Sensors based on eddy currents in a moving disk

A new kind of displacement sensor is proposed, based on the creation of eddy currents in a moving conducting disk, set above an amorphous wire magnetostrictive delay line, which is parallel to a pair of current conductors. Transmission of pulsed current through these conductors causes a pulsed eddy current loop in the conducting disk, which in turn causes an acoustic pulse in the delay line. The amplitude of this acoustic pulse depends on the distance between a moving conducting disk and delay line. Experimental results are given, concerning tests of as-cast and stress-current annealed delay lines. Applications of this sensing idea are presented