Fluxgate magnetic sensors are highly sensitive devices designed to measure magnetic fields. They are particularly important in detecting weak magnetic fields and are based on Faraday's law of electromagnetic induction. The structure of a fluxgate magnetic sensor typically consists of excitation windings, a core, and sensing windings, similar to the structure of a transformer .

The working principle of a fluxgate sensor involves the periodic change of the magnetic permeability of a soft ferromagnetic core, which is driven by a periodic exciting current. When there is no ambient magnetic field, the current in the exciting windings matches the current in the sensing windings. However, when the soft core is exposed to an ambient magnetic field, it becomes more easily saturated in the direction of the ambient magnetic field and less easily saturated in the opposite direction. This causes a mismatch between the currents in the exciting and sensing windings, which is used to estimate the strength of the magnetic field .

Fluxgate sensors are divided into parallel and orthogonal types, depending on the orientation between the excitation magnetic field and the probed magnetic field. They can also be classified as voltage fluxgate sensors or time domain fluxgate sensors, depending on whether the voltage on the sensing windings or the time difference between positive and negative signals is measured to estimate the ambient field .

These sensors have been applied in various fields such as geophysics, astro-observations, wearable electronic devices, and non-destructive testing. Recent progress in fluxgate magnetic sensors includes advancements in lowering noise, improving calibration methods, and increasing sensitivity. The high sensitivity and resolution of fluxgate sensors make them suitable for measurements of weak magnetic fields, such as the Earth's field of approximately 45μT. They also offer low drifts, which means temperature compensation can often be avoided .

Fluxgate sensors have been used in space missions, unmanned aerial vehicles for Earth's magnetic field detection and in various other applications like wearable devices and industrial sensing.

The future of fluxgate sensors looks promising with ongoing research aimed at reducing noise, improving calibration methods, and increasing sensitivity. There is also a trend towards reducing the fabrication cost of these sensors to make them more accessible for a wider range of applications.