An Agile Electrical Capacitance Tomography System With Improved Frame Rates

Abstract

In this paper, an AC-based agile parallel hardware system was introduced for ECT. A multi-frequency excitation and measurement strategy was proposed to minimize the switching time between different channels. For an ECT sensor with 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sup> electrodes, all the mutual capacitances can be measured much faster, which is m/(2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sup> - 1) of the time used by the classical single-frequency excitation and measurement strategy. It implies that the proposed strategy accelerates the capacitance acquisition in an exponential way. Besides the efforts made to reduce the switching times between channels, the operating time of each electronic switch was selected to fasten the demodulation. The hardware fabricated here can be modified agilely by running codes, and different excitation and demodulation methods can be implemented on the chip. To verify the performance of the agile system, ECT sensors with different electrodes are facilitated to measure the mutual capacitances. The capacitances can be achieved with a frame rate of respectively up to 15.15 kilo frames per second (kfps) and 12.82 kfps in the cases of 12 and 16 electrodes. The ignition process of a flame generated by a Bunsen burner can be captured by the proposed system. Also, the discharging of the igniter can be imaged, and it is usually undistinguishable in a low-speed system.