Non-contact and high-precision displacement measurement based on tunnel magnetoresistance

Abstract

High-precision displacement measurement is essential to various industrial fields, but the drawbacks of existing sensors like bulkiness, low compatibility and high cost limit their applications. In this study, a non-contact and high-precision displacement measurement method based on tunnel magnetoresistance is introduced to achieve high accuracy and small size. The displacement of a permanent magnet changes the spatial distribution of the magnetic field and thus the output of the full-bridge tunnel magnetosresistance (TMR)-based component varies. Based on the theoretical analysis, the highest sensitivity of the measurement system is obtained and the corresponding layout of the permanent magnet and TMR component to ensure the system achieves such sensitivity is determined. The results are validated by experiments, and the highest sensitivity is 17.15 mV m−1. The system shows stable and high-quality frequency response below 300 Hz. The resolution reaches to 33 nm and the system is of high resolution compared with the eddy current sensor. The time drift is determined to be 0.121 m h−1, which is 30% lower than the existing laser sensor. All the features of the measurement system imply that it is of high accuracy and robustness. The compact structure and low cost make it a promising alternative to existing displacement sensors and demonstrates its potential for integration with the actuator.