search here

uses and types of magnetic compass

A compass is a navigational instrument that shows directions compassin a frame that is stationary relative to the surface of the earth. the frame of reference defines the four cardinal directions- north, south, east and west. intermediate directions are also defined.north corresponds to zero degree and the angles increase clockwise, so east is 90 degrees, south is 180 and west is 270 degrees. 

 the best way to establish directions accurately is through a magnetic compass. two types pf magnetic compass are used.
a. pivot needle
b. floating disc
pivot needle-  it is an ordinary compass commonly used in  school laboratory with a colored tip, usually in red. due to the magnetic field of the earth, this needle invariably points towards north. the needle of the compass when placed on a leveled surface, starts oscillating. when the needle stops, one should align the coloured tip with N mark on the compass. this N shows the exact north.
floating disc- it is an improved version of the pivot needle. it is an automatic device that point towards the direction automatically. in this kind of compass, a disc is mounted on the needle due to which there is no need to align the tip, as is the case with pivot needle, this kind compass being of superior quality, makes it easier for use to find the accurate direction without being much influenced by external sources like EMI radiation {electra magnetic induction} & BEM {bio electra magnetic} energy. but, while establishing directions with magnetic compass one should take precaution in placing the compass to get the accurate redings, particularly in the case of the pivot needle.
a. the compass should be on a placed on a leveled surface to avoid any kind of error.
b. two redings should be taken to get the correct result. one reading must be taken inside the house and the other outside. if there is a difference between the reading taken inside the house and the other outside the house is considered as the correct one.
c. it is advised to put the compass somewhere near the center of the house. it is very useful when the house is either inclined or diagonal in terms of directions, as in such cases the reading will be different places of the house
d. the best place to keep the compass to establish the right direction is either to place it out side the house or at top of the roof where is no magnetic influence due to electronic appliances inside the house.
e. the compass must be placed minimum of four feet away from iron railing and magnetic gadget like t.v. phone, etc. because the EMI radiations emanating from these object influence the reading of the compass. 

1 comment:

  1. Magnetic compass adjusting and plotting of deviation card.
    Magnetic compass surveys are carried out and large errors are corrected on site, with remnant errors, a deviation card is issued which needs t be displayed on board vessel.


more articles