Linear EMT for the Detection of Faults in Metallic Planar Structures

W. Yin, X. Ma, G. Zysko and A. J. Peyton

School of Electrical and Electronic Engineering, The University of Manchester, Email: wuliang.yin-3@manchester.ac.uk

ABSTRACT

This paper describes a linear planar electromagnetic induction tomography (EMT) system for the detection of conductivity in-homogeneity inside a metallic planar structure. Sensor coils are distributed to form a linear array with their axis parallel but perpendicular to the plate under inspection. The forward solution for the sensor array next to a homogenous conductive planar structure is based on the analytical solution provided by Deeds and Dodd. Numerical results of the forward solution are provided by FEM simulations for several cases of inhomogeneous conductivity distributions. The sensitivity matrix for a prototype sensor was computed by numerical evaluation of the analytical solution. For the inverse solution, a modified Newton-Raphson method was used to adjust the conductivity distribution to fit a set of inductances measured from the sensor array in a least-squared sense. Good estimates for the locations of low conductivity faults were obtained. The differences in mutual inductance of the coil pairs when placed next to a homogenous reference conductor and next to a conductor with faults were used as the input of the inverse solution. Inverse results based on FEM simulated data verified this method.

Keywords Planar array, electromagnetic, induction, tomography, faults, non-destructive testing