PSN-L Email List Message

Subject: Re: Pot and Tube Horizontal Seismometer
From: Christopher Chapman chrisatupw@.......
Date: Thu, 4 Aug 2011 18:52:36 -0400 (EDT)







Subject: Re: Pot and Tube Horizontal Seismometer


Are you by chance talking about fLat on water connected by lever
rm to a potentiometer ? Possibly a strain guage of some kind ?
 know there more to it than that, but this should be the basic idea ?
----- Original Message -----=20
rom: "Chuck / Judy Burch" 
o: 
ent: Monday, August 01, 2011 10:18 AM
ubject: Pot and Tube Horizontal Seismometer
Hi Geoff,=20
    This is a horizontal fluid seismic sensor, basically consisting of=20
a horizontal tube with both short ends upturned vertically and filled=20
with fluid to about half their height. This is like a small manometer=20
with a long connecting tube. If you accelerate the tube horizontally,=20
the fluid level rises in one end and falls in the other. A fluid=20
restriction is connected in the centre of the horizontal tube to=20
prevent the fluid from oscillating. To get a long period, you either=20
need a very long tube, or you can fit much larger diameter cylindrical=20
cans on both tube ends. One of the easier ways of measuring very small=20
changes in the fluid level is to make the fluid electrically conducting=20
and to insert two vertical wires a few mm through the fluid surfaces on=20
both pots.  The coupling between the pairs of wires is measured with an=20
AC voltage, then rectified and the signals from both ends are amplified=20
and subtracted to give the seismic signal.=20
.
    Regards,
.
    Chris Chapman





= Subject: Re: Pot and Tube Horizontal Seismometer

Are you by chance talking about fLat on water connected by lever
arm to a potentiometer ? Possibly a strain guage of some kind ?
I know there more to it than that, but this should be the basic idea ?

----- Original Message -----=20
From: "Chuck / Judy Burch" <cjburch@...........>
To: <psn=
list@..............>
Sent: Monday, August 01, 2011 10:18 AM
Subject: Pot and Tube Horizontal Seismometer

Hi Geoff, 
    This is a horizontal fluid seismic sensor, basically c=
onsisting of 
a horizontal tube with both short ends upturned vertically and filled =
with flu=
id to about half their height. This is like =
a small manometer 
with a long connecting tube. If yo=
u accelerate the tube horizontally, 
the fluid level =
rises in one end and falls in the other. A fluid 
restriction is connected in the centre of the horizontal tube to <=
/PRE>
prevent <=
TT>the fluid from oscillating=
.. To get a long period, you either 
need a very long tube, or you can fit much larger diameter cylindrical 
cans on both tube ends. One of the easier ways of measuring very small
changes in=
 the fluid level is to make the fluid electrically conducting <=
/PRE>
and to insert two ver=
tical wires a few mm through the fluid surfaces on 
both pots.  The coupling between=
 the pairs of wires is measured with an 
AC voltage, then rectified and the signals =
from both ends are amplified 
and subtracted to give the seismic s=
ignal. 
.=
    Rega=
rds,
.
    Chris C=
hapman

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