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一、引言 在超高真空测量,质谱计、粒子加速器、辐射探测器、高空探测技术的应用,以及生物物理研究等工作中,经常需要进行弱电流检测。输入的电流常为10~(-6)—10~(-13)A(甚至更小),而且变化比较大,往往超越线性放大器本身的动态范围。因此,我们要求当输入电流较小时,静电计有比较大的放大倍数;若输入电流信号超过某一界限时,放大倍数能自动降低到某个适当值,使静电计的输出适宜(不大于满度值)。反之,如输入电流信号降低到某一界限时,放大倍数将自动增高到某个适当值,使静电计的输出幅度足够大,极易读数或推动负载。
I. INTRODUCTION In the work of ultra-high vacuum measurement, mass spectrometer, particle accelerator, radiation detector, altitude detection technology and biophysical research, weak current detection is often required. The input current is often 10 -6 (-10) (-13) A (even smaller), and the change is relatively large, often beyond the dynamic range of the linear amplifier itself. Therefore, we request that when the input current is small, the electrometer has a larger magnification; if the input current signal exceeds a certain limit, the magnification can be automatically reduced to an appropriate value, the electrometer output is appropriate (not more than full Degree value). Conversely, if the input current signal drops below a certain limit, the magnification will automatically increase to an appropriate value, allowing the output of the electrometer to be large enough to be easily read or to drive the load.