Excitation and temperature stability of PCB fluxgate sensor

Printed circuit board (PCB) integrated inductors have been adapted for operation as fluxgate sensors. A ring core is made from an electrodeposited permalloy thin film and is sandwiched between the layers of the PCB. The sensor excitation winding is also integrated into the PCB design. The pick-up coil is wound around the frame of the PCB core. Different types of current excitation waveforms with tuned and nontuned pick-up coils were used. The achieved sensitivities for 60 turns of tuned/nontuned pick-up coil, a sinusoidal waveform excitation current of Irms=300 mA, and an excitation frequency of 150 kHz were 13100/1800 V/T. The achieved sensitivity for pulse excitation (Ipeak-peak=900 mA, Irms=184 mA, duty 20%) was 2100 V/T. Noise power density for pulse excitation was 1.2 nTrms/√Hz@1 Hz, noise rms value from 10 mHz to 10 Hz was 3.3 nT. A perming error of 1 μT was measured for a wide range of excitation currents.