Online digital offset voltage compensation method for AMR sensors

The offset voltage is an undesirable voltage included at the output of an anisotropic magnetoresistance angle sensor, which affects the accuracy of the angle measurement. This voltage changes with sensor aging and hence should be compensated not just at the moment of manufacturing but also during the sensor lifetime. This can be accomplished by an online offset voltage compensation method. However, the vast majority of the methods proposed so far cannot be used online. This research proposes an online digital compensation method based on an equations system. It was verified using as input, voltages calculated with a mathematical model of the sensor and also with voltages measured in commercial angle sensors. For all cases, the offset voltages and the angle errors were lower after compensation. These results show the feasibility of the proposed method to improve the accuracy of the sensor.