Fluke CableAnalyzer DSX-5000, Technical Reference Handbook, Page: 212 / 700

Versiv Series Cabling Certification Product Family
Technical Reference Handbook
176
Impedance
Note
The minimum cable length for an impedance
measurement is 13 ft (4 m). For impedance
measurements on shorter cables, the tester shows
Cable too short, and an for the impedance and
overall test results.
The impedance measurement shows the approximate
characteristic impedance of the cable at a point approximately
13 ft (4 m) from the tester.
Characteristic impedance is the impedance a cable would have if
the cable were infinitely long. Good cabling has relatively
constant characteristic impedance throughout the cable and
connectors.
Changes in impedance cause signal reflections in cabling. In
computer networks, signal reflections can cause network faults. In
video systems, reflections can cause poor picture quality.
Figure 81 shows the results from an impedance test.