LANTEK User Manual - Ideal Industries

Chapter 3
Structured Cable Field Calibration and Testing
Wire Length Test
This test measures the length of each wire pair to make sure that the recommended
limits for the particular cable type are not exceeded. The Wire Length Test is mainly
used for informational purpose only. Depending on the units selected in the Setup
menu, length is reported in either feet or meters.
Length and NVP
Figure 3-11: Wire Length Test Screen
Measuring the length of the cable requires that you know the Nominal Velocity of
Propagation (NVP) of the cable. Refer to the specification or the manufacturer of the
cable you are testing for the cable NVP. If the wire specification is not available, use a
known length of good cable (100 - 200 feet) and use the calculate NVP function to
enter the total length of the cable and calculate the correct NVP.
Wire Length Errors
Lengths may differ slightly between pairs in the same cable, due to minor NVP
differences between the pairs and physical length differences due to twisting patterns.
When electrically measured cable length varies too much from actual length, a
problem exists.
Troubleshooting Wire Length Problems
Problem: Length between a pair of the same cables varies by more than 10%.
Probable Causes
Incorrect NVP.
Excessive cable length.
Installed matched terminator not functioning correctly.
Cable insulation damage to longer pairs.
Break or short in a pair.
Elevated capacitance on a pair.
Other Tests Affected Test Possible Result
DC Loop Resistance May be slightly high or fail.
Attenuation
May be slightly high or fail.
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