be noise in the form of a moving, fuzz-like waveform with a few
random spikes.
ac
40.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 2–14: Noise on the Waveform
4. Turn the NOISE FILTER control clockwise to 8. This will average out much
of the noise.
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ac
40.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 2–15: Noise Reduced
5. Increase the NOISE FILTER setting to 128.
NOTE. The higher the setting, the more time the instrument takes to average the
waveform.
ac
40.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 2–16: Noise Reduced to Minimum
n
6. Move the POSITION control and notice how averaging restarts at a low
o
value to allow easy positioning.
The 50 W terminator was used here because it gives a good impedance match.
Because there are no large discontinuities, it appears to the instrument as an
endless cable. The noise seen in this demonstration is noise picked up on the
cable and a tiny amount of internal noise in the 1502C. When testing cables, the
noise filter is extremely effective in reducing noise.
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Set Ref (Delta Mode)
HORZ SET REF
Horizontal Set Reference establishes the starting point at which the distance
window begins reading the distance to the cursor. If, for example, you have a
3-foot cable leading to a patch panel, you could eliminate this jumper from your
distance readings.
1. Set the 1502C front-panel controls to:
CABLE
Attach 3-ft cable
1 avg
500 mr (default)
1 ft/div (0.25 m)
NOISE FILTER
VERT SCALE
DIST/DIV
NOTE. If the POWER was left on from the previous step, return the distance
window reading to 0.000 ft with the
POSITION control.
ac
0.000 ft
O
N
O
F
F
O
F
F
move cursor to reference and Press STORE
O
F
F
Figure 2–17: Incident and Reflected Pulses with Cursor at 0.00 ft
2. Turn the NOISE FILTER control counterclockwise to HORZ SET REF. The
noise filter reading on the LCD will indicate set D.
3. Adjust the
POSITION control so the cursor is on the rising edge of the
reflected pulse. In this case, the distance window should read 3.000 ft.
4. Press STORE.
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ac
3.000 ft
O
N
O
F
F
O
F
F
return FILTER to desire setting . . .
O
F
F
Figure 2–18: Cursor at 3.000 ft
5. Turn the NOISE FILTER control to 1 avg. Note that the distance window
now reads 0.00 ftD. This means that everything from the front panel BNC to
the end of the cable is subtracted from the distance calculations. You have set
zero at the far end of the test cable.
ac
0.000 ft
D
O
N
O
F
F
O
F
F
O
F
F
Figure 2–19: New Zero Set at End of Test Cable
6. To change the HORZ SET REF position, turn the NOISE FILTER back to
HORZ SET REF and repeat the above procedure with a new cursor location.
7. To exit HORZ SET REF, do the following:
a. Set the
POSITION control to exactly 0.00 ft (you might have to set
DIST/DIV to .1 ft/div).
b. Push STORE.
c. Turn the NOISE FILTER control to the desired noise setting.
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VERT SET REF
This control is nearly the same as HORZ SET REF except it sets the vertical
zero reference. It would be helpful to read the section of VERT SET REF in the
Operating Instructions chapter to give you some technical background.
The VERT SET REF function allows manual control of the vertical calibration
of the 1502C. This can be used to compensate for cable loss or to increase the
resolution of the millirho scale. The following example shows how to compen-
sate for cable loss.
The reflection from an open or a short at the far end of a long cable is often less
than two divisions high at 500 mr/div. This is because of the energy lost in the
cable. Here is how to correct for this loss and be able to make accurate measure-
ments at the far end of the cable.
1. Connect the test cable.
2. Create a short across the far end of the cable.
3. Turn the NOISE FILTER all the way counterclockwise to VERT SET REF.
A prompt will appear and the LCD will indicate set ref.
ac
0.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 2–20: Display with 3-ft Cable and NOISE FILTER turned to VERT SET REF
4. Adjust the VERT SCALE control until the reflection from the short is two
divisions high.
5. Push STORE.
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ac
0.000 ft
O
N
O
F
F
O
F
F
return FILTER to desired setting ...
O
F
F
Figure 2–21: VERT SCALE adjusted to Make Pulse Two Divisions High
6. Return NOISE FILTER to the desired setting.
The vertical scale now reads 500 mr/div.
Return-loss measurements at the far end of the cable (or a similar cable in that
bundle) can now be made using normal methods. To make measurements closer
or farther from the instrument requires that you reset the VERT SET REF.
NOTE. Care must be taken in changing the VERT SET REF because of the
calibration change. The 1502C automatically starts the pulse at two divisions
high. When you change the vertical reference, you essentially defeat this
function.
7. To change the VERT SET REF, turn the noise filter back to VERT SET REF
and repeat the preceding procedure.
8. If you wish to totally exit VERT SET REF, do the following:
a. Turn NOISE FILTER to VERT SET REF.
b. Turn VERT SCALE for a pulse two divisions high.
c. Push STORE.
d. Return the NOISE FILTER control to the desired setting.
This function can also be exited by turning the instrument power off and
back on again. The automatic function will adjust the pulse to two divisions
high.
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VIEW INPUT
This push button allows you to view what is coming in the CABLE connector, or
to eliminate it from the display.
1. Set the 1502C front-panel controls to:
CABLE
Attach 3-ft cable
1 avg
500 mr
NOISE FILTER
VERT SCALE
DIST/DIV
1 ft/div (0.25 m)
2. Press VIEW INPUT. The indicator block on the LCD should read OFF and
the waveform should disappear from the display.
ac
0.000 ft
O
F
F
O
F
F
O
F
F
O
F
F
Figure 2–22: Display with VIEW INPUT Turned Off
3. Press VIEW INPUT again. The indicator block will reappear and the
waveform should be displayed again.
ac
0.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 2–23: Display with VIEW INPUT Turned On
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This function can be used to make the display less busy when viewing stored
waveforms.
STORE and VIEW STORE
These functions allow you to store a waveform and view the stored waveform.
1. Set the 1502C front-panel controls to:
CABLE
Attach 3-ft cable
NOISE FILTER
VERT SCALE
DIST/DIV
1 avg
500 mr
1 ft/div (0.25 m)
n
2. Make sure you have a waveform on the LCD, then adjust the POSITION
o
control to place the waveform in the upper section of the display.
ac
0.000 ft
O
N
O
F
F
O
F
F
O
N
Figure 2–24: Waveform Moved to Upper Portion of the Display
3. Press STORE. The indicator block should become highlighted (black) and
read ON. The waveform is now stored in non-volatile memory in the
instrument.
4. Turn the POWER off for a few seconds, then turn it back on. Note that the
STORE indicator block is ON, showing that there is a waveform in memory.
5. Short the connector at the far end of the test cable. The reflected pulse will
invert from the previous open position.
n
6. Adjust the POSITION control to place the waveform in the middle portion
o
of the LCD.
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ac
0.000 ft
O
N
O
F
F
O
F
F
O
N
Figure 2–25: Waveform with Cable Shorted
7. Press VIEW STORE to view the stored waveform. What you see on the
display is the waveform you stored previously with the open cable and the
current waveform with the shorted cable.
Stored Waveform
VIEW STORE
ac
0.000 ft
O
N
Current Waveform
VIEW INPUT
O
N
O
FF
F
F
O
N
Figure 2–26: Waveform with Both Current and Stored Waveforms
Comparing new cables with old cables, or repaired cables with damaged cables
is easy using these two pushbuttons.
Leave the instrument in this condition for the next lesson.
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VIEW DIFF
Press VIEW DIFF. This adds a waveform in the lower portion of the display that
is the mathematical difference between the stored waveform and the current
waveform.
ac
0.000 ft
O
N
O
N
O
O
F
N
O
N
Difference
VIEW DIFF
Figure 2–27: Stored, Current, and Difference Waveforms
NOTE. There must be a waveform stored before it can be compared by the VIEW
DIFF function. Pressing this button with no waveform in storage will caused an
error message to be displayed.
If the stored waveform and the current waveform are identical, the difference
waveform will appear as a straight line.
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Menu-Accessed Functions
NOTE. If you get lost or confused while in a menu, repeatedly press the MENU
button until the instrument returns to normal operation mode.
Max Hold
1. Set the 1502C front-panel controls to:
CABLE
Attach 3-ft cable
1 avg
500 mr (default)
1 ft/div (0.25 m)
NOISE FILTER
VERT SCALE
DIST/DIV
2. Pull POWER on.
3. Press MENU to access the Main Menu.
n
4. Using the POSITION control, scroll down to Setup Menu.
o
5. Press MENU to accept this selection.
6. Scroll down to Acquisition Control Menu.
7. Press MENU to accept this selection.
8. Scroll down to Max Hold is: Off.
9. Press MENU to toggle this selection. It should now read Max Hold is: On.
The Max Hold function is now ready.
10. Read the instructions on the display and press MENU again.
11. Press MENU again to exit the Acquisition Control Menu.
12. Press MENU again to exit the Setup Menu.
ac
0.000 ft
O
N
O
F
F
Figure 2–28: Display with VIEW STORE and VIEW DIFF Disabled
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13. Press MENU again to enter normal operations mode. Note that the VIEW
STORE and VIEW DIFF indicator blocks have disappeared. This tells you
that both of these functions have been disabled.
14. Press STORE. This activates the Max Hold function. Notice that the STORE
indicator block has darkened.
15. With a clip lead or other device, short the far end of the test cable, then
remove the short. Note that both conditions now appear on the display.
ac
0.000 ft
O
N
O
N
Figure 2–29: Short and Open Viewed via Max Hold
n
16. Turn the POSITION control counterclockwise. THe waveform will strobe
o
down the display, leaving traces of its movement.
ac
0.000 ft
O
N
O
N
Figure 2–30: Waveform Strobed Down Display in Max Hold
17. Press STORE. The display will clear, awaiting STORE to be pressed again,
which would activate another Max Hold monitor cycle.
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You can probably see how this function is useful for monitoring lines for
changes over a period of time, or for intermittent conditions. For example:
H
H
A coastal phone line only has problems during high tide. Overnight
monitoring reveals water in the line during the high tide period.
A data communications line is monitored for an intermittent short. Three
days of monitoring reveals the shorts occur only during the hours of
darkness. Rodents are found in the cable ducts.
