Determination of the optimal axial length of the electrode in an electrical capacitance tomography sensor

Abstract

Electrical capacitance tomography (ECT) is one of the most successful process tomography techniques, which has been developed for more than a decade. Thus far, most of the research on ECT has been based on two-dimensional modeling, which simplifies the ECT sensor structure as two dimensional. However, certain key issues such as the three-dimensional effect of the ECT sensor are not considered at all. In this paper, the finite element method is used to solve the partial differential equation governing the ECT sensing zone, which is actually three dimensional. The sensitivity distributions between different electrode pairs are calculated and compared with those based on the two-dimensional modeling. The impacts of the length of both the measurement electrode and the guard electrode on the sensitivity distribution are investigated. The effect of the length of the measurement electrode on the normalized capacitance is also discussed. According to the numerical results presented in this paper, it is suggested that the optimal length of the measurement electrode for electrical capacitance tomography is the same as the width or diameter of the sensor.