[time-nuts] DC Voltage Ramp?

Magnus Danielson cfmd at bredband.net
Sat Sep 3 18:48:54 EDT 2005

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:

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 
> ramp.

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.


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