Determination of the conductivity and thickness of conductive layers on conductive base materials

An eddy current technique for the simultaneous determination of the layer thickness and conductivity of a uniform conductive layer on a known conductive base material is presented. Layer thickness and conductivity are determined by fitting apparent conductivity measurements taken on the surface of the part at a discrete set of frequencies to a calibration volume. The calibration volume is constructed from apparent conductivity measurements taken on a set of known layer materials, of various known thicknesses, as a function of frequency. Experimental results that support the technique are presented.