Hi Now that it is “free for all”, Stable-32 is another good program to run your data past. It will do nice plots and a *lot* of different statistics.
Bob > On Apr 25, 2018, at 7:01 AM, Tom Van Baak <[email protected]> wrote: > > Hi Gary, > >> A little coding later and there are nice plots. They were compared to >> the output of tvb's adev.c program. Results are similar. > > Whoa there cowboy. That doesn't mean it's right. Comments: > >> gps.png looks as expected. > > 1. No, it would appear something is wrong with your data. You show the ADEV > for tau 1 s to be about 1e-2. That seems off by a factor of a million. It's > probably not your reference, or your TICC, or the NEO-M8M, but something in > how you are scaling the data? or glitches in your data? Hard to say without > more info. > > 2. The artifacts at the end of the traces are weird. That's either too small > a statistics sample or you have one or more bad data points that are ruining > your data set. > > 3. It's best not to show ADEV or MDEV on the same plot as TDEV. They are > different concepts and have different units. Also use ADEV as a label not > OADEV. > > 4. At this stage of being a time-nut, it's best not make canned ADEV plots > without first making phase and frequency plots. ADEV is just a statistic and > you can feed it garbage and it will still happily compute numbers. By > plotting phase (or phase residuals) and frequency (or relative frequency > error) your eye can catch most of the bugs that occur to first-time ADEV'ers. > Creating phase and frequency plots also makes you aware of the units, scale, > and magnitude of your data, something you can use as a sanity check. > > 5. Since you are using batch tools instead of interactive tools, I suggest > showing the first few and last few raw data lines from the TICC. Also the > first and last few lines of the data that you input to your ADEV calculation. > Or just post the raw data. This is helpful to debug bad plots like this. > >> GPSTLXO.png shows the quality of the JL part, > > 1. Hmm, that just looks like some self-test data. I'm suspicious when I see > 1e-17 MDEV numbers. Something's not right. The TICC is nice, but not that > good. > > 2. Wait, you're using the JL 10 MHz as the TICC reference and then you're > measuring the JL 1PPS with the TICC? So that's not really a measurement of > the "quality of the JL part"; it's more just a self-test of a TICC channel. > > 3. Once you get correct-looking ADEV plots for NEO-M8M and JL then we can > talk about what effect (if any) using Rb as a TICC reference will have. > Remember that for time interval measurements the quality of the reference is > not that important. > > > I strongly, pretty please, strongly advise you to use TimeLab for a while > before you roll your own tools and plots. That is, "learn to drive before you > design your own car". I know you have a grumpy old man aversion to using > Windows, but lots of people on the list seem to run TimeLab easily on their > non-Windows systems. > > If nothing else, at least look at what TimeLab does. The PDF user manual is a > superb tutorial on working with time & frequency data. > > Anyway, a good start to your NTP measurement project. Thanks for posting. > > /tvb > > > ----- Original Message ----- > From: "Gary E. Miller" <[email protected]> > To: "time-nuts" <[email protected]> > Sent: Tuesday, April 24, 2018 8:45 PM > Subject: Re: [time-nuts] Cheap jitter measurements > > > Time-nuts! > > I went ahead and bought the TAPR-TICC, it is a very impressive > instrument. For this setup it is combined with a Jackson Labs > GPSTLXO as the 10MHz reference. The JL is a GPS disciplined temperature > compensated crystal oscillator. > > The first setup uses the TAPR-TICC in Period mode, outputting the PPS > period individually for channel A and channel B. > > Channel A is the PPS of a plain u-blox NEO-M8N. Channel B is the > PPS of the JL GPSTLXO. > > Simple to get the cycle times from the USB serial port. > > Then I grabbed a copy of the easy to use Python Allantools. > https://github.com/aewallin/allantools > > A little coding later and there are nice plots. They were compared to > the output of tvb's adev.c program. Results are similar. > > Results are attached. gps.png is the plain NEO-M8N. GPSTLXO is the > JL part. > > gps.png looks as expected. GPSTLXO.png shows the quality of the JL part, > but does have some odd divots in the plot. Maybe artifacts of using the > PPS derived from the reference 10MHz? Or an artifact of the 10e6 divider? > > There are adev's of Rb standards here: http://www.ke5fx.com/rb.htm > > My guess is that the oadev at 1s would be about 50x better with > a Rubidium? But similar at 10k seconds? > > Comments? > > RGDS > GARY > --------------------------------------------------------------------------- > Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703 > [email protected] Tel:+1 541 382 8588 > > Veritas liberabit vos. -- Quid est veritas? > "If you can’t measure it, you can’t improve it." - Lord Kelvin > > > > -------------------------------------------------------------------------------- > > >> _______________________________________________ >> 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. _______________________________________________ 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.
