Fluke DTX-1800, Technical Reference Handbook

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Certifying Twisted Pair Cabling
Twisted Pair Autotest Results
3-19
3
Propagation Delay and Delay Skew
Propagation delay is the time taken for a test pulse to travel
the length of a cable pair. The delay is measured in
nanoseconds. One nanosecond is one-billionth of a second,
or 0.000000001 second. Propagation delays vary slightly
among pairs because of small differences in electrical
characteristics and length.
Delay skews are the differences in propagation delays
between the shortest delay and the delays of the other
cable pairs. The shortest delay is shown as “0 ns” in the
delay skew results.
The propagation delay and delay skew results show a limit
if the measurements required by the selected test limit.
Otherwise, the results always show PASS. Figure 3-13 shows
the propagation delay and delay skew results screens.
amd88f.eps
Figure 3-13. Propagation Delay and Delay Skew Results
The pair with the shortest electrical length
is usually the shortest pair