Help! Compass 180 deg out!

[nigelmercier]

This could only happen if exposed to a strong external magnetic field while the card was prevented from swinging to align itself with the field. Perhaps if the compass had been laid on its side next to a strong magnet that could happen but it seems unlikely.

It would be impossible to do this without the correct equipment, to make a magnet you need heat and a large current.

http://www.youtube.com/watch?v=noGGcyPHtdI

 

[lenseman]

You know, the more I read about this thread, the more I am thinking that this particular compass is mounted on The Bridge?

Not The Bridge of a ship but a bridge with a load of goats running across?

There must be something we have not yet been told!



.

 

[nigelmercier]

Not The Bridge of a ship but a bridge with a load of goats running across? ....

ROFL!

I made similar comments in the Fathom/Marina San Miguel thread (which was pulled), the OP didn't get it

 

[VicS]

It would be impossible to do this without the correct equipment, to make a magnet you need heat and a large current.

You dont need heat but to make a powerful magnet you do need a strong magnetic field. School labs use a fairly simple coil to re-magnetise the bar magnets they use in physics experiments. This sort of thing: http://www.ibotz.com/physics/aluminium-foil-support-bar-1762.html


Just to orientate itself to the earths magnetic field a compass needle does not have to be all that strongly magnetised . To demonstrate the principle just stroking a steel needle with a bar magnet will adequately magnetise it.

Still difficult to believe that the OP has inadvertently reversed the polarity of the compass card though just by being close to a magnetic screwdriver.

A "sonic" screwdriver though might be a different matter.

 

[Mistroma]

For a compass with a directly top reading card it is difficult to see how any amount of inverting.rolling this way or that way can make it read 180° out. Whatever you do with it the card will settle in the correct orientation.

These are examples of the "135" because I cannot find any reference to a "35" but all the Olympic range seem to have similar cards

As Black Sheep points out the card has to be compensated for "dip" in the magnetic field. If it is no longer floating level then it indicates that it has, somehow or the other, become reverse magnetized.
This could only happen if exposed to a strong external magnetic field while the card was prevented from swinging to align itself with the field. Perhaps if the compass had been laid on its side next to a strong magnet that could happen but it seems unlikely.


I reckon the Op has turned the boat round in its berth.

No change to the card & magnet, it's the orientation wrt the lubber line. If you invert the compass body and turn it upright at 90 degrees to the direction in which you initially inverted, then the card can settle with the lubber line on the opposite side from the initial position.

That's why I suggested a simple check in post #35:
Please check the following: Does the N on the card still point North? Ignore the lubber line.

Just look at the N and is it close to North or is it as actually South. If it is still North but the compass reads 180 at the lubber line then you've just inverted the floating compass inside the bowl.

It is a very simple check and would confirm whether the error lies with the card & magnet (highly unlikely) and N actually point S.

I'm still betting that the card orients N-S correctly and the OP just took a reading wrt lubber line.

 

[VicS]

No change to the card & magnet, it's the orientation wrt the lubber line. If you invert the compass body and turn it upright at 90 degrees to the direction in which you initially inverted, then the card can settle with the lubber line on the opposite side from the initial position.

That's why I suggested a simple check in post #35:
Please check the following: Does the N on the card still point North? Ignore the lubber line.

Just look at the N and is it close to North or is it as actually South. If it is still North but the compass reads 180 at the lubber line then you've just inverted the floating compass inside the bowl.

It is a very simple check and would confirm whether the error lies with the card & magnet (highly unlikely) and N actually point S.

I'm still betting that the card orients N-S correctly and the OP just took a reading wrt lubber line.

So the OP has tossed it about so that the lubber lines are now on the side closer to him instead of the far side, under the cowl if it has one, and he is now reading the wrong side of the card with the numbers upside down!

That should be pretty obvious and would have been easy to diagnose if a photo had been posted as requested.

Earlier the thread he was clear that it is pointing the wrong way, "North is pointing South and vice versa. 180 out."

 

[cliff]

There must be something we have not yet been told!

It always amazes me how long it take some folk to recognise a troll

 

[Mistroma]

So the OP has tossed it about so that the lubber lines are now on the side closer to him instead of the far side, under the cowl if it has one, and he is now reading the wrong side of the card with the numbers upside down!

That should be pretty obvious and would have been easy to diagnose if a photo had been posted as requested.

Earlier the thread he was clear that it is pointing the wrong way, "North is pointing South and vice versa. 180 out."

Photo might not actually help if it has been inverted as suggested. Numbers won't be read upside down either. All that happens is that the lubber line is in the wrong place (180 deg. out). I did this once many years ago and remember thinking that the compass was reading 180 deg. out. Until I spotted that N on the card still pointed N but reading said S. Easily done and I could see the OP saying it was 180 deg. out without realising the error.

A photo won't help unless we can see something in it to confirm the direction we are looking (the compass doesn't count as that's what we're checking ).

 

[VicS]

Photo wouldn't actually help if it has been inverted as suggested. Numbers won't be read upside down either. All that happens is that the lubber line is in the wrong place (180 deg. out). I did this once many years ago and remember thinking that the compass was reading 180 deg. out. Until I spotted that N on the card still pointed N but reading said S. Easily done and I could see the OP saying it was 180 deg. out without realising the error.

A photo won't help unless we can see something in it to confirm the direction we are looking (the compass doesn't count as that's what we're checking ).

If its a compass with a cowl, like the Olympic 135, the lubber line will be on the opposite to the helmsman, under the cowl and the numbers against it will appear the right way up.
If the lubber lines are now 180° out, ie on the side nearest to the helmsman and no longer under the cowl that will be obvious in a photo.
The numbers against it will appear upside down. That will also be obvious in a photo.

