一种精密电容测试系统设计

A design of precision capacitance measurement system

该文介绍一种基于自动平衡电桥的精密电容测试系统设计方法,通过对激励信号与自动平衡电桥输出信号进行鉴相分析,给出被测电容值的计算方法。为使鉴相器处于最佳工作点,得到精度更高的电容值测量结果,系统对自动平衡电桥输出信号进行反馈,并根据反馈结果,结合标准电阻选择与程控放大器对信号进行调理。最后,在1 MHz的测试频率下对系统的电容测试精度进行验证,得出设计的电容测试系统具有较高的测试精度。

In this paper, a method of precision capacitance test system was introduced which was based on an automatic balance bridge. The measured capacitance value was calculated through the identification of the different signal phases between the excitation signal and automatic balance bridge output signal. In order to make the discriminator work at the optimal operating point and get higher accuracy of capacitance value measuring results, the system had rendered feedbacks on the automatic balance bridge output signal and regulated the signal according to the feedback by combining standard reference resistors and programmable amplifiers. Finally, the accuracy of the system has high precision, which was proved under the test frequency of 1 MHz.