H
A cable becomes defective only during daytime hours. Monitoring reveals
the line length increases (sags) during the heat of the day, shorting out on a
tree limb. During the night, the cable cools, tightens, and is no longer
shorted on the tree limb.
18. To exit Max Hold, access the Acquisition Control Menu again, turn off Max
Hold, and push MENU repeatedly until the instrument returns to normal
operation.
Pulse On / Off
1. Set the 1502C front-panel controls to:
CABLE
Attach 3-ft cable
1 avg
500 mr (default)
1 ft/div (0.25 m)
NOISE FILTER
VERT SCALE
DIST/DIV
2. Pull POWER on.
3. Press MENU to access the Main Menu.
n
4. Using the POSITION control, scroll down to Setup Menu.
o
5. Press MENU to accept this selection.
6. Scroll down to Acquisition Control Menu.
7. Press MENU to accept this selection.
8. Scroll down to Pulse is: On.
9. Press MENU to toggle this selection. It should now read Pulse is: Off.
10. Press MENU repeatedly until the instrument returns to normal operation
mode.
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ac
0.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 2–31: Display with Pulse Turned Off
CAUTION. This function is used mostly for troubleshooting by qualified techni-
cians. It is not recommended that you use the 1502C as a stand-alone monitor-
ing device. The input circuitry is very sensitive and can be easily damaged by
even moderate level signals.
11. To turn the pulse back on, enter the Acquisition Control Menu again, scroll
to Pulse is: Off and press MENU to turn the pulse back on. Repeatedly press
MENU until the instrument returns to normal operation.
Single Sweep
1. Set the 1502C front-panel controls to:
CABLE
Attach 3-ft cable
1 avg
500 mr (default)
1 ft/div (0.25 m)
NOISE FILTER
VERT SCALE
DIST/DIV
2. Pull POWER on.
3. Press MENU to access the Main Menu.
n
4. Using the POSITION control, scroll down to Setup Menu.
o
5. Press MENU to accept this selection.
6. Scroll down to Acquisition Control Menu.
7. Press MENU to accept this selection.
8. Scroll down to Single Sweep is: Off.
9. Press MENU to toggle this selection. It should now read Single Sweep is:
On.
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10. Press MENU repeatedly until the instrument returns to normal operation.
The waveform on the display is the familiar test cable.
ac
0.000 ft
O
N
O
F
F
O
F
F
O
N
Figure 2–32: Test Cable
11. Short the far end of the test cable.
12. Press VIEW INPUT. The 1502C has done a single sweep, capturing just one
frame.
ac
0.000 ft
O
N
O
F
F
O
F
F
O
N
Figure 2–33: Captured Single Sweep of Shorted Test Cable
13. Remove the short and notice that the waveform does not change.
14. Press VIEW INPUT again and a new sweep will be made and displayed,
showing the change in the cable.
Single Sweep is useful for snap-shot tests of the cable, capturing only one
waveform.
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15. To exit Single Sweep, access the Acquisition Control Menu again, toggle the
Single Sweep is: line back to Off, then push the MENU button repeatedly
until the instrument returns to normal operations.
TDR Questions and Answers
Q1: What does TDR stand for?
A1: Time-Domain Reflectometer.
Q2: What is the difference between time domain and frequency domain?
A2: Within the time domain, things are expressed in units of time (e.g.,
nanoseconds). In frequency domain, things are expressed in frequency,
cycles per second (e.g., kiloHertz).
Q3: What does a TDR actually measure?
A3: Voltage over time.
Q4: How does a TDR display this information?
A4: Voltage on the vertical axis (as amplitude of the waveform) and time on the
horizontal axis (as distance to the event).
Q5: Does electricity travel the same speed (velocity) in all materials?
A5: No. Electricity is like light; its velocity is affected by the material through
which it passes.
Q6: What is that difference called?
A6: The relative velocity of propagation (Vp). The velocity of the cable is
expressed in time/distance (e.g., feet per nanosecond). The velocity of
electricity traveling in a vacuum is compared to the velocity of electricity
traveling in a cable. This relationship is shown as a decimal number. A
relative propagation velocity of .50 would mean the electricity will travel at
50%, or one-half, as fast as it would in a vacuum.
Q7: If a reflection takes 30 nanoseconds to return in a cable with a Vp of .66, how
far away is the point on the cable that caused the reflection?
A7: The one-way time would be 30 divided by 2, or 15 nanoseconds. The velocity
of 1 ns/ft in a vacuum would mean a distance of 15 feet. Because the cable
is slower, we multiply the distance by the Vp (.66 in this case) and arrive at
a distance of 10 feet. Of course, the 1502C does all this automatically and
displays the information on the LCD.
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Q8: What is resistance?
A8: Resistance is the opposition to DC current flow, or DC voltage divided by DC
current.
Q9: What is impedance?
A9: Impedance is the total opposition (resistance plus reactance) a circuit offers
to the flow of alternating current at a given frequency.
Q10: What factors determine the resistance of a cable?
A10: The cross sectional area (gauge), length, and the type of material the
conductor is made of (usually copper).
Q11: What factors determine the impedance of a cable?
A11: Dielectric value of the insulation and geometry of the conductors.
Q12: Why should cables of the same impedance be used?
A12: Because a mismatch of impedance means a loss of energy at the mismatch.
Q13: Why is that important to us?
A13: Because a TDR displays the energy reflected back from an impedance
mismatch.
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Options and Accessories
The following options are available for the 1502C MTDR:
Option 04: YT-1 Chart Recorder
Option 04 instruments come equipped with a chart printer. Refer to the YT-1/
YT-1S Chart Recorder Instruction Manual that comes with this option for
instructions on operation, paper replacement, and maintenance. Refer to the
table on the following page for manual part numbers.
Option 05: Metric Default
Option 05 instruments will power up in the metric measurements mode.
Standard measurements may be selected from the menu, but metric will be the
default.
Option 07: YT-1S Chart Recorder
Option 07 instruments come equipped with a splashproof chart printer. Refer to
the YT-1/ YT-1S Chart Recorder Instruction Manual that comes with this option
for instructions on operation, paper replacement, and maintenance. Refer to the
table on the following page for manual part numbers.
Power Cord Options
The following power cord options are available for the 1502C TDR. Note that
these options require inserting a 0.15 A fuse in the rear panel fuse holder.
NOTE. The only power cord rated for outdoor use is the standard cord included
with the instrument (unless otherwise specified). All other optional power cords
are rated for indoor use only.
Option A1
Option A2
Option A3
Option A4
Option A5
220 VAC, 16 A, Universal Europe
240 VAC, 13 A, United Kingdom
240 VAC, 10 A, Australia
161-0066-09
161-0066-10
161-0066-11
161-0066-12
161-0154-00
240 VAC, 15 A, North America
240 VAC, 6 A, Switzerland
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Options and Accessories
Test Data Record Option
This option provides the test data record obtained during the Performance
Verification of the instrument and is limited to the primary characteristics of this
instrument type.
Option DE
German language firmware Tektronix part number 160-8999-xx.
Accessories
Standard Accessories
Internal Lead-gel Battery Assembly
Replacement Fuse (AC line fuse, 115 VAC)
Replacement Fuse (AC line fuse, 230 VAC)
Power Cord (outdoor rated)
016-0915-00
159-0029-01
159-0054-00
161-0228-00
200-3737-00
012-1350-00
011-0123-00
103-0028-00
003-0700-00
062-8344-xx
016-0814-00
070-7169-xx
Option Port Cover Assembly
Precision 50 W Test Cable (S/N ≥B010298)
50 W BNC Terminator
BNC Connector, female-to-female
Slide Rule Calculator
Slide Application Note (bound in this manual)
Accessory Pouch
Operator Manual
Optional Accessories
Service Manual
070-7168-xx
040-1276-00
119-3616-00
070–6270–xx
006-7647-00
006-7677-00
006-7681–00
103-0029-00
013-0261-00
013-0076-01
Battery Kit
Chart Recorder, YT-1S
Chart Recorder, YT-1S Service manual.
Chart Paper, single roll
Chart Paper, 25-roll pack
Chart Paper, 100-roll pack
Connector, BNC male to BNC male
Connector, BNC female to Alligator Clip (S/N ≥B010298)
Connector, BNC female to Hook-tip Leads
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Options and Accessories
Connector, BNC female to Dual Banana Plug
Connector, BNC male to Dual Binding Post
Connector, BNC male to N female
Connector, BNC female to N male
Connector, BNC female to UHF male
Connector, BNC female to UHF female
Connector, BNC female to Type F male
Connector, BNC male to Type F female
Connector, BNC female to GR
Connector, BNC male to GR
103-0090-00
103-0035-00
103-0058-00
103-0045-00
103-0015-00
103-0032-00
103-0158-00
013-0126-00
017-0063-00
017-0064-00
011-0102-00
015-0327-00
017-0091-00
017-0092-00
017-0900-00
012-0671-02
Terminator, 75 W BNC
Adapter, Direct Current
Adapter, 50/75 W *
Adapter, 50/93 W *
Adapter, 50/125 W *
Interconnect Cable, 108 inch
*
These adapters should be purchased if GR connectors (Tektronix part numbers
017-0063-00 and/or 017-0064-00) are purchased.
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Appendix A: Specifications
The tables in this chapter list the characteristics and features that apply to this
instrument after it has had a warm-up period of at least five minutes.
The Performance Requirement column describes the limits of the Characteristic.
Supplemental Information describes features and typical values or other helpful
information.
Electrical Characteristics
Table A–1: Electrical Characteristics
Characteristic
Excitation Pulse
Reflected Pulse
Aberrations
Performance Requirement
Supplemental Information
≤200 ps (0.096 feet)
Vp set to 0.99; 10 to 90%, into a precision short
Excluding front panel aberrations
5% peak within 0 to 10 feet after rise
0.5% peak beyond 10 feet
Jitter
≤0.02 feet (≤40 ps) peak-to-peak
Vp set to 0.99, DIST/DIV set to 0.1 ft/div
At 23.4 feet to 46.8 feet, jitter is ≤0.04 feet.
