Natural Amplification of Soft Defects Signatures in Cables Using Binary Time Domain Reflectometry

In our digital world, energy and data transmission play a major role and often rely on electrical wires. Some of these wires are used in harsh or aggressive environments and may be subject to defects. Security and preventive maintenance require tools to detect and precisely locate such defects. This paper details the Binary Time Domain Reflectometry (BTDR) method, presented earlier, which does not rely on the use of expensive and complex digital to analog and analog to digital conversion components. We explain the role of additive white noise and of the use of the time derivative for the improvement of its performances. The study focuses on BTDR's natural capacity of magnifying soft defects' peaks on the reflectogram. The method takes advantage of phase opposition to cancel the contribution of the extremities of the line under test and saturate the amplitudes of the remaining peaks. This can only be achieved if these contributions are equal or very close to each other. A balancing device is added at the cable's interface to meet this requirement. This low complexity additional system, made of two controlable digital potentiometers, is driven by the programmable logic digital system at the heart of the reflectometer. Direct magnification of very low amplitude peaks of incipient defects is obtained without any data post-processing. The amplification performance depends on the adjustment accuracy of the potentiometers and the hysteresis level of the comparator used to replace the converters.