一种具有较大电容动态测量范围的接口电路

An Interface Circuit with Large Capacitance Dynamic Measuring Range

针对应用广泛的电容式传感器信号采集问题,提出了一种具有较大电容动态测量范围的高精度电容式传感器接口电路。该接口电路包括一个电容式有源电桥,以及用于将电容直接转换为频率的张弛振荡器,电路的频率输出用于确定微湿度传感器的响应特性。在基于薄膜的电容湿度传感器上进行了测试,实验结果表明,相比现有的类似电路设计,提出电路的结构更加简单且具有更大的电容测量范围和较高的精度,在1 pF^600 p F测量范围内的精度(误差百分比)<-2.14%,接口电路灵敏度为4.91 Hz/×10^(-6),且输出频率与电容变化成线性关系。

In order to solve the problem of signal acquisition of capacitive sensor,a high precision capacitive sensor interface circuit with large dynamic range is proposed.The interface circuit is composed of a capacitor active bridge circuit and relaxation ossillator which can convert capacitor into frequency directly,and a frequency output circuit which is used to determine the response of the micro humidity sensor.Based on the capacitive humidity film sensor it was tested,the experimental results show that compared with the existing similar circuit design,the capacitance measurement range of the circuit structure is more simple and has greater and higher accuracy,in 1 pF^600 pF measuring range accuracy(error percent)<-2.14%,the interface circuit sensitivity is 4.91.Hz/10-6,and the output frequency and capacitance change with a linear relationship.