Eddy Current Inversion of Lift-off, Conductivity and Permeability Relaxation

We use a stochastic inversion of multifrequency eddy current data for determination of the liftoff, conductivity and permeability of a plate made of magnetic and electrically conductive material. We use a simplified Debye relaxation relation to model the frequency dependent magnetic permeability. The inverted results are posterior probability densities of the plate parameters. The approach is verified using the synthetic data from the impedance model of a coil above a magnetic plate at three excitation frequencies. The inversion of such data leads to significant reduction of the prior uncertainties for all model parameters. The posterior relative deviation of the liftoff and permeability-to-conductivity ratio is better than 0.5 % for impedance measurement uncertainty of 0.1%.