PCB racetrack fluxgate sensor with improved temperature stability

A low-cost flat fluxgate magnetic field sensor with amorphous racetrack core embedded in the printed circuit board (PCB) is presented. The excitation and pick-up coils are formed of copper routes and vias on the PCB. Sensor versions with single and double layer of the core material are compared. The improved core-embedding technique reduced internal temperature-induced stresses and thus significantly increased the temperature stability: 20 nT offset temperature stability in the −20 to +70 °C range was achieved at the excitation frequency of 10 kHz. The untuned sensitivity for 27-turn pick-up coil was increased to 4400 V/T at 200 kHz excitation frequency (double-core sensor), which is the highest reported value for PCB fluxgate sensor. However, sensitivity is not a key parameter for magnetic sensors. We show that high sensitivity at elevated excitation frequencies is paid by degradation of offset stability and noise; from that point the optimum excitation frequency was 10 kHz, where we achieved 24 pTrms/√Hz @ 1 Hz noise PSD level and sensitivity of 241 V/T (for double-core sensor).