Noise Suppression in Parallel Fluxgate Magnetometers by DC-Biased Excitation Method

We experimentally revealed that a direct current (DC) biased excitation method can reduce the noise in parallel fluxgate magnetometers composed of a permalloy ring core. The noise suppression was achieved by decreasing the Barkhausen noise and increasing the open-loop sensitivity using the nonlinearity of the B-H curve with the DC-biased excitation. The noise performance depends on the excitation parameters: frequency, amplitude, and DC-bias. We proposed that the parameters should be determined based on the evaluation of the sensitivity and noise level in both open-loop and closed-loop modes. Specifically, a contour map of the closed-loop noise is useful for understanding the noise decrease with different values of the amplitude and DC-bias. We also demonstrated the effectiveness of the DC-biased excitation method using a commercially available fluxgate magnetometer (APS520A, Applied Physics Systems). Using the DC-biased excitation method, the noise level was approximately one-fourth compared to that of the original electronics.