基于开关电容技术的一种电容式传感器测量电路

A Capacitance Measurement Circuit Based on the Switched-capacitor Technique

电容式传感器输出的电容信号很小,一般为几pF至几十pF,因此其后续测量电路的选择与设计非常关键。本文所提出的基于开关电容技术的测量电路是把被测电容转换成微处理器可直接处理的二进制数字信号,克服了传统测量电路易受寄生电容影响和测量结果精度依赖于电源电压稳定性的不足。本文详细分析了该电路的工作原理和设计要点,实验验证了所述测量电路的正确性。

It is important to select and design the capacitance measurement circuit because the output of capacitance sensor is very small. In this paper a capacitance sensor measurement circuit based on the switched-capacitor technique which can convert a capacitance into a digital signal is proposed. And the measurement circuit can overcome the shortage of the traditional measurement circuits such as the output is easy to be affected on the parasitic capacitance and the precision of measurement results is depent on the stability of the power supply. The working principle and the design key of the circuit are analyzed in detail. Experiments show that this measurement circuit is feasible.