DTX Series CableAnalyzer
Technical Reference Handbook
3-16
Characteristic impedance is the impedance a cable would
have if the cable were infinitely long. Proper network
operation depends on constant characteristic impedance
throughout the system’s cables and connectors. Abrupt
changes in characteristic impedance, called anomalies,
cause signal reflections that can cause network faults.
Length
Length results show the length of each cable pair. The
PASS/FAIL result is assigned based on the shortest
measured length. 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, along with
propagation delay and delay skew results for
comparison.
Notes
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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