David Woolley <[EMAIL PROTECTED]> writes: >Unruh wrote: >> David Woolley <[EMAIL PROTECTED]> writes:
>> >> Not sure what you mean. Do you mean that chrony averages out the offsets, >> so that the actual estimated offset of the clock is less than the offsets >> measured because of statistical averaging, then yes. >> >Yes. And that would be true of any algorithm that was well matched to >the noise characteristics. >> >> Temperature causes true changes in the clock rate. >Exactly. And to that extent, projecting the new clock rate back to >adjust the apparent historic offsets is wrong. Which is why chrony tests its fit to see whether or not a linear fit to the data is a good statistical fit or not. (It tests the number of times that the data changes sign around the fit and if it does not do so often enough, assumes that a straight line is not a good fit, and reduces the number of historic points it saves. Ie, if a linear drift is not a good fit to the data, it assumes that the changes in drift are more important source of error than the random measurement/transmission noise and adjusts the fit model. Effectively it is constantly trying to figure out where the minimum allan variance lies where random offset noise and drift noise are of equal size. ) _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
