Hi, On 2020-02-29 23:10, Taka Kamiya via time-nuts wrote: > One question for Magnus. > > Ch A start - pps (standard)Ch B stop - DUT > On item 4, you said "frequency of the signal on time B". That much is > obvious. But then you said: "give it the time-base of the period on the > A-channel". Will you explain this? > Say I give 1 Hz, period is 1s. Say I give 10Hz, period is 0.1s. Is this > what you mean? Yes. Exactly. > I'm using HP5370A. This instruction is valid on this TI counter, correct?? Yes. It will work. > > A request for everyone: > I am conducting an one hour measurement on HP105B. Does anyone have 1 hour > plot of this signal generator handy? If so, will you DM me a copy? For some > reason, I cannot find one on the great Internet.
I have one of the 00105 oscillator ,as mounted and free-running in a HP5065A, against hydrogen maser at hand. I can locate that and send you if you wish. It's longer than 1 hour, but you get additional precision from this. Cheers, Magnus > > ------------------- clip from Magnus's previous email------------------ > A setup I use a lot is this: > 1) Connect a reference oscillator to produce a 1 Hz or 10 Hz signal and > feed into a counter Channel A/TI-start channel. For PPS signals, I make > sure to trigger a but up on the rising edge not to false-trigger. For > some counters this means turning of automatic trigger and set it to 1 V > manually. It is important that no false triggers occurs. > > 2) Connect a signal under test to Channel B/TI-stop. Adjust trigger to > through-zero or up on the edge as suitable. > > 3) TI-mode, continuous trigger > > 4) Collect data in TimeLab, give TimeLab the frequency of the signal on > B-channel, give it the time-base of the period on the A-channel. > > 5) Look at data as it comes in. Look at phase view, frequency view, > wrapped phase. Look at the ADEV, how the upper end flaps with data, but > how the same tau becomes more and more stable as it comes > in.--------------------- > --------------------------------------- > (Mr.) Taka Kamiya > KB4EMF / ex JF2DKG > > > On Friday, February 21, 2020, 9:26:47 PM EST, Magnus Danielson via > time-nuts <time-nuts@lists.febo.com> wrote: > > Hi Taka, > > On 2020-02-21 23:26, Taka Kamiya via time-nuts wrote: >> I'm sorry, I messed up. I jumped on more advance topic than I intended. >> I'm sure there were answers in the replies but they must have gone way over >> my head because some of original questions still remain. I bulletized (is >> that a word?) the original question with my NEW understanding. Would >> someone please respond for me, point-to-point? > No problem. No worries. I hope you end up reading these and the other > replies again and acquire good knowledge. I know it's like drinking from > a fire-hoze, but you did ask some very relevant and fair questions. >> 1) A frequency counter that measures DUT basically puts out a reading every >> second during the measurement. When TimeLab is well into 1000s or so, it is >> still reading every second; it does not change the gate time to say, 1000s. >> I understand now, Adev is about phase, not the frequency. But assuming DUT >> is sine wave, if there is enough phase change, frequency do change. I think >> of phase change as frequency change that is less than full cycle. So how >> does counters that outputs every 1 second end up in tau of 1000s? It will >> entirely miss phase change that spans more than 1 cycle. > ADEV is about the frequency stability. ADEV can be calculated using > phase or frequency measures. We tend to prefer using phase measures from > Time-Interval Counters for these things. > > OK, so let's say that we want to output a counter which provides output > of frequency estimates but for a time-base which is longer than 1 s, > even if we output results every 1 s? > > Classically counters could not do that. You acquired a start-value, > waited the time-base, acquired a stop-value, calculated a result to > display and then arm to get a new start-value for the next result. Such > counters will have a limit that the rate of readings will be limited by > the time-base, so if it is set to 10 s, only every 10 s and output is > produced. > > To tackle this, one needs a counter that can interleave frequency > measurements, so that it generates new start-points at the update rate > even if the stop-point has not occurred. So, for a time-base of 10 s and > an update rate of 1 s, then every 1 s a new start-trigger is produced, > and then remembered until a stop trigger can be produced, at which time > the start-trigger 10 s back is used to estimate the frequency. In fact, > for this to work, the stop trigger time-stamp is also the start trigger > time-stamp for a new measurement. You can do this with any time-base > really, and the degree of interleaving only depends on the number of > start-points one can keep in memory. > >> 2) I recall reading on TICC manual, in time interval mode, anything that's >> reasonably good is good enough, because it has time stamp and the count >> reading. Clock is used to chunk the data. Is this still true? Through >> this discussion, I ended up with conclusion that there is no inherent >> advantage over TI measurement when compared to frequency measurement. Am I >> understanding this correctly? > There is benefits in time-measures over frequency measures when one > monitors long-term properties. Also, as one tries to create a > phase-curve from frequency estimates, any rounding off errors show in an > slope, as there is a tiny average frequency offset from round-offs. Only > really good such setups does not have significant slope. > >> 3) I understand even the BEST counter