Hi 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.
Bob On Mar 2, 2014, at 12:56 PM, Hal Murray <hmur...@megapathdsl.net> wrote: > > bob91...@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: > http://www.4timing.com/techcrystal.htm > 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 > use. > > >> 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. > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.