Magnetic field sensor system with a magnetic wheel rotatable around a wheel axis and with magnetic sensor elements being arranged within a plane perpendicular to the wheel axis

Abstract

It is described a magnetic field differential sensor system for measuring rotational movements of a shaft. The described magnetic field sensor system () comprises (a) a biasing magnet () configured for generating a biasing magnetic field; (b) a magnetic wheel () having a wheel axis and a circumferential surface which comprises a regular structure of teeth () and gaps () arranged in an alternating manner, wherein (i) the magnetic wheel () is attachable to the shaft and (ii) the magnetic wheel () can be magnetized by the biasing magnetic field; and (c) a magnetic sensor arrangement () comprising four magnetic sensor elements () being connected with each other in a Wheatstone bridge configuration. Respectively two of the magnetic sensor elements () are assigned to one half bridge of the Wheatstone bridge. Further, the four magnetic sensor elements () are arranged within an y-z plane, wherein an x-axis, a y-axis and a z-axis define an orthogonal Cartesian coordinate system in which (i) the x-axis is oriented parallel with the wheel axis of the magnetic wheel (), (ii) the y-axis is oriented tangential to the circumferential surface of the magnetic wheel (), and (iii) the z-axis is the symmetry line through the center of the biasing magnet () and the center of the magnetic wheel (). The magnetic sensor elements can be hall sensor elements or magnetoresistive sensor elements ().