Temperature Drift Compensation for Exponential Hysteresis Characteristics of Higherature Eddy Current Displacement Sensors

The output stability of the displacement sensors is essential to enhance the reliability of active magnetic bearings in the higherature applications. This paper proposes a novel temperature drift compensation method for exponential hysteresis characteristics of higherature eddy current displacement sensors. The transient thermal analysis for the sensing assemblies demonstrate that the temperature drift errors are mainly induced by the temperature variation hysteresis effect: one is the dynamic lag between the probe coil and the air gap, and the other is the dynamic lag between the target material and the air gap. An auxiliary device consisting of compensation probe and compensation plate is designed to solve the hysteresis effect. The thickness of the compensation plate is determined by simulating the transient thermal analysis of the compensation plate and the measured target region. The model analyses also find that the exponential temperature drift at different determined displacement states is similar under the same temperature gradient. With this error characteristic, the differential circuit is used to eliminate the exponential hysteresis temperature drift. Experimental investigations show the effectiveness of the proposed solution.