一种电容式传感器数字化通用检测接口设计

Universal digital detection interface for capacitive sensors

针对电容式传感器的微变电容检测困难的问题,提出了一种数字化的通用检测接口方案。分析了基于"激励-检测"的直接式微变电容测量原理,利用DDS发生载波,并采用离散傅里叶变换分离测量结果的幅值与相位以求得电容变化量。根据接近式电容传感器的测量需要,设计了具体的硬件电路进行验证。实验结果表明,检测正确率在95%以上,该接口方案能够较好地检测设计值在0.1pF以上量级的微变电容,设计简洁,具有较强的移植性。

Aiming at the difficulty in detection of micro capacitance variance in capacitive sensor, a universal digital detec tion method was proposed. Thoroughly analyzed the principle of direct micro capacitance variance detection method based on Drive-Detection which uses DDS to generate carrier and employs discrete fourier transform （DFT） to separate the am plitude and phase of the result, a micro capacitance change can be thus calculated. A detailed circuit was implemented on a capacitive proximity sensor to verify the method. Experimental results showed that the correct rate is above 95%. The prototype circuit is able to detect capacitive sensor with value higher than 0. lpF and is simple to implement and easy to be transplanted.