Pulsed eddy current thickness measurement using phase features immune to liftoff effect |
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Affiliation: | 1. School of Mechatronic Engineering, China University of Mining and Technology, Xuzhou 221116, PR China;2. School of Information and Electrical Engineering, China University of Mining and Technology, Xuzhou 221116, PR China;3. School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU, UK;4. Faculty of Electric Power Engineering, Kunming University of Science and Technology, Kunming 650500, PR China |
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Abstract: | Conventionally, peak value and peak time are extracted from pulsed eddy current (PEC) response as features for thickness measurement. However, they suffer from liftoff variations. In this work, the phase of spectral PEC response from a Hall sensor are proposed to serve as robust features for thickness evaluation. The presented novel features are immune to liftoff effect, because phase signals remain nearly constant against liftoff variations. An analytical model was formulated, and simulations were performed to uncover the physics of the characteristics of the phase feature and establish the relationship between the phase feature and sample thickness. Experiments were carried out to validate the proposed phase feature. Eventually, the proposed phase feature was evaluated for accurate thickness measurement and some key factors were discussed. |
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Keywords: | Pulsed eddy current Nondestructive testing Liftoff Phase Spectral response Thickness measurement Metallic plate |
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