Research on the Z-axis Magnetic Sensor Based on the Giant Magnetoresistance Effect

Magnetoresistive sensors are usually used to measure the magnetic field with the direction parallel to the plane of the magnetic sensor, but a soft magnetic permalloy flux concentrator is integrated in the sensor, and can change the direction of the magnetic field in the magnetic sensor, so that the magnetoresistive unit can also measure the magnetic field (the Z axis) perpendicular to the plane of the magnetic sensor. The magnetic concentrator is usually made of permalloy with high magnetic permeability. The flux concentrator is designed into a grid structure, the magnetic field (the Z axis) perpendicular to the sensing plane of the sensor can generate the magnetic field component in the sensor plane (the XY axis), and the giant magnetoresistance (GMR) magneto-sensitive unit located under the magnetic concentrator can measure the Z-axis magnetic field. The GMR magneto-sensitive unit is composed of four bridge arms, which are connected by metal conductive materials to form a Wheatstone bridge structure. The two magneto-sensitive units on the opposite bridge arms of the bridge are located on both sides of the soft magnetic grid respectively and form the push-pull structure under the action of the magnetic field, so that the strength of the output signal of the sensor is doubled, and the vertical packaging form of the conventional Z-axis sensor is also prevented. According to the experimental results, the sensitivity of the Z-axis giant magnetoresistance sensor with this structure can reach 0.8 mV/Oe, and the magnetic field measurement range can reach 150 Oe. It can be used in various fields such as geomagnetic measurement and current measurement.