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Proceedings Paper

Imaging by electromagnetic induction with resonant circuits
Author(s): Roberta Guilizzoni; Joseph C. Watson; Paul Bartlett; Ferruccio Renzoni
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Paper Abstract

A new electromagnetic induction imaging system is presented which is capable of imaging metallic samples of different conductivities. The system is based on a parallel LCR circuit made up of a cylindrical ferrite-cored coil and a capacitor bank. An AC current is applied to the coil, thus generating an AC magnetic field. This field is modified when a conductive sample is placed within the magnetic field, as a consequence of eddy current induction inside the sample. The electrical properties of the LCR circuit, including the coil inductance, are modified due to the presence of this metallic sample. Position-resolved measurements of these modifications should then allow imaging of conductive objects as well as enable their characterization. A proof-of-principle system is presented in this paper. Two imaging techniques based on Q-factor and resonant frequency measurements are presented. Both techniques produced conductivity maps of 14 metallic objects with different geometries and values of conductivity ranging from 0.54х106 to 59.77х106 S/m. Experimental results highlighted a higher sensitivity for the Q-factor technique compared to the resonant frequency one; the respective measurements were found to vary within the following ranges: ΔQ=[-11,-2]%, Δf=[-0.3,0.7]%. The analysis of the images, conducted using a Canny edge detection algorithm, demonstrated the suitability of the Q-factor technique for accurate edge detection of both magnetic and non-magnetic metallic samples.

Paper Details

Date Published: 13 May 2015
PDF: 12 pages
Proc. SPIE 9481, Image Sensing Technologies: Materials, Devices, Systems, and Applications II, 94810Q (13 May 2015); doi: 10.1117/12.2183180
Show Author Affiliations
Roberta Guilizzoni, Univ. College London (United Kingdom)
Joseph C. Watson, AWE plc (United Kingdom)
Paul Bartlett, Univ. College London (United Kingdom)
Ferruccio Renzoni, Univ. College London (United Kingdom)

Published in SPIE Proceedings Vol. 9481:
Image Sensing Technologies: Materials, Devices, Systems, and Applications II
Nibir K. Dhar; Achyut K. Dutta, Editor(s)

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