I concur, he most probably has
the best I have seen,

I think two horseshoe magnets
with a coil in the center
might be equally as good
but not sure since I have
no way of testing these things.

----- Original Message ----- 
From: "Gary Lindgren" 
To: 
Sent: Wednesday, March 10, 2010 11:22 AM
Subject: RE: Speaker Like Sensor ?


Geoff,
I also recommend Chris' design, it is very good and easy to build. All you
need is a drill press. The rare earth magnets are readily available and low
cost. See http://www.kjmagnetics.com/neomaginfo.asp . Forget the speaker
concept. It would be difficult to support the coil in the very narrow space
between the coil and magnet air gap without the coil touching the magnet's
edges.
Gary





Gary Lindgren
585 Lincoln Ave
Palo Alto CA 94301

650-326-0655

www.blue-eagle-technologies.com Check out Lastest Seismometer Reading
cymonsplace.blogspot.com 
sites.google.com/site/seismicsensorinfo/Home    Design Details for New
Vertical Seismometer 





-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@............... On
Behalf Of Geoffrey
Sent: Tuesday, March 09, 2010 7:46 PM
To: PSN-LIST
Subject: Speaker Like Sensor ?

Hello instrument folks,

Is it possible to get a speaker company to
build the mechanism like a speaker
without a cone that would be like
500 to 10K OHMS or more instead of
the typical 8 ohms ?

I think it may be the best of all sensors
for a velocity type anything geophone ??

Comments ?

It seems to me if you are going to
make the coil a part of the mechanism
you need that special delicate speaker
wire that is braided with cloth 
so that the springy nature of the wire
will not be there to affect your results?

geoff

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