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Electronics and compass

Old 02-29-2004, 08:38 PM
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CD
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Default Electronics and compass

Can a piece of electronic interfere with a compass reading.
If so, how far away
should the piece of electronic be.
Some boats have electronic boxes in the console
and right above it is the compass. Thanks for the help.
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Old 02-29-2004, 09:14 PM
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Default RE: Electronics and compass

yes DC current outputs a constant magnetic field. This can affect the compass by offsetting it's normal sense of north.

How far away is dependent upon the electronic unit itself. I have my GPS on the left, and my fishfinder to the right of my compass on the console. They are only 6 - 8" from it, yet they dont have any affect. It's one of those power it up and see if it moves the compass off kind of things.
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Old 03-01-2004, 01:32 PM
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Default RE: Electronics and compass

Watch out for the speaker in the radio. Try a temporary install with the radio and turn it on. The compass will move if the radio is too close.
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Old 03-01-2004, 03:20 PM
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Default RE: Electronics and compass

Yes it can, however, more often than not, it doesn't. My VHF is 10" from my compass and has NO effect.
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Old 03-02-2004, 09:58 AM
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Default RE: Electronics and compass

My main unit sits directly in front of and below my compass which threw it off by 8 degrees. I had to adjust the compass to have it read true. BTW, electronics do not have to be powered on to affect a compass, any ferrous metalic object, depending on it's mass, in close proximity will affect a compass.
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Old 03-02-2004, 11:04 AM
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Default RE: Electronics and compass

Almost every application for installation of a compass calls for "compensation". This is an adjustment in the compass itself for errors caused by metal surrounding the compass when installed. You can try this to see if you need to adjust your compensators.
Take your compass, (or a handheld if you own one), raise it in the air away from any potential influences, point it in the direction your boat is facing and gently lower it into the position you plan on mounting it. Watch the compass dial to see if it swings while lowering it trying to keep it facing the same direction as close as possible.

I will almost guarentee that just about every compass needs compensating on a boat. At this point you need to go through a compensation method.

here is a link to Ritchie Navigation.
http://www.ritchienavigation.com/ser...pensation.html
They have a detailed page on compensation. It really is extremely important. My initial location for my compass had 30deg. of error due to my helm I believe. Man that will get you lost in no time. My compass can only compensate for 20deg so I needed to find a better place for it.

One note, do not confuse compensation with variation (angle between magnetic and true north)
One thing also to remember now that GPS is so popular, GPS bearing is not boat heading. GPS simply tells you the direction the boat is going not the direction the boat is facing. Only the compass can tell you this. This has been a hot bed subject of people misinformed for a long time.
This comes into play during some compensation tests.

Any more info, I'd be glad to help if I can.

Mike
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Old 03-02-2004, 03:21 PM
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Default RE: Electronics and compass

Whereas a GPS does not tell you your heading, a magnetic compass (e.g. KVH) will.
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