[time-nuts] Restoring GR 1120-AB Frequency Standard
Mike Monett
XDE-L2G3 at myamail.com
Fri Aug 22 13:20:11 UTC 2008
Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:
> Max
> A capacitance bridge using a transformer would be a lot more
> stable than merely using the capacitance to vary the frequency of
> an LC oscillator.
> The advantage of a capacitive sensing technique over a light beam
> is that it has much simpler and potentially more stable mechanical
> system than when a the mercury colum interrupts a light beam.
> Unless of course on has the Mercury column move a moire grating or
> similar setup such as making the top of the mercury column a
> reflector in an interferometer system.
> Bruce
Very clever! According to this web page, interferometry could give a
resolution of 0.15 nm, or close to the radius of a silver atom:
http://www.aerotech.com/products/engref/intexe.html
This video shows the basic principle in case you want to make your
own:
http://www.metacafe.com/watch/1381543/laser_interferometer_homemade_for_20/
You can see from the movement of the fringes how sensitive
interferometry can be. This should give unprecedented temperature
control, so maybe someone has already done it. A google search gives
lots of hits, but it is difficult to distinguish between controlling
the termperature of something, and the need for accurate control of
temperature to get stable fringes!
Great idea!
Regards,
Mike Monett
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