Design of a multi-channel micro-capacitor acquisition system

Abstract

Aiming at the measurement method of electrical capacitance tomography, a set of micro-capacitance acquisition system for planar array capacitance sensor is designed. Using the circuit principle design of high sensitivity and anti-interference, a dual-channel signal generator with adjustable amplitude and phase was designed to excite the capacitance sensor. The core capacitance voltage conversion circuit of the acquisition system adopts an AC excitation type conversion circuit with the ability to resist stray capacitance interference, and analyzes the error influencing factors in combination with the actual circuit components. The array control switch group is designed for multi-channel switching acquisition, and optimized in conjunction with the capacitor voltage conversion circuit. For the phase demodulation method, an orthogonal optimization method based on hardware multiplier is proposed. A micro-capacitor experiment is designed to calibrate the acquisition circuit. The experimental results show that the capacitance acquisition resolution of the micro-capacitor acquisition system within the acquisition range is 2.84fF, the linearity is 0.9998, and the acquisition error is less than 0.12fF.