A magneto resistive (MR) sensor records axis or magnet angle information via the field vector in the chip plane. The AMR effect is a “resistor” effect based on the dependence of electrical resistance on the angle between the directions of the current flow and the magnetization of a ferromagnetic material. An external magnetic field can switch the internal directions of the magnetization of the AMR material and this effect changes in resistance (ΔR/R) that are typically on the order of a few percent.
Several resistors connected in a Wheatstone bridge are used to measure angles. Each component resistor contributes to a change in the differential output voltage of the bridge, depending on the X-Y field direction in the sensor plane and on the direction of current flow in the resistors. This direction of current flow is either given by the alignment of the resistor paths or is forced in another direction by short-circuit contacts (barber poles).