Closed-loop current-feedback, signal-chopped, low noise AMR sensor with high linearity

Over the past twenty years' magnetic sensors have emerged as a preferred choice in many sensory systems due to their high accuracy, reliability and mechanical robustness. This has sparked the development of different types of magnetic sensors for magnetic field measurements as well as for measuring other quantities indirectly. Sensitivity, linearity, signal-to-noise ratio, measurement range and cross-talk between sensors in multi-axis / multi-sensor applications are only some of the magnetic sensor's characteristics that have been studied in the past. The aim of this paper is to present a fully analog current-feedback closed loop system for AMR (Anisotropic Magnetic Resistance) magnetic sensors. The calibration and testing were conducted in a 3D Helmholtz coil setup capable of controlling the magnetic field amplitude and direction in the AMR sensor area. The noise characterization was realized in a multilayer tube of soft magnetic material. Thorough experimental characterization and testing indicates that the proposed close loop architecture improves sensor's linearity while maintaining low noise level.