Coil impedance calculation of an eddy current sensor by the finite element method

An eddy current sensor utilizes the variation of coil impedance to perform the measurement of physical parameters, and the coil impedance is an important parameter for investigating the properties of an eddy current sensor. Therefore, the study of approaches to calculation of coil impedance is very important. In this paper, an integral expression for coil impedance with a magnetic substance is given directly. For the convenience of calculation of the coil impedance, this integral expression is further expanded in series form and the coil impedance is computed using Mathematica. Then, two different finite element models of the eddy current measurement system are built on the basis of the finite element modeling theory. The infinite boundary of model 1 is truncated. On the contrary, the infinite boundary of model 2 is simulated completely by an infinite element. The coil impedance and the magnetic distribution are obtained by the finite element method, respectively. The comparison shows that the result obtained by the finite element method is in good agreement with that of the theoretical calculation approach, which indicates the correctness and reasonability of modeling of the eddy current measurement system and calculation of the coil impedance by the finite element method.