Two approaches to coil impedance calculation of eddy current sensor

Abstract

Eddy current (EC) sensor detects measurand by the change of coil impedance, which is introduced by coupling the magnetic energy between coil and measurement target. Therefore, it is of great significance for both the forward and inverse eddy current problems to study on the approaches to coil impedance calculation. In the current paper, two approaches are presented to calculate coil impedance of EC sensor. First, the theoretical calculation model of coil impedance is simplified as an air-cored cylindrical coil, over an infinite measurement target. And the integral expression of coil impedance is derived according to the sensor operation principle and electromagnetic field theory. Then, the integral expression is expanded as series form in cylindrical coordinate system in order to compute the coil impedance easily, and computed using Mathematica^TM. Next, based on the finite element modeling theory, two different finite element models of eddy current measurement system are built. The infinite boundary in mode1 is truncated, while in model 2, it is simulated completely by an infinite element. Furthermore, the appropriate location where the air domain is truncated at is determined. Finally, the coil impedance and the magnetic distribution of eddy current testing system are obtained by finite element method, respectively. By comparison, the results from the theoretical calculation approach and finite element method are in very good agreement, and the accuracy of two approaches is validated with each other.

Keywords

eddy current sensor coil impedance calculation approaches series expansions finite element method

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References

Weng

Tong

H. Y.

Application and demarcation of eddy current sensor. Sci. Technol. Baotou Steel (Group) Corporation 2005 31(5)36–38.

Kincaid

T. G.

Chari

M. V. K.

The application of finite element method analysis to eddy current nondestructive evaluation. IEEE Trans. Magn. 1979 15(6)1956–1960.

Lei

Y. Z.

The analysis to time-harmonic varied electromagnetic field 2002 35 (Science Press Beijing).

Coffey

M. W.

Theory for coil impedance of a conducting half, space: Analytic results for eddy current analysis. J. Appl. Phys. 2001 89(4)2473–2481.

Theodoulidis

T. P.

Epameinondas

E. K.

Impedance evaluation of rectangular coil for eddy current testing of planar media. NDE Int. 35 (2002)407–414.

Q. H.

Lee

M. Y.

Zheng

Qiao

Y. N.

Yuanning

A new method of computing the coil impedance of an eddy current sensor. In Proceedings of the International Conference on Industrial Electronics, Control, and Instrumentation, New York, USA 1993, pp. 1531–1533.

Lei

Y. Z.

Calculation of impedance in an eddy-current coil by numerical integration method. J. Electr. Eng. Technol. 1996 11(1)17–20.

Theodoulidis

Kriezis

Series expansions in eddy current nondestructive evaluation models. J. Mater. Process. Technol. 2005 161(5)343–347.

Jiang

Q. M.

Zhang

X. F.

Liu

T.G.

The eletromegnetic simulation of eddy current system. Comput. Simul. 2000 17(5)36–39.

10.

C. F.

A finite element approximation of a quasimagnetostatic 3D eddy current model by fractional-step A-Psi; scheme. Math. Comput. Model. 2004 39(4)567–580.

11.

Philip

Zhou

E. P.

Morton

Numerical modeling and implementation of ferrite cored eddy current probes. NDTE Int. 2007 40 566–576.

12.

Y. T.

P. A.

Wang

Z. W.

Study on the electromagnetic properties EC sensor. In Proceedings of the IEEE International Conference on Mechatronics & Automation, Niagara Falls, Canada 2005, pp. 1970–1975.