Effect of electrode-to-gap ratio on electrical capacitance tomography images

In electrical capacitance tomography (ECT), the electrode-to-gap ratio (EGR) of a sensor is one of the design parameters. It is commonly believed that a larger EGR would result in higher quality of tomographic images. However, no quantitative study has been reported. In this paper, the effect of EGR on ECT imaging is investigated quantitatively. ECT sensors with different EGR of 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 and 10:1 are simulated and images are reconstructed using linear back projection (LBP) and Landweber iteration algorithms for two typical permittivity distributions. The relative image errors are calculated against the real permittivity distributions. The sensitivity distributions of the ECT sensors with different EGR are analyzed and compared. The results show that the effect of ECR on ECT imaging can be neglected when it is larger than 6:1.