[time-nuts] Chronometer contest sponsored by IEEE Spectrum

Bill Janssen billj at ieee.org
Fri Nov 30 00:32:10 UTC 2007


Jeff Mock wrote:
> Jeffrey Pawlan wrote:
>   
>> On Thu, 29 Nov 2007, David Forbes wrote:
>>     
>>> It might be more fun to require that an OCXO be designed and built by
>>> the DIY-er out of commercially available crystals and resistors. That
>>> way, it's an engineering challenge instead of a procurement
>>> challenge, since IEEE is about engineering.
>>> --
>>>       
>> I second David's suggestion!   The only REAL challenge would be to design the
>> circuitry. Otherwise this is just a "rack & stack" project which is not
>> engineering.
>>
>>     
>
> I think it's a fantastic challenge.  I imagine starting with a design 
> goal something like tvb's original leapsecond goal.  It would be kind of 
> cool to have a $100 clock that met that criteria.
>
> I don't think an off-the shelf OCXO timebase will be competitive at this 
> price point. I'm not aware of an inexpensive SC-cut oscillator.
>
> I think the parameters for the contest need to be tightened up. 
> Temperature and environment are enemies for this kind of clock, I hope 
> they specify the operating environment and time period for evaluation.
>
> I think that I would start by looking at 32kHz watch crystals, I've 
> often wondered how good a timebase you can make out of one.  The tempco 
> is a parabola around 25C with a max slope of something like 0.05 PPM/C, 
> so they are naturally a pretty good timebase with good aging 
> characteristics. The crystals are really tiny,  maybe insulating it with 
> a material that has an interesting heat of fusion along with a micro to 
> model the physics of the parabolic shape of the crystal performance.
>
> jeff
>
>   
Maybe an ensemble of watch crystal clocks and a PIC microprocessor  per 
David Allan paper
of some years ago. After testing you could assign deferent weighting to 
the different clocks.

Bill K7NOM





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