Abstract: A wire testing method and apparatus test wire in-situ in a rigidly installed state, such as an aircraft. An apparatus for rapidly switching the excitation voltage and ground compensates for stray currents. The apparatus outputs a stray current signal, a detected signal, and a difference signal indicative of a measurement with stray current signal removed.

Abstract: A part of a wire is tested, in situ, for degradation. The part of the wire is optionally enclosed in a jacket. A conductive medium is disposed on the wire. A test unit has a test elements in contact with the conductor of the wire and with the conductive medium. An attempt is made to induce a current along a path from the test unit, through the conductor, through the conductive medium, and back to the test unit. If a current is induced, degradation is detected. The test unit receives a cable of wires, and a selector switch of the test unit electrically couples a voltage source to selected elements of the cable in turn. Wires are tested in situ in an aircraft or other restrictive location.