电容层析成象系统中微小电容测量法

The Measurement of Low Value Capacitance in Electrical Capacitance Tomography System

电容层析成象技术（ＥＣＴ）是一种最早发展起来的过程成象技术。由于为重建图象所需测量的电容变化量相对于ＥＣＴ传感器的固有电容非常小，总的杂散电容值又远大于待测电容，因此ＥＣＴ对电容检测提出了极为严格地要求。本文介绍了ＥＣＴ系统中最常用的３种微小电容检测电路—充电／放电电路、带反馈补偿的交流测量电路以及自平衡电容测量电路，并指出了它们的优缺点。

Electrical capacitance tomography(ECT) is one of the techniques which were firstly developed for process tomography.ECT presents a particularly stirct demand for capacitance measurement because the capacitance changes to be measured for image reconstruction are very small relative to the ECT sensor standing capacitances,and the total stray capaciance is much larger than the to be measured.In this paper three types of low value capacitance measuring circuits,the charge/discharge circuit,the AC measuring circuit with feedback compensation,and the self-balancing capacitance measuring circuit are described,which are most suitable for the use in ECT system,Their advantages and disadvantages are also pointed out.