Optimization of an Eddy Current Sensor Using Finite Element Method

To optimize the structure of an eddy current sensor (ECS) coil, the computation process of the coil impedance is firstly derived using finite element method according to the Ponying Theorem; Then the 3D and 2D finite element model are built based on the modeling theory and the relative magnetic theory; Next, the influence of the coil shapes and its geometric parameters on the properties of ECS are investigated; Finally, the influence of the ferrite core and its geometric parameters on the properties of ECS are studied. The following conclusions can be drawn from this paper: (1) the sensitivity of ECS with rectangular coil is higher than that with cylindrical coil. However, the cylindrical coil is the better choice in displacement quantity ECS; (2) The coil cross section area and the ratio of turn number verse the cross-section area have considerable influence on the properties of ECS. When the coil turn number is a constant, the bigger inner and outer radius, the smaller thickness, all result in the improvement on the sensitivity of ECS and decrease in the linearity; while the ratio of turn number verse the cross-section area is unchanged, the smaller inner radius, the bigger outer radius, and the thicker of the coil, will cause the higher sensitivity and the worse linearity. (3) The coil cross-section shape has important influence on the properties of ECS due to the influence of it on the distribution of the magnetic field. (4) The ferrite core improves the sensitivity of eddy current sensor, either the measurement target is magnetic or nonmagnetic. And the ratio of the height verse the radius of ferrite core has significant influence on the properties of ECS when the measurement target is non-magnetic.