Hi Tom:
Here's a web page that has an annotated list of some patents applicable to
pendulums:
http://www.prc68.com/I/Pendulums.shtml
Many of the early gravity meters were just pendulums, then came the falling
corner reflectors.
There are a couple of patents by Dicke and this one:
3036465 <http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=3036465>
Gravity Meter,
It may be close to your "Dream pendulum" has a Q of about a million.
PS When I was working in microwave electronics we talked about the Dicke radiometer, but I haven't found any definitive
web page about that.
It was just a SPDT switch on the input to a low noise amplifier that alternated between an antenna and a termination at
a known temperature (kTBR).
One of our employes used that idea with a piston driven by a PN code to change the input pressure to a steam generating
plant and using a correlation function on the electrical output electrical power to get the plant's impulse response.
http://en.wikipedia.org/wiki/Lock-in_amplifier
"The lock-in amplifier is commonly believed to be invented by Princeton University
<http://en.wikipedia.org/wiki/Princeton_University> physicist Robert H. Dicke
<http://en.wikipedia.org/wiki/Robert_H._Dicke> who founded the company Princeton Applied Research (PAR) to market the
product."
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
Tom Van Baak wrote:
The Wiki page for the Shortt pendulum clock has a "Recent Measurements" (1984)
paragraph that's in error.
http://en.wikipedia.org/wiki/Shortt-Synchronome_clock#Recent_accuracy_measurement
While it's probably true that the clock is stable to 200 uS per day (i.e. 2E-9)
I believe Alfred Loomis discovered the
effect of the moon on this clock a long time ago.
Hi Brooke,
The wiki page is correct. The heading is "Recent Measurements" and Pierre
Boucheron's 1984 effort certainly qualifies. Note the wiki doesn't claim Boucheron was
the first. In fact, even 30 years old, it is still the most recent, and the only Shortt
experiment for which we have raw data. See http://leapsecond.com/pend/shortt/ for details.
One could try claiming that Loomis was the first to make detailed measurements of a Shortt, but it
would take some digging to prove he was "first" and not just "one of the
first". I mean, if you look at the list of who received the one hundred Shortt's that were
manufactured, many laboratories had more than one, not to mention the ones that William Shortt
himself owned at the factory. Certainly there was a lot of time measurement going on in the 20's
and 30's. It would take a lot of work to uncover what was known by whom and when. Or who published
first or not.
I think Loomis took it a wonderful extreme with his spark chronograph and
quartz oscillator via telephone time transfer setup. And that be bought three
clocks at once is classic and inspiring to any time nut! So I agree, Loomis
deserves mention on the Shortt wiki page.
Unrelated to gravity and tides, is the role that vacuum pendulum and ovenized
quartz clocks had in confirming that earth rotation was itself irregular at the
millisecond level. Credit for that usually goes to Scheibe and Adelsberger in
the late 30's, not Shortt or Loomis. And that of course blends into the story
of the leap second...
See my scan/OCR historical pendulum collection: http://leapsecond.com/pend/pdf/
And my own precision pendulum-nut articles: http://leapsecond.com/hsn2006/
Some of you readers might wonder why in this GPS age, two time nuts, each with
plenty of atomic clocks at home, would be talking about vintage pendulum
clocks. It turns out that pendulum clocks are still extremely interesting
timekeepers, from an experimental, scientific, and historical perspective.
/tvb
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