Simplified Calculation Method of Planar Coil Impedance Considering the Eddy Current Distribution by Using Finite Element Method
Eddy current sensors have various uses. However, there are few studies which show theinfluence of a conductor on the impedance of a detector coil using theoretical formulae. This papershows a simplified calculation method for impedance of a planar coil while considering the influenceof eddy current. An eddy current distribution in a metal plate facing to planar coil was calculatedusing finite element method. It assumed the metal plate to be a one-turn coil that can change shape.Therefore, the impedance of a planar coil considering the influence of the eddy current can beestimated from an equivalent circuit. In addition, calculations were simplified by estimating mutualinductance between the planar coil and the metal plate from an area ratio. This simplified calculationmethod can estimate impedance with the same accuracy as finite element method. The calculatedvalue agrees to within ±2.44 % of the measured value. The computation time was shortened by 1/20.Therefore, it can be immediately estimated how each parameter of a planar coil or a target influencesthe characteristic of the eddy current sensor. This simplified calculation method is useful for anoptimum design of an eddy current sensor.
A.G. Mamalis, A. Kladas and M. Enokizono
H. Wakiwaka et al., "Simplified Calculation Method of Planar Coil Impedance Considering the Eddy Current Distribution by Using Finite Element Method", Materials Science Forum, Vol. 792, pp. 215-220, 2014