Variable capacitor admittance measuring appts., esp. for level probe - contains oscillator supplying measurement capacitance and evaluation circuit controlled by switching signal derived from oscillator

摘要

The measurement capacitance (14) is supplied by an oscillator (1) and is connected to an evaluation circuit controlled by a switching signal derived from the oscillator and delivered via a phase shifter (33). The phase shifter is coupled to and controls an ac-dc converter. The evaluation circuit produces a d.c. signal corresp. to the admittance of the measurement capacitance. The evaluation circuit contains a synchronous demodulator (21-24) with a switch (23) controlled by the switching signal. The switch contacts are held at null potential. USE/ADVANTAGE - Esp. for capacitive level measurement probes. High accuracy with few components.