Electrical wiring is used to conduct electrical current in a variety of applications. For example, electrical wiring is used to conduct electrical energy for the purposes of power delivery. Electrical wiring is also used in data transmissions between electronics devices. Exceptionally important applications include the various power and data delivery uses in human related services, such as transportation (e.g., plane, automobile, etc.) and medical care.
Over time, wiring can deteriorate due to environmental conditions and ultimately degrade wire integrity. For example, excessive flex, chafing between adjacent wires, lack of strain relief, altitude, temperature, humidity, and/or acceleration can jeopardize the integrity of the wire. When a wire breaks, open circuit conditions are created that contribute to a loss of signal integrity, component failures, or even catastrophic fires. Due to the intermittent nature of most of cable failures, these problems are often difficult to detect and more difficult to repair.
Hard faults (i.e., those fault where a wire has completely failed) are quickly detected using common circuit testing equipment. Intermittent faults, however, are much more difficult to detect because the faults are generally only detectable when the wire is live (e.g., operational). Time domain reflectometry can detect intermittent events in live wires by monitoring the wire over a period of time. For example, a time domain reflectometer (TDR) may transmit a relatively short rise time pulse along a conductor. If the conductor is of a uniform impedance and properly terminated, the entire transmitted pulse is absorbed in the far-end termination. Thus, no signal is reflected towards the time domain reflectometer. Impedance discontinuities in the wire, however, cause a portion of the incident signal to be reflected back towards the source. The intermittent fault and even the location of the fault may be determined from the reflected signal. Accordingly, if the faulty wire is monitored over some period of time with the time domain reflectometer, a fault in the wire is likely to be detected by the time domain reflectometer.
Detection of wire faults is possible after the fault occurs. However, detection after the fact may be too late. For example, an aircraft with aging deteriorating wires may begin to experience intermittent faults in the wiring. TDR testing of the wires may be performed as part of maintenance on the aircraft while the aircraft is not in-flight to repair/replace faulty wires. But, intermittent faults are likely to occur while the aircraft is in flight, jeopardizing the safety of the people on board.