Our increasingly automated society has resulted in factories, offices, institutions, and even homes being filled with more and more wires and cables. Network cables, telephones wires, power cables, CATV cables, etc. all compete for space in cramped conditions with runs that can span impressive distances. With so much wire and cable hidden underground or inside walls, it's difficult to identify issues and pinpoint the area when problems arise. Cable fault testers / TDR meters are electronic devices designed to test electrical connections and identify the location of cable faults.

Cable Faults

Cable faults are issues which effect the performance of cables and wires. Faults can be caused by open circuits, shorts, kinks, taps, shield damage, thermal damage, UV damage, water ingress, loosened or corroded interconnects, poor-quality cables and connectors, and anything else that affects system performance. If faults are not identified and repaired, a costly voltage breakdown can occur.

There are different types of cable faults, which must first be classified before they can be located.

Ground or Earth Faults are caused by damage to-- or a breakdown of-- cable insulation which allows current to come in contact with an ungrounded conductor.

Short Circuit Faults occur when insulation between two cables is damaged or degrades and allows current to pass from one cable to the next without passing through the load.

Open Circuit Faults are when there is a break in the conductor of a cable thus interrupting the circuit.

Cable Fault Tester / TDR Meter Technology

Though cable fault testers vary in the features they possess, most are based on Time Domain Reflectometry or TDR technology. Time-domain reflectometry uses a pulse echo range-finding technique, similar to that used by sonar systems, and observes the reflected waveform as a way to determine the characteristics of electrical lines.

A short-duration, low-voltage pulse is transmitted into the cable at a high-repetition rate. If there are no faults and the cable is properly terminated, no signal will be reflected back. Any type of fault will cause irregularities in impedance and the signal will be reflected back. The amplitude of the reflected signal will provide characteristics of the impedance. The distance to the fault is also calculated by the time it takes for the pulse to return, thus avoiding the need to rip into walls and floors to locate the fault. TDR technology can pinpoint a fault to within centimeters.

Because of the sensitivity to impedance variations found in cable fault testers with TDR technology, they can be used to verify cable impedance characteristics, splice and connector locations and associated losses, and estimate cable lengths. Cable fault testers with TDR technology are used for testing very long cable runs or other instances where it is impractical to disturb cables for testing. They are also important preventive maintenance tools for telecommunication lines as they will identify, well before catastrophic failure occurs, increasing resistance levels on joints and connectors caused by corrosion, as well as insulation leakage as it degrades and absorbs moisture.

Applications for Cable Fault Testers / TDR Meters

  • Identify wiring faults
  • Find distances to opens and shorts
  • Test patch cords
  • Trace cable locations
  • Measure cable length (in location or on a reel, coil, etc.)
  • Map network layout

If you have any questions regarding cable fault testers / TDR meters please don't hesitate to speak with one of our engineers by e-mailing us at sales@instrumart.com or calling 1-800-884-4967.