That's a wonderful paper by those Woods Hole guys. Their temperature-compensated 5 milliwatt crystal oscillators can be back-corrected (linear drift model) to a few tens of milliseconds over a year and they make a convincing case they know how to do this.
Their similar graphs for CSAC oscillators are maybe a factor of three better. Tim N3QE On Thu, Jan 25, 2018 at 12:39 PM, gandalfg8--- via time-nuts < time-nuts@febo.com> wrote: > > > Hi > > The CSAC spec sheet calls out an aging rate of 0.9 ppb per month as > “typical”. There is also a temperature spec of 0.4 ppb. If both are correct > for your sample (*and* aging is linear ) you would be out by roughly 10 ppb > per year. There also is a voltage stability spec that might be impacted > depending > on how you manage power. > > Taking the 30 ppb = 1 second number, you are at a 1 second / year rate > after 3 years. > At that point, you have already drifted by a second, if the assumptions > are correct. > This makes a massive assumption that the aging stays at the “typical” rate > for years. It’s a very good guess that it does not. Is it going to be 1/3 > or 1/10 > of typical over that period? Who knows. > > Bottom line, you are going to be pretty far from 1 second per 100 years > with > a CSAC based wrist watch, if it runs for years (or even for months). It > *will* > do *way* better than a TCXO or OCXO based watch over months or years. > It’s still not perfect. > > Bob > > ----------------- > > "if it runs for years (or even months)" sounds like an informed comment:-) > > When searching for some data recently I came across a report which might > be relevant. > > "A Second Look at Chip Scale Atomic Clocks for Long Term Precision > Timing", written by > Alan T. Gardner and John A. Collins of the Woods Hole Oceanographic > Institution, details their > experience with a number of earlier and more recent CSAC modules and their > findings make > for very interesting reading. > > At the time of writing a copy is available here.... > > www.obsip.org/documents/Gardner_IEEE_Oceans_2016.pdf > > Nigel > GM8PZR > > > > > > _______________________________________________ > 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.