Certifying Twisted Pair Cabling
Twisted Pair Autotest Results
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Length
Length results show the length of each cable pair. The
PASS/FAIL result is assigned based on the shortest measured
length. The lengths of the other pairs are shown for
informational purposes. A 2 % to 5 % difference in
measured length among cable pairs is normal because of
the following:
•
Signals travel at slightly different speeds in each cable
pair, but the tester uses the same speed to calculate the
length of each pair.
•
The twist rate varies slightly among cable pairs. If you
untwisted and straightened all the pairs, they would
have slightly different lengths.
Figure 3-10 shows a length results screen.
Note
Differences between measured and actual length
values can be caused by variations in the cable’s NVP
value. NVP values can vary among cable types, lots,
and manufacturers. In most cases, these differences
are minor and may be disregarded.
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Figure 3-10. Length Results
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