Giant Magnetoresistive Current Sensor Based On The Principle Of Magnetic Shielding

Current sensors play an important role in detecting electric currents for the purpose of power monitoring in electric vehicle and smart power grid systems.Electric vehicles are equipped with the current sensors able to measure the currents up to hundreds or even thousands of amps in the rapid current charging and discharging process;The smart grid environment is more complicated,where accuracy and reliability are more emphasized for the current sensors.Although the Hall sensor can detect large currents,it is accompanied with shortcomings of large temperature interference,insufficient measurement accuracy,and poor stability.Recently the giant magneto resistance(GMR)sensor has received much attention as a result of its small size,high sensitivity and low power as well as reliability.However,GMR sensor is with a narrow operation range,and it cannot directly used to measure large currents.In this paper a new current sensor structure is proposed,where GMR sensor is used to measure large electric currents by effectively expanding its operation range with a configuration in which the magnetic fields generated by electric currents are attenuated with a shielding cover made of soft magnetic materials.Finally,the sensitivity drift of the sensor due to changing temperature is investigated and corrected by the algorithm,resulting in better accuracy.The current sensor constructed in this paper could be divided into four parts: magnetic signal detection,signal processing,software optimization and display.The magnetic signal detection module attenuates the magnetic field generated by the current and convert the attenuated magnetic signal into a stable differential voltage signal.The signal processing circuit amplifies the output voltage signal of the sensor.STM32 corrects the sensitivity according to the temperature and calculates the detected current based on the collected voltage.The LCD displays the detected results.In this work,the functionality of the magnetic shielding structure is first simulated,and then the sensor is built and tested.The sensor exhibits a reasonable performance with a operation range of 500 A,a zero drift of-0.481 A and a linearity of 0.964% as well as a measurement accuracy of 0.209%.