I meant ideal at the noise floor of the picPET (i.e in this case the generated 60Hz).
On Mon, Nov 18, 2013 at 8:08 PM, Bob Camp <li...@rtty.us> wrote: > Hi > > An “ideal” curve would go to the bottom of the scale as soon as the plot > started. Anything that shows on the ADEV curve is by definition noise. The > slope of the ADEV curve can help you determine what sort of noise it is. > The slope(s) on an modified ADEV curve can do that slightly better. > > Bob > > On Nov 18, 2013, at 8:03 PM, Bill Dailey <docdai...@gmail.com> wrote: > > > tom, > > > > nice plots. how do you figure out what the contribution of variability > vs > > noise? In other words there is a differential between the "ideal" and the > > actual a dev curves... is there a way to tease out how much nose > contribute > > to that differential? It does seem to me that there should be far less > > short term variability (< 100s) than there appears to be. Clearly in the > > very short tau (< 0.1 s) the picPET can't tease that out but as the > curves > > diverge, how much of that is noise? between say 0.1s and 100s? Being a > > power plant operator I would say quite a bit although I am rethinking > that > > some due to the way the turbines push and pull each other. I can > envision > > some fine whole grid oscillations due to that push and pull. > > > > bill > > > > > > On Mon, Nov 18, 2013 at 4:15 PM, Tom Van Baak <t...@leapsecond.com> > wrote: > > > >> Magnus, > >> > >> I'm going to push back a bit on your mains sampling claim. Mostly, I'd > >> like to see the results of the professional I-Q demodulated gear that > you > >> mentioned. Can you post raw data, or a sample plot? > >> > >> I agree that looking at power line voltage with 16- or 24-bits at 1 Msps > >> is going to reveal interesting amplitude and phase noise information. > But > >> see how well a $1 PIC can do. > >> > >> Attached is a plot made using TimeLab + picPET just now. The picPET is > >> fast enough to capture the zero-crossing of every 60 Hz cycle with 400 > ns > >> resolution; the TimeLab plots have tau0 of 16.67 ms. > >> > >> -- The blue trace was simply plugging a 9 VAC wall-wart into the picPET > >> though a 10k resistor. > >> -- The pink trace was adding a 10 nF cap across the input. > >> -- The green trace was unplugging my laptop switching power supply from > >> the same outlet! > >> -- The red trace is replacing the mains wall-wart with a hp 33120A set > to > >> 9VAC at 60 Hz, a tentative noise floor measurement of the picPET when > used > >> this way. > >> > >> My conclusions are that at least here in the US, or at least at my > house, > >> the short-term stability of mains hits about 5e-6, at about tau 0.2 > >> seconds. The attached short-term plot is also not-inconsistent with the > >> long-term plot at http://leapsecond.com/pages/mains/ > >> > >> My other conclusion is that the picPET (a simple PIC-based time-stamping > >> counter) is doing a pretty good job measuring this. Note, no software or > >> data filtering was used. This is just raw serial/USB data going into > >> TimeLab. > >> > >> /tvb > >> > >> _______________________________________________ > >> 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. > >> > > > > > > > > -- > > Doc > > > > Bill Dailey > > KXØO > > _______________________________________________ > > 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. > -- Doc Bill Dailey KXØO _______________________________________________ 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.