Design and analysis of an eddy current displacement sensor with extended linear range

Abstract

Eddy current displacement sensor (ECDS) is a non-contact sensing device. This paper proposes an ECDS by using the colpitts circuit with the characteristics of longer measurement range and better linearity. The parameter Rp is separated from an improved colpitts circuit. By measuring Rp and optimizing probe sensitivity, the measurement range of the sensor is increased, which extends to 56% of probe diameter, the maximum measurement distance reaches 72% of probe diameter. A linear-fitting method based on MCU is proposed, which improves the linearity, consistency, and response speed of the sensor. The principle and design are explained in detail, and verified through field circuit coupling simulation. Finally, the ECDS is tested by using a precision electronically controlled displacement platform, the experiment results show that the sensor performance has a high consistency, and linearity can be reduced to within ± 0.4%, sensitivity is 0.28 V/mm, resolution is 6 µm. The ECDS is identified to be practical, the method proposed in this article effectively improves the measurement range and linearity, therefore, the ECDS is widely used in displacement measurement, which need long distance, high precision and fast response.