Determination of the drift of the maximum angle error in AMR sensors due to aging

An Anisotropic Magnetoresistance (AMR) sensor is magnetic sensor often used to angle measurements. In case the sensor is configured with two Wheatstone bridges, it provides two sinusoidal outputs useful to calculate the angle of a magnetic field. However, due to non-ideal properties of the sensor, its output signals present undesired characteristics such as offset voltage, amplitude imbalance and additional harmonics. All of them are sources of errors in the angle calculation and they change during the sensor lifetime due to wearing and aging effects. Until now, it is considered that the angle error variations are small enough not to affect the sensor accuracy. However, the future trend is to have applications that will demand more accurate angle measurements. Therefore, it is important to understand the trend of drift of the error sources in order to take appropriate actions to guaranty the sensor accuracy. The aim of this paper is to study the drift of the different sources of angle error due to aging effects. An aging test was performed with commercial sensors submitted to different stress conditions in terms of magnetic field, power supply and temperature. The angle error due to offset voltage showed the largest variation, being faster at the start and becoming more constant with time. The angle error due to amplitude imbalance and harmonics show less and more constant variations during the test. This information is very useful to determine the best approach to perform compensation in AMR sensors.