The United States of America as Represented by the United States

Kenneth O Morey

Bruce W DuVall

James W Valentine

An inductive level sensor has inductively coupled primary and secondary windings. Circuitry drives the primary with an AC signal of constant current magnitude and selected frequency f to induce in the secondary, a voltage signal V of magnitude .vertline.V.vertline., frequency f and phase difference .phi. from the driving signal. Circuitry operates to generate a voltage output signal proportional to .vertline.V.vertline. cos (.phi.-.theta.), where .theta. is a selectively set phase shift factor. By properly and selectively adjusting the frequency f and phase shift factor .theta., an output signal .vertline.V.vertline. cos (.phi.-.theta.) can be provided which self-compensates for changes in mutual inductance caused by operating temperature variations so that an output signal is produced which is substantially linearly proportional to changes in the level of a pool of liquid metal being monitored. Disclosed also is calibration circuitry and circuitry for converting the voltage signal .vertline.V.vertline. cos (.phi.-.theta.) into a current signal.

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Colorado Springs, CO, United States of America

Kenneth O Morey