New Signal Conditioning Circuit for MR Angle Transducers With Full-Circle Range

Abstract

An efficient signal conditioning (SC) scheme that helps to obtain a linear output from a magnetoresistive (MR) angle sensor for 0°-360° range is presented in this paper. Most of the existing MR angle sensors have a sine/cosine relationship between the output and sensing angle, but a linear characteristic will be very useful. The new SC circuit of the proposed transducer accepts and processes output signals from an MR sensor that is sine/cosine in nature and gives an output directly proportional to the sensing angle. The sensitivity of the transducer output to variations in different circuit and mechanical parameters has been analyzed in detail, and their effect has been quantified. The functionality of the SC has been studied using SPICE simulations. A prototype of the proposed SC circuit has been built and tested using emulated sensor output signals. The output of the prototype circuit was linear from 0° to 360°, and worst case error was less than 0.08%. An angle sensor unit has been built using an MR sensor IC, interfaced to the SC circuit and tested. As expected, the output was found to be linear for a full-circle range.