It is challenging to achieve high accuracy, low noise for the humidity measurements in the field of upper-air meteorological observation. To tackle this problem, a capacitance measuring circuit based on charge amplifier principle has been developed for sounding humidity sensors. It includes crystal oscillation, charge amplifiter, rectifying filter, A/D converter and MCU. The measurement results demonstrate that the circuit features several advantages, stray-immune, the linearity, and a high measurement accuracy of 0. 04% error. This circuit can achieve a capacitance resolution of 100×10-6(PPM,RMS) from a nominal sensor capacitance of 100 pF, which indicates that the circuit is feasible for high altitude humidity sensing.%针对高空气象湿度测量对高精度和低噪声提出的需求,设计了一种基于电荷放大器原理、用于探空湿度传感器的微弱电容检测电路.该电路由晶体振荡电路、电荷放大器电路、整流滤波、A/D转换、MCU等部分组成.实验结果表明:研制的检测电路具有较强的抗杂散电容性能,线性度良好,准确度优于0.04％.对于标称100 pF的待测电容,噪声引起的误差仅相当于待测电容的100×10-6 (PPM),约10 fF,能满足高空探测的要求.
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