Abstract
A validated analytical model of a transmit-receive eddy current (EC) coil pair, situated above two parallel plates, separated by an air gap, was used as the basis for an Inversion Algorithm (IA) to extract probe liftoff, second layer plate resistivity, and plate-to-plate gap from multi-frequency EC data. The IA was tested over a large range of first layer wall thickness (3.80 mm and 4.64 mm), second layer plate resistivity (1.7-174 ???cm), second layer wall thickness (1.20 mm to 4.85 mm), probe liftoff (2.8 mm to 7.9 mm), and plate-to-plate gap (0 mm to 13.3 mm). At nominal liftoff (2.8 mm) the IA achieved a gap measurement accuracy of ±0.7 mm, and was able to return good estimates of second layer resistivity to within ±1 ???cm for low resistivity samples, but decreasing accuracy for higher resistivity. When gap was fixed, the IA was able to measure changes in probe liftoff (relative to nominal) to an accuracy of ±0.2 mm. The reported accuracy and a demonstration of the ability to accurately estimate parameters outside of the calibration range provides confidence in the potential utility of the algorithm.
How to Cite:
Luloff, M., Contant, S., Krause, T. & Morelli, J., (2019) “Simultaneous extraction of multiple parameters from a transmit-receive eddy current probe above a layered planar conductive structure”, Review of Progress in Quantitative Nondestructive Evaluation .
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