Aluminum cased compass vs all plastic compass ?

[Eugene Hollingsworth]

 

Are compasses that are cased in aluminum or brass, like the lensatic or sighting compasses, protected from things like phones, etc. when in a pack?

I’ve always used the flat plastic Silva compass when off trail or on really bad trails, but always cautious about packing it near anything magnetic or by my phone, which can be a pain, and I wouldn’t always recognize know if the compass is screwed up when in the field.

I sometimes use my phone showing my location, then put that away and use the compass navigate to my destination. Trying to keep everything separate is problematic for me.

 

[Matthew / BPL]

I don’t see how aluminum or brass would protect from magnetic interference. If they blocked magnetic forces the compass wouldn’t work, right?

[Ken Thompson]

Usually no problems where they are stored. It’s in use that you have to be aware of external magnetic forces. I keep my compass near my phone and have had zero issues.

[Eugene Hollingsworth]

Yeah, you have a point that if it was shielded it wouldn’t work …. I was thinking when the case is closed the alu or brass would shield the compass. But a few minutes googling didn’t pop any obvious answers.

[Roger Caffin]

Neither aluminium nor brass will have any effect on a compass. Any form of steel on the other hand will almost completely wreck any compass working.

I have some doubts that a phone would have any effect on a compass. If you put the phone away in your pack (or your pocket) before getting the compass out I am sure you would be fine.

Cheers
(Roger, with a PhD in Physics)

[Ken Thompson]

Steel won’t wreck it, just effect it.

[David Thomas]

Yeah, iron or steel will temporarily mess up compass readings, but the compass is fine once the ferrous metal is removed from the immediate vicinity.

What could mess up a compass is a powerful magnetic field as might be generated around large electric motors or strong magnets.  For instance, those electro-magnets used in scrap metal yards to move tons of steel around?  One of those could easily ruin the compass needle by remagnetizing it in some other orientation.

I can’t think of anything going on in a smart phone that would generate any large magnetic field (beside, it doesn’t have the battery power to do so).  There are some steel parts inside a phone and I just checked: My compass points towards my iPhone 6.

Here’s a video on how demagnetize, remagnetize, or strengthen a compass’ needle using a strong magnet.  https://www.youtube.com/watch?v=GuIkvUTxYdU

[Eugene Hollingsworth]

Thanks! I was overthinking it I guess. I’ll just keep my compass away from magnets. My shirt pocket has worked well, and I’ll start utilizing my backpack straps or pockets.

[two pints]

My son borrowed one of my Silva Starter’s.  After he returned it, I noticed pretty quickly that it’s polarity was flipped.  I had to think about it for a while to figure out how he accidentally did it.  He was storing it in his scout bag….  which he routinely throws in a pile of his music gear….  which means he put it by his guitar amp.  That will do it.

I have heard that you can fix the polarity with another strong magnet, but I’m keep in this one in its damaged state as a demonstration model for the boys in his troop.  (clearly marked to warn against confusion)

[David Thomas]

The amplifier or the speaker?  Speakers have powerful magnets in them.

Send the reversed one to Roger. It’ll point towards his closest polar region.

[Author]

Posts