Status of electrical tomography in industrial applications

The paper surveys the status of electrical tomography for industrial applications. For the present purposes this is considered to include "low" excitation frequencies, up to about 1 MHz, comprising resistance (electrical resistance tomography), capacitance (electrical capacitance tomography), inductance (electromagnetic tomography) and impedance (electrical impedance tomography) modalities. Introductory background material is followed by comparisons between the instruments that have emerged. Data processing is considered with emphasis on the trade-offs that are necessary in implementing algorithms for reconstructing images. Recent applications are tabulated and case studies are presented for six contrasting areas that illustrate significant progress towards industrial benefit. Some comparison is made with applications to medical tomography and a number of issues are identified for future research. (C) 2001 SPIE and IS&T.