基于电荷平衡原理的微弱电流测量研究

Study on Weak Current Measurement Based on Charge Balance Principle

针对电离室输出宽量程双极性微弱电流的测量需求,在积分电路的基础上,研究了基于电荷平衡原理的多斜积分电路测量系统。在对输入电流的积分过程中,通过切换正负参考电源实现对电容的充电或放电,电容充电和放电所占的周期数形成测量系统的高位读数。利用一个测量周期开始和结束时电容电压的差值,形成测量系统的低位读数。通过标准电流源进行测试,该测量系统能够实现±24.5 nA的双极性微弱电流测量,满量程的最大线性误差为0.014 3%。重复测试100 pA输入电流,得到标准差分为0.088 97。实验结果表明:测量系统的线性度和重复性很好、精度高、量程广,能满足实际测量的需求并且应用领域广泛。

In order to meet the demand of measuring the weak bipolar current with wide range output of ionization chamber,a multi⁃inclination integrating circuit measuring system based on charge balance principle was studied on the basis of integrating circuit.In the process of integrating the input current,it realizes the charging or discharging of the capacitor by switching the posi⁃tive and negative reference power sources.The number of cycles occupied by the capacitor charging and discharging forms the high reading of the measurement system.The difference between the capacitor voltage at the beginning and the end of a measurement period was used to form the low reading of the measurement system.The measurement system is capable of measuring bipolar weak currents of±24.5 nA with a maximum linear error of 0.0143%at full scale when tested with a standard current source.The 100 pA input current was tested repeatedly,and the standard deviation was 0.08897.The experimental results show that the measure⁃ment system has good linearity and repeatability,high precision and wide range,which can meet the needs of practical measure⁃ment and wide application field.