Jim, Thanks for your message. Answers to some of your questions below.... At 07:14 PM 8/15/99 -0700, you wrote: >Larry-and PSN Members (The Can-Do Folks), > >I am in the process of developing seismic systems (as cheap as possible, >so I can get them in as many schools as possible) for Clark County >Schools, here in Las Vegas, which has over 200,00 students. I am >thinking along the lines of PEPP, but with a much more affordable system. > > >Recording at UNLV: >I recently purchased your Amp/Filter (3 Channels) and the A/D board and >hooked it up to the UNLV, 20 year old, Lehman (E-W) and 3 S-13's (X,Y,Z). >The Lehman went thru your Amp/Filter (set at 2K gain) while the S-13's >went thru a Geotech amplifier of 1K gain, and all 4 were recorded on a >Gateway PC (8Mb Ram & 400Mb HD) at 50 sps. I was able to record the >Scotty Castle sequence (M=5.7, 8/1/99), was I impressed, even the Event >Detector worked! Now, all channels went off scale on the Main Shock, it >appeared either the Amp or A/D clipped on the Lehman, while it appeared >the S-13 seismometer, it self, was saturated, as the recording was very >peculiar looking, not the normal clipping. We were 250 Km's away from >the epicenter. The Lehman also has a 10hz oscillation which is small on >the seismogram and comes out as a spike on the spexa. >Question 1. Is it likely the S-13 seismometer itself would get saturated >from this Eq ? >Question 1a. How do I tell rather the Amp or A/D board clipped? I don't think the sensor saturated. Its probably too much gain through the system. >Question 1b. Does the Lehman have another resonant frequency at 10 HZ? My Lehman has several resonances. Its hard too say where they will show up. > > Geophone Testing (L-4): > I live about 5 Km's from a recent M=2.5, May 6, which I felt. UNR has >two sites 30 Km's and 50 Km's away in opposite directions from Boulder >City, (BC), (BC is 30km's South-East of Las Vegas), UNR recorded the >M=2.5, but they need a third site to get a better location. I hope to be >that third site to pin down these small shocks which go unnoticed on >their Network, here in BC. I just started testing 3 L4's, 2 H & 1 Z, >here at my house in Boulder City, NV . I have them on my patio with 100' >of coaxial cable which came with the sensors. I borrowed them from UNLV >to determine if they would be good for detecting local EQ's. I put their >output directly into a DataQ A/D board, (DI-194, 16 bit, 4 channel, 10V >FS, sells for $100) thru the 100' cable, which hooks up externally to my >PC( HP 96 Mb Ram & 4 GB HD) thru the Com1 port. I obviously need a >preamplifier as I don't even see road traffic, they do slightly pick me >up when I walk by. >Question 2. What is the L-4 output? Sorry, I don't know the sensitivity of this sensor. >Question 3. Can I use your Amp/Filt board as a Pre-amp? and do I need to >place it very close to the L4 seismometer to keep a short input cable? If your A/D card input is from 0 to 10 vdc and not +-10 vdc there will be a problem using my Amp card. It produces a +- output voltage. >Question 4. Should your Filter board setting be something like 0.5 to 30 >Hz for the L4. For geophones I have been using .5 to 20 hz, but I can make it 30 hz if needed. >Question 5. I have a program, Atomic Clock, which calls Boulder or Fort >Collins, CO to reset my PC clock. I am wondering if that is >satisfactory, as my main interest is just S-P values, to locate local >Eq's. Don't know. > >At the present time I have the Lehman, 3 S-13's and 2 Z L-4's recording >at UNLV using your Amp/filter board on the Lehman and L-4's. I believe >you set two of the channels to 20 hz for the Geophones and 10 hz for the >Lehman. Yes, this is correct. > >I am ready to order another Amp/Filter board unless someone can suggest a >cheaper pre-amp.....for the L-4's. > >Jim O'Donnell >Retired Geophysicist -Larry Cochrane Redwood City, PSN _____________________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>