Output Impedance
Pulse Amplitude
Pulse Width
Pulse Repetition Time
Vertical
50 W 2%
After risetime stabilizes into 50 W termination
300 mV nominal into 50 W load
25 ms nominal
200 ms nominal
Scales
0.5 mr/div to 500 mr/div, >240 values
Within 3% of full scale
Includes 1, 2, 5 sequences
Accuracy
Set Adj
Set incident pulse within 3%
Combined with VERT SCALE control
Vertical Position
Any waveform point is moveable to center
screen
Displayed Noise
5 mr peak or less, filter set to 1
2 mr peak or less, filter set to 8
Input Susceptibility
Distance Cursor
Resolution
1 A
Into diode clamps
1/25th of 1 major division
Cursor Readout
Range
–2 ft to ≥2,000 ft
Resolution
0.004 ft
A–1
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Appendix A: Specifications
Table A–1: Electrical Characteristics (Cont.)
Characteristic
Distance Measurement
Accuracy
Performance Requirement
Supplemental Information
1.6 inches or 1% of distance measured,
whichever is greater
For cables with Vp = 0.66
For delta mode measurements
Error ≤0.5% for distance ≥27 ft
Error ≤1.0% for distance ≥14 ft
Error ≤2.0% for distance ≥7 ft
Error ≤10% for distance ≥1.5 ft
Cursor Ohms Readout
Range
1 W to 1 kW
Resolution
3 significant digits
Accuracy
10% with serial cable impedance
correction (relative impedance
measurements 2%)
Horizontal
Scales
0.1 ft/div to 200 ft/div (0.25 m/div to 50 m/div)
1 ft to 2,000 ft (0.25 m to 500 m)
Range
Horizontal Position
Any distance to full scale can be moved on
screen
Vp
Propagation velocity relative to air
Range
0.30 to 0.99
0.01
Resolution
Accuracy
Custom Option Port
Within 1%
Included in total timebase error tolerance
Tektronix Chart Recorders YT–1 and YT–1S are
designed to operate with the 1502C. Produces
a high resolution thermal dot matrix recording of
waveform and switch values.
Line Voltage
115 VAC (90 to 132 VAC) 45 to 440 Hz
230 VAC (180 to 250 VAC) 45 to 440 Hz
Fused at 0.3 A
Fused at 0.15 A
Battery Pack
Operation
8 hours minimum, 30 chart recordings maxi-
mum
+15°C to +25°C charge and discharge temp,
LCD backlight off. Operation of instrument with
backlight on or at temps below +10°C will
degrade battery operation specification
Full Charge Time
20 hours maximum
Overcharge Protection
Charging discontinues once full charge is
attained
Discharge Protection
Charge Capacity
Charge Indicator
Operation terminates prior to battery damage
3.4 Amp-hours typical
Bat/low will be indicated on LCD when capacity
reaches approximately 10%
A–2
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Appendix A: Specifications
Environmental Characteristics
Table A–2: Environmental Characteristics
Characteristic
Temperature
Operating
Performance Requirement
Supplemental Information
–10°C to +55°C
Battery capacity reduced at other than +15°C to
+25°C
Non-operating
–62°C to +85°C
With battery pack removed. Storage temp with
battery pack in is –35°C to +65°C. Contents on
non-volatile memory (stored waveform) might
be lost at temps below –40°C.
Humidity
to 100%
Internal desiccant with cover on and option port
cover installed.
Altitude
Operating
Non-operating
Vibration
to 15,000 ft
to 40,000 ft
MIL–T–28800C, Class 3
5 to 15 Hz, 0.06 inch p-p
15 to 25 Hz, 0.04 inch p-p
25 to 55 Hz, 0.013 inch p-p
MIL–T–28800C, Class 3
Shock, Mechanical
Pulse
30 g, 11 ms 1/2 sine wave, total of 18 shocks
MIL–T–28800C, Class 3
Bench Handling
Operating
MIL–STD–810, Method 516, Procedure V
Cabinet on, front cover off
4 drops each face at 4 inches or 45 degrees
with opposite edge as pivot
Non-operating
4 drops each face at 4 inches or 45 degrees
with opposite edge as pivot. Satisfactory
operation after drops.
Cabinet off, front cover off
Loose Cargo Bounce
1 inch double-amplitude orbital path at 5 Hz,
6 faces
MIL–STD–810, Method 514, Procedure XI,
Part 2
Water Resistance
Operating
Splash-proof and drip-proof
MIL–T–28800C, Style A, Front cover off
Salt Atmosphere
Withstand 48 hours, 20% solution without
corrosion
Sand and Dust
Washability
Operates after test with cover on, non-operating MIL–STD–810, Method 510, Procedure I
Capable of being washed
Materials are fungus inert
Fungus Inert
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Appendix A: Specifications
Certifications and Compliances
Category
Standard or description
EC Declaration of Conformity – Meets intent of Directive 89/336/EEC for Electromagnetic Compatibility. Compliance was demonstrated
EMC
to the following specifications as listed in the Official Journal of the European Union:
EN 50081-1 Emissions:
EN 55022
EN 60555-2
Class B Radiated and Conducted Emissions
AC Power Line Harmonic Emissions
EN 50082-1 Immunity:
IEC 801-2
Electrostatic Discharge Immunity
RF Electromagnetic Field Immunity
Electrical Fast Transient/Burst Immunity
Power Line Surge Immunity
IEC 801-3
IEC 801-4
IEC 801-5
Australia/New Zealand
Complies with EMC provision of Radiocommunications Act per the following standard(s):
Declaration of Conformity – EMC
AS/NZS 2064.1/2
Industrial, Scientific, and Medical Equipment: 1992
EMC Compliance
Meets the intent of Directive 89/336/EEC for Electromagnetic Compatibility when it is used with the
product(s) stated in the specifications table. Refer to the EMC specification published for the stated
products. May not meet the intent of the directive if used with other products.
FCC Compliance
Safety Standards
Emissions comply with FCC Code of Federal Regulations 47, Part 15, Subpart B, Class A Limits.
U.S. Nationally Recognized UL1244
Testing Laboratory Listing
Standard for electrical and electronic measuring and test equipment.
Canadian Certification
CAN/CSA C22.2 No. 231
CSA safety requirements for electrical and electronic measuring and
test equipment.
European Union Compliance Low Voltage Directive 73/23/EEC, amended by 93/68/EEC
EN 61010-1/A2
Safety requirements for electrical equipment for measurement,
control, and laboratory use.
Additional Compliance
IEC61010-1/A2
Safety requirements for electrical equipment for measurement,
control, and laboratory use.
Safety Certification Compliance
Equipment Type
Test and measuring
Safety Class
Class 1 (as defined in IEC 61010-1, Annex H) – grounded product
Overvoltage Category II (as defined in IEC 61010-1, Annex J)
Pollution Degree 3 (as defined in IEC 61010-1).
Overvoltage Category
Pollution Degree
Installation (Overvoltage)
Category
Terminals on this product may have different installation (overvoltage) category designations. The
installation categories are:
CAT III Distribution-level mains (usually permanently connected). Equipment at this level is
typically in a fixed industrial location.
CAT II Local-level mains (wall sockets). Equipment at this level includes appliances, portable
tools, and similar products. Equipment is usually cord-connected.
CAT I
Secondary (signal level) or battery operated circuits of electronic equipment.
(continued next page)
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Appendix A: Specifications
Category
Standard or description
Pollution Degree
A measure of the contaminates that could occur in the environment around and within a product.
Typically the internal environment inside a product is considered to be the same as the external. Products
should be used only in the environment for which they are rated.
Pollution Degree 1
No pollution or only dry, nonconductive pollution occurs. Products in this
category are generally encapsulated, hermetically sealed, or located in
clean rooms.
Pollution Degree 2
Normally only dry, nonconductive pollution occurs. Occasionally a
temporary conductivity that is caused by condensation must be
expected. This location is a typical office/home environment. Temporary
condensation occurs only when the product is out of service.
Pollution Degree 3
Pollution Degree 4
Conductive pollution, or dry, nonconductive pollution that becomes
conductive due to condensation. These are sheltered locations where
neither temperature nor humidity is controlled. The area is protected from
direct sunshine, rain, or direct wind.
Pollution that generates persistent conductivity through conductive dust,
rain, or snow. Typical outdoor locations.
Physical Characteristics
Table A–3: Physical Characteristics
Characteristic
Weight
without cover
Description
14.25 lbs (6.46 kg)
15.75 lbs (7.14 kg)
19.75 lbs (8.96 kg)
with cover
with cover, chart recorder, and battery pack
Shipping Weight
domestic
25.5 lbs (11.57 kg)
25.5 lbs (11.57 kg)
5.0 inches (127 mm)
export
Height
Width
with handle
without handle
Depth
12.4 inches (315 mm)
11.8 inches (300 mm)
with cover on
with handle extended to front
16.5 inches (436 mm)
18.7 inches (490 mm)
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Appendix A: Specifications
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Appendix B: Operator Performance Checks
This appendix contains performance checks for many of the functions of the
1502C. They are recommended for incoming inspections to verify that the
instrument is functioning properly. Procedures to verify the actual performance
requirements are provided in the 1502C Service Manual.
Performing these checks will assure you that your instrument is in good working
condition. These checks should be performed upon receipt of a new instrument
or one that has been serviced or repaired. It does not test all portions of the
instrument to Calibration specifications.
The purpose of these checks is not to familiarize a new operator with the
instrument. If you are not experienced with the instrument, you should read the
Operating Instructions chapter of this manual before going on with these checks.
If the instrument fails any of these checks, it should be serviced. Many failure
modes affect only some of the instrument functions.
Equipment Required
Getting Ready
Item
Tektronix Part Number
011-0123-00
50 W precision terminator
3-foot precision coaxial cable
012-1350-00
Disconnect any cables from the front-panel CABLE connector. Connect the
instrument to a suitable power source (a fully charged battery pack or AC line
source). If you are using AC power, make sure the fuse and power switch are
correct for the voltage you are using (115 VAC requires a different fuse than
230 VAC).
Power On
Pull the POWER switch on the front panel. If a message does not appear on the
display within a second or two, turn the instrument off. There are some failure
modes that could permanently damage or ruin the LCD if the power is left on for
more than a minute or so. Refer to Appendix C: Operator Troubleshooting in this
manual.
