Steel tank affecting compass?

[Jim Lapenta]

I'd also ask how old is the compass and what kind. Though I have some of the generics for students in bungee wrist mounts, I use two SK7's. One in a bungee mount and the other on a retractor. The only time I had issues was during a charity treasure dive. Someone went and got a flea market table full of costume jewelry. It was great fun finding "diamond necklaces, pearl rings, and lot of gold bracelets" in the really low vis.
My student/buddy had a great time hanging out just above me watching me swim in circles as the "gold" bracelets I was putting on my arm were magnetic and my compass that was on the same arm saw the needle stayed pointed to them.
Turd let me go for about 5 minutes before he tapped me on the head and told me. No visual references so I was "following" the compass exclusively.
As for the OP I dive steel tanks pretty much exclusively. First back mount, then back mount doubles, and now sidemount. Don't see any effect on the compass.

 

[Doc]

Kharon made me think and then go look: Q & A: magnets under water | Department of Physics | University of Illinois at Urbana-Champaign

 

[archer1960]

Thanks for the comments, guys, and particularly the confirmation that whatever is going on, it's probably not the tank. I'll do some testing to isolate the problem to either the compass, or something external affecting it. I had forgotten that my console has a compass on the back, that I could have used to compare with the Suunto SK8 on my wrist.

 

[BoltSnap]

I have been using strictly Steel tanks and I use the compass a great deal, no issues whatsoever because of the steel tanks.

 

[archer1960]

After a bit of testing, it looks like I need to hold the compass out away from my body a bit more than I was. The south end of the compass wants to point at the tank if I get it too close (a foot or so).

 

[Neilwood]

Test the compass period. I had one start acting up intermittently, not tracking north properly and acting sluggish. My buddy convinced me it was my skills because a compass does not go bad. It was settled one day after a deep cold dive, as we checked it on shore after the dive, it pointed east and when moved the needle changed at about half the distance the compass was turned. I think the pressure and temperature at depth may have changed the consistency of the oil as it tracked properly the next day in my garage. I got another compass and my navigation improved considerably.



Bob

I would second the "test the compass". Use known points to verify it is functioning correctly before use.

Even "dry land" compasses have been known to become inaccurate. This can be due to storage (near to magnetic fields), iron in the landscape (the Cuillin mountains on Skye contain high amounts of ferrous materials). A good piece of literature on the subject if you want to look it up - link.

 

[CT-Rich]

I've replaced compasses that stopped working at depth. I assume it was because the pressure squeezes the housing against the card and it stops free floating.