Preliminary Studies Of Planar Capacitance Tomography

Alan Somerville, Iwan Evans and Trevor York

Department of Electrical Engineering and Electronics, UMIST, PO Box 88, Sackville Street, Manchester, M60 1QD, UK

AS, TY and IE are members of the Virtual Centre for Industrial Process Tomography

Tel: 0161 200 4790 Fax: 0161 200 4789 email: aso@skoda.ee.umist.ac.uk

Abstract - Almost all previously reported applications of Electrical Capacitance Tomography (ECT) have concentrated on relatively large-scale geometries to give image resolution of the order of centimetres. There are a number of applications, for instance particle sizing, which may benefit from significantly higher spatial resolution. The present work aims, ultimately, to develop ECT for use with electrodes as small as 10 µm wide using custom silicon technology and therefore it is natural to consider planar arrays of electrodes. This paper describes finite element simulations and measurements on laboratory scale planar arrays with the aim of identifying appropriate geometries to migrate to small scale. Preliminary results suggest that it is possible to identify bulk changes in particle size, of the order of the electrode dimensions. In addition, linear back projection has been used to produce reconstructed images of 'holes' directly above the electrodes.

Keywords: Capacitance, VLSI, planar electrodes, tomography.