Eddy current-based material loss imaging system prototype

Systems that associate positions with eddy current probe readings present inspection data more directly and usefully than the more common impedance plane display. We have economically constructed such an integration of an eddy current testing device with a position feedback device which gives 0.005” achievable resolution. The position and probe readings are fed to a PC and plotted in real-time as a projection into a user-defined rectangle in 3-space. All spatial coordinates and all inspection data are retained for model building and record keeping. Unsampled eddy-current readings are interpolated using a spatial average, consistent with the observed averaging effect of the probe. An empirically-determined convolution kernel permits an estimate of the surface profile on the opposite side of the sample by deconvolution. This can then be combined with the position to provide a model of the sampled area.