Systematic optimization of the sensing properties of ring-core fluxgate sensors with different core diameters and materials

In this study, a series of cobalt-riched alloy compositions Co71-xFexCr7Si8B14 (x = 0, 2.0, 3.2, 4.0, 6.0 and 8.0) in the form of ribbons were produced to change magnetization characteristics and constants of magnetostriction in a controllable manner. In this way dominant parameters for the design of low-noise fluxgate sensor were determined. The studies were carried out in ring-core geometry for different diameters from 6 mm to 20 mm. Our experiments have shown that low values of the saturation magnetic induction Bs inherent for this alloy system had a crucial role for the noise level. With the cores having Bs of ∼0.4 T, we could achieve a noise level of ∼1 pT/√Hz @ 1 Hz. The specific features of design of the ring-core fluxgates having different dynamical ranges were also discussed thoroughly. The ring-core diameter of 15 mm was found to be optimal geometry for outdoor applications.