Magnetoresistance Effect Sensor

The magnetoresistance effect sensor is made based on the magnetoresistance effect of the magnetic material. A magnetic material (such as permalloy) has an anisotropy, and when it is magnetized, its magnetization direction will depend on the axis of easy magnetization of the material, the shape of the material, and the direction of the magnetizing magnetic field. As shown, when the current is given to the banded permalloy material, the electrical resistance of the material depends on the angle between the direction of the current and the direction of magnetization. If a magnetic field B (the measured magnetic field) is applied to the material, the original magnetization direction is rotated. If the direction of magnetization turns in a direction perpendicular to the current, the resistance of the material will decrease; if the direction of magnetization turns parallel to the direction of the current, the resistance of the material will increase. Magnetoresistive effect sensors typically have four such resistors and connect them into a bridge. Under the action of the measured magnetic field B, the resistance values of the two resistors located at the relative positions in the bridge increase, and the resistance values of the other two resistors decrease. In its linear range, the output voltage of the bridge is proportional to the measured magnetic field. Magnetoresistive sensors have been fabricated on silicon wafers to form products. Its sensitivity and linearity have been able to meet the requirements of the magnetic compass, and the performance in all aspects is significantly better than that of the Hall device. Hysteresis error and zero temperature drift can also be eliminated by alternating forward and reverse magnetization of the sensor. Due to these superior properties of magnetoresistive sensors, it is able to compete with fluxgates in certain applications. The main problem with magnetoresistive sensors is their flipping effect, which is inherent in their principle.

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