As already stated here, the best measurement mode is the time-interval mode. The 5335A is a 2ns single-shot resolution counter. Use the PPS output from the GPSDO, route it to the A (start) input and to a coaxial cable used as a delay line (10m, 50ns, should be enough). The other end of the cable into the B input (stop), select the time interval mode TIME A -> B. Let the internal reference clock the counter. Set trigger levels and the various parameter to get stable readings and collect your data.
On Thu, Nov 16, 2017 at 3:59 AM, Mike Garvey <r3m...@verizon.net> wrote: > Could you post some phase plots? The data you show is not 1/tau and very > likely not white phase noise. > Mike > > -----Original Message----- > From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of CubeCentral > Sent: Wednesday, November 15, 2017 11:12 > To: time-nuts@febo.com > Subject: [time-nuts] Interpreting and Understanding Allen Deviation Results > > Greetings, time-nuts! > > After reading [ http://www.leapsecond.com/pages/adev/adev-why.htm ] I felt > that I better understood how an Allan Deviation is calculated and endeavored > to try an experiment. It should be noted that I have a hobbyist-level > understanding of the concepts described and tools used below. If my thinking > or test methodology is incorrect, please let me know so that I might learn > something. > > A GPSDO with a 10MHz output was run into the EXT TIME BASE input on the back > of an HP5335A. > Then, the TIME BASE OUT on the back was run to the A input on the front of > the HP5335A. > My intention was to characterize the performance of the HP5335A counter > itself so that I might understand better future plots involving other GPSDO > and the counter's internal clock (which was bypassed for this test). > > The settings of the HP5335A were as follows: > Gate Mode: Normal > Cycle: Normal > > A Input ------------------------------ > Trigger Adjust: Full left to 'Preset' detent > Z select = in = 50ohm > x10 ATTN = in = x10 ATTN (should have been out/off?) > Slope = out = up > AC = in = AC coupled > COMA = out = Not ComA > AutoTrig = out = Not Auto Tiggered (should have been in/on?) > > (Tangentially, if someone has a good 'primer' or how-to resource detailing > Universal Counter operation, showing when/why/how to set the knobs in certain > situations it would be welcome!) > > I then set the Time Lab V1.29 software to repeatedly acquire data for 12 > hours, starting the next test as soon as I could. This means that, normally, > a test was run during the day for 12 hours, and then overnight for > 12 hours. > > The results are shown here: [ https://i.imgur.com/0sMVMfk.png ] The > associated .TIM files are available upon request. > > So, now we get to the heart of the matter and the questions this test and > results have raised. > I am trying to understand what the data is telling me about the test, and > therefore the character of the counter. > > 1) Why are the plots a straight line from ~0.25s until ~100s? > 2) Why, after falling at the start, do the plots all seem to go back up from > ~100s to ~1000s? > 3) What do the "peaks" mean, after the plot has fallen and begin to rise > again? > 4) Why is the period from ~1000s to ~10000s so chaotic? > 5) The pattern "Fall to a minimum point, then rise to a peak, then fall > again" seems to be prevalent. What does that indicate? > 6) Why does that pattern in question (5) seem to repeat sometimes? What is > that showing me? > > And finally, some general questions about looking at these plots. > a) Would a "perfect" plot be a straight line falling from left to right? > (Meaning a hypothetical "ideal" source with perfect timing?) > b) Is there some example showing plots from two different sources that then > describes why one source is better than the other (based upon the ADEV plot)? > c) I believe that if I understood the math better, these types of plots > would be more telling. Without having to dive back into my college Calculus > or Statistics books, is there a good resource for me to be able to understand > this better? > > Lastly, thank you for your patience and for keeping this brain-trust alive. > I am quite grateful for all the time and energy members pour into this list. > The archives have been a good source of learning material. > > -Randal (at CubeCentral Labs...) > > > > > > > > > > > > > > > > > _______________________________________________ > 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. _______________________________________________ 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.
