一种微电流测量方法的研究

为实现一种高准确度、快速、稳定测量微电流信号的方法,从而运用开关调制、低通滤波、运放反馈、多级放大、差分、状态判别电路等构成整个测量系统,解决了多级放大与运放电路饱和的问题,提高了测量系统的信噪比。设计出最小量程10pA,最小分辨率0.5pA,准确度可达0.5级的微电流测量仪。试验结果表明,影响微电流测量的主要因素是工频干扰和电路失调,设计所采用的低通滤波、屏蔽能够有效抑制工频噪声;开关调制放大电路、差分电路能够有效消除电路失调带来的测量误差。

Research on a micro-current measuring method

In order to obtain a sort of high-accuracy,rapid and stable signal to measure micro-currents,the switch modulation,lowpass filtering,operational amplifier feedback,multistage amplification,difference and state discrimination circuits and so on have been applied to constitute the entire measuring system,which solves the issues of multistage amplification and operational amplifier circuit saturation,and improves the signal to noise ratio（SNR） of the measuring system.The micro-current measurement instrument with the minimum measuring range of 10 pA,the minimum resolution ratio of 0.5 pA,and the degree of accuracy up to 0.5 level has been designed.The test results suggest：the main elements influencing the micro-current measurement are power frequency interference and circuit disorder.The lowpass filtering and shield applied in this design can effectively suppress the industrial frequency noises; and the switch modulation amplifier circuit and difference circuit can effectively eliminate the measuring errors caused by circuit disorders.