Temp. compensating circuitry for capacitative sensors - has differential amplifier with bipolar output stage with temp.-dependent saturation voltages and internal signal propagation time increasing with temp.

摘要

The measuring capacitance (Cmess) of the sensor and the capacitance (Co) of a trimmable capacitor lie at the inverting input of a differential amplifier (DV). A voltage divider consisting of two resistors (R1,R2) for the operating voltage has its centre tap connected to the non-inverting input of the amplifier. The output of the latter is connected to the second terminal of the measuring capacitor and the resistor (R2) representing the earth point of the circuit via a load resistor (RL). The output of the amplifier is also connected to its inverting input via another resistor (R3). Its output is also connected to the non-inverting input via a drive (OV1) and a further resistor (R4). The output of the amplifier lies at the frequency analogue output voltage of the sensor which is dependent on the measured value. USE/ADVANTAGE - Capacitative transducer converting mechanical values to electrical, e.g. by variation in distance between capacitor plates to convert esp. small pressures, forces, displacement paths and inclinations. Negative transmission factor of sensor adjustably reduced.