John Tacinelli wrote: > My problem is that at 8:45 PM every night I get a sudden increase (or decrease) in voltage through my amplifier that causes the trace to move off to the right hand side of the screen. It stays there until 5:45 every morning. Then it goes right back. The seismograph itself doesnt seem to move. I have run it on an uninterruptible power supply and it still does it. I watche d it happen tonight and I could detect no environmental change in the area of the seismograph. > The seismograph is set up at the school where I teach. Maintenance thought it might be the outside lights turning on but tha t happens much earlier. That timing happens to coincide with the setting and rising of the sun (pretty close) but I can't thin k of anything solar that could affect a magnetic coil inside a building in a time span of about 2 seconds. If it's synchronized with sunrise & sunset, then it's probably related to the streetlights that are turned on/off with photoelectric cells. I would look for noise on the power line though, I like the battery operation experiment. At Geometrics, we had a problem with a new magnetometer design that was noisy until about 3 AM. Turns out that BART, the Bay Area Rapid Transit, generated a magnetic field running DC trains that we could see 50 miles away. At 3 AM the trains stopped and the noise went away. Of course that wasn't technically an instrument noise problem, it was a real magnetic field we were measuring. Doug Crice __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>