Metric Instruments
Option 05 instruments default to metric; however, you can change the metric
scale to ft/div in the Setup Menu or use the metric numbers provided. To change
n
the readings, press the MENU button. Using the o POSITION control, scroll
down to Setup Menu and press MENU again. Scroll down to Distance/Div is:
m/div and press MENU again. This will change to ft/div. Press the MENU button
repeatedly to return to normal operation mode. If the instrument power is turned
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Appendix B: Operator Performance Checks
off, these checks must be repeated again when the instrument is powered on
again.
Set Up
Set the 1502C front-panel controls:
NOISE FILTER
VERT SCALE
DIST/DIV
Vp
1 avg
no adjustment
1 ft/div (0.25 m)
.66
1. Horizontal Scale
(Timebase) Check
If the instrument fails this check, it must be repaired before any distance
measurements can be made with it.
1. Turn the 1502C power on. The display should look very similar to Fig-
ure B–1.
ac
0.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure B–1: Start-up Measurement Display
2. Connect the 3-foot cable to the front-panel CABLE connector. The display
should now look like Figure B–2.
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Appendix B: Operator Performance Checks
ac
0.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure B–2: Measurement Display with 3-foot Cable
3. Using the
POSITION control, measure the distance to the rising edge of
the waveform at the open end of the cable. The distance shown on the
display distance window (upper right corner of the LCD) should be from
2.87 to 3.13 feet (0.875 to 0.954 m).
ac
3.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure B–3: Cursor at End of 3-foot Cable
4. Change the Vp to .30.
5. Using the
POSITION control, measure the distance to the rising edge of
the waveform at the open end of the cable. The distance shown on the
display distance window should be from 1.30 to 1.42 feet (0.396 to
0.433 m).
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Appendix B: Operator Performance Checks
ac
1.360 ft
O
N
O
F
F
O
F
F
O
F
F
Figure B–4: Cursor at End of 3-foot Cable, Vp Set to .30
6. Remove the 3-foot cable and connect the 50 W terminator.
7. Change the DIST/DIV to 200 ft/div (50 m/div)
8. Turn the
POSITION control clockwise until the distance window shows a
distance greater than 2,000 feet (> 600 m). The waveform should be a flat
line from the pulse to this point.
ac
2051.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure B–5: Flat-Line Display Out to 50,0000+ Feet
9. Turn the
POSITION control counterclockwise until the distance window
shows a distance less than 10.000 feet (< 3.1 m).
10. Set the DIST/DIV control to .1 ft/div (0.025 m/div).
11. Turn the POSITION control counterclockwise until the distance window
shows a distance of –2.000 feet (–0.611 m).
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Appendix B: Operator Performance Checks
ac
–2.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure B–6: Flat-Line Display at –2.000 ft
This last step has set up the instrument for the next check.
2. Vertical Position
(Offset) Check
If the instrument fails this test, it can be used, but should be serviced when
possible. Not all of the waveforms will be viewable at all gain settings.
n
1. Using the o POSITION control, verify that the entire waveform can be
moved to the very top of the display (off the graticule area).
ac
–2.000 ft
Waveform
off display
O
N
O
F
F
O
F
F
O
F
F
Figure B–7: Waveform Off the Top of the Display
n
2. Using the o POSITION control, verify that the entire waveform can be
moved to the very bottom of the display (to the bottom graticule line).
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Appendix B: Operator Performance Checks
ac
–2.000 ft
O
N
O
F
F
O
F
F
Waveform
O
F
F
Figure B–8: Waveform at the Bottom of the Display
3. Noise Check
If the instrument fails this check, it can still be usable for measurements of large
faults that do not require a lot of gain, but send the instrument to be serviced
when possible. A great deal of noise reduction can be made using the NOISE
FILTER control.
1. Adjust the
POSITION control to obtain 100.000 ft (30.500 m) in the
distance window.
ac
100.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure B–9: Waveform with Gain at 5.00 mr/div
n
2. Using the o POSITION control and VERT SCALE control, set the gain to
5.00 mr/div. Keep the waveform centered vertically in the display.
3. Press MENU.
n
4. Using the o POSITION control, select Diagnostics Menu.
5. Press MENU again.
n
6. Using the o POSITION control, select Service Diagnostic Menu.
B–6
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Appendix B: Operator Performance Checks
7. Press MENU again.
n
8. Using the o POSITION control, select Noise Diagnostics.
9. Press MENU again and follow the instructions on the display.
10. Exit from Noise Diagnostics, but do not exit from the Service Diagnostic
Menu yet.
4. Offset/Gain Check
If the instrument fails this check, it should not be used for loss or impedance
measurements. Send it to be serviced when possible.
1. In the Service Diagnostic Menu, select the Offset/Gain Diagnostic and
follow the directions on the display.
There are three screens of data presented in this diagnostic. The Pass/Fail level is
3% for any single gain setting tested. A failure message is displayed if the 3%
limit for any combination of gains over the three ranges is exceeded.
2. Exit from Offset/Gain Diagnostic, but do not leave the Service Diagnostic
Menu yet.
5. Sampling Efficiency
Check
If the instrument fails this check, the waveforms might not look normal. If the
efficiency is more than 100%, the waveforms will appear noisy. If the efficiency
is below the lower limit, the waveform will take longer (more pixels) to move
from the bottom to the top of the reflected pulse. This smoothing effect might
completely hide some faults that would normally only be one or two pixels wide
on the display.
1. In the Service Diagnostic Menu, select Sampling Efficiency and follow the
directions on the screen.
2. When done with the test, press the MENU button repeatedly until the
instrument returns to normal operation.
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Appendix B: Operator Performance Checks
6. Aberrations Check
If the aberrations are out of specification, the ohms-at-cursor function might be
less accurate than specified.
1. Connect the 50 W precision terminator to the front-panel CABLE connector.
2. Set the DIST/DIV control to 5 ft/div (1 m/div).
3. Increase the VERT SCALE control to 50 mr/div.
n
4. Using the o POSITION control, move the top of the pulse to the center
graticule line.
ac
–1.872 ft
O
N
O
F
F
O
F
F
O
F
F
Figure B–10: Top of Pulse on Center Graticule
5. Set the DIST/DIV control to 0.2 ft/div (0.05 m/div).
6. Turn the POSITION control clockwise until the rising edge of the
incident pulse is in the left-most major division on the display.
ac
1.744 ft
O
N
O
F
F
O
F
F
O
F
F
Figure B–11: Rising Edge of Incident Pulse in Left-most Major Division
7. Using the
POSITION control, move the cursor back to 0.000 ft (0.00 m).
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Appendix B: Operator Performance Checks
All the aberrations, except the one under the cursor (see Figure B–12), must
be within one division of the center graticule line from out to 10 feet (3.5 m)
past the rising edge of the pulse.
To verify distances past the right edge of the display, scroll along the
waveform by turning the
POSITION control clockwise.
ac
0.000 ft
O
N
O
F
F
O
F
F
O
F
F
Figure B–12: Waveform Centered, Cursor at 0.000 ft
7. Risetime Check
If the risetime is out of specification, it might be difficult to make accurate
short-distance measurements near the front panel.
1. Set the 1502C front-panel controls:
NOISE FILTER
VERT SCALE
DIST/DIV
Vp
1 avg
500 mr/div
0.2 ft/div (0.05 m)
.99
2. Using the
POSITION control, move the incident pulse to the center of the
display as shown below.
ac
–1.432 ft
O
N
O
F
F
O
F
F
O
F
F
Figure B–13: Pulse Centered on Display
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Appendix B: Operator Performance Checks
3. Turn the VERT SCALE control clockwise until the leading edge of the
incident pulse is five major divisions high (about 205 mr).
4. Position the waveform so that it is centered about the middle graticule line.
ac
–0.848 ft
O
N
O
F
F
Crosses
Lowest
Point
O
F
F
O
F
F
Figure B–14: Cursor on Lowest Major Graticule that Rising Edge crosses
5. Using the POSITION control, and noting the distances displayed, verify
that the distance between the points where the leading edge crosses the
highest and lowest major graticule lines is less than or equal to 0.096 feet
(0.029 m).
ac
–0.768 ft
Crosses
Highest
Point
O
N
O
F
F
O
F
F
O
F
F
Figure B–15: Cursor on Highest Major Graticule that Rising Edge crosses
In the above example, the distances are –0.848 feet and –0.768 feet. The
difference between these two measurements is 0.080 feet, which is well within
specification.
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Appendix B: Operator Performance Checks
8. Jitter Check
Jitter is the uncertainty in the timebase. Its main effect is that the waveform
appears to move back and forth a very small amount. If the jitter is too great, it
will affect the repeatability of very precise distance measurements.
1. Set the VERT SCALE less than or equal to 1.0 mρ/div.
2. Watch the leading edge of the pulse move and verify that this movement is
less than five pixels, or < 0.02 ft (0.006 m).
ac
–1.624 ft
O
N
O
F
F
O
F
F
Jitter
O
F
F
Figure B–16: Jitter Apparent on Leading Edge of Incident Pulse
Using the Max Hold function (accessed in the Setup Menu, Acquisition Control)
can simplify your observation of jitter. Max Hold allows you to observe the
accumulated jitter without having to stare continuously at the display.
ac
–1.624 ft
O
N
O
F
F
Accumulated
Jitter
O
F
F
O
F
F
Figure B–17: Jitter Captured Using Max Hold
B–11
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Appendix B: Operator Performance Checks
Conclusions
If the instrument failed Jitter or Risetime checks, it is probably still adequate for
all but extremely precise distance measurements. If it failed the Horizontal Scale
check, you should not use the instrument until the cause of the failure has been
identified and corrected.
All of the previous checks only test the major functional blocks of the instrument
that could prevent you from being able to make measurements. It is possible for
the front-panel controls or the LCD to have problems that would interfere with
controlling or displaying measurements. Most problems of this type would
become evident as you perform the checks. If you suspect a problem of this
nature, you should have the instrument checked by a qualified service technician,
using the diagnostics in the 1502C Service Manual.
