Apparatus and method for monitoring the presence of a conductive media

摘要

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 ¦V¦, frequency f and phase difference phi from the driving signal. Circuitry operates to generate a voltage output signal proportional to ¦V¦ 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 ¦V¦ 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 ¦V¦ cos ( phi - theta ) into a current signal.