SEARCH WITHIN CONTENT
Citation Information : International Journal on Smart Sensing and Intelligent Systems. Volume 1, Issue 3, Pages 812-823, DOI: https://doi.org/10.21307/ijssis-2017-322
License : (CC BY-NC-ND 4.0)
Published Online: 13-December-2017
This paper presents an inverse method for determining the conductivity distribution of a flat, layered conductor using a multi-frequency electromagnetic sensor based on phase signature alone. Eddy current sensors are used in a wide range of non-destructive testing (NDT) applications. Single frequency sensors are very common, however, the potential of an eddy current sensor with spectroscopic techniques offer the ability to extract depth profiles and examine more fully the internal structure of the test piece. In this paper, we found a simplified model that can estimate the phase signature of a cylindrical coil above a conductor with an arbitrary conductivity profile. This simplified model improves the computational efficiency by many fold compared to the complete analytic solution. For inverse solution, a simplex search method was used to fit a set of multi-frequency phase values in a least-squared sense. Experimental eddy-current tests are performed by taking the difference in inductance of the coil when placed in free space and next to a layered conductor over the range 100Hz -1MHz. Good estimates for the conductivity profile from experimental and simulated data were obtained.
 A. Allers, and F. Santosa, Stability and resolution analysis of a linearized problem in electrical impedance tomography, Inverse problems, 7 1991 515
 E. Somersalo, M. Cheney, D. Isaacson, and E. Isaacson, Layer stripping: a direct numerical method for impedance tomography, Inverse problems, 7 1991 899
 J. H. Rose, and S. M. Nair, Exact recovery of the DC electrical conductivity of a layered solid Inverse problem 7 1991 L31
 S. M. Nair, and J. H. Rose, Reconstruction of thee dimensional conductivity variations from eddy current (electromagnetic induction) data Inverse problems 6 1990 1007
 S. J. Norton, A. H. Kahn and M. L. Mester, (1989) Reconstructing electrical conductivity profiles from variable-frequency eddy current measurements, Res. Nondestructive Eval., 1 167
 J. C. Moulder, E. Uzal, and J. H. Rose, (1992) Thickness and conductivity of layers from eddy current measurements, Rev. Sci. Instrum. 63 3455
 S. J. Norton and J. R. Bowler, (1993) Theory of eddy current inversion, J. Appl. Phys. 73 501
 S. J. Norton and J. R. Bowler, (1992) Eddy current inversion for layered conductors, Res. Nondestructive Eval. 4 205
 J. C. Moulder, E. Uzal, and J. H. Rose, (1994) Experimental determination of the near-surface conductivity profiles of metals from electromagnetic induction (eddy current) measurements, Inverse problems 10 753-764
 W. Yin, S. J. Dickenson, and A. J. Peyton, Imaging the Continuous Conductivity Profile Within Layered Metal Structures Using Inductance Spectroscopy, IEEE Sensors Journal 5 161-166
 W. Yin, S. J. Dickenson, and A. J. Peyton, “Analysis of the lift-off effect of phase spectra for eddy current sensors” IEEE IMTC 2005, Ottawa, Canada, 17-19 May 2005.
 W. Yin, S. J. Dickenson, and A. J. Peyton, “Simultaneous measurement of distance and thickness of a thin metal plate with an electromagnetic sensor using a simplified model”, IEEE Trans. Instrum. Meas. Vol. 53 pp1335–9 2004.
 C. C. Cheng, C. V. Dodd, and W. E. Deeds, (1971) General analysis of probe coils near stratified conductors, Int. J. Nondestructive Testing 3 109
 E. Uzal, and J. H. Rose, (1993) The impedance of eddy current probes over layered metals whose conductivity and permeability vary continuously, IEEE Trans. Mag. 29 1869
 C. Glorieux, J. C. Moulder, J. Basart and J. Thoen (1999) The determination of electrical conductivity profiles using neural network inversion of multi-frequency eddy-current data J. Phys. D: Appl. Phys. 32 616-622