The Loop Resistance Tester is a portable electronic instrument for measuring the resistance of electronic cable shielding as installed in aircraft, without requiring the cables to be disconnected. It comprises three elements: couplers, joint probes, and an instrument assembly. The couplers are used to measure the loop resistance formed by the shielding in the cable under test and airplane structure. The joint probes are used to measure the resistance of joints in the cable (cable-to-backshell, connector-to-bracket) to isolate bad joints if the loop measurement is out of tolerance. The algorithms and circuitry the Loop Resistance Tester uses to measure the loop and joint resistances are described.
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