Optimization Method for Weak Magnetic Measurement Environments Using Active–Passive Coupled Magnetic Shielding Analysis

The calibration of vector fluxgate sensors imposes stringent requirements on background magnetic field purity. Magnetic shielding devices (MSDs) can provide the appropriate environment for such applications. The externally mounted geomagnetic nulling coil (GNC) hybrid shielding is widely recognized as a highly promising methodology. However, the absence of accurate analytical models prevents researchers from precisely evaluating the distorted magnetic field distribution inside the MSD, significantly limiting its adoption in high-precision magnetic measurement applications. This article proposes a direct analytical computation method, combining conformal mapping with the multiple image method. Based on this approach, an optimized design for the GNC is developed to enhance the weak magnetic measurement environment performance. Experimental results indicate that the proposed method can reduce the residual magnetic field magnitude near the center point from 681.03 to 8.15 nT, while decreasing the Z -axis field gradient to 20.56% of its initial value. This demonstrates that this optimization method can readily achieve a uniform near-zero magnetic field environment even in a single-layer preliminary prototype. This study utilizes ferromagnetic coupling effects to achieve high-performance weak magnetic environments, which effectively lowers calibration costs for multipurpose fluxgate sensors. The method demonstrates extensibility to MSDs of arbitrary dimensions, which facilitates broader adoption of weak magnetic measurement technologies.