Differential capacitor alternating-current bridge sensing measurement and control circuit

Abstract

The invention provides a differential capacitor alternating-current bridge sensing measurement and control circuit, which comprises an alternating-current excitation source, two voltage-controlled operational amplifiers with reverse output are arranged at an alternating-current signal output end to form an alternating-current excitation source with double-end differential output; a program-controlled DAC unit provides reference voltage for the voltage-controlled operational amplifier; by controlling the reference voltage, the amplitudes of signals at the two ends of the differential excitationsource can be changed, so that the central point of differential excitation is bidirectionally shifted; the differential capacitance sensor is composed of a three-pole-plate capacitor, the distance between pole plates on the two sides is kept unchanged, and a middle pole plate can move towards the two sides. Polar plates on two sides of the differential capacitance sensor are respectively connected with two ends of a differential output alternating current excitation source to form an alternating current bridge; by adjusting the central point of the differential excitation source, the AC bridge can reach a near-balance state. At the moment, the middle polar plate moves, resulting in that bridge imbalance voltage is output after signal amplification, phase sensitive detection and low-passfiltering, so that the displacement of the middle polar plate in the capacitor is converted into a voltage signal.

Description

technical field [0001] The invention relates to the technical field of displacement measurement and differential AC bridge measurement, in particular to a differential capacitance AC bridge sensing measurement and control circuit. Background technique [0002] The differential capacitance AC bridge circuit is a high-precision measurement circuit, which is often used for displacement measurement. In the prior art, the balance adjustment and measurement and control of the electric bridge are generally realized by changing the grounding point of the center tap of the ratio transformer, or by mechanically adjusting the distance between the plates of the capacitive sensor. The above adjustment methods all need to introduce a special mechanical adjustment mechanism, electronic switch components or power, which will increase the hardware cost of the equipment, and will introduce certain interference, which will affect the accuracy of the measurement circuit. Contents of the inven...

AI Technical Summary

Problems solved by technology

The above adjustment methods all need to introduce special mechanical adjustment mechanism, electronic switch components or power, which will increase the hardware cost of the equipment, and will introduce certain interference, which will affect the accuracy of the measurement circuit

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