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

Max Robinson max at maxsmusicplace.com
Thu Aug 21 23:38:51 EDT 2008

Hmmm.  That sounds like something to be stored away for the day when my 
thermostat goes bad.  Sounds like it would work.


Max.  K 4 O D S.

Email: max at maxsmusicplace.com

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----- Original Message ----- 
From: "Mike Monett" <XDE-L2G3 at myamail.com>
To: <time-nuts at febo.com>
Sent: Thursday, August 21, 2008 2:07 PM
Subject: Re: [time-nuts] Restoring GR 1120-AB Frequency Standard

> "Max Robinson" <max at maxsmusicplace.com> wrote:
>>When I was at the university I saw and worked on a thermostatic switch 
>>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 
>>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 
>>unless you had a very narrow range thermometer with a small capillary. 
>>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.
> Regards,
> Mike Monett
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