Design And Experimental Research Of Shielded Eddy Current Sensor

The eddy current sensor has been widely used in various engineering fields due to its advantages such as good reliability,fast response,and strong anti-interference.However,ordinary eddy current sensors have their limitations for some situations where the installation space is small and the environment is greatly disturbed.In order to meet this kind of special measurement demands,a shielded eddy current sensor is designed through the experimental verification and optimization based on the theoretical analysis,,which with a small metal casing but satisfying the actual measurement needs.Firstly,a preliminary shielded eddy current sensor mathematical model is established,according to the theoretical analysis of the coil model,the equivalent vortex ring of the measured body and the mutual inductance between them.Combined with the experimental values,a correction function was proposed to provide a theoretical basis for coil optimization.The correction-function of mutual inductance based on the ratio of the inner diameter of the metal shell and the outer diameter of the coil.The correction function of impedance is displacement-based.Secondly,combined with the modified mathematical model of the shielded eddy current sensor and taking the nonlinear error and sensitivity of the two performance indexes of eddy current sensor as references,the optimal solution range is obtained.The optimal structure of the sensor is finally determined through experiments.The best wire diameter for temperature stability is obtained through temperature drift experiment.The optimum excitation frequency is obtained through frequency experiment.Finally,the measurement circuit of shielded eddy current sensor is designed.Frequency conversion amplitude measurement circuit is used to realize the power conversion of the sensor.The main structure includes the oscillator,amplifier,detection filter and nonlinear compensation circuit.After non-linear compensation,the optimal measurement range of the sensor reaches 0.25-4.25 mm.Within this measurement range,the sensitivity reaches 0.498v/mm and the maximum relative linearity error is 4.856%.