Hi On a properly working crystal oscillator, EFC is essentially instantaneous at the "many seconds" level. The main delay you see is from the R/C time constant between the R's in the tuning attenuator and any bypass C's that are present. Time constants rarely get over 50 ms. Twenty * tau would only be 1 seconds at the 50 ms case. There's not much settling left to do after 20 time constants.
Bob On Mar 27, 2010, at 1:21 PM, WarrenS wrote: > > Pete2 > > Addressing your first question only, I'll let the experts address the why. > > Yes, I 'think' it does in principal, I would not guess on how long it takes > though. > But > I have not checked that close to be sure. > I'd never do something that gross during the middle of a test that I was > trying to see 1e-12 things. > I do that first thing, long before the high resolution test starts and then > let things resettle before proceeding. > Any change in cable position or the Osc moving a bit in its Box or a dozen > other things could also change it that much, including temp gradients in the > box, so Don't do that if you want 1e-12 results. > Use the wedge, that I have tested, and is completely reversible and > repeatable at those levels. > I have noticed that the OSC will even take a long time to resettle (hrs+ ) > if the EFC voltage is change a lot and then put back. > Which is why I limit the clamp voltage of my Tbolt to typ + - 100 mv or less > from its nominal. > > ws > > ******************** > > >> Warren, >> If you turn over an oscillator, is the frequency change >> completely reversible (to your "under 1e-12 resolution") when it is >> restored? Thinking aloud, if an hour-glass is turned over twice, the >> final level will be the same, but the grains will be mixed. A quartz >> crystal, however, is solid, so hopefully nothing actually moves. >> Presumably the zero-G axis is with the axis of oscillation at 90 >> degrees to gravity? >> >> Peter (the "other" one :-) >> > ***************************> >> >>> Another thing I use it for is to test high resolution Freq meters. >>> Using a calibrated wedge that I can then slide under one edge of the zero-G >>> Osc box, I can >>> make small, variable, repeatable, freq changes of under 1e-12 resolution, >>> something pretty hard to do otherwise. >>> If I want to make BIG changes like 1e-10, I can rotate the box on any of its >>> sides and still use the wedge, >>> and for a quick check of new equipment, I just turn the box over which then >>> gives a couple of parts in 1e-9 freq change. >>> It makes a weird but simple and indispensable variable freq source that is >>> useful for many things, such as checking the LOOP TC of a TBolt. >> >> > > > _______________________________________________ > 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.
