Cable Length Calculator (TDR)

TDR technology sends electrical pulses down a cable and measures the time it takes for reflections to return. By analyzing these reflections and knowing the cable's velocity factor, it can accurately determine cable length and locate faults.

Velocity factor (VF) is the ratio of signal propagation speed in the cable compared to the speed of light in vacuum. Different cable types have different VF values - coax typically has 0.66, while data cables are around 0.64. Using the correct VF is crucial for accurate length measurements.

TDR measurements are typically accurate within ±2% plus 3 feet for most cable types. Accuracy depends on using the correct velocity factor for your specific cable type and proper calibration of the TDR instrument.

TDR can measure most electrical cables including coaxial cables, twisted pair data cables (CAT5/CAT6), Romex electrical cables, twin lead cables, and many other wire types. Each cable type requires its specific velocity factor for accurate results.

Yes, TDR technology can locate opens, shorts, and impedance mismatches in cables. The reflection characteristics change at fault locations, allowing technicians to pinpoint the exact distance to the problem area.

Round-trip time is the total time for a signal to travel from the TDR instrument to the end of the cable and back. This time, combined with the velocity factor, is used to calculate the actual cable length.

Check your cable specifications or use standard values: Coax (0.66), CAT5/CAT6 (0.64), Romex (0.62), Twin Lead (0.82). For unknown cables, you can measure a known length sample to determine the correct velocity factor.

TDR provides non-destructive testing, can measure installed cables without access to both ends, locates faults precisely, works on energized or de-energized circuits, and offers high accuracy for both length measurement and fault location.