[time-nuts] Another "atomic" clock question
lists at rtty.us
Sun Mar 2 13:02:34 EST 2014
These days, you can get some *very* low cost crystals. They sell by the pound rather than by the piece. The tolerance as delivered may be 0.1% for temperature plus calibration. Aging is likely to be “who knows”. The temperature characteristic could be a third order curve. More likely it’s a straight line in one direction or the other. Cost is the driver, and not much else matters. They make millions of them a week.
On Mar 2, 2014, at 12:56 PM, Hal Murray <hmurray at megapathdsl.net> wrote:
> bob91343 at yahoo.com said:
>> But I thought conventional wisdom is that most crystals are AT cut and an
>> attempt at zero average coefficient is made, causing a nonlinear
>> characteristic. But perhaps over a limited range it's linear. The problem
>> of course is calibration.
> Most crystals are low cost. They will have a temperature characteristic
> similar to the graph about half way down this URL:
> The specs on the standard oscillator packages vary from 100ppm to 20ppm.
> That covers temperature and voltage and initial manufacturing and some amount
> of aging. (I haven't looked at the spec sheets recently. I don't remember
> seeing anything about aging.) The point is that they are low cost and the
> specs are reasonably clear, something a digital designer can understand and
>> Again, how does one calibrate those 3 MHz ovenized units?
> I plug mine into a HP 5334B which is clocked by a TBolt.
> These are my opinions. I hate spam.
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