Computers and compasses

[pyre24]

My dive shop told me that something from the compter affects the accuracy of the compass. And that the compass will always be of a few degrees. Does anyone know if this is true? Some say it is some say no.

[texdiveguy]

I know my Dive Rite computers do not effect my compass. Though steel objects will effect to accuracy such as boat hulls.

[Osprey]

I have heard it depends on the make of the computer, what the internal mechanics are and such, since some use different metals

Of course, I am new to all this computer info, so don't ask me to vouch for more than second hand info LOL!

[CompuDude]

Hold compass. Hold computer away from compass.

Bring computer next to compass. Did the compass move?

Answer.

[cummings66]

Mine doesn't affect it, but I could believe there might be a model out there somewhere that might.

To be fair though, a compass for diving doesn't exactly need to be all that accurate.

[mitsuguy]

the amount of metal in the computer would have to be pretty extreme to affect a compass... realistically, all compasses are affected by quantities of metal being close to them, but also realistically, that amount has to be more than what you'll find in a computer... I actually don't know if anything inside a computer would actually attract a magnet at all, maybe the battery???

[CompuDude]

Originally Posted by mitsuguy

the amount of metal in the computer would have to be pretty extreme to affect a compass... realistically, all compasses are affected by quantities of metal being close to them, but also realistically, that amount has to be more than what you'll find in a computer... I actually don't know if anything inside a computer would actually attract a magnet at all, maybe the battery???

Some circuits can form an electromagnet. Not necessarily a super strong one, but perhaps strong enough to throw a compass off a little bit. I don't see it being much of an issue, though... if it does affect it, probably not much, and only when they're right next to each other. The only way they would be right next to each other for an extended time period is if you have them side by side on the same wrist, or in the same console. In that case, it should be consistently off, since the relative position is the same, and you should see it hanging if you slowly turn in place. Otherwise, unless you're trying to follow a series of written headings, it really doesn't matter, since everything is relative.

And that's all IF there is any effect. Which I pretty much doubt in the vast majority of cases.

Wrecks and bridges, OTOH... those have lots of iron and can seriously tweak a compass reading.

[cummings66]

It doesn't take as much metal as you think. I can put a GPS on my glareshield and my aircraft compass will swing, and it will do so as long as it's in the front seat.

The GPS is just a plastic housing with some circuit boards inside it, no magnets. It's actually smaller and lighter than my dive computer is.

[Duckydiver]

So thats why my compass is leading in circles!!

[FOUNDATIONER]

Puter on wrist, compass in SPG. No prob bob.