The Micro-Miniature Capacitance Sensor Based on Light-Trigger Technology and Its Hardware Design in the Electrical Capacitance Tomography System

摘要

Electrical capacitance tomography (ECT) technology can monitor the multi-phase flow in closed pipes or vessels. The monitoring technology has the advantages of anti-intrusion, low manufacturing cost, high-temperature resistance, and simple structure. At present, ECT systems use small-scale sensors for signal capture, but such sensors have problems such as low sensitivity and poor anti-interference, which have attracted the attention of researchers. In this study, a light-trigger sensor was proposed, which was equipped with a special light window to receive optical signals. At the same time, in terms of the problem of electromagnetic shielding and optical window protection, a light window structure that transmitted optical signals and shields electromagnetic waves was designed. Based on the light-trigger sensor, the other modules of the ECT system were designed, considering that the sensor would be interfered by the measurement of stray capacitance, the intra-isoelectric driver cable shielding technology, the double T-type simulation switch matrix, and the digital-mode demodulation technology was introduced. Consequently, the performance of the sensor was tested. During the experiment, the sucrose flow pattern was used as the test object. The results showed that compared with the traditional sensors, the image distortion of the sensor based on the ECT system was lower; while in the performance test of the ECT system, the introduction of the double T-type simulation switch matrix, the digital-analogy demodulation technology, and the bipolar plate excitation mode could further optimize the signal-to-noise ratio index of the image; in the sensitivity test of the ECT system, the introduction of bipolar plate excitation mode could improve the output sensitivity of the capacitance.