If the instrument passed all of the previous checks, it is ready for use.
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Appendix C: Operator Troubleshooting
For assistance in troubleshooting, use the following flow chart to determine if
you have a simple problem you can fix or if the instrument needs to be sent to a
Tektronix Service Center.
Use this process to determine whether the instrument should be repaired or is
OK to use when you have a problem.
CAUTION: Any time the instrument smells hot, repeatedly blows fuses, or
repeats the same error message, you should have the instrument serviced by
qualified technicians using the procedures in the 1502C Service Manual.
These are the first checks you should perform when you think you might have a
problem with the instrument.
The first step asks you to preset the instrument controls. Here is how to do that:
Set Vp to .66; turn the IMPEDANCE knob all the way counterclockwise; turn the
FILTER knob all the way counterclockwise, then back two clicks; turn the
DIST/DIV knob all the way counterclockwise, then back three clicks; turn the
PULSE WIDTH knob all the way counterclockwise; remove any accessories that
might be plugged into the Option Port (e.g., chart printer), and disconnect any
cable that might be attached to the front-panel connector.
To complete the tests, you might need a Volt-Ohmmeter (VOM), a flat-bladed
screw driver (to set the line voltage switch) and possibly, some spare fuses.
When you have completed these tests, you will know that it is safe to use the
instrument or that it needs repair or adjustment internally. You do not remove
the case for these tests.
IMPORTANT: It is possible for the instrument to continue to make some
measurements even after reporting an error message. Do not ignore repeated
error messages! They indicate something is wrong and should be used with the
1502C Service Manual troubleshooting procedures.
This procedure will give you confidence that the instrument is functioning
properly. It is not an exhaustive set of tests that guarantee that the instrument
meets all specifications and is perfectly calibrated. The calibration procedures in
the 1502C Service Manual are the best method for assuring that the instrument
meets all specifications.
C–1
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Appendix C: Operator Troubleshooting
Operator Troubleshooting
(with cases on)
Preset front panel and
turn the
power on.
Is
Did
YES
Is the
YES
NO
YES
there a
greed display?
“Initializing”
message appear
on LCD?
power source a
battery?
NO
NO
If error
message(s)
appear, follow
the displayed
instructions.
Check line voltage switch for correct setting
and change if necessary. With VOM, check
wall outlet voltage and plug in somewhere
else if no voltage. Check fuse and power
cord for near zero Ohms.
Turn instrument off
immediately to avoid
possible damage to
LCD display.
Using VOM, check for
near zero Ohms in
fuse.
Is
waveform
missing, erratic or
badly
YES
distorted?
Is
fuse
OK?
YES
NO
Perform initial
operator
performance
verification checks.
NO
DO NOT USE INSTRUMENT.
Serious problems need repair. Refer
to 1502C Service Manual
Troubleshooting procedures.
NO
Did instrument pass
checks?
Refer to Option Port
and Accessories Troubleshooting
procedure.
If no accessories, then OK to use
instrument.
Replace fuse.
YES
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Appendix C: Operator Troubleshooting
Error Messages
Any time the instrument displays an error message, the troubleshooting
procedures should be used to judge the extent and severity of the problem.
Some errors will still permit some kinds of measurements. If there is any doubt
about the ability to make a particular kind of measurement, do not make that
measurement until the problem has been corrected.
Message:
Option Port Device Not Responding...
Please check for correct installation.
– push MENU button to Continue –
Occurrences:
Meanings:
This can occur anytime a chart printer, SP-232, or other Option Port device
requests attention from the TDR.
This error indicates that the TDR has received a signal indicating a request from
the Option Port device and either there is no device installed or the device is not
responding with a recognized ID byte when polled by the TDR.
This error might be very annoying because the Option Port is checked once each
time the TDR gets a waveform. If the TDR is being controlled by or through the
Option Port device, you will probably have to remove that device and make
manual measurements until the failure is corrected.
This type of failure will not affect measurements made manually.
Remedies:
If there is no Option Port device, there is probably a failure in the option port
logic circuitry on the main circuit board, or in the cable between the main board
and the Option Port connector. Refer the instrument to a qualified service
technician.
If the error is in response to a chart printer request, the PRINT switch on the
chart printer, or the wires to that switch, are probably bad or shorted to the
chassis or other ground point. Refer the chart printer to a qualified service
technician.
If the error is in response to another Option Port device, remove that device. If
the error ceases, have the device serviced. If the error persists, have the TDR
serviced.
Message:
ERROR:
TYPE:
Acquisition Initialization
Pulse gap > 3.75 dB
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Occurrences:
Meanings:
At power on during initialization only.
The instrument expects the pulse height to be slightly less than two major
divisions high and adds gain to make the pulse exactly two divisions high. This
message indicates that the pulse is non-existent, too small, or that the gain
circuitry is not working correctly.
If there is no pulse after pushing the MENU button, no measurements can be
made. Have the instrument repaired.
If the pulse is there and less than two divisions high, you probably can make
useful measurements. Run the Offset/Gain Service Diagnostic.
Remedies:
Message:
Refer the instrument for repair. If the instrument passes, use the SET VERT REF
to make the pulse exactly two divisions high. The instrument’s front-end board
needs repair, but it is often possible to make measurements.
ERROR:
TYPE:
Acquisition Initialization
Initial Pulse Height > 2 Divs at 0 dB
Occurrences:
Meanings:
At power on during initialization only.
The instrument expects the pulse height to be slightly less than two major
divisions high. This message indicates that the pulse is greater than two divisions
in amplitude with no additional gain added.
This message usually means that the front-end board pulse circuitry is no longer
properly terminated. If the waveform does not change when a 50 W terminator or
cable is attached, the internal cable or front-panel connector is probably
disconnected or broken and no measurements can be made until they are
repaired.
If the waveform does respond normally when a 50 W terminator or cable is
connected, the failure might be in the gain circuitry on the Main board or in the
hybrid circuit.
Remedies:
Message:
Have the instrument repaired. If a pulse is present, distance measurements can be
made. If the pulse is more than two divisions high, the millirho scale is not
calibrated and loss measurements should not be made.
ERROR:
TYPE:
Acquisition Initialization
Vertical Scale failure
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Appendix C: Operator Troubleshooting
Occurrences:
Meanings:
At power on during initialization only.
The instrument changed the gain while adjusting the pulse to be two divisions
high and the change in the gain circuitry did not make the expected change in the
signal size.
Remedies:
Message:
Have the instrument repaired. If no other error messages occurred and the pulse
is present, distance measurements can be made. Do not make loss measurements
until the instrument has been repaired.
ERROR:
TYPE:
Acquisition Initialization
Vertical Position failure
Pulse base off top of LCD
ERROR:
TYPE:
Acquisition Initialization
Vertical Position failure
Pulse top below base of LCD
ERROR:
TYPE:
Acquisition Initialization
Vertical Position failure
Occurrences:
Meanings:
At power on during initialization only.
The instrument attempts to center the pulse before making it two divisions high.
These messages indicate that the waveform could not be properly placed on the
display. This usually means that the offset or gain circuitry on the Main board is
not working properly.
Remedies:
Message:
The instrument must be repaired. If it is possible to adjust the pulse vertically on
the display and no other error messages have been displayed, it might be possible
to make measurements. If the pulse is not two divisions high, do not make
measurements.
ERROR:
TYPE:
Acquisition Initialization
Leading edge of pulse not found
ERROR:
TYPE:
Acquisition Initialization
Top of 50 nsec ramp not found
Occurrences:
This message can occur at power on initialization only. These are common error
messages because they are triggered by many kinds of failures and come from
one of the very first routines that the instrument executes. They are usually fatal
C–5
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Appendix C: Operator Troubleshooting
errors, which means that no measurements should be made with this instrument
before it is repaired.
Meanings:
Remedies:
The instrument searches for a point on the leading edge of the pulse that is on the
cable inside the instrument (about 10% up the pulse). This message indicates that
the search failed. This could be because the pulse is not there, or because the
sampler or gain circuitry is broken, or even because the timebase is not function-
ing properly.
The instrument must be sent to service for repair.
C–6
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Appendix D: Application Note
Pulse Echo Testing of Electrical Transmission Lines
Using the Tektronix Time-Domain Reflectometry Slide Rule
Most people who make quantitative reflectometry tests or measurements should
find the Tektronix TDR Slide Rule helpful. Those new to the subject will find
the slide rule graphically summarizes a wealth of information on reflectometry.
H
H
H
Voltage Standing Wave Ratio vs. Percent Reflected Voltage
Return Loss, dB, vs. Percent Reflected Voltage
Percent Reflected Voltage vs. Characteristic Line Impedance (for either 50 W
or 75 W source)
H
H
Percent Reflected Voltage vs. Load Resistance (for either 50 W or 75 W
source)
Characteristic Line Impedance or Load Resistance vs. Reflection Amplitude
(as seen on your TDR)
H
H
H
Dielectric Constant vs. Velocity Factor
Time vs. Short Distance in centimeters or inches (any dielectric)
Time vs. Long Distances in meters or feet (any dielectric)
Terms and Symbols
RS
ZS
ZO
ZL
RL
r
Source Resistance of a signal generator
Source Impedance of a signal generator
Characteristic Impedance of a transmission line
Load Impedance for a transmission line
Load Resistance for a transmission line
Reflection Coefficient (rho): the ratio of incident to reflected voltage
Reflection Coefficient divided by 1,000 (millirho)
Ratio of the incident voltage to reflected voltage multiplied by 100
mr
%
VSWR Voltage Standing Wave Ration (peak-to-valley)
c
Velocity of light in air
VP
Vt
κ
Propagation Velocity of a signal in a transmission line
Velocity Factor (fraction of the velocity of light)
Dielectric Constant
D
d
L
C
Outer Diameter of the dielectric in a coaxial cable
Diameter of the center conductor in a coaxial cable
Inductance in nanoHenries (nH) per foot
Capacitance in picoFarads (pF) per foot
D–1
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Appendix D: Application Note
Relationships
ZO
%
= (138 / pκ (log10 D / d) for coaxial cable
)*
= r 100
*
VSWR = (1 + r) + (1 – r) for the case where VSWR is the same for all
frequencies
c
= 30 cm / nanosecond = 0.984 ft / ns
= 1 / pκ
VF
VP
C
= 30 / pκ cm / ns = 0.984 / pκ ft /ns
= 7.36 κ + (log10 D / d)
= 140 log10 D / d
L
1 in
1 ft
1 m
= 2.54 cm
= 30.48 cm
= 3.28 ft
VSWR vs. Percent Reflected Voltage
To find the Voltage Standing Wave Ratio (VSWR), knowing the percent reflected
voltage (%), or vice versa, use the Frequency Domain Conversions section of the
slide rule (see Figure D–1).