is only good for Adev nE-12 >> measurement. Then, with my collection of counters, HP53132A (which averages >> tons of short period measurement), 5335A (not enough resolution), HP5370A >> (interval reading is no better than frequency), TICC by TAPR, Do I even >> have a chance of doing any meaningful work? (say work with GPSDO and Rb >> which some of it does reach E-13) Yes, I know now, it is NOT possible to do >> 1 sec Adev but say over 100 seconds? Right now, I don't have any standard >> that has adev that good at 1 sec anyway. > The resolution of your counter tells you about where your 1/tau curve > will cut tau = 1 s, and it goes from there. There is a slight scaling > factor, but if we assume it is 1 for now, it is pretty simple. Your > 5335A has 1 ns single-shot resolution, this gives 1E-9 at 1 s, but 1E-10 > at 10 s, 1E-11 at 100 s and 1E-12 at 1000 s. You see very clearly when > the linear slope ends and "lands" in the noise, at which time the noise > becomes dominant and is giving you the interesting reading. The 5370A is > 20 ps single-shot resolution, giving you a whopping 2E-11 at 1 s, 2E-12 > at 10 s, 2E-13 at 100 s and 2E-14 at 1000 s. It's some serious > improvement. You are more likely to be limited by your oscillators as > ref and under test at 1000 s with that one, than the instrument itself. > >> 4) Would one person who has infinite patience and experience guide me >> through getting one reading done correctly with what I already have? That >> may include email and phone call. (I speak English and Japanese) I don't >> want to lower S/N of this mailing list by doing this here. > I think you have contributed by asking some really good questions. > > A setup I use a lot is this: > > 1) Connect a reference oscillator to produce a 1 Hz or 10 Hz signal and > feed into a counter Channel A/TI-start channel. For PPS signals, I make > sure to trigger a but up on the rising edge not to false-trigger. For > some counters this means turning of automatic trigger and set it to 1 V > manually. It is important that no false triggers occurs. > > 2) Connect a signal under test to Channel B/TI-stop. Adjust trigger to > through-zero or up on the edge as suitable. > > 3) TI-mode, continuous trigger > > 4) Collect data in TimeLab, give TimeLab the frequency of the signal on > B-channel, give it the time-base of the period on the A-channel. > > 5) Look at data as it comes in. Look at phase view, frequency view, > wrapped phase. Look at the ADEV, how the upper end flaps with data, but > how the same tau becomes more and more stable as it comes in. > > Using even old counters this setup have helped a lot for many measures. > It is simple and sturdy for many measures. Remember to save traces, to > annotate it carefully so one can understand afterwards what one did. > > Using this setup, I swapped a HP53132A (150 ps) for a HP5335A (1 ns) and > then PM6853A (2 ns) to show that a particular problem did not needed the > best counter in the house to be well characterized. > >> 5) One time, it was mentioned many of Adev graphs posted are basically a >> graph of instruments noise graph. How do I tell when a given reading/graph >> is exceeding the limit of a setup? I did do base line where same signal >> goes to counter's reference input and signal input. I always have that on >> my chart so traces does not go below. Is that enough? > Almost. It's a good start. The first slope for lower taus is due to the > instrument for sure. If you look carefully you will notice that the > actual performance shifts around, because it is more complex than just > being instrument limit, but it is the right ball-park for that part of > the plots. For the upper end, you can be limited by your device under > test drift. This can be handled by simply letting them be turned on > longer. Sub-sequent measurement will have that rising slope move more > and more towards higher taus and thus becomming less like a limit-issue > for a certain tau. >> I appreciate everyone's input. I am learning a lot but just not digesting >> well enough. I'd like to do DMTD after I understand the basics. > Good spirit. DMTD takes some care, but once you learned it, it can be a > magnificent tool. > > Cheers, > Magnus > >> --------------------------------------- >> (Mr.) Taka Kamiya >> KB4EMF / ex JF2DKG >> >> >> On Thursday, February 20, 2020, 1:41:06 PM EST, Taka Kamiya via >> time-nuts <time-nuts@lists.febo.com> wrote: >> >> I have a question concerning frequency standard and their Allen deviation. >> (to measure Allen Dev in frequency mode using TimeLab) >> >> It is commonly said that for shorter tau measurement, I'd need OCXO because >> it's short tau jitter is superior to just about anything else. Also, it is >> said that for longer tau measurement, I'd need something like Rb or Cs which >> has superior stability over longer term. >> Here's the question part. A frequency counter that measures DUT basically >> puts out a reading every second during the measurement. When TimeLab is >> well into 1000s or so, it is still reading every second; it does not change >> the gate time to say, 1000s. >> That being the case, why this consensus of what time source to use for what >> tau? >> I recall reading on TICC, in time interval mode, anything that's reasonably >> good is good enough. I'm aware TI mode and Freq mode is entirely different, >> but it is the same in fact that measurement is made for very short time span >> AT A TIME. >> I'm still trying to wrap my small head around this. >> >> --------------------------------------- >> (Mr.) Taka Kamiya >> KB4EMF / ex JF2DKG >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
