Abstract: An electronic circuit utilizing a parallel tuned resonant circuit and time variant frequency multiplying to eliminate undesired response changes of the tuned circuit due to temperature is disclosed. The electronic circuit illustrated permits accurate measuring of the change of inductance in a parallel tuned circuit where such change of inductance is due to an input parameter to be measured. The inductive component being measured may be located in environmental conditions which include a large variation in ambient temperature. While normally such wide temperature variations may substantially interfere with the measurement of the value of the inductance in question, the disclosed invention provides for compensation of such undesired changes so that the actual change of the inductance can be monitored without interference.

Abstract: A magnetic sensor for the collection and measurement of ferrous particles through the use of an electronic tuned circuit is disclosed. The sensor contains an electrical inductance along with an integral magnet to attract ferrous particles suspended in the fluid. The ferrous particles collecting on the magnetic surface of the sensor causes a change in the inductance of the integral coil which is measured by an electronic circuit. The electronic circuit operating in conjunction with the sensor utilizes a parallel tuned resonant circuit and time variant frequency multiplying to eliminate undesired response changes of the tuned circuit due to the temperature change of the sensor. The sensor may be located in environmental conditions which include a large variation in ambient temperature. The disclosed invention provides for compensation of such undesired changes caused by temperature change so that the actual change of the inductance in the sensor can be monitored without interference.