High Speed and High Resolution Capacitance Measuring Circuit for Electrical Capacitance Tomography

摘要

Electrical capacitance tomography (ECT) provides a promising technique for measuring industrial multiphase processes. A new capacitance measuring circuit for ECT was developed based on the charge amplification principle. This circuit charges and discharges the capacitance only once during one measurement cycle. Filter, which is a bottleneck to improve the data sample rate, isn't needed in this capacitance measuring circuit. A data acquisition system was developed on the basis of this new circuit. Optimization step of parallel measurement, high speed CMOS chip and fast communication were adopted. This circuit has the advantage of stray-immune small capacitance measurement, nigh sampling, speed, high resolution and good linearity. Test results show that the data capture rate of 600 frames/s and the resolution of 0.1684fF can be achieved, which satisfies the requirement for industrial online operation.