Multiplexing aircraft wiring for non-destructive testing.

摘要

Significant research is being done at Utah State University to detect faults or breaks in aircraft wiring by using Frequency Domain Reflectometry (FDR). A complicated problem is to test several wires with FDR without physical intervention by switching the wires. Thus, the multiplexer becomes an important link between FDR electronics and the aircraft wires. Commercially available multiplexers have common ground which short circuits the wires, and are not acceptable. Evaluating suitable switching methods design a multiplexer with separate ground, multiplexer with PIN diodes as switching components seemed to be the most suitable option. A common ground PIN diode multiplexer and a separate ground PIN diode multiplexer were built and tested. The results obtained were analyzed and compared with the results obtained without a multiplexer. Low frequency components and phase shifts present in the results obtained were taken care of to obtain the final result which were found to be satisfactory.