Digital bridge capacitive measuring module

Abstract

The invention provides a digital bridge capacitive measuring module. According to the following technical scheme, a balancing bridge arm and a measuring bridge arm form a digital balancing mechanism, wherein the phase difference between alternating signals of the balancing bridge arm and the measuring bridge arm is 180 degrees; an excitation source unit generates three kinds of signals, wherein the 0-degree phase driving signals are used for driving a synchronous amplification circuit to send orthogonal filtering measuring signals into a zero-position balancing unit to generate rebalancing monitoring signals, the AC reference signals are used for driving a capacitor-balanced bridge arm circuit, and the AC excitation signals are used for driving a BITE detection bridge arm circuit in different times; the two alternating signals, with the phase difference being 180 degrees, of the balancing bridge arm and the measuring bridge arm are summed through a summing circuit and are filtered into a 0-degree phase driving signal and a 90-degree phase driving signal through a band-pass filter circuit; a CPU control unit conducts balance control on a D / A converter in the zero-position balancing unit, data of the D / A converter are compared with theoretical data pre-stored in the CPU control unit, and the CPU control unit uses the data, obtained when it is detected that the balancing bridge arm and the measuring bridge arm are balanced, of the D / A converter as the currently measured capacitance value.

Description

technical field

[0001] The invention relates to a conditioning conversion measurement module mainly used for analog capacitance signals such as pressure, liquid level and displacement on aircraft, automobile and ship engines. Background technique

[0002] Capacitance is the most used basic component in many measurement systems. Capacitance changes slightly at different temperatures, dielectric constant and pole spacing, and its technical parameters will change. Based on this characteristic, the capacitive sensor converts the measured mechanical quantity, such as displacement and pressure, into the change of capacitance. It has been widely used in industry, medicine, military and other fields. Capacitive sensors can be divided into three types: pole distance change type, area change type, and medium change type. The pole distance change type, such as capacitive pressure sensor, is generally used to measure small linear displacement or pole distance changes caused by force, ...

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