Modelling the Inductance of a Novel Eddy-Current Position Sensor for High-Precision Applications

Due to its immunity to ambient conditions, the eddy current position sensor is considered a good candidate for use in high-precision applications. Currently, the eddy-current sensor is not often used in such applications, due to its poor resolution as compared to, for example, the capacitive position sensor. A novel eddy-current sensor is proposed that uses small standoff distances in combination with a high excitation frequency to decrease the skin depth, thus aiming at an improved resolution. This paper studies how well some analytic models describe the sensor's inductance at small standoff distances and high excitation frequencies. It is shown that the analytic methods can be used in the design process of the sensor but that some care must be taken, as the analytic methods do not fully model skin effect.