[time-nuts] DC Voltage Ramp?

Brooke Clarke brooke at pacific.net
Sat Sep 3 18:56:32 EDT 2005

Hi Magnus:

I was thinking of using a Datum 1000B Ultra Stable Oscillator (the one 
used in the FTS 4060 Cesium standard).  The data sheet says that after a 
few years the aging rate gets down to parts in E-12/day.  I would think 
that the Allan plot would be cleaner if the control voltage was well 
behaved than if it was derived from a noisy process like GPS or maybe 

I think the dewar oven holds the temperature pretty well.

Have Fun,


Magnus Danielson wrote:

> From: Brooke Clarke <brooke at pacific.net>
> Subject: [time-nuts] DC Voltage Ramp?
> Date: Sat, 03 Sep 2005 15:30:10 -0700
> Message-ID: <431A23F2.9010503 at pacific.net>
> Hi Brooke,
>>The actual oscillator that provides the output from a Cesium standard is 
>>  in fact a crystal whose fine tuning voltage has been locked to the 
>>Cesium source.
>>If the oscillator was run standalone and it's aging rate determined by 
>>using GPS then if the proper voltage ramp was applied the output would 
>>be very close to a Cesium source.  This may be a linear or parabolic 
> It would be a bit of both actually. But not quite, the aging is not as simple
> that it is fully wrapped inside the model of a fixed drift rate. Proper
> stabilizing of the crystal temperature simplifies the model alot thought,
> since shift in temperature would not have the crystal beging a new aging
> period. Infact, you don't want to drive the crystal until you have it
> stabilized on temperature to avoid drift. Some measurement apparatous actually
> will not turn on until the crystal heating has been on for sufficient time,
> when it has only then the power button works.
>> An example is plotted at: http://www.rt66.com/%7Eshera/index_fs.htm
>>but for Cesium quality the tuning voltage needs orders of magnitude 
>>smaller steps.
>>The problem is coming up with the voltage ramp.  I hear that the Austron 
>>2010B Disciplined Oscillator has steps that are too crude.  Has anyone 
>>come up with a viable way to do this?
> Have you read about HPs SmartClock technology? If not, this is a good time to
> do that.
> The HP Z3801A contains the SmartClock technology, and it sure monitors quite
> alot of things. Mine seems to fail to converge into tighter specs thought.
> In a simple model, you compensate for frequency error (linear phase ramp) and
> frequency drift (parabolic phase ramp). In a little more complex model, you
> compensate for the temperature dependence. In an even more complex model, you
> compensate for the aging process, the magnetic field etc.
> Cheers,
> Magnus

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