Examination of Dodd and Deeds solutions for a transmit-receive eddy current probe above a layered planar structure

Exact solutions for the electromagnetic response of a transmit-receive coil pair situated above two parallel plates separated by a gap, were developed using the recently published general model of Desjardins et al. that accounts for all electromagnetic interactions between the voltage-driven probe and the conducting samples. This model was then compared to the well-known model developed by Dodd and Deeds, which assumes a constant amplitude sinusoidal current and an open-circuit pick-up coil. Both models were compared with experimental results that measured the gap profile for a Grade 2 Titanium plate (54 μΩ·cm) over a SS-316 stainless steel second layer plate (74 μΩ·cm). These materials simulated the electromagnetic properties of a Zr 2.5% Nb pressure tube and Zr-2 calandria tube, respectively, as found in the fuel channels of CANDU® reactors. It was observed that while the Dodd and Deeds’ model as applied to this work achieved a good shape agreement with experimental data for excitation frequencies at 2 ...