Optimization Design of a Giant Magneto Resistive Effect Based Current Sensor With a Magnetic Shielding

As giant magneto resistive (GMR) effect based current sensors are susceptive to stray magnetic fields, this paper proposes a GMR current sensor with a magnetic shielding. Magnetic shielding effectiveness and magnetic gain coefficient of the shielding are analyzed by finite element method (FEM), and some concerned parameters affecting the shielding effects are also discussed. In order to achieve accurate measurement for ac and dc, this paper proposed two methods for providing bias magnetic field. One method is using a coil winding and the other is using permanent magnet. Based on theoretical analysis and simulation results, a prototype was designed. Hysteresis effects on the sensor, the sensitivity of the GMR current sensor, and relative error of the measurement of the current sensor with and without magnetic shielding were tested and compared. The two methods for producing bias magnetic field were also tested and discussed. The designed GMR current sensor has the advantages of high sensitivity and accuracy, low nonlinear error (0.8%). It can measure currents from dc up to 200 kHz with the nominal primary current value of 20 A.