PSN-L Email List Message

Subject: Re: idea for an axis
From: "Geoff" gmvoeth@...........
Date: Fri, 9 Nov 2007 09:25:24 -0700

Hello PSN;

You guys sound more like scientists
than laymen ??

Sort of like the American Association
for the Advancement of Science that once
showed on a cover of their magazine the
secrets of how a thermo-nuke is first
initiated by converging shock waves
of a detonated wafer of high explosive
looked at through some kind of XRAY
photography. It made me think of how
Tim McVey might have improved the
performance of his already deadly

I am not sure you want to make motion just be
all in one axis of motion I have
in the past had very good EQ signatures
using a free hanging pendulum with
a 5 lb lead mass which had a circular
speaker magnet attached. It was damped in
synthetic motor oil and free to move
over the coil in any horizontal direction.
You do not know the direction of motion
you only see the various phases as well as
first time of arrival. I have never understood
the amature infatuation with knowing
all the fine details when they are really not
necessary to keep a layman happy.

Also I have been looking at free periods
in relation to gravity and how to
oppose or reduce the 32.17fpss to more like
18.9 inpss I am thinking in terms of
maybe a five pound mass with a specific
gravity of like 1.0516 or so that could be
immersed in pure water and use a very delicate
spring extended by 12 inches to get a 5
second period or so.
There must be some way to emulate specific gravity by
the use of bouyancy ( eg using a cylinder or cone
or other primative shape to displace water and
achieve the right response in free period. I am
looking for a cheap way to get maybe 4 second period
so I do not need to filter or equalize when I amplify( except anti-alise). It seems there are many different ways to attack this 
problem and I am certain it has
been done so before, so why do we not see any basic
research on the part of science to invent the best
and cheapest vertical sensor.

I really like a free swinging pendulum ( just the horizontal ) and free vertical whatever.
with a magnetic damper but not sure the best
magnet coil relationship to get the best
signal strength. Such a thing in a vacuum
and properly shielded should be free of
most interference.
I guess I am two dimensional in my thinking
and not three like the rest of you.
The best of all sensors would just
be a single unit to measure motion
no matter what the dimension it happens in.
Now I am ALL DIMENSIONAL and after thinking
out loud was wondering to you guys
if such an all dimensional ( single unit ) velocity
sensor has ever been made ??

Possibly a mass suspended in a magnetic field
to be restored to a fixed point in some
strange fashion I have never seen ??
Sort of like that (REAL) levitating ball in the movie
"Flying Saucers Vs The Earth"

This is not a free period kind of issue
but more the energy required to recenter the mass
once it has been disturbed in whatever direction.

Any Thoughts about any of this ?

I know where I stand on this world
so please do not make fun unless
I can laugh too :-)

Is there any reason to keep
Seismometer Research Secret ??
Almost noone wants these things.


----- Original Message ----- 
From: "Jerry Payton" 
Sent: Friday, November 09, 2007 5:20 AM
Subject: Re: idea for an axis

> Hi,
> I have been following this discussion with great interest.  I have been
> wondering how you would control the rotation of the free end of the
> suspended pendulum?  As Ted pointed out in his email, it rotated.  How would
> one maintain the motion in a horizontal plane - - AND - - what kind (size,
> weight, &etc.) of coil.  Of course, Meredith suggested a light bulb.
> I'm just trying to wrap my brain around this idea as a whole assembly.
> Best Regards,
> Jerry Payton


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