By any chance are you the same Dave Saum that used to work for GE in Syracuse about 15 years ago? The one I knew migrated to somewhere in Va, I think. Hope you get some good answers to your question. I too have been trying to get a handle on whether my typical background is just noisy or really really noisy. It would also be interesting to see some FFTs of "typical" background. Larry Conklin lconklin@............ ----- Original Message ----- From: "David Saum"
To: Sent: Tuesday, November 14, 2000 5:07 PM Subject: seismograph calibration? > I read Bob Barns' 1996 article about seismograph calibration > and I wonder if there is not a much simpler method that does > not require any special equipment. > > Suppose you just take the damping off a Lehman pendulum and > give it a little shove. It will begin to oscillate and if you > know the period and the amplitude then you can calculate > the peak velocity in nm/s. Then you read the peak value > from your ADC and that allows you to compute the > velocity sensitivity of your seismograph in nm/s per bit. > By observing your backgraound noise level in bits during normal > damped operation you can convert it to nm/s. > > Or am I making a stupid mistake? > > And what is a good value for sensitivity and background noise level? > When I do the tests above, it looks like I have a sensitivity of > about 120nm/s/bit and my noise level is about +/- 3. I have > a 16 bit ADC so should I crank up the analog gain a tad? > > The reason I am trying to calibrate my Lehman is that I just > got it working and I can not figure why it detects some quakes > well and others poorly. I am comparing my results with those > posted on seismicnet. Especially the results from Herndon, VA > which is just a few miles away from me at Bailey's Xroads, VA. > I am trying to figure out whether I need more gain or is my location > on a office building basement slab next to a busy street just too noisy? > > TIA for any help, > > Dave Saum > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>