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 Post subject: Re: Detecting a magnet... from a distance.
PostPosted: Thu Feb 08, 2018 1:38 pm 
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Joined: Thu Oct 26, 2006 7:11 pm
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Location: Maryland
And..
House trailers attract tornados
Pleasure boats attract 'friends'
Wills attract relatives.....



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Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)
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 Post subject: Re: Detecting a magnet... from a distance.
PostPosted: Thu Feb 08, 2018 1:51 pm 
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Joined: Thu Oct 26, 2006 7:11 pm
Posts: 1308
Location: Maryland
Externet, I have been following this thread, and added a few comments, but the question now is...
Why do you want to measure this minuscule magnetic field?

I would think that the earth's much larger magnetic influence, and the clutter all else around this magnet's minor field, would swamp it completely, and if not, why would not a common compass point to it?
At first glance it would seem akin to hearing a whisper from across a rock concert venue without lip reading!



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Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)
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 Post subject: Re: Detecting a magnet... from a distance.
PostPosted: Thu Feb 08, 2018 4:17 pm 

Joined: Fri Aug 22, 2003 12:01 am
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Location: (somewhere), Afghanistan; from Rochester, NY
In post 1 he said he wanted more posts on the forum.



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 Post subject: Re: Detecting a magnet... from a distance.
PostPosted: Sat Feb 10, 2018 8:09 pm 
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Joined: Sat Nov 08, 2003 1:01 am
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Location: Phoenixville, PA USA
I'll say it one more time:
1200 dollars, eh?
:D



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 Post subject: Re: Detecting a magnet... from a distance.
PostPosted: Sun Feb 25, 2018 1:36 am 
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Joined: Fri Jan 11, 2002 1:01 am
Posts: 3831
Location: NewJersey
Hello,

I like the replies so far, very interesting. The 'rube' one was funny too thanks to Len for that one.

Detecting a magnet from a distance isnt that easy because it's a static field so you cant use radio methods like tuned circuits to detect some frequency. Here are a few lesser ideas though just to keep it interesting. BTW i have one of those 1200 dollar sensors but blew it out yesterday so today i claimed bankruptcy :-)

Ok so first we have the rotating coil. With a rotating coil you can detect a static field. The current will vary as it is rotated.
Next up we have the Hall Effect Device. These can be used at no too large distances.

A DIY method would be to rotate a very strong magnet.that is suspended by a long sewing thread. When the fields attract, the push or pull will be greater so the magnet will swing slightly. If the magnet to be detected is also on a thread, it will rotate with the first magnet, so you can control the orientation of the magnet to be detected with the large magnet. This can work at distances of some 2 feet with rare earth magnets.

There are many sources of interference though so it gets sticky to get long distance.

The thing about magnetic fields is that the strength drops off quickly because it is a reciprocal power function. Even if just 1/r^2 at twice the distance you go down to 1/4 the signal for example, so we lose field strength fast as we move away.

BTW a magnet suspended by a long sewing thread is sensitive enough to align itself with the Earths magnetic field so it can function as a compass. A rare earth magnet will align itself pretty fast, possibly within a couple seconds.



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 Post subject: Re: Detecting a magnet... from a distance.
PostPosted: Wed Apr 11, 2018 1:49 pm 
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FWIW, just saw on the science channel that our sun's magnetic field extends out to the Ort Cloud- way past Pluto. :o


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 Post subject: Re: Detecting a magnet... from a distance.
PostPosted: Thu Apr 12, 2018 6:06 am 
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Joined: Fri Feb 01, 2002 1:01 am
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Location: Mideast USA
Hi John.
So far I reached a 3 metre distance detection, with a 39000 turns coil. Ideal would be at least 50 metres. Perhaps am lacking mechanical dimensions (length) for the coil core bar. :sad:
And refuse to spend too much $ for experimenting. Whenever you find how they detected the sun's magnetism reach to Pluto, advise. :smile:



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 Post subject: Re: Detecting a magnet... from a distance.
PostPosted: Thu Apr 12, 2018 7:02 am 
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May have already seen this article: https://en.wikipedia.org/wiki/Spacecraft_magnetometer


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