Vector Magnetometer with Dual-Bridge GMR Sensors

A three-axis vector magnetometer based on two sets of dual-bridge GMR sensors and a fluxguide was investigated in this work. The sensors were mounted on a printed circuit board (PCB) with their sensing directions along the x- and y-axes respectively. A cylindrical ferrite fluxguide was put at the center of four sensors with the symmetric axis normal to the PCB plane. The fluxguide deflects the magnetic flux lines of an out-of-plane field to generate the in-plane components, making it possible to detect the z-axis field component with the x-y plane sensor pairs. When the device was driven by a peak-to-peak excitation voltage of 0.4 V, the demodulated dV/dB were found to be 230, 240, and 220 V/T, respectively, for the x, y, and z sensing axes. The field noise spectral densities at 1 Hz were found to be between 3 and 9 nT/root Hz for all three sensing axes. The proposed magnetometer design can be adapted to reduce the size and to lower the power consumption by integrating all the components on a chip.