3D image reconstruction using an ECT sensor with a single layer of electrodes

Sensor design is important for electrical capacitance tomography (ECT) that is to be used for a particular application and for generating high-quality images from the measured data. An ECT sensor with long electrodes is commonly used to obtain stable and reliable measurement signals and to ensure the quality of 2D cross-sectional images, but it neglects the effect of electrode length on the entire 3D image. To analyze the effect of electrode length on the measured signals, sensitivity distribution and the quality of reconstructed images, especially the distortion of 3D images, ECT sensors with different electrode lengths of 5, 7, 10, 20 and 30 mm are designed and fabricated. The electrodes are mounted on the internal surface of the ECT sensor wall to eliminate the negative effect of the wall. A dual-electrode excitation strategy is chosen to enhance the signal intensity. The results show that the reconstructed 3D images of the measured objects, which can be divided into three parts, are stretched in the axial direction and narrowed in the radial direction because of the axial average effect, and longer electrodes result in a more serious problem. Comprehensive analysis of the performance of the ECT sensors with different electrode lengths, including the measured signals, sensitivity distribution and reconstructed 3D images, concludes that an ECT sensor with an electrode length of 10 mm is recommended. (paper)