Signal processing circuit for inductivity measuring sensor

PURPOSE: To prevent the error or temperature variation of a sensor from having effect on the output signal by providing means for connecting the coil of an inductivity measuring sensor with a comparator through a coupling capacitor and compensating for the charging thereof. CONSTITUTION: A signal induced in the coil 10 of an inductivity measuring sensor is applied through a coupling capacitor 11 with a peak value detector 14. A peak value memory capacitor 18 is charged with the positive half wave of a measuring sensor through a diode 17. Charges taken away tram the coupling capacitor 11 are compensated by a current flowing into a charge compensation resistor 12. Voltage of the peak value memory capacitor 18 is used for varying the threshold voltage of a differential amplifier 16. When the output signal from the coil 10 exceeds a variable threshold voltage, an output signal appears at the output terminal 28 of the differential amplifier 16. COPYRIGHT: (C)1989,JPO