Optimizing the Geometry of Three-Dimensional Electrical Capacitance Tomography Sensors

Electrical capacitance tomography (ECT) is well established for 2D imaging of multiphase distributions. Increasingly, ECT is being used to image in 3D. In this paper, we discuss the design of 3D ECT sensors using simulations of a 24-electrode sensor (four layers of six electrodes each). The effect of length of the sensor on the sensitivity maps and image reconstruction is studied. It is demonstrated that the condition number for 3D imaging increases rapidly with increasing length of the sensor. In addition, as the length increases, significant distortions are observed in the shape of the reconstructed image and the intensity of the reconstructed image decreases. Thus, a long sensor provides a greater sensing volume; however, it causes significant distortion to the reconstructed images, while a short sensor provides a more accurate image reconstruction but the volume of the sensor is limited. Based on simulations, we propose that an optimal design of the 3D ECT sensor would have an aspect ratio for the electrodes of 0.75, which for this four-plane sensor gives a total sensor length of 1.5 times the pipe diameter.