Micro Fluxgate Sensor using Solenoid Coils Fabricated by MEMS Technology

In this paper, we present a micro fluxgate sensor with solenoid coils. Micro-solenoid coils were used in this fluxgate sensor as excitation and sensing elements. Two identical excitation coils in inverse series were wound around the opposite sides of the rectangular-ring-shaped magnetic core, respectively. The sensing coil was placed vertically to the excitation coils and between them. Adopting gluing and chemical wet etching, iron-based nanocrystalline alloy was used as magnetic core material. This fluxgate sensor was designed to operate based on second harmonic operation principle. 100 kHz excitation currents with different effective values were selected to characterize the fabricated fluxgate sensor. From these experiments, we obtained some results from which we found out that the greatest sensitivity of 583.1 V/T was achieved with the effective excitation current of 150 mA. In the range from -500 μT to +500 μT, the fabricated fluxgate sensor can keep a good linearity. The noise power density was 13.57 nT/Hz0.5 at 1Hz and the noise RMS level was 23 nT in the frequency range of 10 mHz-25 Hz.