PSN-L Email List Message
Subject: Re: Geophone questions
From: "tchannel" tchannel@..............
Date: Mon, 28 May 2007 08:21:10 -0600
Hi Geoffrey, This is a follow up question.
Which would create the most useful current, under these conditions:
The coil, being a donut, 1" hole, 3/4" thick.
The magnet inserted into the 1" hole, is a ring, 1/4" thick, 3/4" OD, with a
1/4" hole in the center.
1 The N pole enters and exit the top 1/4" of the coil, in and out. This
results in only the N pole entering the coil.
2 The magnet, at rest, is now midway inserted into the coil. This results
in both the N and S poles actively engaging the coil. My thinking is that
you would be getting a push/pull affect, as it moves in either direction.
----- Original Message -----
Sent: Monday, May 28, 2007 4:22 AM
Subject: Re: Geophone questions
> Ideally you want a uniform magnetic field through which the wire moves
> puhsing the electrons all in the same direction.
> Take that idea and you will see that the B fields seems to need
> to be n-s at one side and s-n at the other of any kind of coil
> but I would imagine that a rectangular loop is better than a circular one
> so that the coil moves at right angle to the fiels on both sides.
> The strength of the B field is ectremely important, the stronger the
> I once saw an impressive demonstration of magnetic field strength at
> Arizona State University where an aluminum bar was dropped from vertical
> (hinged at one end) and was stopped cold by the magnetic field alone. but
> the magnet was absolutely huge. it was tapered to concentrate the magnetic
> lines of force.
> You want a uniform field through which the wire moves. The current is
> dependent upon the B field strength and the voltage the number of loops.of
> wire I would think the same amount of energy is present no matter what the
> coil so if you could make an ideal current sensor that looks only at hole
> flow is really what you may want instead of lots of turns og 40ga wire. I
> can only imagine what the researchers are using today with technology
> being what it is and everything I suspect they have sensors we have never
> imagined before.
> Coils and magnets are ancient history but that about all po-folk can play
> ----- Original Message -----
> From: "tchannel"
> Sent: Sunday, May 27, 2007 05:43
> Subject: Geophone questions
> I have a few questions about magnets and coils:
> 1 I have seen a cross section of a Geophone, magnet, spring and mass etc.
> When used in a Seismic Sensor, how is it dampened, or is it do
> 2 I am making a new vertical sensor, and this question has to do with the
> coil and magnet. The coil is a spool with a 1" dia. hole in the center.
> The thickness of the coil is 3/4" The value of the coil is 500ohms.
> The magnet will be suspended from a rod and centered in this 1" hole. Left
> to Right and Top to Bottom.
> I can choose from three magnets. One magnet 1/4" thick x 3/4" dia.
> centered leaving 1/4" of coil above and below the magnet......... OR Two
> magnets 1/4" thick, together to equal 1/2" x 3/4", leaving 1/8" of coil
> above and below the two magnets when centered........... Lastly I could
> use One magnet 1/2" thick x 3/4" dia. leaving 1/8" above and below.
> This is a basic question about the magnet's surface and the N/S poles, I
> do not know the science, but just curious about just these three
> scenarios, which arrangement is the best?.....I could try all three and
> measure the result, but in theory is it better one way or the other?
> Thanks, Ted
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