Author Topic: Nova or Stenlight and Influence on a Compass?  (Read 9037 times)

Offline MatthiasM

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Nova or Stenlight and Influence on a Compass?
« on: May 29, 2007, 02:40:00 am »
These two cap lamps have reed relay switches with little magnets, reason is waterproofness. But I would guess these lamps would influence any compass measurements severely. Any experiences? The new Scurion claims to be totally antimagnetic.

Thanks, regards
Matthias

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Nova or Stenlight and Influence on a Compass?
« on: May 29, 2007, 02:40:00 am »
Warmbac

Offline Duncan

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #1 on: May 29, 2007, 06:04:55 am »
There's a thread on the Stenlight's magnetic influence on the NSS board, where compass deflections of around 2 degrees are reported.

Offline AndyF

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #2 on: May 29, 2007, 08:50:59 am »
IMHO there is no way that the tiny magnet in the switch would influence a compass held at, say, waist height.

Its an easy test to do though for someone with both items...
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Offline Peter Burgess

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #3 on: May 29, 2007, 09:19:58 am »
These two cap lamps have reed relay switches with little magnets, reason is waterproofness. But I would guess these lamps would influence any compass measurements severely. Any experiences? The new Scurion claims to be totally antimagnetic.

Thanks, regards
Matthias

Links to Stenlight - Nova - Scurion


Matthias. Do you already have one? In which case it is an easy thing to check on the surface. Otherwise is there anyone who has one and a surveying compass who could do a quick check for Matthias? It would only take a couple of minutes.

There's no way I could read the compass I use by holding it at waist level. The steel or magnetic components of lamps, helmets and spectacles always have the potential to affect compass readings. The only way to see if they do is to try it.

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #4 on: May 29, 2007, 09:42:15 am »
During a recent DP practice survey in Swan mine we noticed that the Nova3 gave up to a 10 degree compass error.

Offline SamT

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #5 on: May 29, 2007, 10:09:19 am »

AndyF - I assume that folks are using SUNNTO compasses that have to be 'sighted' by looking through them - so they are at eye level, not waist level i.e. right under the cap lamp.

As mentioned by me many times on this site, tape a very small (i.e. 1" by about 2mm) glow stick (available at fishing tackle shops for night fishing) to the compass/clino for perfect self illuminating compass - that way, you can remove your helmet when taking readings and have no fear of any interference.

Its the future


Offline Rob

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #6 on: May 29, 2007, 10:54:57 am »
tape a very small (i.e. 1" by about 2mm) glow stick (available at fishing tackle shops for night fishing) to the compass/clino for perfect self illuminating compass

A nice idea Mr T   :thumbsup:
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Offline MatthiasM

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #7 on: May 29, 2007, 02:10:42 pm »
Peter,

no, I don't own any of these lamps. I was considering to build something similar but never had a good idea for a really waterproof switch without reed contact and magnet (was considering vandal-proof piezo-switches....). The Scurion claims to be antimagnetic by design, and I think I will drop my own development (meanwhile wasted time for re-inventing existing stuff again and again) and just purchase one.... It is definitely less expensive than my own ideas.....

Offline AndyF

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #8 on: May 29, 2007, 05:39:50 pm »
SamT

Ah yes, see what you mean...

Nontheless, even lamps without switches still have current flowing in the wires, and that means stray field, so making a design "anti magnetic" short of encasing the whole lamp in mu-metal, is not really possible.

Still sceptical that a tiny reed relay magnet would have a discernable effect though. And surely it would be eliminated by back-sighting.... ?  ;)

Andy
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Offline SamT

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #9 on: May 29, 2007, 10:40:52 pm »
SamT

Ah yes, see what you mean...

Nontheless, even lamps without switches still have current flowing in the wires, and that means stray field,

hence the removing of the helmet.

anyhows, all the good ideas can be done if you use the metal gate as one of the survey stations  :-[ silly me

or as I've heard of - using your ammo can to rest  the compass on for each shot.  :chair:

Online shotlighter

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #10 on: May 29, 2007, 11:11:36 pm »
SamT

Ah yes, see what you mean...

Nontheless, even lamps without switches still have current flowing in the wires, and that means stray field,

hence the removing of the helmet.

anyhows, all the good ideas can be done if you use the metal gate as one of the survey stations  :-[ silly me

or as I've heard of - using your ammo can to rest  the compass on for each shot.  :chair:
What's up with ammo cans Sam? - Don't bother to reply ;D

Offline MatthiasM

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #11 on: July 12, 2007, 12:32:36 pm »
I would say, the electromagnetic influence of the small currents in these lamps (normally stright wires, and, if coils, then shielded and with RF AC fields in any electronic current sources) will be much less than the stationary field of any permanent magnets which must actuate a reed contact on the other side of the housing material. The permanent magnet will be able to lift small iron parts, much stronger than any electromagnetic field.

Influence from AC fields to cave radio stuff is another subject here.

Regards
Matthias

PS.: I own an Scurion now, will test the influence on compass etc. and post it here.

Offline potholer

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #12 on: July 12, 2007, 01:28:30 pm »
I'm not sure what inductor-based switching regulators might do, but magnetic fields from currents in cables from battery boxes will essentially cancel out due to having parallel supply and return wires.

