Magnetic Compass

Frequently Asked Questions


A Magnetic Compass is a finely constructed instrument with a number of delicate parts, and should be handled with extreme care at all times. Many consider only the strong metal bowl, and the heavy glass, and the sturdy box, and forget entirely the precision ground pivot and delicate jeweled bearing. A compass, properly handled handled and maintained, should give satisfactory service for years.

 

Will my compass still work if I do not hook up the light wires?

Yes; unlike electronics, i.e., gyro compass, etc., magnetic compasses do not need electrical power to work. The only part of the compass affected by a loss of power is the night lighting.

Why is my Magnetic Compass accurate in one direction but not in another?

Magnetic compasses work by aligning the internal dial magnets with the earth’s magnetic field. However, the earth is not the only object with a magnetic field. Objects on your vessel may have a magnetic field which will interfere with the compass’ accuracy. This is known as on board compass deviation.

Can I adjust my Magnetic Compass?

Yes. Although you can perform compensation yourself, professionals are generally available and recommended.We can be a great help to anyone who has a difficult compass installation. If your compass has a considerable amount of deviation (more than 20°), the built-in compensator may not be enough. A compass adjuster is trained to help you locate potential causes of deviation and make recommendations to reduce them. We also have a working knowledge of deck magnets. Deck magnets can increase the amount of deviation that can be corrected during compensation.

Can I use GPS instead of Magnetic Compass ?

No, GPS can tell you where you are, it knows where you have been, and it can calculate where you are going. But, It can never give you heading. GPS provides Course over Ground (COG). COG is calculated from historical position data to give average COG. It is important to realize that COG and heading are both an integral part of navigation. Conditions such as wind, tide, current and even physical properties of your boat, can cause differences between COG and heading. Heading is the only reliable reference to steer your vessel accurately under all conditions. A properly compensated magnetic compass is a good device for real time heading information.

My Magnetic Compass has bubbles or is very low on fluid. Is this a problem?

Generally, magnetic compasses are designed to not have a bubble; if you see a bubble, the chances of a leak is high. This may seem unlikely to you, because you may not have noticed any fluid escaping from the compass. Bubbles may cause a number of problems, so it is recommended that you have the compass repaired as soon as possible.

My compass has a bubble in the morning, but it goes away in the afternoon. Why?

Your compass has most likely developed a very small leak, which has allowed some fluid to escape. When you observe the bubble in the morning, your compass is cool and the missing fluid has caused a bubble to form. As the temperature rises, the fluid expands, thereby taking up volume and making the bubble disappear. This condition is a good warning that you need to have your compass serviced before more fluid escapes.

Is the content of my Magnetic Compass Alcohol-Water based liquid or Oil based liquid?

The liquid compass is available in two distinct types, namely the alcohol-water based type and the oil based model. The alcohol-water based compass, in addition to having a faster action, is also able to withstand extreme cold. The oil based compass has a tendency to become sluggish in cold weather, and where the drop in temperatures are extreme the compass may become inactive due to the thickening of the oil.

Many liquid compasses have been ruined by refilling them with the wrong type fluid. Water, when used in an oil based compass, will rust the magnets and discolor the card. Same goes to the alcohol-water based compass, and in addition to ruining the card, may cause the card to float up off the pivot. There is also danger of adding too much water to the mixture in a alcohol-water based compass, causing it to freeze in cold weather

 

An example of defective Magnetic Compass due to wrong type of liquid added.

The picture above shows an example of defective Magnetic Compass due to wrong type of liquid added.