An eddy current ring computation model with variable size which has distance-depending property is proposed. The depending relationships between the inner radius and the outer radius

and the distance are calculated

respectively

and get the correcting formulas by fitting. In order to validate the new model

an eddy current sensor experimental device is built. Based on MATLAB

input and output curve of sensor is obtained by simulation and calculation by fitted size and variable size eddy current ring model. The input-output characteristic curves are both simulated with the two different models and compared with the experimental curve. It is proved that the eddy current ring model with variable size parameters has higher precision.