A linear hall effect displacement sensor using a stationary two-pair coil system

Abstract

In this work, a linear position sensor based on a Hall Effect element with electromagnetic coils for measuring long displacement is presented. This paper proposes a novel stationary system using one pair of Helmholtz coils and one pair of Maxwell coils. The Maxwell coil pair is chose to generate uniform gradient magnetic flux intensity. The Helmholtz coil pair is used to increase the magnetic field without sacrificing linearity for reducing the measurement error near the center. Then, a computation of the quasi-static electromagnetic field of the sensor using the finite element method has been performed. Secondary model has been created on the basis of finite element results. Then this model has been optimized with respect to two criteria: linearity and sensitivity. The designed electromagnetic coils pair combining with a Hall sensor has the advantage of displacement measurement with wider range, lower cost and simple structure.