What Are The Principles Of The Magnetic Compass

The principle of the magnetic compass

Before analyzing the error of the magnetic compass, we should understand some basic concepts, which are the basis for our discussion of the causes of errors later.

1) Earth's magnetic field

The earth has a magnetic field. The north pole of the geomagnetic field is close to the geographic north pole, which is called the north magnetic pole; the south pole of the geomagnetic field is close to the geographic south pole, which is called the south magnetic pole. The north magnetic pole actually has the magnetism of the magnetic south pole; the south magnetic pole actually has the magnetism of the magnetic north pole. The strength of the Earth's magnetic field is weakest near the equator and strongest near the magnetic poles.

2) Magnetic inclination

Since the magnetic field lines of the earth's magnetic field converge at the north and south poles, the direction of the earth's magnetic field strength is not parallel to the horizontal plane. The angle between the earth's magnetic strength and the horizontal plane is called the magnetic dip. The magnitude of a certain geomagnetic dip is also called the magnetic latitude. Generally speaking, the closer to the geomagnetic pole, the greater the magnetic dip, that is, the higher the magnetic latitude.

3) Aircraft magnetic field

The magnetic field formed by the iron and steel materials on the aircraft and the working electrical equipment is called the aircraft magnetic field. The magnetic field of each aircraft is different. The composite magnetic field direction line of the horizontal component of the aircraft magnetic field and the horizontal component of the earth's magnetic field is called a compass. A magnetic needle placed on the plane will point in the direction of the compass.

4) The basic principle of magnetic compass

The basic principle of the magnetic compass is to use the characteristics of the free-rotating magnetic strip to track the compass line to indicate the aircraft's heading. The sensitive element of a magnetic compass is a magnetic strip that can rotate freely in the horizontal plane. A circular dial is fixed on the magnetic strip, and the 0°~180° scale line is consistent with the direction of the magnetic strip. The heading mark is fixed on the case and represents the longitudinal axis of the aircraft.