Capacitive sensor evaluation circuit - periodically separates sensor from reference voltage source and transfers charge to reference capacitance

摘要

The evaluation circuit has a reference voltage source (14) coupled to the sensor (11) and a constant reference capacitance (17). The sensor is periodically disconnected from the reference voltage source with simultaneous transfer of the sensor charge to the reference capacitance, the voltage across which is evaluated. Pref. the sensor is coupled to the reference voltage source via a semiconductor switch controlled by the signal from an oscillator (16). USE - Provides output signal proportional to measured parameter value.