Fluke Networks CertiFiber Pro Users Manual - Manual (Page 107)

Chapter 3: How to Certify Twisted Pair Cabling
Twisted Pair Autotest Results
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The selected test limit does not have a limit for the test, or
a dB rule applies. See “About dB Rules” on page 116.
The results are within the range of accuracy uncertainty for
the tester. See “PASS*/FAIL* Results” on page 79.
The measurement shown for frequency-domain results is the
worst margin. (The insertion loss plot is different. See “Insertion
Loss” on page 94.)
 When more than one button shows at the bottom of the screen,
the tester highlights one in yellow to recommend which one to
tap. See “Buttons to Do Tests and Save Results” on page 53.
Scalar Results
Scalar results are measurements that do not change with
frequency. These are the Length, Propagation Delay, Delay Skew
and Resistance results. These results do not have plot data.
Length, Propagation Delay, and Delay Skew
The length results show the length, propagation delay, and delay
skew of each cable pair. See Figure 36.
The length shown on the PERFORMANCE screen is the length of
the shortest pair. The tester uses the length of only the shortest
pair to get a PASS or FAIL result for the length test.
Note
If the length of the shortest pair does not exceed
the limit by 10 %, then the length test passes even
if other pairs exceed the limit. This is the 10 % rule
for length, as given in the ANSI/TIA standard. See
the Fluke Networks Knowledge base for details.
A 2 % to 5 % difference in measured lengths of wire pairs in a
cable is normal for these reasons:
 Signals travel at slightly different speeds in each wire pair, but
the tester uses the same NVP to calculate the length of each
pair.