a circuit for measuring the reactance of a reactance sensor which varies responsive to a condition to be sensed , such as pressure , and which provides an output signal representative of the sensed condition is disclosed . the circuit comprises an oscillator coupled to the sensor for providing a time varying oscillator signal to the sensor , and a plurality of rectifiers coupled to the oscillator and to the sensor for providing charging signals to the sensor and for providing discharging signals from the sensor . a control amplifier is coupled to the sensor charging and discharging signals and to the oscillator for providing an input control signal to the oscillator as a function of the sum of at least two sensor signals wherein at least one of the sensor signals is selectively amplified to enhance the relationship between the output signal and the sensed condition .