测控技术与仪器论文

测控技术与仪器论文脉宽调制型差动电容位移传感器的研究

学院名称：机械工程学院

专业：测控技术与仪器

脉宽调制型差动位移传感器的研究

摘要电容式传感器是将被测非电量的变化转换成电容量变化的一种传感器。结构简单、分辨率高、可非接触测量，并能在高温、辐射和强烈振动等恶劣条件下工作。目前在位移、振动、角度、加速度、压力、压差、液面和成分含量测量等方面获得广泛应用。然而，电容式传感器将被测非电量变换为电容变化后，其信号十分微弱，不便于直接测量，所以为了测出被测非电量必须采用测量电路将其转换成电压、电流或频率信号。

本论文主要研究的内容是电容式位移传感器及其测量电路。设计中电容器由三片相同的金属板构成，三块板平行放置，连成差动结构，然后配以脉宽调制信号处理电路从而实现对微小位移的检测。这种电路无需相敏检波电路即可判定产生位移的板的运动位置，由于采用差动结构，整体电路具有线性度高、灵敏度高和温漂小的特点。

设计时将系统分为两部分，即传感器制作部分和测量电路部分，通过分步测试调理，最后建立一个完整的实验系统，研制出一台微位移测试仪。当动极板与两固定极板的相对位置发生变化时，即产生相对位移时，电路的输出电压产生变化，电压变化与位移呈现线性关系。

关键词：电容式传感器差动结构脉宽调制微小位移线性关系

Study of Displacement Sensor Based on Pulse Width Modulated Differential

Capacitors

Abstract The capacitive sensor is a type of sensor which is used to convent the measured non electrical quantity to the changes of the capacity.It has many characteristics ,such as simple structure, high resolution.It can be used for non-contact measurement.Moreover,the capacitive sensor can also work under harsh conditions such as heat, radiation, and strong vibration.Now, it is widely used in the displacement, vibration, angle, acceleration, pressure, differential pressure, liquid level and component content measurement.However，after the capacitive sensors transform the measured non-electricity into the changes of the capacitance,the output signal is so weak that it can not be measured directly.So the measuring circuit is needed to change the measured non-electrical quantity into the voltage, current or frequency signals.

The contents of this thesis are the design of the capacitive displacement sensor and its measurement circuit.In this design,the capacitor consists of three metal plates which are placed parallel,so it is connected as a differential structure.And then using a pulse width modulation signal processing circuit so that we can achieve the detection of small displacements.This circuit can judge the position of the board which causes the displacement without a phase sensitive detection circuit.Due to the differential structure, the overall circuit has the following characteristics ,high linearity, high sensitivity and small temperature drift .

The system is divided into two parts.One is the production of the sensor.The other is the measuring circuit portion.By a step-by-step test,we build a complete experimental system and develop a micro-displacement testing instrument.When the relative position of the moving plate and the two fixed plates which is called relative displacement changes,the output voltage of the circuit changes.There is a linear relationship between the voltage and the displacement.

Key words :Capacitive sensors Differential structure Pulse width modulation Micro-displacement Linear relationship