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Admittance evaluating circuitry for variable measurement capacitance esp. for level gauge probe - includes evaluation circuit controlled by switching signal derived from oscillator and supplied via phase shifter to produce DC signal corresp. to admittance of capacitor
Admittance evaluating circuitry for variable measurement capacitance esp. for level gauge probe - includes evaluation circuit controlled by switching signal derived from oscillator and supplied via phase shifter to produce DC signal corresp. to admittance of capacitor
The evaluation circuit has a sync. demodulator (21-34) with a switch (23) controlled by the switching signal derived from the supplied oscillator (1). A first regulating circuit (35-37) is connected to the output of the phase shifter for regulating the key ratio of the switching signal. The output signal of the first regulating circuit is preconnected to the phase shifter (33), controlled with the sine-rectangular wave converter (30) coupled to the oscillator (1). A second regulating circuit (39-45) regulates the phase position of the phase shifter. This circuit is coupled on the input side to the oscillator. Its output signal lies at a phase position control input (33') of the phase shifter. A third regulating circuit (48-55) regulates the amplitude of the output signal of the oscillator (1). ADVANTAGE - Ensures high evaluation accuracy.
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