PSN-L Email List Message

Subject: Re: Damping Resistor - D Saum
From: hsvham hsvham@.........
Date: Mon, 13 Feb 2012 10:41:48 -0800 (PST)


Hi Dave,
I would like=A0to know more about your system, for possible application to =
some schools I am working with in this area, for classroom seismograph inst=
allations.
=A0
Please take a look at http://alabamaquake.com and the 18-hr Huntsville seis=
micity heliplot display that shows the record I captured today of the M5.8 =
Costa Rica event this morning - the front-page display is the output of a F=
BV instrument, LP filtered at 12.5 sec., and the unfiltered channels are sh=
own at http://alabamaquake.com/seismicity.html.
=A0
Regards,
Steve =A0=20
=A0
--- On Mon, 2/13/12, Dave Saum  wrote:


From: Dave Saum 
Subject: Re: Damping Resistor - D Saum
To: psnlist@..............
Date: Monday, February 13, 2012, 12:19 PM


Hi Chris


Thanks for the Lennartz information.


I seem to get AS1 comparable performance on a 4.5 Hz
geophone system without ANY=A0frequency compensation,
all the way down to surface wave frequencies around 0.04 Hz.


I am concentrating on getting the lowest possible system
noise by using one of the newest ultralow noise auto-zero opamps
that has NO 1/F noise. =A0I run it at 100,000x gain. =A0These opamps
are less than $2, but they are very small surface mount parts that
are tricky to hand solder, at least for me
http://www.analog.com/en/precision-op-amps/low-voltage-noise-amplifiers/ada=
4528-1/products/product.html=20


My system is sitting on a carpeted basement floor of a busy office building
near Washington, DC and my online helicorder display shows todays
Costa Rica 5.8 quake at around 11 UTC.
http://www.infiltec.com/seismo/qm45.htm=20
I use the typical AS1 bandpass filtering of 10 to 25 seconds to
get the most sensitivity to teleseismic events.


My helicorder today looks a lot like the Columbia University broadband disp=
lay
showing the Costa Rica quake.
http://www.ldeo.columbia.edu/cgi-bin/LCSN/WebSeis/24hr_heli.pl=A0


I am about 30 degrees from Costa Rica and Columbia University is near NYC
and about 32.5 degrees acording to usgs.
http://neic.usgs.gov/neis/bulletin/neic_b0007ztb_t.html=A0


The P wave does not show up very well on my filtered helicorder, or on the =
Columbia
U broadband. =A0But if I set my helicorder to unfiltered and get the whole =
..01 to 1.0 Hz band
it shows up well, just like the Columbia University short period display.


I am amazed a how much performance you can get without any compensation
for the 4.5 Hz geophone steep 1/f^2 loss.


I do not think any of the IRIS AS1 display shows the Costa Rica quake today
http://www.iris.edu/hq/ssn/schools/realtime=A0


Cheers,


Dave



Hi Dave,
I would like to know more about your system, for possible applica= tion to some schools I am working with in this area, for classroom seismogr= aph installations.
 
Please take a look at http://alaba= maquake.com and the 18-hr Huntsville seismicity heliplot display that s= hows the record I captured today of the M5.8 Costa Rica event this morning = - the front-page display is the output of a FBV instrument, LP filtered at = 12.5 sec., and the unfiltered channels are shown at http://alabamaquake.com/seismicity.html.
 
Regards,
Steve  
 
--- On Mon, 2/13/12, Dave Saum <dsaum@............> wrote:

From: Dave Saum <dsaum@............>
Sub= ject: Re: Damping Resistor - D Saum
To: psnlist@..............
Date: = Monday, February 13, 2012, 12:19 PM

Hi Chris

Thanks for the Lennartz information.

I seem to get AS1 comparable performance on a 4.5 Hz
geophone system without ANY frequency compensation,
all the way down to surface wave frequencies around 0.04 Hz.

I am concentrating on getting the lowest possible system
noise by using one of the newest ultralow noise auto-zero opamps
that has NO 1/F noise.  I run it at 100,000x gain.  These op= amps
are less than $2, but they are very small surface mount parts that
are tricky to hand solder, at least for me

My system is sitting on a carpeted basement floor of a busy office bui= lding
near Washington, DC and my online helicorder display shows todays
Costa Rica 5.8 quake at around 11 UTC.
I use the typical AS1 bandpass filtering of 10 to 25 seconds to
get the most sensitivity to teleseismic events.

My helicorder today looks a lot like the Columbia University broadband= display
showing the Costa Rica quake.

I am about 30 degrees from Costa Rica and Columbia University is near = NYC
and about 32.5 degrees acording to usgs.

The P wave does not show up very well on my filtered helicorder, or on= the Columbia
U broadband.  But if I set my helicorder to unfiltered and get th= e whole .01 to 1.0 Hz band
it shows up well, just like the Columbia University short period displ= ay.

I am amazed a how much performance you can get without any compensatio= n
for the 4.5 Hz geophone steep 1/f^2 loss.

I do not think any of the IRIS AS1 display shows the Costa Rica quake = today

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