Re: [time-nuts] TimeLab phase difference (slope sec/sec)
Hi If the data is GPS referenced it is not at all uncommon to see a roughly 24 hour pattern in the data. Ionospheric changes are one significant contributor. The further down into the mud you get, the more other things pop up (multipath repeating with the same constalation ….) Bob > On Jul 3, 2019, at 1:44 PM, Chris Burford wrote: > > Hello David, > > It could quite possibly be tempco induced. I have this on my schedule of > future events for additional analysis. > > Thanks, > > Chris > >> >> Chris, >> >> Just looking at the graph reminds me of a daily variation - perhaps due to >> temperature. Is that likely? Would a two-day graph be worth doing in this >> particular case? >> >> Cheers, >> David > > ___ > 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.
Re: [time-nuts] TimeLab phase difference (slope sec/sec)
Hello David, It could quite possibly be tempco induced. I have this on my schedule of future events for additional analysis. Thanks, Chris Chris, Just looking at the graph reminds me of a daily variation - perhaps due to temperature. Is that likely? Would a two-day graph be worth doing in this particular case? Cheers, David ___ 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.
Re: [time-nuts] TimeLab phase difference (slope sec/sec)
Hi Dana, My PRS10 is the DUT that has its 1PPS(Out) wired into the TICC on ChA. The reference is my GPSDO which has a 8663-XS DOCXO and has its 1PPS(Out) wired into the TICC on ChB. The 10 MHz clock signal for the TICC comes from my GPSDO also, which as I understand, need not be quite so precise when measuring in time interval mode. Chris On 07/03/19 04:01:38, Dana Whitlow wrote: Chris, Ok, one source is a PRS-10. Is it the DUT or the reference? And if it's the DUT, what is the reference source? Dana On Tue, Jul 2, 2019 at 8:00 PM Chris Burford wrote: Hi Bob, I'm seeing 4.22E-12 as the slope value in the upper right of the TimeLab phase difference plot. Is that telling me that my DUT is within +4.22ps / sec from my reference 1PPS for the 24 hour measurement duration? I have attached a screen capture that will hopefully make its way through for viewing. Thanks, Chris On 07/02/19 11:50:10, Bob kb8tq wrote: Hi The difference in seconds between the start phase and the end phase divided by the number of seconds duration gives you the parts in whatever of the error. If you see 1us ( = 1x10^-6 seconds) of change in a second, you are off by 1 ppm (or 1x10^-6). If you see 1 us of change in 1,000 seconds you are off by 1 ppb (or 1x10^-9). At a bit over 10 days (1,000,000 seconds) your 1 us change is 1 ppt (or 1x10^-12). Bob On Jul 2, 2019, at 10:17 AM, Chris Burford wrote: Is the slope value for the phase difference shown in TimeLab an average of the overall data sample duration? The reason I ask is that my service manual for my RFS says: /"//A faster way to make the comparison between the reference frequency and the DUT is to use the time interval measurement mode of the counters. In this case, the time intervals between the 10MHz zero crossings of the reference frequency and the DUT are measured and averaged. If this time interval changes by less than 10ps per second, then the DUT is within 1 part in //10^11 of the frequency reference."/ I'm just curious if the phase difference slope value can be plugged in to this equation. Regards, Chris ___ time-nuts mailing list --time-nuts@lists.febo.com To unsubscribe, go tohttp:// 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 tohttp:// 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 tohttp://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.
