Determination of the aging offset voltage of AMR sensors based on accelerated degradation test

Abstract

Usually Anisotropic Magnetoresistance angle sensors are configured with two Wheatstone bridges, but an undesirable offset voltage included in the sensor output affects its accuracy. The total offset voltage combines a voltage due to resistance mismatches during manufacturing and a voltage from inequalities in the magnetic sensitivity. This paper focuses on identifying a consistent trend between the bridges' offset voltages. Compared with previous studies that focus on lifetime tests using high temperatures, this research uses temperature cycling to study offset voltage and sensitivity variations due to aging effects.A consistent trend between the bridges' offset voltages could not be found. The two offset components can add to or subtract from each other and their interaction can change over time due to variations in the sensor's material properties. To achieve a precise angle measurement, the offset voltage must be compensated continuously over the entire sensor lifetime.

A dependable anisotropic magnetoresistance sensor system for automotive applications

“…The trend of the drift of the offset voltage can be described as higher at the start but then slowing down over time, which is most likely linked to a stress relaxation effect in the sensor. The undesired parameters amplitude imbalance between the sinusoidal signals at the sensor outputs and additional harmonics present smaller and more stable values over time and are hence considered to be a second-order effect concerning the angle error [Zam15a,Zam16a].…”