【摘要】 为设计1种具有较高精度和较好重复再现性的微弱电流测量仪器,采用开关调制、差分对消技术,消除微弱电流测量系统的直流误差;通过屏蔽、低通滤波有效抑制工频噪声和放大电路的噪声;边放大信号边衰减噪声提高系统的信噪比;多级放大和预调零解决高放大倍数与运算放大器饱和的矛盾.对设计的微弱电流测量仪进行测试,仪器最小量程达10 pA,最小分辨率达0.5 pA;结果显示工频噪声和直流失调对微弱电流测量有重要影响,表明设计所采用的技术有效.更多还原

【Abstract】 In order to design a ultra weak current detector,which has the properties of higher accuracy and good repetition,the virtue of switch modulation differential balancing technology is used to eliminate the DC offset of weak current measurement system.The power-frequency noise and amplifier noise are suppressed with shielding and low-pass filters.The Signal-to-Noise Ratio(SNR) of the system is enhanced by amplifying signal and suppressing noise simultaneously. Meantime,multi-level amplification and pre-zero adjustment are applied to achieve a great magnification without saturation.The tests show that the minimum range of this device is as low as 10 pA,and the minimum resolution is 0.5 pA,and the power-frequency noise and DC offset on the weak current measurement have a material influence.It also testifies the efficiency of the technology.更多还原