[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.
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