1.04 VSWR = 2% REFLECTION
20% = 1.5 VSWR
0
2
4
6
8
10
12
14
16
18
20 %
SINGLE
RESISTIVE
DISCONTINUITY
ONLY1.00
1.05 1.10 1.15 1.20 1.25 1.30 1.35 1.40 1.45 1.50 VWSR
.01 .02.03 .05 .10 .2 .3 .5 .7 1.0 5 7 10 20 30 50 100 %
2
3
RETURN LOSS
(IMPULSE ONLY)
80 75 70 65 60 55 50 45 40 35 30 25 20 15 10
5
0
Figure D–1: Slide Rule of VSWR vs. Percent Reflected Voltage
On the upper scale, locate the known value of VSWR (or %). Adjacent to that
point is the corresponding value for % (or VSWR). VSWR is the peak-to-valley
ratio of standing sine waves.
D–2
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Appendix D: Application Note
NOTE. The relationship between % holds only when the loss is a single imped-
ance discontinuity with negligible capacitive or inductive components (e.g., a
75 W termination at the end of a 50 W cable). The VSWR must be essentially the
same for all sine-wave frequencies.
Return Loss (dB) vs. Percent Reflected Voltage
To find return loss in decibels, knowing the % (or vice versa), use the bottom
scale of the Frequency Domain Conversions section of the slide rule (see Figure
D–2).
0
2
4
6
8
10
12
14
16
18
20 %
SINGLE
RESISTIVE
DISCONTINUITY
ONLY1.00
1.05 1.10 1.15 1.20 1.25 1.30 1.35 1.40 1.45 1.50 VWSR
.01 .02.03 .05 .10 .2 .3 .5 .7 1.0 5 7 10 20 30 50 100 %
2
3
RETURN LOSS
(IMPULSE ONLY)
80 75 70 65 60 55 50 45 40 35 30 25 20 15 10
5
0
1% REFLECTION = 40 dB RETURN LOSS
Figure D–2: Slide Rule of Return Loss vs. Percent Reflected Voltage
Locate the known value of % or the known dB return loss, then locate the value
of the corresponding expression on the adjacent scale.
NOTE. Only the impulse mode of Time-Domain Reflectometry can be accurately
expressed in terms of return loss.
A narrow impulse will be attenuated by losses in the cable and reflections will be
attenuated likewise.
As with measurements on VSWR, there is only a simple mathematical relation-
ship between reflection measurements using sine waves and reflection measure-
ments using pulses when one resistive discontinuity is the whole cause for the
sizable reflections.
D–3
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Appendix D: Application Note
Percent Reflected Voltage vs. Characteristic Line Impedance (50 or 75 ohm Source)
To find the characteristic impedance of a line, or section of a line, knowing the
reflection coefficient or the %, you should first know the impedance of the pulse
generator. It should be as close as possible to the nominal impedance of the line
and should be connected to the line through a length of cable having the same
impedance as the source. Select the side of the slide rule that corresponds to the
source resistance (RS) of the generator used, then select the longest scale as
follows:
Size of Reflection
% / division
r / division
100% to 80% (1r to 0.8r)
80% to 40% (0.8r to 0.4r)
40% to 16% (0.4r to 0.16r)
16% to 8% (0.16r to 0.08r)
8% to 4% (0.08r to 0.04r)
4% or less (< 0.04 r)
20
10
5
.20
.10
.05
.02
.01
.005
2
1
0.5
1 W
+100%
+1r =
SOURCE
LINE
R
Z
O
50 W
150 W
50 W
S
+50%
0%
+0.5r=
0r =
50 W
-50%
-0.5r=
16.7 W
D2E
DE
-100%
-1r =
0 W
REFLECTED
VOLTAGE
LOAD
STEP
GENERATOR
INCIDENT
VOLTAGE
R
L
r = REFLECTION COEFFICIENT
1r = 100%
OHMS
r / DIV r / DIV
OHMS
OHMS
r / DIV
r / DIV
1000
600
59
.20
.10 .05
70 .02 .01
.005
120
400
300
68
66
54
58
57
100
90
64
62
200
53
56
55
54
53
52
51
1
80
70
150
1000
60
58
500
52
51
300
200
100
90
80
56
54
100 70
60
52
70 60
50W
50W
50W
45
40
49
48
40
50 W SOURCE
50 W SOURCE
50 W SOURCE
The risetime or amplitude of received reflections may be signi-
ficantly degraded or attenuated by two-way losses of the line .
+1r = ∞ W
+.03r = 53.1W
Figure D–3: Slide Rule 50 ohm Source
D–4
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Appendix D: Application Note
If the reflection is downward from the 50 W or 75 W reference level, set the
reference level to the top of the chosen scale. If the reflection is toward a higher
impedance than the reference level, set the reference level to the bottom of the
chosen scale. Then count off the right number of divisions and subdivisions to
locate the level corresponding to the peak of the reflection and read the corre-
sponding impedance levels (Ohms) on the adjacent sliding scale.
1 W
+100%
–0dB =
SOURCE
R
75 W
E
PEAK
225 W
75 W
25 W
S
+50%
0%
–6dB =
1dB =
–6dB =
–0dB =
LINE
Z
O
75 W
-50%
-100%
2E
PEAK
0 W
LOAD
REFLECTED
VOLTAGE
IMPULSE
GENERATOR
INCIDENT
VOLTAGE
R
L
OHMS
OHMS
OHMS
% / DIV % / DIV
% / DIV
% / DIV
10
90
100
80
75W
76
75W
20
5
2
1
.5
75W
34
60
70
65
74
50
60
40
74
73
72
70
65
40
46
50
30
45
20
60
55
50
45
73
72
71
70
69
68
67
40
15
10
35
30
25
1
5
0
46
60
55
71
70
69
20
15
40
34
40
35
66
65
64
10
5
30
63
75 W SOURCE
75 W SOURCE
75 W SOURCE
(20% / division, downward 5 major divisions)
–100% = 0 W
Figure D–4: Slide Rule 75 ohm Source
If the line impedance and the source resistance are known, the expected
amplitude of a reflection can be approximated. First, select the side of the slide
rule having the correct source impedance. For cables having a higher impedance
than the selected source resistance, put the sliding reference level even with the
bottom stationary scale markings. For cables having a lower impedance than the
selected source resistance, move the reference level even with the top of the scale
markings. For best accuracy, select the scale farthest to your right in which the
impedance level of interest is in view. Read from the adjacent stationary scale the
reflection coefficient or percent reflected voltage that corresponds to the Ohms
selected.
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Appendix D: Application Note
Percent Reflected Voltage vs. Load Resistance
To find the terminating load resistance (RL) of a line, knowing the percent
reflected voltage or reflection coefficient, use the preceding instructions.
If the load resistance is known, the previous procedures can be used to approxi-
mate the size of the return reflection. An error might be introduced if the
impedance of the connecting cable does not match the source resistance of the
pulse generator.
Characteristic Line Impedance or Load Resistance vs. Reflection Amplitude
(as seen on your TDR)
Line Impedance (ZO) or Load Resistance (RL) can be derived directly from the
amplitude of a reflection displayed on a TDR display. The displayed reflection
should be positioned vertically to a known 50 W reference level. For a reference
level, use either a section of line of known impedance ahead of the line under
test/load, or use a termination of known resistance at the end of the line. The
slide rule can then be used by selecting the side with the same source resistance
and the same scale as the TDR.
r / DIV
OHMS
55
.01
.005
52
54
53
52
51
51
RG8/U
51.5 W
50W
RG213/U
49.5 W
49
49
48
47
.01r/div
48
46
2 ns / div
50 W SOURCE
Precision Load Resistor used for 50 W Reference Level
Figure D–5: Calculating Resistance/Impedance from Waveform Amplitude
Position the 50 W or 75 W reference level on the sliding scale to correspond with
the one selected as the reference level on the TDR display. The impedance
(Ohms) causing the reflection can then be read from the sliding scale by noting
the position on the fixed scale that corresponds to the position of the reflection
on the TDR display.
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Appendix D: Application Note
You should note that the peak level of any reflection that does not have a
discernable plateau might be an erroneous indication of the impedance disconti-
nuity that caused it. There might be several reasons for the error. 1) The
discontinuity might occupy such a short segment of the line compared to the VP
of the line and the risetime of the test pulse wavefront that part of the wavefront
starts to emerge from the segment while the remainder is still entering. This
causes a spike-shaped reflection, the amplitude of which might vary depending
on the risetime of the test pulse, how badly the risetime has been degraded by the
cable before it arrives, and how much attenuation the cable might impose on the
reflection before it arrives back at the source. 2) If the risetime of the TDR
system is too long, a reflection with a plateau will appear as a spike.
Centimeters vs. Inches or Meters vs. Feet
Inches and Centimeters: A given number of inches can be converted to
centimeters by placing the point on the sliding scale that corresponds to that
number next to the stationary arrow labeled INCHES, then reading the distance
in centimeters next to the point of the arrow labeled CENTIMETERS. Likewise,
centimeters are converted to inches using these directions in reverse.
1 inch = 2.54 cm
INCHES
CENTIMETERS
5
.6 .7 .8
1.0
1.5
2.0
3
4
ONE–WAY DISTANCE
TO OR BETWEEN FAULT, SPLICE,
CONNECTOR, LOAD, END, OR OTHER
IMPEDANCE DISCONTINUITY
0
15
20
30
40 50 60 70 8
METERS
FEET
15 m = 49.2 ft
Figure D–6: English-Metric, Metric-English Conversion Scales
Meters and Feet: A given number of meters can be converted to feet by placing
the point on the sliding scale that corresponds to that number next to the
stationary arrow labeled METERS, then reading the distance in feet next to the
point of the arrow labeled FEET. Likewise, feet are converted to meters using
these directions in reverse.
