Determination of Electrical Conductivity Profiles from Multi-Frequency Impedance Measurements

Abstract

Most existing eddy current methods implicitly assume uniform electrical conductivity throughout the sample. However, eddy current measurements recorded over a range of frequencies extract conductivity information over a range of depths, and, thus, are sensitive to spatial variations in conductivity. Determination of spatial profiles of conductivity offers the potential of a new technique in metals processing, where variations in conductivity may arise in composite materials or from non-uniform temperature distributions. We describe here a conductivity profiling method based on an iterative nonlinear least-squares algorithm that operates on multi-frequency impedance data.