纳米级变间隙半球电容计算及其测量电路研究

为了实现高精度球形转子的平衡测量，讨论半球电极支承下静电悬浮装置的变间隙电容的计算公式和纳米级电容精密测量问题。基于半球支承下的转子位移测量原理，分析转子与电极间电容和间隙的关系，给出高精度转子位移测量方案。测试结果表明，电路性能与理论分析结果吻合较好，转子位移测量电路的位移分辨率优于0．2nm、5h零位漂移小于0．01μm、通频带大于20kHz，可以满足高精度球形转子平衡测量的要求。

Calculation and Measurement of Variable-gap Hemisphere Capacitance with Nanometer Resolution

In order to realize balance measurement of the spherical rotor with high accuracy, the formulae are derived to calculate the capacitance under hemisphere electrodes with variable gap for the electrostatic suspension device and a method for detecting capacitance with nanometer resolution is presented. Based on the principle of displacement measurement of the rotor under hemisphere electrostatic suspension, the relationship between the capacitance and the gap between rotor and electrodes is given. Then a high accuracy rotor displacement measuring circuit is introduced. Experimental results are given to confirm the analyses, and the resolution of rotor displacement measuring circuit is less than 0.2nm, the zero drift in five hours is less than 0.01um, and the pass band is greater than 20kHz. It can satisfy the requirements of balance measurement of the spherical rotor with high accuracy electrostatic suspension.