An Improved Normalisation Approach for Electrical Capacitance Tomography

W Q Yang*

Department of Electrical Engineering and Electronics, Process Tomography Group, UMIST, P O Box 88, Manchester M60 1QD, UK, email w.yang@umist.ac.uk

M Byars

Process Tomography Ltd, 86 Water Lane, Wilmslow, Cheshire SK9 5BB, UK, email MByars@tomography.com

Abstract - An electrical capacitance tomography (ECT) system is calibrated at the upper and lower values of permittivity. The measured capacitances are usually normalised and then used for image reconstruction. The conventional normalisation approach assumes that the distribution of the materials is in parallel and hence the normalised capacitance is a linear function of the measured capacitance. This approach is not appropriate in most situations. In this paper an alternative normalisation approach is derived from a series sensor model. Preliminary experimental results show that the quality of reconstructed images can be improved with the new normalisation approach for the situations tested.

Keywords: Capacitance measurement, Physical modelling, Image reconstruction, Capacitance tomography