Online Ed W

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #13 on: July 12, 2007, 02:32:24 pm »
It's definitely not just the magnetic switch!  I recall Petzl zooms throwing compasses off many yers ago, and I demonstrated the effect on a compass from a Petzl Tikka on Saturday, neither of these have a magnetic switch.  Compasses are very sensitive instruments, and it does not take much of a magnetic field (from electrical equipment, permanent magnets or even ferrous metals) to alter the local field enough to noticebly affect the reading.

For this reason I always remove my helmet when taking readings, and illuminate the dials with a small low powered light I take in specially for the job.  This is held far enough away (about a foot is enough) that it won't affect the compass (remember that the field strength is related to eith square or cube of distance).  This should elliminate your illumination screwing your survey up.  I do like Sam T's method of using small glo sticks - one I must get round to trying.

Back sights will tell you if you have made an error, and as long as any magnetic deviation is constant, the included angle method can be used to correct for it.  However deviation caused by a head mounted light is unlikely to be constant for two readings, even a slight difference in the relative position of compass and light will alter the deviation.  This is unlike magnetic anomalies due to the rock the cave is in, where the anomaly is constant at a given point (i.e. survey station).

Call me a sceptic, but I would like to see some hard eveidence before shelling out over £200 on a new light on the basis that it won't affcet my compass!

Offline Peter Burgess

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #14 on: July 12, 2007, 02:37:07 pm »
Perhaps the Hidden Earth surveying competition should be run after dark wearing a helmet and lamp to see who really has got it sussed!

Offline MatthiasM

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #15 on: July 12, 2007, 02:59:37 pm »
Call me a sceptic, but I would like to see some hard eveidence before shelling out over £200 on a new light on the basis that it won't affcet my compass!
I purchased this light not only because it claims with good reasons to be more antimagnetic than lights with included permanent magnets (as said befor, I'll check any influences), but also because it fits all my requirements better than any other home-made oder commercial available lights.

Just look at http://www.scurion.ch/ms

Regards
Matthias

Offline prahja

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #16 on: July 20, 2007, 12:30:59 pm »
The old Nova (dont know about newer ones) causes a massive deflection on sighting compasses. Definitely. It's a bit of a design fault for a caving light.

Andy

Offline SamT

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #17 on: July 20, 2007, 12:59:14 pm »

Oh for goodness sake, Arrrrhhhhhhhhhhhhh

all caving lights will affect compasses, they have bits of metal, electricity and shit. Of course they're gonna pull a compass out slightly.

Thats why you have to avoid proximity to anything magnetic, Wrist watch, screws on you helmet, ammo cans etc etc.

Its not f**king rocket science is it.

So, again,
I'll say it again.

USE A GLOW STICK TO ILLUMINATE YOU COMPASS.

you can get very small 1" long ones from fishing tackle shops for about 50p each. jeez.

http://www.glowsticks.co.uk/acatalog/small_glow_sticks.html

GLOW STICKS, GLOW STICKS, GLOWSTICKS
gimme a G
gimme a L
gimme a O

wanders off to have a cup of tea and a calm down.  :coffee:
« Last Edit: July 20, 2007, 01:05:35 pm by SamT »

Offline SamT

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #18 on: July 20, 2007, 01:10:27 pm »

oh - and you can always keep a couple taped into the inside of you helmet as extra extra backup.

You could find you way out under the light of one. especially if you put in inside the reflector unit behind the glass.

but not if you got a the much revered nova or somesuch. shame. At least speleo stuff is 100% reliable, never heard anyone have any trouble, no siree, never

(I'll shut up now :-[)

Offline Rob

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #19 on: July 20, 2007, 01:16:56 pm »
Oh, but there's so many different colours to choose from. Which is the best?  :shrug:

Sam please help us! We would be totally lost without your guidance!  ;D
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Offline prahja

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #20 on: July 20, 2007, 01:48:53 pm »
SamT - before you spout off - go and see how much a magnetic relay affects a compass and what distance you have to move the helmet to. I agree you should never have anything ferrous near a compass and there are alternative lighting methods for compasses. The question was about the Nova. It deflects a compass a hell of a lot more than other helmet lights that I have used. I have looked at the deflection with the helmets and lights that I wear whilst surveying and at the deflection from a Nova. Mine are negligible - the Nova will cause up to 180 degrees deflection. Before you start ranting take a deep breath and chill out.

Offline mountaingoat

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #21 on: July 21, 2007, 06:45:50 am »
all caving lights will affect compasses, they have bits of metal, electricity and shit.
There are lots of non-magnetic metals and the electricity's influence (if designed correctly) is negligible. I've tried it with the Scurion and could not see any influence within my accuracy (which is not bad).
Actually, when the Swiss look at it as good for surveying, it should be more than perfect for the rest of the world....
Using additional lights may cause more errors due to the handling.

darkplaces

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #22 on: July 21, 2007, 11:28:54 am »
I wanna black glowstick!

Yes Nova3's affect compass's when sighting for survey. On and 'antimagnetic' what's that then? As opposed to non-magnetic?

Offline SamT

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #23 on: July 24, 2007, 10:33:29 am »

Its my party and and I'll rant if I want to - rant if I want to - rant if I want to etc etc.

Offline Bob G

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Re: Nova or Stenlight and Influence on a Compass?
« Reply #24 on: July 24, 2007, 11:29:19 am »
I've done a fair bit of surveying in constricted spaces using a Premier carbide lamp - no problem.

 

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