Development Of Ring Shaped Eddy Current Sensor

With the rapid development of the eddy current testing technique and its industrial application needs, it is important to develop high-performance eddy current sensor.First of all, the development and the trend of eddy current testing is introduced. The unique advantage of eddy current sensors in a particular environment is given in comparison with other non-contact displacement sensors. Then, the relevant theories of eddy current distribution is overviewed from the viewpoint of the principle of the distance measurement using eddy current sensors.In order to design and develop an eddy current sensor with a ring shaped probe, firstly the factors the affect all aspects of sensor performance is analyzed, then the finite element method and its application in the design of the eddy current sensor are analyzed in detail. According to the model of distance measurement system using eddy current sensors, the electrical and magnetic properties of eddy current sensor are analyzed using the finite element analysis software COMSOL Multiphysics. The affect of the coil shape of the eddy current probe on the sensor sensitivity and linearity has been investigated, and the radial and vertical eddy current distribution in metallic conductors has been simulated. Furthermore, the conductivity and magnetic permeability of the measured part and the impact of the operating frequency on the eddy current sensor has been explored, and the relationship between the inductance and resistance of the coil with the distance has been given.An eddy current probe with ring shaped structure has been designed and fabricated. Through the experiments with the coils of different structural parameters, the impact of the coil structure of the probe on the sensor properties has been verified.At last, several signal processing circuits for eddy current sensor are described, and a detailed analysis and simulation, including oscillation, square-wave conversion circuit, resonant circuit, AC amplifier circuit, filtering rectifier circuit, and so on, of fixed-frequency amplitude measurement circuit are given in the thesis.