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Appendix D: Application Note
Dielectric Constant vs. Velocity Factor
Dielectric Constant and Velocity Factor appear on two identical scales next to a
sliding scale labeled ROUND TRIP TIME. To find one, knowing the other, read
across the sliding scale. Any major division on the sliding scale can be placed
next to the known value to help read directly across the sliding scale.
Time vs. Short Distances, in Centimeters or Inches (any dielectric)
To find the distances to or between discontinuities in a transmission line,
knowing the time for a pulse edge to travel that distance and back (round trip
time), it is necessary to know either the dielectric constant of the material
between the conductors or the velocity factor of the line. For distances less than
about three meters (or 10 feet), use the INCHES and CENTIMETERS scale.
1.0 1.5 2.0
3
4
5 6
DIELECTRIC
CONSTANT
Dieletric is Air
Time = 200 ps
ROUND
TRIP
TIME
00ps
150ps
200ps
300ps
500ps
800
VELOCITY
FACTOR
Velocity Factor = 1
1.0 .8 .7 .6 .5 .4
INCHES
CENTIMETERS
Distance is
3.0 cm or 1.18 inches
.6 .7 .8
1.0
1.5
2.0
3
4
ONE–WAY DISTANCE
TO OR BETWEEN FAULT, SPLICE,
CONNECTOR, LOAD, END, OR OTHER
IMPEDANCE DISCONTINUITY
Figure D–7: Dielectric Constant and Velocity Factor, Short Distance
The round trip time should be located on the sliding scale that is above the
INCHES and CENTIMETERS scale. Place the point on the sliding scale next to
a point on one of the stationary scales that corresponds to the value of the
dielectric constant or velocity factor. Then read the distance on the INCHES and
CENTIMETERS scale.
If the distance to or between faults is known and you want to find the time or
velocity factor, set the distance under the appropriate arrow first, then read the
answer on the ROUND TRIP TIME scales.
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Appendix D: Application Note
Time vs. Long Distances, in Meters or Feet (any dielectric)
Distances to or between discontinuities farther apart than about three meters
(10 feet) can be found on the METERS and FEET scale. Use the sliding
ROUND TRIP TIME scale just below it and follow the same procedure as
above.
ONE–WAY DISTANCE
TO OR BETWEEN FAULT, SPLICE,
CONNECTOR, LOAD, END, OR OTHER
IMPEDANCE DISCONTINUITY
20
30
40 50 60 70 80 100
15 Distance is
30 m or 99 ft
METERS
FEET
Dieletric is Solid
Polyethylene
1.0 1.5 2.0
3
4
5 6
DIELECTRIC
CONSTANT
ROUND
TRIP
TIME
00ns 150ns 200ns
300ns
500ns
700n
Time = 300 ns
VELOCITY
FACTOR
Velocity Factor = .66
1.0 .8 .7 .6 .5 .4
Figure D–8: Dielectric Constant and Velocity Factor, Long Distance
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Appendix D: Application Note
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Glossary
Aberrations
Imperfections or variations from a desired signal. In TDRs, a pulse of
electrical energy is sent out over the cable. As the pulse-generating circuitry
is turned on and off, the pulse is often distorted slightly and no longer is a
perfect step or sine-shaped waveform.
AC
Alternating current is a method of delivering electrical energy by periodical-
ly changing the direction of the flow of electrons in the circuit or cable. Even
electrical signals designed to deliver direct current (DC) usually fluctuate
enough to have an AC component.
Accuracy
The difference between a measured, generated, or displayed value and the
true value.
Cable
Electrical conductors that are usually insulated and often shielded. Most
cables are made of metal and are designed to deliver electrical energy from a
source (such as a radio transmitter) across a distance to a load (such as an
antenna) with minimal energy loss. Most cables consist of two conductors,
one to deliver the electrical signal and another to act as a return path, which
keeps both ends of the circuit at nearly the same electrical potential. In early
electrical systems and modern systems that over long distances use the earth
and/or air as the return path, and the term “ground” or “ground wire” is often
used to describe one of the wires in a cable pair.
Cable Attenuation
The amount of signal that is absorbed in the cable as the signal propagates
down it. Cable attenuation is typically low at low frequencies and higher at
high frequencies and should be corrected for in some TDR measurements.
Cable attenuation is usually expressed in decibels at one or several frequen-
cies. See also: dB and Series Loss.
Cable Fault
Any condition that makes the cable less efficient at delivering electrical
energy than it was designed to be. Water leaking through the insulation,
poorly mated connectors, and bad splices are typical types cable faults.
Capacitance
(see Reactance)
Glossary–1
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Glossary
Characteristic Impedance
Cables are designed to match the source and load for the electrical energy
that they carry. The designed impedance is often called the characteristic
impedance of the cable. The arrangement of the conductors with respect to
each other is the major factor in designing the impedance of cables.
Conductor
Any substance that will readily allow electricity to flow through it. Good
conductors are metals such as silver, copper, gold, aluminum, and zinc (in
that order).
dB
dB is an abbreviation for decibel. Decibels are a method of expressing power
or voltage ratios. The decibel scale is logarithmic. It is often used to express
the efficiency of power distribution systems when the ratio consists of the
energy put into the system divided by the energy delivered (or is some cases,
lost) by the system. Our instrument measures return loss. The formula for
decibels is: dB = 2– log (Vi/Vl) where Vi is the voltage of the incident pulse,
Vl is the voltage reflected back by the load, and log is the decimal-based
logarithmic function. The dB vertical scale on our instrument refers to the
amount of voltage gain (amplification) the instrument applies to the signal
before displaying it. For example, when the instrument is amplifying the
voltage by one hundred, the dB scale would read 40 dB, which is 20 log 100.
DC
Direct current is a method of delivering electrical energy by maintaining a
constant flow of electrons in one direction. Even circuits designed to
generate only AC often have a DC component.
Dielectric
(see Insulation)
Domain
A mathematical term that refers to the set of numbers that can be put into a
function (the set of numbers that comes out of the function is called the
“range”). A time-domain instrument performs its function by measuring
time.
Impedance
The total opposition to the flow of electrical energy is a cable or circuit.
Impedance is made partly of resistance (frequency independent) and partly of
reactance (frequency dependent). Although impedance is expressed in units
of Ohms, it must not be confused with the simple resistance that only applies
to DC signals. Technically, impedance is a function of the frequency of the
electrical signal, so it should be specified at a frequency. As a practical
matter, the impedance of most cables changes very little over the range of
frequencies they are designed for.
Glossary–2
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Glossary
Impedance Mismatch
A point in a cable or system where the incident electrical energy is redistrib-
uted into absorbed, reflected, and/or transmitted electrical energy. The
transmitted electrical energy after the mismatch is less than the incident
electrical energy.
Incident Pulse
The pulse of electrical energy sent out by the TDR. The waveform shown by
the TDR consists of this pulse and the reflections of it coming back from the
cable or circuit being tested.
Inductance
(see Reactance)
Insulation
A protective coating on an electrical conductor that will not readily allow
electrical energy to flow away from the conductive part of the cable or
circuit. Insulation is also called dielectric. The kind of dielectric used in a
cable determines how fast electricity can travel through the cable (see
Velocity of Propagation).
Jitter
The short term error or uncertainty in the clock (timebase) of a TDR. If the
timing from sample to sample is not exact, the waveform will appear to
move back and forth rapidly.
LCD
An acronym for Liquid Crystal Display. It is the kind of display used on this
instrument, so the terms display and LCD are often used interchangeably.
Millirho
rho (r) is the reflection coefficient of a cable or power delivery system. It is
the ratio of the voltage reflected back from the cable or circuit due to cable
faults or an impedance mismatch at the load, divided by the voltage applied
to the cable. Millirho are thousandths of one rho. Rho measurements are
often used to judge how well the cable is matched to the load at the other end
of the cable. If there is an open circuit in the cable, nearly all the energy will
be reflected back when a pulse is sent down the cable. The reflected voltage
will equal the incident pulse voltage and rho will be +1. If there is a short
circuit in the cable, nearly all the energy will be delivered back to the
instrument through the ground or return conductor instead of being sent to
the load. The polarity of the reflected pulse will be the opposite of the
incident pulse and rho will be –1. If there is no mismatch between the cable
and the load, almost no energy will be reflected back and rho will be 0. In
general, a load or fault with higher impedance than the cable will return a rho
measurement of 0 to +1, and a load or fault with a lower impedance will
return a rho measurement of 0 to –1. The scale for rho measurements is
determined by the height of the incident pulse. A pulse two divisions high
Glossary–3
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Glossary
means that each division is 0.5 rho (500 millirho). A pulse set to be four
divisions high would make each division 0.25 rho (250 millirho).
Noise
Any unwanted electrical energy that interferes with a signal or measurement.
Most noise is random with respect to the signals sent by the TDR to make a
measurement and will appear on the waveform, constantly constantly
moving up and down on the display. The NOISE FILTER control sets how
many waveforms will be averaged together to make the waveform displayed.
Noisy waveforms appear to fluctuate around the real signal. Because it is
random, noise will sometimes add to the real signal and sometimes subtract
energy from the real signal. By adding several noisy waveforms together, the
noise can be “averaged” out of the signal because the average amount of
noise adding to the signal will be nearly the same as the average amount of
noise subtracting from the signal. More waveforms in an average are more
likely to approach the real signal (although it takes longer to acquire and add
together more waveforms).
Open Circuit
In a cable, a broken conductor will not allow electrical energy to flow
through it. These circuits are also called broken circuits. The circuit is open
to the air (which looks like a very high impedance).
Precision
The statistical spread or variation in a value repeatedly measured, generated,
or displayed under constant conditions. Also called repeatability.
Reactance
A conductor’s opposition to the flow of AC electrical energy through it. All
conductors have some reactance. Reactance is made up of capacitance and
inductance. Capacitance is the ability of conductors separated by thin layers
if insulation (dielectric) to store energy between them. Inductance is the
ability of a conductor to produce induced voltage when the electrical current
through it varies. All conductors have some capacitance and inductance, so
all conductors have some reactance, which means they all have impedance.
