[time-nuts] oscillators

Neville Michie namichie at gmail.com
Thu Aug 30 00:12:34 EDT 2012


Does anyone know about what technology is used in Swiss watches to get much better performance from 
their xtals than you might expect?
I assumed that they had look up lists to insert extra counts to compensate for ambient variations,
but I have never heard any details.
cheers,
Neville Michie






On 30/08/2012, at 1:45 PM, Richard (Rick) Karlquist wrote:

> 
> On 8/27/2012 11:45 PM, WB6BNQ wrote:
>> 
>> 
>> A microprocessor controlled XO is a non oven crystal oscillator system that has
>> additional computational control providing a bit more than just mere passive
>> temperature compensation.  The additional computational capability deals with
>> having coefficients of that particular oscillator's behavior pre coded to
>> compensate for the nonlinear behavior over a given temperature rang
> 
> It doesn't use coefficients.  It has a look up table of frequency vs
> temperature.
> 
>> 
>> A microprocessor controlled XO system allows for using cheap crystals with
>> minimum processing time and costs.  Because of limited storage space there is no
> 
> No it doesn't use a cheap crystal.  It uses a *special* SC cut crystal.
> This crystal could very easily cost more than an OCXO crystal.
> 
>> way for the system to have enough data to even try to compete with the quality of
>> a decent OCXO.  Beyond its initial calibration setup, it has no way of keeping it
>> tied to a known reference, like the Thunderbolt is doing.
>> 
>> Bill....WB6BNQ
> 
> An MCXO is a very good, but expensive TCXO.  Only temperature, not aging is corrected.
> 
> It has nothing to do with "smart clocks".
> 
> Rick Karlquist N6RK
> 
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