HI Yes, at 1 second vs 10 seconds the data suggests that the counter is the limit. Unfortunately you can’t make a judgement between 10 an 100 seconds. Certainly at 100 seconds and beyond, the counter is doing just fine.
Bottom line: This is why people mess with single and dual mixer setups or SDR like gizmos. Bob > On Jun 3, 2016, at 3:07 AM, Nick Sayer <[email protected]> wrote: > > So what’s going on is that the TIA is “Mr. Magoo” and isn’t seeing > sufficiently well to evaluate these oscillators? > > I can believe that. > > I might just have to stop there, then. I can’t justify an upgrade today. > >> On Jun 2, 2016, at 7:24 PM, Bob Camp <[email protected]> wrote: >> >> Hi >> >> If the counter is the limiting factor, it should scale by 10 as the timebase >> scales by 10. Your data goes from >> 90 ppt at 1 second to 9 ppt at 10 seconds. That is the expected outcome. >> >> Bob >> >> >>> On Jun 2, 2016, at 8:57 PM, Nick Sayer via time-nuts <[email protected]> >>> wrote: >>> >>> Oh, the limitation is on the TimeLab side? I was blaming the TIA. :) >>> >>> Since then, I have found an advanced gate setting that appears to add 500 >>> ms after start. The time intervals seem to be without that delay, so it >>> works. The resulting ADEV is unchanged (other than obviously truncated at >>> low tau and having a longer duration). >>> >>> Looking at the phase and frequency data, I don't see anything wrong. The >>> ADEV plot is linear, and it arrives to the spec at around tau 10s or so... >>> It's just way steeper than I expect. An order of magnitude north of spec at >>> tau 1s. >>> >>> The only thing I can think of is that it's compounding the error because >>> I'm comparing two (of the same) oscillators to each other, but my >>> understanding is that I can only attempt to compensate for that by scaling >>> by sqrt(2). >>> >>> Sent from my iPhone >>> >>>> On Jun 2, 2016, at 11:12 AM, John Miles <[email protected]> wrote: >>>> >>>> One workaround for the 1-million point limitation on imported data is to >>>> use "Acquire->Acquire from live ASCII file" instead of "File->Import ASCII >>>> phase/frequency data." Most of the same code is used for both cases, but >>>> unlike the static file-import version of the dialog, the live data >>>> importer will let you specify the expected duration yourself. So you can >>>> give it a duration value that you know will be long enough to cover the >>>> whole data set. >>>> >>>> I'm not too familiar with the 532x0A counters myself, but 8.9E-11 at t=1s >>>> doesn't sound too unrealistic. When in doubt, look at the 'f'requency >>>> and/or 'p'hase trends and residuals to sanity-check your data, rather than >>>> trying to puzzle out what's going wrong with the ADEV plot as many users >>>> seem to do. First you should satisfy yourself that the data makes sense, >>>> is unwrapped and scaled properly, and doesn't contain glitches, large >>>> crystal jumps, obvious beatnotes or other interference, or unexpected >>>> amounts of drift. >>>> >>>> -- john, KE5FX >>>> Miles Design LLC >>>> >>>>> I’ve gotten a little further with this. If I capture 60 seconds worth of >>>>> time >>>>> interval measurements (between two FE-5680As that are GPS disciplined, but >>>>> with a long enough time constant that they’re basically free-running), I >>>>> get >>>>> 60,000 of them. So I imported at a sample interval of 1e-3 and got the >>>>> right >>>>> duration. There are a couple of problems, however. 1 is that even if I >>>>> attempt to >>>>> log to a USB stick, it appears I can only log 1e6 samples before it >>>>> stops. That’s >>>>> 16:40 or so, which isn’t very long. I haven’t figured out how to change >>>>> the >>>>> sample gate for time intervals (I’m assuming that a million samples is a >>>>> hard >>>>> limit). Also, importing the interval samples into TimeLab still shows me >>>>> a graph >>>>> that’s still much steeper than I would expect. The graph is linear, with >>>>> points at >>>>> tau 1s = 8.9E-11, 10s = 9.47E-12, 100s = 1.5E-12 (by then, the ADEV graph >>>>> is >>>>> starting to flatten out a bit, which probably indicates the noise floor >>>>> of the >>>>> 53220A near 1E-12), but the FEI datasheet shows a spec with points more >>>>> like >>>>> tau 1s = 1.5E-11, 10s = 4.5E-12 and 100s = 1.5E-12. >>>> >>>> _______________________________________________ >>>> 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.