Look at the pictures of the Olympic 135 that I posted and you will see what I mean.

One of the lubber lines coincides with 240. The number appears the right way up. If the line was 180° out so that the reading was 60° it would be obvious in a picture that it was in the wrong place. If you could see it the number 60 would appear upside down. that would also be obvious.

Id flipping well realise it if I was suddenly reading upside down numbers!

 

[Mistroma]

If its a compass with a cowl, like the Olympic 135, the lubber line will be on the opposite to the helmsman, under the cowl and the numbers against it will appear the right way up.
If the lubber lines are now 180° out, ie on the side nearest to the helmsman and no longer under the cowl that will be obvious in a photo.
The numbers against it will appear upside down. That will also be obvious in a photo.

Look at the pictures of the Olympic 135 that I posted and you will see what I mean.

One of the lubber lines coincides with 240. The number appears the right way up. If the line was 180° out so that the reading was 60° it would be obvious in a picture that it was in the wrong place. If you could see it the number 60 would appear upside down. that would also be obvious.

Id flipping well realise it if I was suddenly reading upside down numbers!

Ah, penny finally dropped regarding the cowl. I see what you mean about numbers adjacent to lubber line being upside down. It was about 20 or 30 years ago when I did this so memory obviously playing tricks. I do remember being confused for a couple of moments and then twigging what had happened and flipping it back again. But as you say, it'd be difficult to get it wrong that way with a compass like the 135.

Ah well, back to the drawing board.

 

[Black Sheep]

This could only happen if exposed to a strong external magnetic field while the card was prevented from swinging to align itself with the field. Perhaps if the compass had been laid on its side next to a strong magnet that could happen but it seems unlikely.

It would be impossible to do this without the correct equipment, to make a magnet you need heat and a large current.

I understand your scepticism, and I can't offer a mechanism. But it did happen to me. No great heat was involved (this was a geology field trip in Ireland); I'm not aware of any strong magnetic fields, but I agree that there was likely to be one. It took a while to realise why I couldn't take a decent bearing!

Whether or not this is what happened to the OP's compass.... well, at least we have a simple test (does the card float level?). So we can rule it out if necessary and get back to different forms of user error (which is always more attractive if the user is someone else!).

Now, Forest Girl, if you can get a photo sorted that would be grand.

 

[john_morris_uk]

Pretty certain that the same thing happened to me about 20+ years ago. If I remember correctly, I'd put it down and it fell over and then read 108 deg. out. Nothing to do with the removable deviation adjustment magnets in my case. It was just a matter of the floating compass section turning upside down and coming upright 180 deg. out. I fixed it by holding it upside down and turning the body around around before bringing it upright again. Difficult to describe but pretty easy to manage.

I'm guessing that the same thing has happened here. i.e. The lubber line is now on the wrong side of the floating part.

Exactly right I suspect and you've saved me the problem of describing how to fix it!

 

[nigelmercier]

I thought it was the other way around: that the North Pole was N, and the "North seeking pole" on a compass was a south pole, as seems logical from the name.

OK, I was wrong. From the horse's mouth:

Hello Mr. Mercier,
I am the geomagnetic data manager at NGDC. I have reviewed your question, and it is a good one, and I think I have come up with a satisfactory answer for you.
When explorers first noticed that a magnetized piece of metal, or a compass, would consistently point North, they labeled this as the North end of the compass, and often paint it a separate color. But as we gained more knowledge of how magnetism works, as you stated, they realized that opposites attract. Since the Northward direction had already taken hold in the vocabulary and due to its proximity to the geographic North pole, the name remained the North pole, but is in fact a south magnetic pole.


Regards,
Brian Meyer - NOAA Affiliate

 

[Woodlouse]

OK, I was wrong. From the horse's mouth:

Hello Mr. Mercier,
I am the geomagnetic data manager at NGDC. I have reviewed your question, and it is a good one, and I think I have come up with a satisfactory answer for you.
When explorers first noticed that a magnetized piece of metal, or a compass, would consistently point North, they labeled this as the North end of the compass, and often paint it a separate color. But as we gained more knowledge of how magnetism works, as you stated, they realized that opposites attract. Since the Northward direction had already taken hold in the vocabulary and due to its proximity to the geographic North pole, the name remained the North pole, but is in fact a south magnetic pole.


Regards,
Brian Meyer - NOAA Affiliate

Looks like the horse read my post last week.

 

[nigelmercier]

Looks like the horse read my post last week.

You were not alone, but I'm pleased to have found out something new.

 

[sailorman]

it was possible to inadvertently do that with a bosun type grid compass.
does this compass have a hood /cover that pivots over, it could well be the wrong way round

Ah, penny finally dropped regarding the cowl. I see what you mean about numbers adjacent to lubber line being upside down. It was about 20 or 30 years ago when I did this so memory obviously playing tricks. I do remember being confused for a couple of moments and then twigging what had happened and flipping it back again. But as you say, it'd be difficult to get it wrong that way with a compass like the 135.

Ah well, back to the drawing board.

See #5

 

[VicS]

See #5

If the compass is an Olympic 135 then ITYWF that the position of the cowl is fixed. It would be pretty obvious if the compass was re-fitted the wrong way round.

 

[myquest]

The magnetic poles are due to flip fairly soon anyway. Just hang onto it for now and you'll soon be right as rain.

You could wait ages for the poles to flip.I am installing new lights in a soon to be opened shop. The theme for the shop is time travel. We actually had a time traveller pop his head through the door to find out when it will open. He was very exited! If you pop over to my neck of the woods with the compass I'm sure I could get him to take it back a couple of days and presto, back to normal.