Shieldless Eddy-Current Displacement Sensor with Improved Measurement Sensitivity

Abstract

The major limitations of eddy-current displacement sensors, such as low measurement sensitivity and low stability, can be mitigated by using low-inductance flat coils in combination with a ratiometric measurement and a high excitation frequency, thus making eddy-current sensors of interest for high-precision applications. For the ratiometric measurement, the sensing coil is used in combination with a constant inductance reference coil, which are magnetically isolated from each other by a shield. In this paper, the implications of omitting the shield are studied. It is shown that a shieldless design brings several advantages related to sensitivity, compactness and manufacturability.