World's Largest Wheatstone Bridge
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From: Bret Cahill on 9 May 2010 19:39 > >> >> Take a wooden pencil and very slowly bend it. You will begin to hear > >> >> small cracking noises > > >> >I can predict that pretty good with strain sensors. > > >> No, you can't. You won't get a 10 millisecond warning as to when the > >> pencil will break. > > >Depends on how fast you load the pencil. If you load it over several > >months or years I'll get at least some warning that it is being > >loaded. > > >The linearity / non linearity allows for even better predictions. > > >> Now imagine only being able to place a few surface > >> sensors on one face > > >It's not really on one face. It's several miles above from what may > >be a thousands of faces. > > >No one said it was a easy problem, just that there might be some > >additional information to exploit. > > >Distance metrology needs to get the error down to a few microns over > >100 km. Apparently laser interferometry is just for short distances, > >even turbulence will mess up the measurement. > > >The strain sensor might not work for the simple reason the strains > >would be so low. > > >What is the best resolution possible with a bridge? > > >Another solution might be the World's Largest Seismometer, a proof > >mass of hundreds of tons. > > >> of literally millions of cubic miles of complex, > >> fractured, stressed, moving subsurface stuff. > > >There might be some hope in averages here. > > Absolutely. You can probably estimate the average time between > earthquakes. Numbers like 300 +-250 years. You'll be trying a little harder after a few hours trapped under some rubble. Here's an effort to circumvent massive machined commercial seismometers with smarter electronics: http://physics.mercer.edu/petepag/eigen.html Some waves travel much faster than the 2 mps Raleigh waves that do all the damage. 30 seconds isn't enough time to fix a lunch but it's better than nothing. Bret Cahill
From: jimp on 9 May 2010 20:01
In sci.physics Bret Cahill <BretCahill(a)aol.com> wrote: > Here's an effort to circumvent massive machined commercial > seismometers with smarter electronics: > > http://physics.mercer.edu/petepag/eigen.html No, it is not, and seismometers have been mechanically trivial to build for many decades. -- Jim Pennino Remove .spam.sux to reply. |