Re: [time-nuts] TimeLab phase difference (slope sec/sec)
> I'm just curious if the phase difference slope value can be plugged in to this equation. > I'm seeing 4.22E-12 as the slope value in the upper right of the > TimeLab phase difference plot. Is that telling me that my DUT is > within +4.22ps / sec from my reference 1PPS for the 24 hour > measurement duration? > > I have attached a screen capture that will hopefully make its way > through for viewing. Chris, The answer is yes. But let's consider why instead of plugging numbers into equations. Your measurements are not that different from comparing two wrist watches. Since two watches never actually run at the same rate you know that on average one is fast and one is slow, relative to each other. We often measure clock or oscillator rate using a unit-less number like percent. Your left watch may be 0.01% faster than your right watch. Or maybe it's 15 ppm slower, or 50 ppb faster. These are all dimensionless numbers; ratios. So when we talk about an oscillator being 4.22E-12 fast it's just 4.22 ppt, or 0.0004 or 0.0422%. You get the idea. So where does the 4.22 ps/s thing come from? Well, it turns out that the way that we measure two clocks is not to directly compare their frequency. You can't tell with a glance at two wristwatches which is fast and which is slow. Sure, one may be ahead and one may be behind. But that is the time (phase) of the clocks; not their rate. The best way to find out which clock is fast or slow is to compare their times *over a long time*. Eventually a *trend* will be evident. You might have to wait an hour before one watch gets a second ahead of the other. This is where the "second/second" thing comes in. If a watch is fast by 1 second an hour then it must be running 1s/3600s = 0.028% = 278 ppm faster. Note how both the units of the amount of time gain (1 s) and the amount of time spent doing the measurement (3600 s) cancel and you're left with a dimensionless number. In general a frequency difference measurement is just a phase (aka time) difference measurement made over some elapsed time (aka measurement duration). So you are using a TAPR/TICC to measure the phase difference between your two clocks. It appears you ran it for an entire day (1 d = 86400 s) and the net change in phase between the two clocks was 382 ns. That means the frequency difference between the two clocks is 382 ns / 86400 s = 382e-9 / 86400 = 4.22e-012. The reason this wasn't obvious is that you had the TimeLab 'r' (residual) command in effect. In a sense, this removes the very slope you're trying to see. If you undo the 'r' you should see one clock gradually gaining time relative to the other. The advantage of the 'r' command is that it shows you "what's left" if the two clocks were running at the same rate; it shows the wander, the short- and mid-term noise between the two. And TimeLab also reports the now-removed slope in the upper corner. Now back to 4.22 ps/s. It is true that 4.22e-12 is equal to 4.22 ps/s. Mathematically, it is also equal to 382 ns/d, or 133 us/year for that matter. Yet, it may be misleading to claim 133 us/year because the word "year" may be interpreted as how long the measurement was. But it wasn't a year-long experiment, not even close. Similarly, claiming the clock is 4.22 ps/s may imply to the reader that both the DUT and the REF and the TICC are all clean signals at the sub-ps level. But they aren't, not even close. To complete the picture you need both the frequency difference value and the duration over which the measurement was made. So that's why you often see frequency differences reported using scientific notation, as in 4.22e-12, rather than ps/s or ns/d or us/y. /tvb ___ 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.
Re: [time-nuts] TimeLab phase difference (slope sec/sec)
Chris, Ok, one source is a PRS-10. Is it the DUT or the reference? And if it's the DUT, what is the reference source? Dana On Tue, Jul 2, 2019 at 8:00 PM Chris Burford wrote: > Hi Bob, > > I'm seeing 4.22E-12 as the slope value in the upper right of the TimeLab > phase difference plot. Is that telling me that my DUT is within +4.22ps > / sec from my reference 1PPS for the 24 hour measurement duration? > > I have attached a screen capture that will hopefully make its way > through for viewing. > > Thanks, > > Chris > > On 07/02/19 11:50:10, Bob kb8tq wrote: > > Hi > > > > The difference in seconds between the start phase and the end phase > divided by the number > > of seconds duration gives you the parts in whatever of the error. > > > > If you see 1us ( = 1x10^-6 seconds) of change in a second, you are off > by 1 ppm (or 1x10^-6). > > If you see 1 us of change in 1,000 seconds you are off by 1 ppb (or > 1x10^-9). At a bit over 10 > > days (1,000,000 seconds) your 1 us change is 1 ppt (or 1x10^-12). > > > > Bob > > > >> On Jul 2, 2019, at 10:17 AM, Chris Burford > wrote: > >> > >> Is the slope value for the phase difference shown in TimeLab an average > of the overall data sample duration? The reason I ask is that my service > manual for my RFS says: > >> > >> /"//A faster way to make the comparison between the reference frequency > and the DUT is to use the time interval measurement mode of the counters. > In this case, the time intervals between the 10MHz zero crossings of the > reference frequency and the DUT are measured and averaged. If this time > interval changes by less than 10ps per second, then the DUT is within 1 > part in //10^11 of the frequency reference."/ > >> > >> I'm just curious if the phase difference slope value can be plugged in > to this equation. > >> > >> Regards, > >> > >> Chris > >> > >> > >> ___ > >> time-nuts mailing list --time-nuts@lists.febo.com > >> To unsubscribe, go tohttp:// > 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 tohttp:// > 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.
Re: [time-nuts] TimeLab phase difference (slope sec/sec)
Hi Bob, I'm seeing 4.22E-12 as the slope value in the upper right of the TimeLab phase difference plot. Is that telling me that my DUT is within +4.22ps / sec from my reference 1PPS for the 24 hour measurement duration? I have attached a screen capture that will hopefully make its way through for viewing. Thanks, Chris == Chris, Just looking at the graph reminds me of a daily variation - perhaps due to temperature. Is that likely? Would a two-day graph be worth doing in this particular case? Cheers, David -- SatSignal Software - Quality software for you Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk Twitter: @gm8arv ___ 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.
