ABSTRACT
It has always been a research hotspot for geologists and geophysicists to know the interior material structure of the earth by observing the geomagnetic field. How to realize a long-term observation of the geomagnetic field with high precision is also one of the challenges currently faced by developers of geophysical instruments. In order to solve this problem, it is obliged to overcome diculties such as low noise, low-power dissipation, and high reliability and stability of front-end sensor and back-end acquisition circuit. Common magnetic sensors used for the observation of the geomagnetic field mainly include proton magnetometer, optical pump, superconductivity, fluxgate, inductive coil, and so on. A proton magnetometer, similar to the optical pumping magnetometer, can only obtain the geomagnetic total field instead of the unidirectional magnetic-field component. The noise level of the superconducting magnetometer is extremely low. But it requires the support of the superconducting cryogenic box due to its large volume, so the field construction is limited. The inductive coil has excellent noise features, whereas it is insucient in geomagnetic field observation. It can only observe the alternating geomagnetic field and the magnetic-field components of a certain direction. The fluxgate sensor features small volume, multiple components, and low noise, so it is an ideal choice for the observation of the geomagnetic field.
