## PSN-L Email List Message

Subject: Geophone questions
From: "tchannel" tchannel@..............
Date: Sun, 27 May 2007 06:43:11 -0600

```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 =
electronically?

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?

I have a few questions about magnets =
and=20
coils:

1  I have seen a cross section of =
a Geophone,=20
magnet, spring and mass etc.  When used in a Seismic Sensor, how is =
it=20
dampened, or is it do electronically?

2 I am making a new vertical sensor, =
and this=20
question has to do with the coil and magnet.  The coil is a spool =
with a 1"=20
dia. hole in the center.  The thickness of the coil is =
3/4"   The=20
value of the coil is 500ohms.   The magnet will be suspended =
from a=20
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"=20
of coil above and below the magnet......... OR Two magnets 1/4" =
thick,=20
together to equal 1/2" x 3/4", leaving 1/8" of coil above and below the =
two=20
magnets when centered........... Lastly I could use One magnet 1/2" =
thick x 3/4"=20
dia. leaving 1/8" above and below.

This is a basic question about the =
magnet's surface=20
and the N/S poles,  I do not know the science, but just curious =