Tunneling magneto-resistor based angle transducer

Abstract

An angle transducer that provides a linear output for full-circle range (0–360°) of operation is presented in this paper. The sensor part of the transducer is made of two pairs of Tunneling Magneto-Resistors (TMR) and the signal conditioning part consists of a couple of sinusoids having same frequency but differing in phase by 90° and a phase detector. The novel signal conditioning circuit proposed here operates on the sine/cosine outputs of the TMRs and provides a voltage that is linear to the angle being sensed. Simulation studies conducted using SPICE demonstrate the efficacy of the transducer in providing a linear output across the entire full-scale range with a worst case error less than ± 0.15 %. Results obtained from a prototype unit built and tested establish the practicality of the proposed transducer. The worst case error of the prototype was < ± 1 %.