Brett
With respect to capacitive sensors, I was thinking of making the diaphragm =
portion of the faces of the cube one side of a variable capacitors. The opp=
osing sensors would measure movement in one direction and have a common "gr=
ound". I'm not sure how that would work in a wheatstone bridge or instrumen=
tation amp. Stray capacitance has always bothered me in capacitive sensors.=
 I guess it's my limited knowledge in ac circuitry.
Barry =A0=20

--- On Mon, 9/28/09, Brett Nordgren  wrote:

From: Brett Nordgren 
Subject: Re: Seismometer Siting
To: psn-l@..............
Date: Monday, September 28, 2009, 8:30 PM

Barry,

What you are suggesting sounds slightly like Dave Nelson's (CA) FMES sensor=
s.=A0 N & E are not combined in a single assembly, but it works very roughl=
y along the lines you were mentioning--and from the results he is getting, =
it appears that it makes a very good (and also very simple) horizontal.

Brett.

At 08:07 PM 9/28/2009 -0700, you wrote:
> Geoff
> Along that line, a P wave being a pressure wave and a s wave being a shea=
r wave. It seems that if one could see two directions simultaneously during=
 an event one be able to combine the p wave vectors and obtain the directio=
n of max and min p wave contribution and thus the approx direction of the e=
vent. I thought one could make a liquid filled cube sensor with a piezoelec=
tric disk in each face. Opposing faces would go into an instrumentation amp=
 to measure the seismic forces on the liquid inside. To increase the mass i=
n each face the center of each face could have a perpendicular tube with th=
e piezo disk at the end of the tube. It would look like a kids "jack". I bu=
ild one but didn't get the electronics complete. Since a peizo measures vel=
ocity, there may be a better way to measure pressure on each face=A0 (diaph=
ram with displacement sensor?).
> Regards
> Barry

Watch our wiggles
http://bnordgren.org/seismo/gif_images.htm

or watch some very very good wiggles
http://aslwww.cr.usgs.gov/Seismic_Data/telemetry_data/ANMO_24hr.html


__________________________________________________________

Public Seismic Network Mailing List (PSN-L)

Brett
With respect to capacitive sensors, =
I was thinking of making the diaphragm portion of the faces of the cube one=
 side of a variable capacitors. The opposing sensors would measure movement=
 in one direction and have a common "ground". I'm not sure how that would w=
ork in a wheatstone bridge or instrumentation amp. Stray capacitance has al=
ways bothered me in capacitive sensors. I guess it's my limited knowledge i=
n ac circuitry.
Barry   

--- On Mon, 9/28/09, Brett Nordg=
ren <brett3nt@.............> wrote:

From: Brett Nordgren <brett3nt@.............>
Subject:=
 Re: Seismometer Siting
To: psn-l@..............
Date: Monday, Septem=
ber 28, 2009, 8:30 PM

Barry,

What yo=
u are
 suggesting sounds slightly like Dave Nelson's (CA) FMES sensors.  N &=
amp; E are not combined in a single assembly, but it works very roughly alo=
ng the lines you were mentioning--and from the results he is getting, it ap=
pears that it makes a very good (and also very simple) horizontal.

B=
rett.

At 08:07 PM 9/28/2009 -0700, you wrote:
> Geoff
> =
Along that line, a P wave being a pressure wave and a s wave being a shear =
wave. It seems that if one could see two directions simultaneously during a=
n event one be able to combine the p wave vectors and obtain the direction =
of max and min p wave contribution and thus the approx direction of the eve=
nt. I thought one could make a liquid filled cube sensor with a piezoelectr=
ic disk in each face. Opposing faces would go into an instrumentation amp t=
o measure the seismic forces on the liquid inside. To increase the mass in =
each face the center of each face could have a perpendicular tube
 with the piezo disk at the end of the tube. It would look like a kids "jac=
k". I build one but didn't get the electronics complete. Since a peizo meas=
ures velocity, there may be a better way to measure pressure on each face&n=
bsp; (diaphram with displacement sensor?).
> Regards
> Barry
Watch our wiggles
http://bnordgren.org/seismo/gif_images.htm
<=
br>or watch some very very good wiggles
http://a=
slwww.cr.usgs.gov/Seismic_Data/telemetry_data/ANMO_24hr.html

__________________________________________________________

Public S=
eismic Network Mailing List (PSN-L)

To leave this list email PSN-L-REQUEST@.............. with the body of t=
he
 message (first line only): unsubscribe
See http://www.seismicnet.com/maillis=

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