Principles and characteristics of magnetic compass

The magnetic compass is a pointing instrument made using the principle that a magnetic needle can point to the earth's magnetic north (south) pole under the action of geomagnetic force. As an important navigation instrument, magnetic compasses have a long history of being installed and used on ocean ships. At present, although modern ships are equipped with advanced navigational instruments such as gyroscopes (gyros) and satellite navigation (GPS), modern magnetic compasses are still necessary due to their simple structure, reliable performance, and independence from external conditions Navigation instruments are installed and used by ocean ships. The International Maritime Organization (IMO), classification societies, and ship inspection agencies of various countries have clearly stipulated that marine ships should be equipped with magnetic compasses, and the deviation should be corrected correctly and a deviation table should be prepared.

    1 Classification of magnetic compasses

　　A According to whether there is liquid in the magnetic compass, there are two types: liquid compass and dry compass. The compass of a liquid compass is suspended in a compass full of liquid. Due to the damping effect of the liquid, the compass has better stability when the ship is rocking. In addition, due to the buoyancy of the liquid, the friction between the compass support shaft needle and the bearing can be reduced, thereby improving the sensitivity of the compass. Our products are all liquid compasses.

　　B According to the purpose of magnetic compass, there are mainly standard compass and steering compass. The standard compass is generally vertical and installed on the top deck of the cab (compass deck). Because of its high position, no shelter, and little influence from ship magnetism, it is used to observe the course, determine the orientation of objects and correct the steering compass, so it is called the standard compass.

　　The steering compass is generally a desktop type, installed in the cockpit, for observing the heading and steering. The company produces standard compasses and steering compasses of various models.

　　C According to the diameter of the compass surface, the commonly used ones are 190mm, 165mm, 130mm, 100mm.

    2 Magnetic compass deviation and correction

　　The magnetization of steel ships by the geomagnetic field will produce ship magnetism, which will affect the pointing accuracy of the magnetic compass, which is the so-called "difference". This deviation can be corrected by the Master Luo Jing. The magnetic compass produced by our company is equipped with an efficient self-difference correction device.

    3 Installation of magnetic compass

　　A The magnetic compass should be installed on the longitudinal centerline as much as possible, and the first line of the compass cabinet should be coincident with the longitudinal centerline of the ship (or parallel).

　　B The distance between the standard magnetic compass and any ferromagnetic material is 1 meter.

4 Daily maintenance of magnetic compass

　　A The magnetic compass should be covered with a compass cap (standard compass should be covered with a compass sleeve).

　　B Keep the liquid in the Luopan colorless and transparent and eliminate bubbles.

　　C Keep the compass shaft and the constant flat ring shaft lubricated, and rotate flexibly.

　　D Regularly check the half cycle and sensitivity of the compass, and if necessary, refill the compass.

　　E No magnetic objects should be placed near the compass, and the compass should not be exposed to high temperature and vibration for a long time.