PSN-L Email List Message

Subject: Re: Etc.
From: twleiper@........
Date: Fri, 21 Jan 2000 18:29:46 -0500

>>> 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
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.


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Larry Cochrane <cochrane@..............>