Accurate Distance Measurement Using an Eddy Current Sensor Based on an Analytical Model

This paper presents a novel method to measure the distance of a metallic target using an eddy current sensor based on an analytical solution. It has been discovered that a feature in multi-frequency eddy current (MEC) testing, i.e. the imaginary part of the inductance value at the peak frequency (the frequency when the imaginary part of the inductance reaches peak) is linked to the distance of the sample. In this paper, we show mathematically that as the lift-off increases, the inductance value decreases. Experimental results suggest that the accuracy of distance measurements is within 2%.