Hi all,

If you're contemplating building a (?type) seismo, you might check out acouple items
I see at the web site for the "Electronic Goldmine" surplus in Arizona, USA.

http://www.goldmine-elec-products.com

Item #G13502 is a two piece magnet on what seems to be on a "soft iron" (purer iron)
bracket.  Its "looks like" a old giant computer read head unit, but could have been
used for a early tape drive speed brake/dampening control.  Its on sale for $3.95 till
11/30/04.  I estimate its rating is ~N35.  These normally sell for ~$9-$12 each.   This
is definitely a finger/skin/bone pinching/breaking dangerious item; but good for
small diameter copper wound sensing coils that pass over the two magnet junction.
It might work for copper plate dampening.  Two assemblys facing each other and
spaced with threaded bolts/nuts would probably do either function of sensing/dampening
and/or both at once...or with additional assemblys for whatever function....but....be
very careful in doing this...use wood inbetween for initial "gap" spacing!  The soft iron
bracket material seems to be very unusual ....its very hard to find, normally very 
expensive material in itself, and does a excellent job with the magnets field.  Forcefield/
Wonder magnet souce has sold gobs of these in the past; but, has none at the present.

Item #G13644, is a BPW33 photodiode (photo-generative).  Four for $1, or other
higher quanities is available.  I think alot of people in the "know", rate this item as
very good.  For a obvious light sensing, mass movement seismo; normally used in
a electronic "bridge" pair.   Unfortunately there is no web page photo.

For a fast review, use the "product Search" box, and item code in the upper left of the
web page for the Electronic Goldmine web page reference.

I've bought from this source with no trouble; but seen web search engine complaints
too.






Hi all,
 
If you're contemplating building a (?type) seismo, you might check out acouple items
I see at the web site for the "Electronic Goldmine" surplus in Arizona, USA.
 
http://www.goldmine-elec-products.com
 
Item #G13502 is a two piece magnet on what seems to be on a "soft iron" (purer iron)
bracket.  Its "looks like" a old giant computer read head unit, but could have been
used for a early tape drive speed brake/dampening control.  Its on sale for $3.95 till
11/30/04.  I estimate its rating is ~N35.  These normally sell for ~$9-$12 each.   This
is definitely a finger/skin/bone pinching/breaking dangerious item; but good for
small diameter copper wound sensing coils that pass over the two magnet junction.
It might work for copper plate dampening.  Two assemblys facing each other and
spaced with threaded bolts/nuts would probably do either function of sensing/dampening
and/or both at once...or with additional assemblys for whatever function....but....be
very careful in doing this...use wood inbetween for initial "gap" spacing!  The soft iron
bracket material seems to be very unusual ....its very hard to find, normally very 
expensive material in itself, and does a excellent job with the magnets field.  Forcefield/
Wonder magnet souce has sold gobs of these in the past; but, has none at the present.
 
Item #G13644, is a BPW33 photodiode (photo-generative).  Four for $1, or other
higher quanities is available.  I think alot of people in the "know", rate this item as
very good.  For a obvious light sensing, mass movement seismo; normally used in
a electronic "bridge" pair.   Unfortunately there is no web page photo.
 
For a fast review, use the "product Search" box, and item code in the upper left of the
web page for the Electronic Goldmine web page reference.
 
I've bought from this source with no trouble; but seen web search engine complaints
too.
 
Take care, Meredith Lamb