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 Saumwrote: 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.= DIV>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 ChrisThanks for the Lennartz information.I seem to get AS1 comparable performance on a 4.5 Hzgeophone 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 systemnoise by using one of the newest ultralow noise auto-zero opampsthat has NO 1/F noise. I run it at 100,000x gain. These op= ampsare less than $2, but they are very small surface mount parts thatare tricky to hand solder, at least for meMy system is sitting on a carpeted basement floor of a busy office bui= ldingnear Washington, DC and my online helicorder display shows todaysCosta Rica 5.8 quake at around 11 UTC.I use the typical AS1 bandpass filtering of 10 to 25 seconds toget the most sensitivity to teleseismic events.My helicorder today looks a lot like the Columbia University broadband= displayshowing the Costa Rica quake.I am about 30 degrees from Costa Rica and Columbia University is near = NYCand about 32.5 degrees acording to usgs.The P wave does not show up very well on my filtered helicorder, or on= the ColumbiaU broadband. But if I set my helicorder to unfiltered and get th= e whole .01 to 1.0 Hz bandit 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= nfor 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 = todayCheers,Dave
[ Top ] [ Back ] [ Home Page ]