Performance Analysis of a Readout Circuit With Oscillator and Diode Feedback Rectifier for Capacitive Proximity Sensor

Enhancing the sensitivity and resolution of the readout circuit is a pivotal technological approach to extending the detection range of capacitive proximity sensors (CPSs). This article introduces a novel high-sensitivity readout circuit that leverages the resonant amplification effect of the LC network in an oscillator to generate high-voltage excitation signals. By incorporating a feedback diode rectifier circuit, the circuit achieves a significant boost in sensitivity and resolution. Experimental results demonstrate an ultrahigh sensitivity of 55.8 V/pF and a resolution of 0.45 fF, far surpassing conventional methods. In various detection scenarios with different electrode sizes, the proposed circuit exhibits a superior detection distance compared with commercial CDC chips and capacitive proximity switches. Furthermore, this article systematically investigates the influence of circuit parameters on its performance. With its simple structure, low cost, and exceptional performance, this circuit is well-suited for applications in capacitive proximity switches and smart environmental monitoring.