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

Mike Monett XDE-L2G3 at myamail.com
Thu Aug 21 15:07:43 EDT 2008

"Max Robinson" <max at maxsmusicplace.com> wrote:
>When I was at the university I saw and worked on a thermostatic switch that 
>used a standard mercury thermometer.  The little thing that clipped on to 
>the thermometer was the capacitor in an oscillator.  The detector for 
>opening and closing the relay was a high Q tuned circuit.  I saw them 
>regularly because I had to keep teaching lab instructors how to tune them up 
>before each use.  In a controlled environment it might be possible to 
>optimize such a circuit for stable operation and tight control.  My 
>intuition tells me that 1 degree is about as fine a control as you could get 
>unless you had a very narrow range thermometer with a small capillary.  You 
>might be able to convert the existing thermostat to capacitive sensing. 
>That is apparently what Magnus is suggesting.
>Max.  K 4 O D S.

Optical might work better. Maybe use the lens and laser from an old CDROM.
It might be fun getting it to focus on the mercury column through a round
glass tube. Or maybe the glass wouldn't even pass the infrared. I got a bad
burn once picking up an empty wine glass that was sitting beside a
fireplace. But I understand new systems use a blue laser, which might work
even better.

I wonder what kind of temperature control it would give, and what the
long-term drift might be. Sounds like a fun project.


Mike Monett

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