TDR Cable Length Meter Measure length, determine (NVP/VoP) factor, measure distance to faults and track electrical, data, two-wire and Romex® cables. The Klein Tools Cable Length Meter is a portable time domain reflectometer (TDR) for cable length testing. It measures cable lengths, determines the (NVP/VoP) factor, measures distance to cable faults and features a tone generator for cable location. This cost-effective tester provides accurate cable length measurement for various cable types. Includes test leads and carrying case.