Kyle, I suggest that you contact David Allan directly, via his website, with this question. Going to the source is most likely to produce a useful answer.
Pete Rawson On Apr 22, 2010, at 3:07 PM, Kyle Wesson wrote: > Hello, > > I am working to determine the Allan variance of an individual > oscillator from a series of three paired measurements as described in > the paper by Gray and Allan "A Method for Estimating the Frequency > Stability of An Individual Oscillator" (NIST, 1974, > tf.nist.gov/general/pdf/57.pdf). In this report they make reference to > the statistical uncertainty of the measurement due to ensemble noise > and potential clock phase correlation which can potentially make the > Allan variance for an individual oscillator have a negative value. > They write: > > "If the noise level of the oscillator being measured is low enough, > and the scatter high enough, equation (4) may occasionally give a > negative value for the variance." > > My question is: how should I treat negative variance values in this > case? For example, if my data set were to produce an individual > oscillator Allan variance with a value of -5e-12, should I convert > this value to 0 (ie. the closest valid sigma value to the number since > 0 <= sigma < inf ), take the absolute value of the result (ie. turn > -5e-12 to +5e-12), or drop the result from my estimate of individual > oscillator frequency stability altogether? > > Is there another method that will produce estimates of individual > oscillators from an ensemble approach but assures non-negative output > variances? > > Thank you in advance, > Kyle > > _______________________________________________ > 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.