Reflectometer
An instrument that uses reflections to make measurements. Our reflectome-
ters use electrical energy that is reflected back from points along a cable.
Resistance
A conductor’s opposition to the flow of DC electrical energy through it. All
conductors have a certain amount of resistance. Resistance is the low (or
zero) frequency part of impedance.
Resolution
For a given parameter, the smallest increment or change in value that can be
measured, generated, or displayed.
Glossary–4
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Glossary
Return Loss
The amount of energy reflected or returned from a cable indicates how much
the impedance in the system is mismatched. The ratio of the energy sent out
by the TDR, divided by the energy reflected back, expressed in the logarith-
mic dB scale, is called return loss.
Rho (r)
(see Millirho)
Risetime
The time it takes a pulse signal to go from 10% to 90% of the change in
voltage.
RMS
An acronym for Root Mean Squared. RMS is a way of measuring how much
deviation there is from a known (or desired) waveform. It is also the method
used to calculate how much power is contained in an AC waveform.
Sampling Efficiency
Our instruments make measurements by taking a succession of samples in
time and displaying them as a waveform with voltage on the vertical scale
(up and down) and time along the horizontal scale (across the display). The
circuitry that captures and holds the samples cannot instantly change from
one voltage level to another. It might take the circuit several samples to settle
in at the new voltage after a rapid change in the waveform. How efficiently
the circuit moves from one sampled voltage level to the next is called
sampling efficiency. If the efficiency is too low, the waveforms will be
smoothed or rounded. If the efficiency is too high (above 100%), the circuit
will actually move beyond the new voltage level in a phenomenon known as
overshoot, which becomes an unwanted source of noise in the waveform.
Series Loss
Conductors all have some DC resistance to the flow of electrical energy
through them. The amount of resistance per unit length is usually nearly
constant for a cable. The energy lost overcoming this series resistance is
called series loss. The series loss must be compensated for when measuring
the return loss or impedance mismatch at the far end of long cables.
Short Circuit
In a cable, a short circuit is a place where the signal conductor comes into
electrical contact with the return path or ground conductor. The electrical
circuit is actually shorter than was intended. Short circuits are caused by
worn, leaky, or missing insulation.
Stability
The change in accuracy of a standard or item of test equipment over an
extended period of time. Unless otherwise specified, the period of time is
assumed to be the calibration interval (might also apply to range, resolution,
or precision as a function of time). The term stability might also be used to
Glossary–5
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Glossary
denote changes resulting from environmental influences, such as tempera-
ture, humidity, vibration, and shock.
TDR
An acronym for Time-Domain Reflectometer. These instruments are also
called cable radar. They send out pulses of energy and time the interval to
reflections. If the velocity of the energy through the cable is known,
distances to faults in the cable can be displayed or computed. Conversely, the
speed that the energy travels through a cable of known length can also be
computed. The way in which the energy is reflected and the amount of the
energy reflected indicate the condition of the cable.
Velocity of Propagation (Vp)
Electrical energy travels at the same speed as light in a vacuum. It travels
slower than that everywhere else. The speed that it travels in a cable is often
expressed as the relative velocity of propagation. This value is just a ration
of the speed in the cable to the speed of light (so it is always a number
between 0 and 1). A velocity of propagation value of 0.50 indicates that the
electrical energy moves through the cable at half the speed of light.
Waveform Averaging
(see Noise)
Glossary–6
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Index
Controls
Cable Connector, 1–7
A
AC (see Power), xii
Accessories, 3–2
Distance / Division, 1–7
Front Panel, 1–5, 1–7
Horizontal Position, 1–7
Menu Button, 1–8
Optional, 3–2
Standard, 3–2
accessories, standard, 3–2
Address, Tektronix, x
Altitude Spec, A–3
Noise Filter, 1–7
Power, 1–7
Store Button, 1–8
Velocity of Propagation, 1–7
Vertical Position, 1–7
Vertical Scale, 1–7
View Difference Button, 1–8
View Input Button, 1–8
View Store Button, 1–8
B
Battery (see Power), 1–2
Battery Pack Spec, A–2
BNC Connector, 3–2
D
C
Cable
Delta Mode, 2–13
Depth Spec, A–4
Open, 1–15
Scrolling, 2–8
Short, 1–15, 2–19
E
Test Procedure, 1–14
Distance to Fault, 1–14
Horizontal Set Reference, 1–24
Reflection Coefficient, 1–17
Return Loss, 1–18
Electromagnetic Spec, A–4
Error Messages, C–3
F
Store Waveform, 1–20
Vertical Set Reference, 1–26
View Difference, 1–21
View Input, 1–20
Features (see Menu), 1–29
Fungus Spec, A–3
Fuse, 3–2
View Store, 1–21
Fuse (see Power), 1–2
Characteristics
Electrical, A–1
Environmental, A–3
Physical, A–4
G
Checks (see Performance Checks), B–1
Connectors
Getting Started, 2–2
BNC – BNC, 3–2
H
BNC to Alligator, 3–2
BNC to Banana, 3–2
BNC to Binding Post, 3–2
BNC to F Type, 3–2
BNC to GR, 3–2
BNC to Hook Tips, 3–2
BNC to N Type, 3–2
BNC to UHF, 3–2
Handling, 1–1
Height Spec, A–4
Help, 2–1
Horizontal Set Reference, 1–24, 2–13
HORZ SET REF (see Horizontal Set Reference), 2–13
Humidity Spec, A–3
Contacting Tektronix, x
Index–1
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Index
Velocity of Propagation, 1–8
View Stored Waveform, 1–11
I
Indicators, 1–6
Inspection, viii
N
Noise, 2–11
L
Reduced, 2–12
List of Figures, iii
List of Tables, vi
Loss, 1–18
Noise (see also Controls), 1–7
Noise Filter, 2–13, 2–14, 2–15
O
M
Ohms-at-Cursor, 1–19, 2–9, 2–10
Open, 1–15, 2–4
Option Port Cover, 3–2
Options, vii, 3–1
Maintenance, C–1, D–1
Manual Changes, vii
Max Hold (see Maximum Hold), 2–21
Maximum Hold, 1–29, 2–21
Menu, 1–8, 1–29, 2–1, 2–21
Cables, 1–8
Chart Recorder (04), 3–1
Chart Recorder (07), 3–1
Metric Default (05), 3–1
Power Cords, 3–1
Diagnostics, 1–9
Chart Recorder, 1–10
Head Alignment, 1-10
LCD Chart, 1-10
Front Panel, 1–10
LCD, 1–10
Alignment, 1-10
Contrast, 1-10
Drive Test, 1-10
Response Time, 1-10
Service, 1–9
P
Performance Checks, B–1
Aberrations, B–8
Conclusions, B–12
Equipment Required, B–1
Horizontal Scale, B–2
Jitter, B–11
Noise, 1-10
Noise, B–6
Offset / Gain, B–7
Risetime, B–9
Sampling Efficiency, B–7
Set Up, B–2
Offset / Gain, 1-10
RAM / ROM, 1-10
Sampling Efficiency, 1-9
Timebase, 1-10
Display Contrast, 1–11
Impedance, 1–8
Main, 1–8
Vertical Position, B–5
Phone number, Tektronix, x
Pouch, 3–2
Maximum Hold, 1–29
Option Port, 1–11
Debugging, 1–11
Diagnostic, 1–11
Timing, 1–11
Power
AC, viii
AC Receptacle, 1–2
Battery, vii, viii
Low Indicator, 1–3
Battery Pack
Pulse, 1–30
Setup, 1–9
Acquisition Control, 1–9
Backlight, 1–9
Care of, 1–2
Charging, 1–2
Cords, 3–1
Safety, xii
Fuse, xii, 1–2
Distance / Division, 1–9
Maximum Hold, 1–9
Pulse, 1–9
Fuse Rating, 1–2
Requirements, viii
Safety, xii
Single Sweep, 1–9
Vertical Scale, 1–9
Single Sweep, 1–31
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Index
Source, viii
Voltage Rating, 1–2
Physical, A–4
Store, 2–18
Voltage Selector, 1–2
Voltages, 1–1
Store the Waveform, 1–20
Product Description, vii
Product support, contact information, x
Pulse, 1–30, 2–1, 2–23
Incident, 2–3, 2–6, 2–13
Reflected, 2–3, 2–13
T
Table of Contents, i
Tektronix, contacting, x
Temperature, Low, 1–4
Terminator, 3–2
Troubleshooting, C–1, D–1
Tutorial, 2–1
Q
Questions and Answers, 2–26
U
R
Unpacking, viii
References, vii
URL, Tektronix, x
Reflection Coefficient, 1–17
Repacking, viii
Return Loss, 1–18
V
Velocity of Propagation, 1–12
Table of Types, 1–12
S
Unknown Vp, 1–12
Safety
Velocity of Propagation (See also Controls), 1–7
Covers, xii
Explosive Atmosphere, xii
Grounding, xii
VERT SET REF (see Vertical Set Reference), 2–15
Vertical Scale, 2–6, 2–15
Vertical Set Reference, 1–26, 2–15
Vibration Spec, A–3
Symbols, xi
Terminology, xi
View Diff (see View Difference), 2–20
View Difference, 1–21, 2–20
View Input, 1–20, 2–17
View Store, 1–21, 2–18
Voltage (see Power), 1–2
Safety Summary, xi
Salt Atmosphere Spec, A–3
Sand and Dust Spec, A–3
Scale (see Controls), 1–7
Service Manual, 3–2
Service support, contact information, x
Ship Carton Strength, ix
Shock Spec, A–3
Short, 1–15, 2–4, 2–19
Single Sweep, 1–31, 2–24
Slide Rule, 3–2
Specifications, A–1
Electrical, A–1
Voltage Spec, A–2
Vp (see Velocity of Propagation), 1–12
W
Water Resistance Spec, A–3
Waveform Storage, 1–20
Web site address, Tektronix, x
Weight Spec, A–4
Environmental, A–3
What is a 1503B?, 2–1
Index–3
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Index
Index–4
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