Suppression of Low-Frequency Magnetic Interference on Eddy Current Displacement Sensor with Nanometer Resolution

Since eddy current displacement sensors (ECDSs) are based on phenomenon of electromagnetic induction, their measurement results would be seriously disturbed by the magnetic interference. Traditional solution is to add a shield integrated in the sensing probe, but it will also affect the property of sensing coil. In this paper, an alternative solution is proposed to suppress the low-frequency magnetic interference by high-frequency signal conditioning circuits with deliberate filtering segments. Prototype ECDS provides a resolution of 20 nm with measuring range of 50 μm and bandwidth of 3 kHz, under magnetic interference of 6000 A/m at 1 kHz.