We present a new method to realize a vector magnetometer that has been optically referenced to an external coordinate system. The vector magnetometer is made up of three Hall sensors attached to orthogonal faces of a glass cube. When placed in a homogeneous magnetic field, rotating the vector magnetometer around two axes allows the orientation of each sensor to be determined with respect to the glass cube. The orientation of the glass cube is detected by an autocollimator and optically referenced to an external coordinate system. A direction uncertainty below 130 µrad (which is traceable to angle standards) is achieved.

Abstract. A precise and efficient way to calibrate 3D magnetometers is by utilizing triaxial coil systems. We describe the development and characterization of a 3D coil system that generates magnetic flux densities up to 2 mT in arbitrary field direction. Coil parameters, such as coil constants and the misalignment of its spacial axes are determined with nuclear magnetic resonance (NMR) techniques, ensuring traceability to SI standards. Besides the generation of a constant magnetic field inside a sphere of radius 1 cm in the center of the coil, the 3D coil system enables the realization of gradient and saddle field profiles, which allow a precise estimate of sensor positions in 3D. Fluxgate and Hall sensor measurements are carried out to characterize the quality of the generated magnetic fields. The homogeneity achieved the orthogonality, and the position and structure of the saddles are determined experimentally and compared to calculated values.