Giant magnetoresistance (GMR) spin-valve based magnetic sensor with linear and bipolar characteristics for low current detection

High sensitivity linear, bipolar, and hysteresis-free magnetic field sensor is necessary for low current measurement of the order of 1000 mA with a resolution of 1 mA. Magnetoresistive technology has evolved into popular magnetic sensing technology where magnetic multilayered structures were tailored to obtain linear output characteristics. In this report, a GMR spin-valve structure was used to develop magnetic field sensing elements. Mechanical assembly of the sensing elements in the form of a Wheatstone bridge configuration was made to have the linear and bipolar characteristics of the sensor. Application of the constant DC biasing field perpendicular to the sensitivity axis was made to have fully hysteresis-free output characteristics and the maximum sensitivity was achieved of the order 2 to 2.5 mV/G with a supply of 1 mA current to the bridge circuit. The in-house developed spin valve sensor was then used to measure the current in the range of ± 1 A, having a sensitivity of the order of 2 mV/mA with a resolution down to 1 mA by using non-intrusive current sensing technology. A core-based sensor has a large aperture size that accommodates a current-carrying conductor with an ampacity of 1 kA. The calibrated output shows the sensor can measure the field in the range of ± 0.4 mT with a resolution of ∼ 200 nT and has the potential for floating current measurement application in the battery management system.