cfharris at erols.com
Thu Aug 30 00:21:14 EDT 2012
Well, basically the temperature of a wrist watch is very
constant at around 90F. That and a table lookup that gives
an adjustment for number of cycles per tick vs temperature.
All quartz watches since about 1990 are microprocessor based,
and have a table lookup. They can only be regulated using
a special computer interface provided by the manufacturer.
Neville Michie wrote:
> 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.
> 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
>>> 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.
>> 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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