The digital compass is divided into a magnetoresistive effect sensor, a Hall effect sensor, and a fluxgate sensor according to the sensor. Among the fluxgate sensors:
The magnetic saturation method is based on the principle of magnetic modulation, which is a method for measuring the weak magnetic field by using the nonlinear relationship between the magnetic induction intensity and the magnetic field strength of the magnetic core of the ferromagnetic material in the measured magnetic field under the saturation excitation of the alternating magnetic field. A magnetometer that uses a magnetic saturation method to measure a magnetic field is called a magnetic saturation magnetometer, also known as a fluxgate magnetometer or a ferromagnetic probe magnetometer. The magnetic saturation method is roughly divided into two categories: harmonic selection method and harmonic non-selection method. The harmonic selection method only considers the even harmonics (mainly the second harmonic) of the probe induced electromotive force, and filters out other harmonics; the harmonic non-selection method directly measures the entire spectrum of the probe induced electromotive force without filtering, and utilizes The differential pair magnetic saturation probe can form a magnetic saturation gradiometer that can measure non-uniform magnetic fields, while using a gradiometer to overcome the influence of the geomagnetic field and suppress external interference. This magnetometer has been continuously developed and improved since it was used in geomagnetic surveys in the 1930s. It is still one of the basic instruments for measuring weak magnetic fields. The magnetic saturation magnetometer has a high resolution and a wide range of weak magnetic fields. It is reliable, simple, inexpensive, and durable. It can directly measure the magnetic field component and is suitable for use in high-speed motion systems. Therefore, it is widely used in various fields, such as geomagnetic research, geological exploration, weapons reconnaissance, non-destructive testing of materials, and measurement of spatial magnetic fields. In recent years, magnetic saturation magnetometers have gained important applications in aerospace engineering, such as controlling the attitude of satellites and rockets, as well as mapping the "solar wind" from the sun and the spatial magnetic field, the magnetic field of the moon, A graph of the planetary magnetic field and the interplanetary magnetic field.