>>> Why not use a Klein bottle to achieve infinite period? > You have lost me there. What is a Klein bottle? > Has it anything to do with the 'Happy Hour'? A Klein bottle is a three dimensional Mobius strip. Search on "topology" >Great. It sounded pretty good to me too.... but it is an 'open >loop' device. Yes. there is no feedback, just damping (resistive) >How about devising an auto-zero circuit for the seismometer, so >that you never have to readjust it? Basically, a force balanced instrument (using a displacement sensor to create an "error" signal used to apply a balancing force to "hold" the mass in a fixed position relative to earth) would never need adjustment, except perhaps for optimum performance. The error signal may not be "zeroed" because of non-centered mechanics, but dynamic element of that signal (variation) would still reflect the acceleration required to hold the mass stationary with respect to the quivering earth. All one has to do is pass a sample of that error voltage through a high pass filter (only dynamic elements with a period LESS than say 300 seconds are measured) and on to the signal processing circuittry. After one or two integrations (this always seems to kick up a few postings...let's see. The first integration of acceleration would give velocity and then integrating velocity gives displacement...I think. But there again, is the high pass filter actually the first integration? I think so, so the signal at that point would be velocity. See what I mean? ). So, with the "natural" adjustments out of whack, the instrument would still remain centered with the only consequence being some non-linearity in signal response and reduced dynamic range. Several good examples of this type instrument are described on Larry's site. I frankly could care less whether the squiggles on my adding machine paper are acceleration, velocity or displacement, and my mechanical drive for the pen is deliberately non-linear to maximize the dynamic range, so accuracy in signal and timing has never mattered to me. I just like watching that thing come alive and speculating on the "where" and "how big". Chelsea and I have recordings of all the major quakes of '99 (Mexico(s), Turkey(s), Taiwan, Greece, etc.) and probably 90% of all the mag 6 and above quakes worldwide. The most inporatnt thing is that this can coexist with N'Sync. I just want to make somethinng that is simple, cheap, and gets good squiggles for others. _____________________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>