Sensor arrangement producing one output signal depending on sensor internal resistance and another, depending on a measured variable

摘要

The sensor circuit arrangement includes a sensor (23; 53) that produces an alternating voltage sensor signal that varies according to a measured variable; first and second current supplying circuits (21, 51) connected to respective sensor terminals to apply first and second output voltages (U1, U2) to the respective terminals; a counter-coupling network (24, 54) coupling the current supplying circuits to provide respective constant currents to the sensor (23, 53) and a sensor signal processing circuit portion. The sensor signal processing circuit portion includes an operational amplifier (13,46) connected across the sensor terminals, a low-pass filter (20,50) connected to the operational amplifier and a capacitor (19, 46) connected to the operational amplifier to generate an alternating output signal having an amplitude depending on the magnitude of the measured variable. The low-pass filter produces a filter output signal indicative of a temperature-dependent internal sensor resistance. The sensor is at an ungrounded floating potential so that common-mode interference is compensated.