杂散电容对交流法微电容测量电路噪声特性影响的分析  

Analysis of the effect of stray capacitance on noise characteristics of AC-based capacitance measurement circuit

作　　者：薛鹏[1] 彭黎辉[1] 

机构地区：[1]清华大学自动化系,北京100084

出　　处：《仪器仪表学报》2011年第2期284-288,共5页Chinese Journal of Scientific Instrument

基　　金：国家自然科学基金(6097209760532020)资助项目

摘　　要：对电容成像交流法微电容测量电路由杂散电容导致的测量噪声进行了研究。利用运算放大器的噪声模型,对运算放大器输入电压噪声、输入电流噪声以及周边电阻元件的热噪声通过杂散电容作用于交流法微电容测量电路输出的影响进行了理论分析,给出了测量电路输出中噪声峰峰值的理论计算公式并进行了实验验证。理论分析及实验结果表明:交流法微电容测量电路前级运算放大器输入电压噪声通过测量端与地之间的杂散电容形成的噪声是该微电容测量电路输出噪声的主要来源。最后给出了电容成像系统前级运算放大器选型的指导原则。The noise induced by stray capacitance in an AC-based capacitance measurement circuit for tomography application is studied.Using the noise model of Op-AMP,the effects of voltage noise,current noise and resistance noise on the output of AC-based capacitance measurement circuit are analyzed.A calculation formula for the estimation of peak to peak noise value of AC-based capacitance measurement circuit is presented and verified through experiments.Theoretical analysis and experimental result both demonstrate that the voltage noise of Op-AMp plays dominant role in the output noises of an AC-based capacitance measurement circuit.Finally proposes a selection guide for the Op-AMp in AC-based capacitance measurement circuit for tomography application.

关 键 词：电容成像 杂散电容 噪声 

分 类 号：TP216.3[自动化与计算机技术—检测技术与自动化装置]