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 > On Jan 24, 2018, at 3:59 PM, Ronald Held <[email protected]> wrote: > > Jim: > One around 1s/y, one 6 s/y and one 11 s/y. I was looking to do > better than 1 s/100 years, but that was for the CSAC. > Ronald > > > 1 second/year is quite good - about 30 ppb. It's a bit tricky (like all > things time-nutty) - the "aging" on a TCXO could be that good - but the > instantaneous frequency control might not be that good. 1ppm is pretty > vanilla for a TCXO over a fairly wide temperature range, so 30 ppb at > "constant skin temp" (say, 5 C range) is probably reasonable. > > I've got some test data here for some fancy TCXOs intended for space > with a spec of 2ppm aging first year and then 1ppm/year after that. The > actual aging in the first year was 0.08 ppm, at 70C. Some of the other > oscillators in the lot were 0.02ppm, 0.05ppm. > > So, I think the spec here is "covers all the things that can go wrong", > but by cherry picking, you could do better. > > (or, our system design could tolerate several ppm aging over years, and > "run of the mill" for Vectron was actually a lot better) > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
