关键词: 电容层析成像;图像重建;现场可编程门阵列;传感器优化;信噪比

Abstract: In order to reduce the noise value of capacitance measurement caused by the coupling capacitance between adjacent plates of Electrical Capacitance Tomography (ECT) sensor, a differential electrode sensor system is designed and the parameters of differential electrode and measuring electrode distance are optimized. The experimental system uses Field Programmable Gate Array （FPGA） direct digital frequency generation module to generate digital quantity. The sinusoidal excitation signal is converted into a positive and negative alternating current signal by D/A to excite the measuring electrode and the differential electrode, respectively. The sensor sensitivity is best when the ratio of the distance between the differential electrode and the measuring electrode to the midpoint of the pipe is about 1:1.2, the error of the simulation image is reduced to 0.23, and the image correlation coefficient increased to 0.84. The average signal-to-noise ratio of the actual experimental hollow field increased by 5.10dB. The average signal-to-noise ratio of the system at full field increased by 4.50dB, the static capacitance of adjacent pairs is reduced to 38%, and the change in capacitance takes up the most measured value, or 62%.The differential electrode sensor system is optimized by the distance between the electrodes, and the performance of the sensor system is improved. The feasibility is verified by experiments, and it can be applied to the oil monitoring.

Key words: Electrical capacitance tomography;Image reconstruction;FPGA;Sensor optimization;Signal to noise ratio