Simply put, stability is a measure of how much something varies from a constant value. A stable value doesn't mean an accurate value; accuracy is a measure of how close to some standard value a device emits (in this case) or measures, for a meter.
So, you could have something that's perfectly stable but not accurate. You can also have something that's accurate but not stable. In theory, they can be perfectly (ok, nearly perfectly) accurate because their lack of stability is averaged out over a long period of time, and the average value is an accurate representation of the time kept by the satellites, which themselves provide an accurate representation of 'true', i.e., NIST time. In practice they wander around a bit, and that wandering is the stability measurement you see. What you can tell from the stability figures is that the unit is that close to perfect accuracy most of the time. The stability figure is really a measure of the statistical probability that at any given time the accuracy is within that bound. Why do they wander? Many factors contribute, ranging from the stability and accuracy of the local VCXO and its control loop to atmospheric propagation variations to variations in the satellite clocks themselves, etc. Bill Ezell ---------- They said 'Windows or better' so I used Linux. Richard Dabney wrote: > I'm not a scientist or engineer but have a question to those of you who are. > > The many recent posts regarding the GPSDOs and comparisons between the > various ones have been comparing stability. How about accuracy compared with > the national frequency standard? > Are stability and accuracy the same? Stability to E-13.5 with the > Thunderbolt. How close to > perfect time and frequency?............ Thanks...Dick W5UFZ FMT-nut > > > > > > _______________________________________________ > 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.