一种电容薄膜真空计检测电路的设计
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摘要
针对电容薄膜真空计的电容检测精度要求高以及非线性的问题,文中设计了一种基于二极管桥的检测电路。该电路检测电容薄膜真空计的测量电容与参考电容的差值,能有效抑制共模噪声的干扰,并采用负反馈的方法对非线性进行补偿。仿真表明负反馈的方法能够有效降低真空计的非线性,在仿真数据上非线性度从7.27%降低到0.662%。实际测试结果表明该电路能准确地检测电容,电路灵敏度为1.85 V/pF,非线性度为0.4%,电路稳定性较好。
In view of the high capacitance detection accuracy of capacitance film vacuum gauge and the non-linearity problem,this paper designed a detection circuit based on diode-quad bridge circuit.The circuit detected the difference between the measured capacitance and the reference capacitance of the capacitance film vacuum gauge,which can effectively suppress the interference of the common mode noise and compensate the nonlinearity by using the negative feedback method.The simulation shows that the negative feedback method can effectively reduce the nonlinearity of the sensor.The nonlinearity of the simulation data decreases from 7.27% to 0.662%.The actual test shows that the circuit can accurately detect the differential capacitance,the circuit sensitivity is 1.85 V/pF,the nonlinearity is 0.4%,and the circuit has high stability.This shows that this circuit can be applied to the capacitance of the film vacuum gauge,and has certain engineering value.
In view of the high capacitance detection accuracy of capacitance film vacuum gauge and the non-linearity problem,this paper designed a detection circuit based on diode-quad bridge circuit.The circuit detected the difference between the measured capacitance and the reference capacitance of the capacitance film vacuum gauge,which can effectively suppress the interference of the common mode noise and compensate the nonlinearity by using the negative feedback method.The simulation shows that the negative feedback method can effectively reduce the nonlinearity of the sensor.The nonlinearity of the simulation data decreases from 7.27% to 0.662%.The actual test shows that the circuit can accurately detect the differential capacitance,the circuit sensitivity is 1.85 V/pF,the nonlinearity is 0.4%,and the circuit has high stability.This shows that this circuit can be applied to the capacitance of the film vacuum gauge,and has certain engineering value.
引文
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[8] DAI C L,LU P W,CHANG C,et al.Capacitive micro pressure sensor integrated with a ring oscillator circuit on chip[J].Sensors,2009,9(12):10158-10170.
[2] 杨仕本,张宇声,李凤宇,等.压力测量膜片的形变计算[J].海军工程大学学报,2003,15(6):29-32.
[3] 刘家澍,余民森,杨忠宝.电容式薄膜真空计[J].自动化仪表,1981(5):003.
[4] HUANG S M,STOTT A L,GREEN R G,et al.Electronic transducers for industrial measurement of low value capacitances[J].Journal of Physics E:Scientific Instruments,1988,21(3):242.
[5] SULLIVAN J J.Development of variable capacitance pressure transducers for vacuum applications[J].Journal of Vacuum Science & Technology A:Vacuum,Surfaces,and Films,1985,3(3):1721-1730.
[6] HARRISON D R,DIMEFF J.A diode-quad bridge circuit for use with capacitance transducers[J].Review of Scientific Instruments,1973,44(10):1468-1472.
[7] PATRA J C,PANDA G,BALIARSINGH R.Artificial neural network-based nonlinearity estimation of pressure sensors[J].IEEE Transactions on Instrumentation and Measurement,1994,43(6):874-881.
[8] DAI C L,LU P W,CHANG C,et al.Capacitive micro pressure sensor integrated with a ring oscillator circuit on chip[J].Sensors,2009,9(12):10158-10170.