Tektronix 1502C Appendix D: Application Note

1502C MTDR User Manual D–1

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.

HVoltage Standing Wave Ratio vs. Percent Reflected Voltage

HReturn Loss, dB, vs. Percent Reflected Voltage

HPercent Reflected Voltage vs. Characteristic Line Impedance (for either 50 W

or 75 W source)

HPercent Reflected Voltage vs. Load Resistance (for either 50 W or 75 W

source)

HCharacteristic Line Impedance or Load Resistance vs. Reflection Amplitude

(as seen on your TDR)

HDielectric Constant vs. Velocity Factor

HTime vs. Short Distance in centimeters or inches (any dielectric)

HTime vs. Long Distances in meters or feet (any dielectric)

Terms and Symbols RSSource Resistance of a signal generator

ZSSource Impedance of a signal generator

ZOCharacteristic Impedance of a transmission line

ZLLoad Impedance for a transmission line

RLLoad Resistance for a transmission line

rReflection Coefficient (rho): the ratio of incident to reflected voltage

mrReflection Coefficient divided by 1,000 (millirho)

% Ratio of the incident voltage to reflected voltage multiplied by 100

VSWR Voltage Standing Wave Ration (peak-to-valley)

c Velocity of light in air

VPPropagation Velocity of a signal in a transmission line

VtVelocity Factor (fraction of the velocity of light)

κDielectric Constant

D Outer Diameter of the dielectric in a coaxial cable

d Diameter of the center conductor in a coaxial cable

L Inductance in nanoHenries (nH) per foot

C Capacitance in picoFarads (pF) per foot

Contents

Main Page WARRANTY Contacting Tektronix Table of Contents Page List of Figures Page Page Page General Information Installation and Repacking Unpacking and Initial Inspection Repacking for Shipment Power Source and Power Requirements Page Page General Safety Summary Safety Terms and Symbols Page Page Page Operating Instructions Overview Powering the 1502C Handling Care of the Battery Pack Battery Charging Low Battery Low Temperature Operation Preparing to Use the 1502C 1502C Tektronix Operating Instructions 161502C MTDR User Manual Display Figure 14: Display and Indicators Front-Panel Controls Menu Selections Main Menu Page Page Page Test Preparations The Importance of Vp (Velocity of Propagation) Finding an Unknown Vp Operating Instructions 1502C MTDR User Manual 113 Figure 17: Vp Set at .66, Cursor at Reflected Pulse (Set Correctly) Figure 15: Vp Set at .30, Cursor Beyond Reflected Pulse (Set Too Low) Figure 16: Vp Set at .99, Cursor Less Than Reflected Pulse (Set Too High) Cable Test Procedure Distance to the Fault Page Page Reflection Coefficient Measurements Return Loss Measurements Ohms-at-Cursor Using VIEW INPUT How to Store the Waveform Using VIEW STORE Using VIEW DIFF Page Page Using Horizontal Set Reference Page Using Vertical Set Reference Vertical Compensation for Higher Impedance Cable Page Page Additional Features (Menu Selected) Max Hold Pulse On/Off Single Sweep Page Operator Tutorial What is the Tektronix 1502C? How Does It Do It? You, the Operator Menus and Help Getting Started Page Page The Waveform Up Close Page A Longer Cable Ohms-at-Cursor Page Page Noise Page Set Ref (Delta Mode) HORZ SET REF Page VERT SET REF Page VIEW INPUT STORE and VIEW STORE Page VIEW DIFF Menu-Accessed Functions Max Hold Page Pulse On / Off Single Sweep Page TDR Questions and Answers Page Page 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 Optional Accessories Accessories Standard Accessories Options and Accessories 1502C MTDR User Manual 33 Page Appendix A: Specifications Electrical Characteristics A21502C MTDR User Manual Table A1: Electrical Characteristics (Cont.) 1502C MTDR User Manual A3 Environmental Characteristics Table A2: Environmental Characteristics A41502C MTDR User Manual Certifications and Compliances (continued next page) 1502C MTDR User Manual A5 Physical Characteristics Table A3: Physical Characteristics Page Appendix B: Operator Performance Checks Equipment Required Getting Ready Power On Metric Instruments Set Up 1. Horizontal Scale (Timebase) Check Page Page 2. Vertical Position (Offset) Check 3. Noise Check 4. Offset/Gain Check 5. Sampling Efficiency Check 6. Aberrations Check 7. Risetime Check Page 8. Jitter Check Conclusions Appendix C: Operator Troubleshooting Appendix C: Operator Troubleshooting C21502C MTDR User Manual Operator Troubleshooting (with cases on) Error Messages Message: Occurrences: Meanings: Message: Remedies: Page Page Page Appendix D: Application Note Pulse Echo Testing of Electrical Transmission Lines Using the Tektronix Time-Domain Reflectometry Slide Rule Terms and Symbols Relationships VSWR vs. Percent Reflected Voltage Return Loss (dB) vs. Percent Reflected Voltage Appendix D: Application Note D41502C MTDR User Manual Percent Reflected Voltage vs. Characteristic Line Impedance Figure D3: Slide Rule 50 ohm Source +1r = W+.03r = 53.1W Appendix D: Application Note 1502C MTDR User Manual D5 Percent Reflected Voltage vs. Load Resistance Characteristic Line Impedance or Load Resistance vs. Reflection Amplitude (as seen on your TDR) Centimeters vs. Inches or Meters vs. Feet Dielectric Constant vs. Velocity Factor Time vs. Short Distances, in Centimeters or Inches Time vs. Long Distances, in Meters or Feet Page Glossary Page Page Page Page Page 1502C MTDR User Manual Index1 Index A B C D I L M N O Q R S T U