What are the types of Magnetic compass ?

Types of  Magnetic compass :

  1. Dry card compass.
  2. Wet card compass.
Dry card compass: il_570xN.684690348_9ebl

In olden days there used to be a dry card compass on the upper bridge for use in navigation. It is now part of history.

  • Made by rice paper.
  • Diameter 254mm (10 inches)
  • Cover aluminum ring.
  • Silk thread used to be attached.
  • The weight of the card is usually around is grams.
Wet card compass:
  • Made of mica
  • Diameter 15cm
  • Bowl diameter 23cm

The ring magnet wet card compass is the most efficient type of marine magnetic compass.92

The bowl is filled with a mixture of distilled water and pure ethyl alcohol so that the mixture has the following properties.

  1. Low freezing point about  -300C
  2. Small coefficient of expansion
  3. Does not discolor the card.
  4. Low relative density about 0.93

By immersing the card in a liquid, oscillations caused by vibration, rolling & pitching are damped, without loss of accuracy. The card therefore has a dead beat movement which is convenient.

INDERJEET SINGH
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