[time-nuts] Restoring GR 1120-AB Frequency Standard

Mike Monett XDE-L2G3 at myamail.com
Fri Aug 22 09:20:11 EDT 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



More information about the time-nuts mailing list