[ntp:questions] Re: drifting on crystal

David J Taylor david-taylor at invalid.com
Thu Jan 13 10:24:25 UTC 2005


Brad Knowles wrote:
> At 6:33 AM +0000 2005-01-13, Marc Brett wrote:
>
>>  That's the hardware cost.  How many watts does it consume?
>
> No more than the low-quality oscillator that is actually included
> by the hardware vendor.
>
>>                   why would an engineer include a component with
>>  "oven" in its name if he didn't have to?
>
> There is no actual oven included with the crystal.  The issue is
> that the OXCO has gone through a more rigorous testing process which
> includes testing in an oven, and has been certified to work to
> certain tighter performance standards than your average everyday
> crystal, and either actively compensates for temperature variations
> or is relatively immune to them.

An OCXO is a crystal oscillator assembly contained inside a temperature 
regulated oven to keep it at a constant temperature.  The crystal itself 
will be chosen to have a low temperature coefficient, but over a more 
limited range than a non-ovened crystal.  I.e. a normal crystal might be 
specified to be +/- 10ppm over 0C..45C, but one intended for oven 
operation might be +/- 1ppm over 60-65C.  (I mage the figures up, by the 
way).  Such characteristics may be achieved by a different cut of crystal.

Cheers,
David 





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