电容式位移传感器的研制

Development of Capacitive Displacement Transducer

本文讨论了连接电缆分布参数对电桥平衡方程及电桥灵敏度的影响,认为可进行三端测量的变压器比率臂电桥能在很大程度上消除这些分布参数的影响。二个非完全包围导体之间的电容量的不确定性,可以通过引入一个三端电容来消除。因此,若把电容式位移传感器做成三端式结构,就可以用变压器比率臂电桥精确地测量出传感器电容量的微小变化。由此,研制了一种电容式位移传感器,设计并制作了变压器比率臂电桥及其有关检测电路。实验结果表明,当载波频率为100kHz时,能在100m长的连接电缆处测量出10^(-3)pF量级的电容变化量;并且认为,能在更长的连接电缆下进行精确地测量。

The effects of stray parameters mainly from connecting cables on balance equation and sensitivity of bridge are discussed in this paper. It is possible to remove the effects of stray parameters, to a great extent, with a transformer-ratio-bridge adaptable to three terminal measurements. The undefinition of capacitance between two conductors without complete surrounding each other may be eliminated with a three terminal capacitor introduced. Therfore, it is possible to measure small variation of transducer capacity with a transformer-ratio-bridge, if a capacitive transducer is made with three terminal construction. A capacitive displacement transducer, transformer-ratio-bridge, and associated electronic circuit are developed according to this theory. It is shown by testing that a small variation down to 10^(-3) pF of capacitance can be measured at 100m long cables, when the carrier frequency is 100 kHz. It is also possible to make accuracy measurement at longer cables.