Pulsed eddy current thickness measurement of conductive layers over ferromagnetic substrates

Article type: Research Article

Authors: Lefebvre, J.H.V.^a | Mandache, C.^{b; *}

Affiliations: [a] Air Vehicles Research Section, Defence R&D Canada, 1200 Montreal Road, Bldg. M14, Ottawa, ON, K1A 0R6, Canada | [b] National Research Council Canada, Institute for Aerospace Research, 1200 Montreal Road, Bldg. M14, Ottawa, ON, K1A 0R6, Canada

Correspondence: [*] Corresponding author: Catalin Mandache, Tel.: +1 613 991 2132; Fax: +1 613 952 7136; E-mail: [email protected]

Abstract: The focus of this study is the behaviour of the lift-off point of intersection (LOI) under various test conditions: lift-off, thickness and conductivity of metallic layers with and without a ferromagnetic substrate. The pulsed eddy current (PEC) signal response is analyzed and a lift-off independent method to measure the thickness of conductive layers over ferromagnetic substrates is presented. This approach is tested by scanning specimens with varying lift-off and conductive layer thickness. The test articles have different substrate permeabilities, but identical lift-off and conductive layer conditions. The results demonstrate that the LOI feature can be used to measure the thickness of conductive layers over ferromagnetic substrates.

Keywords: Pulsed eddy current (PEC), lift-off point of intersection (LOI), ferromagnetic substrate

DOI: 10.3233/JAE-2008-922

Journal: International Journal of Applied Electromagnetics and Mechanics, vol. 27, no. 1-2, pp. 1-8, 2008