Chapter 3
Structured Cable Field Calibration and Testing
3-35
TROUBLESHOOTING TOOLS: TDR
Time Domain Reflectometer is one of the most powerful diagnostic tools available for
metallic cable troubleshooting. While conventional test methods cannot locate the
fault, TDR is used to reveal conditions about a cable that simple Pass/Fail reports and
raw measurements may not show.
The LANTEK tester uses the TDR test to scan the length of a cable for impedance
problems, or to accurately verify the cable length. TDR is not limited to identifying just
shorts or opens; it also points out any disturbances in the cable.
HOW TDR WORKS
The TDR function transmits energy into a cable pair, and the returning reflections are
monitored in a manner similar to radar.
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The shape of the reflection identifies a cable deformity, open, short, or
termination.
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The length of time it takes a transmitted pulse to return is used to calculate
cable length.
HOW TO PERFORM A TDR TEST
Prior to running the TDR, connect the LANTEK DH to the cable or link to be tested. The
TDR function is not a selected test available through custom cable setting.
TDR Test Setup
1.
Select the Cable Type.
Note: All TDR numerical information is NVP details of custom cables can be derived
from the data in the cable database.
2.
Calibrate and configure the tester as required.
3.
Disconnect the cable to be tested from all network equipment.
4.
Connect the required test lead to the Display Handset and to one end of the link
(TDR does not require a Remote Handset). Refer to Overview of Link Testing and
Requirements.
5.
Press ON/OFF to power up the Display Handset.
Performing a TDR Analyze Function
1.
Select the Analyze on the Ready screen. The Analyze screen appears.
2.
Press the ARROW keys to highlight the TDR function.
3.
Press ENTER to start the TDR test.
Note: When TDR is running, relays will be heard clicking in the Display Handset.
4.
At the completion of the TDR test, a graph is displayed.
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