PSN-L Email List Message

Subject: Re: Seismograph for school
From: "meredith lamb" paleoartifact@.........
Date: Sun, 1 Oct 2006 14:04:12 -0600


Hi all,

There is a choice of magnet distributors one can entertain for purchasing
magnets of course.  "Magnets4less" Lists magnets roughly for alot less
(~1/3 to 1/4) the price of KJMagnetics.  The problem with Magnet4less
is they have a minimum order of ~$30.00.....and....their shipping/handling
charge of ~$8 or so, is afew dollars more, and its the ultra slow UPS, and
their personnel at that place.  KJMagnetics ships fast, and usually a flat
rate
via USPS.  KJMagnetics also has a minimum quantity order (~usually 10
of whatever size), as does Magnets4less which can get up to 20 minimum
....for the sizes entertained here.  Its worth comparison shopping I suppose
.....for example:

KJMagnetics:    1x1x1/8"= qty of 10 @ 29.15 ($2.91 each)
Magnets4less:   1x1x1/8"= qty of 20 @..... ($0.98 each)

Well made horizontal Chris!  Still trying to quess what the boom
pivot actually is.....perhaps a single wire vertical between the blocks and
the boom end center pivots on such?? (can't see on the photo)

Take care, Meredith Lamb


On 9/30/06, ChrisAtUpw@.......  wrote:
>
> In a message dated 2006/10/01, gmvoeth@........... writes:
>
> Hello Chris;
> Can you tell us how to get a uniform magnetic field
> to cut the coil at right angles (normal) to the windings ?
>
>
>
> Hi Geoff,
>
>        I use 4 off 1" sq x 1/8" rectangular NdFeB magnets on two 3.5" x 2"
> x 1/4" thick mild steel backing plates and mount the coil in between. You
> have N+S magnets on one face opposite to S+N magnets on the other face. This
> gives a high central field and a linear movement response. I use a
> rectangular pancake coil of about 2000 turns. It is quite effective!
>
>        See  http://jclahr.com/science/psn/chapman/lehman/index.html
>
> can you use two opposing horse shoe magnets
> with a coil in the middle ?
>
>
>
>        This is likely to give a lower sensitivity and is more difficult to
> make / mount. Large Alnico U magnets are quite expensive. You benefit from
> the relatively high flux of the NdFeB magnets.
>
>        Regards,
>
>        Chris Chapman
Hi all,

There is a choice of magnet distributors one can entertain for purchasing
magnets of course.  "Magnets4less" Lists magnets roughly for alot less
(~1/3 to 1/4) the price of KJMagnetics.  The problem with Magnet4less
is they have a minimum order of ~$30.00.....and....their shipping/handling
charge of ~$8 or so, is afew dollars more, and its the ultra slow UPS, and
their personnel at that place.  KJMagnetics ships fast, and usually a flat rate
via USPS.  KJMagnetics also has a minimum quantity order (~usually 10
of whatever size), as does Magnets4less which can get up to 20 minimum
....for the sizes entertained here.  Its worth comparison shopping I suppose
.....for example:

KJMagnetics:    1x1x1/8"= qty of 10 @ 29.15 ($2.91 each)
Magnets4less:   1x1x1/8"= qty of 20 @..... ($0.98 each)

Well made horizontal Chris!  Still trying to quess what the boom
pivot actually is.....perhaps a single wire vertical between the blocks and
the boom end center pivots on such?? (can't see on the photo)

Take care, Meredith Lamb

 
On 9/30/06, ChrisAtUpw@....... <ChrisAtUpw@.......> wrote:
In a message dated 2006/10/01, gmvoeth@........... writes:

Hello Chris;
Can you tell us how to get a uniform magnetic field
to cut the coil at right angles (normal) to the windings ?


Hi Geoff,

       I use 4 off 1" sq x 1/8" rectangular NdFeB magnets on two 3.5" x 2" x 1/4" thick mild steel backing plates and mount the coil in between. You have N+S magnets on one face opposite to S+N magnets on the other face. This gives a high central field and a linear movement response. I use a rectangular pancake coil of about 2000 turns. It is quite effective!

       See  http://jclahr.com/science/psn/chapman/lehman/index.html

can you use two opposing horse shoe magnets
with a coil in the middle ?


       This is likely to give a lower sensitivity and is more difficult to make / mount. Large Alnico U magnets are quite expensive. You benefit from the relatively high flux of the NdFeB magnets.

       Regards,

       Chris Chapman


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