Re: [time-nuts] TimeLab phase difference (slope sec/sec)
Hi Bob, I'm seeing 4.22E-12 as the slope value in the upper right of the TimeLab phase difference plot. Is that telling me that my DUT is within +4.22ps / sec from my reference 1PPS for the 24 hour measurement duration? I have attached a screen capture that will hopefully make its way through for viewing. Thanks, Chris On 07/02/19 11:50:10, Bob kb8tq wrote: Hi The difference in seconds between the start phase and the end phase divided by the number of seconds duration gives you the parts in whatever of the error. If you see 1us ( = 1x10^-6 seconds) of change in a second, you are off by 1 ppm (or 1x10^-6). If you see 1 us of change in 1,000 seconds you are off by 1 ppb (or 1x10^-9). At a bit over 10 days (1,000,000 seconds) your 1 us change is 1 ppt (or 1x10^-12). Bob On Jul 2, 2019, at 10:17 AM, Chris Burford wrote: Is the slope value for the phase difference shown in TimeLab an average of the overall data sample duration? The reason I ask is that my service manual for my RFS says: /"//A faster way to make the comparison between the reference frequency and the DUT is to use the time interval measurement mode of the counters. In this case, the time intervals between the 10MHz zero crossings of the reference frequency and the DUT are measured and averaged. If this time interval changes by less than 10ps per second, then the DUT is within 1 part in //10^11 of the frequency reference."/ I'm just curious if the phase difference slope value can be plugged in to this equation. Regards, Chris ___ time-nuts mailing list --time-nuts@lists.febo.com To unsubscribe, go tohttp://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 tohttp://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.
Re: [time-nuts] TimeLab phase difference (slope sec/sec)
Hi The gotcha is that if the duration gets long enough, the numbers on a GPSDO will get silly small. You very much have to decide what time duration is appropriate to your system / application. If you always run your frequency counter on a 1 or 10 second gate …. you really don’t care about 10,000 seconds. Bob > On Jul 2, 2019, at 7:15 PM, Chris Burford wrote: > > Hi Bob, > > I'm seeing 4.22E-12 as the slope value in the upper right of the TimeLab > phase difference plot. Is that telling me that my DUT is within +4.22ps / sec > from my reference 1PPS for the 24 hour measurement duration? > > I have attached a screen capture that will hopefully make its way through for > viewing. > > Thanks, > > Chris > > On 07/02/19 11:50:10, Bob kb8tq wrote: >> Hi >> >> The difference in seconds between the start phase and the end phase divided >> by the number >> of seconds duration gives you the parts in whatever of the error. >> >> If you see 1us ( = 1x10^-6 seconds) of change in a second, you are off by 1 >> ppm (or 1x10^-6). >> If you see 1 us of change in 1,000 seconds you are off by 1 ppb (or >> 1x10^-9). At a bit over 10 >> days (1,000,000 seconds) your 1 us change is 1 ppt (or 1x10^-12). >> >> Bob >> >>> On Jul 2, 2019, at 10:17 AM, Chris Burford wrote: >>> >>> Is the slope value for the phase difference shown in TimeLab an average of >>> the overall data sample duration? The reason I ask is that my service >>> manual for my RFS says: >>> >>> /"//A faster way to make the comparison between the reference frequency and >>> the DUT is to use the time interval measurement mode of the counters. In >>> this case, the time intervals between the 10MHz zero crossings of the >>> reference frequency and the DUT are measured and averaged. If this time >>> interval changes by less than 10ps per second, then the DUT is within 1 >>> part in //10^11 of the frequency reference."/ >>> >>> I'm just curious if the phase difference slope value can be plugged in to >>> this equation. >>> >>> Regards, >>> >>> Chris >>> >>> >>> ___ >>> time-nuts mailing list --time-nuts@lists.febo.com >>> To unsubscribe, go >>> tohttp://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 >> tohttp://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.
Re: [time-nuts] TimeLab phase difference (slope sec/sec)
Hi The difference in seconds between the start phase and the end phase divided by the number of seconds duration gives you the parts in whatever of the error. If you see 1us ( = 1x10^-6 seconds) of change in a second, you are off by 1 ppm (or 1x10^-6). If you see 1 us of change in 1,000 seconds you are off by 1 ppb (or 1x10^-9). At a bit over 10 days (1,000,000 seconds) your 1 us change is 1 ppt (or 1x10^-12). Bob > On Jul 2, 2019, at 10:17 AM, Chris Burford wrote: > > Is the slope value for the phase difference shown in TimeLab an average of > the overall data sample duration? The reason I ask is that my service manual > for my RFS says: > > /"//A faster way to make the comparison between the reference frequency and > the DUT is to use the time interval measurement mode of the counters. In this > case, the time intervals between the 10MHz zero crossings of the reference > frequency and the DUT are measured and averaged. If this time interval > changes by less than 10ps per second, then the DUT is within 1 part in > //10^11 of the frequency reference."/ > > I'm just curious if the phase difference slope value can be plugged in to > this equation. > > Regards, > > Chris > > > ___ > 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] TimeLab phase difference (slope sec/sec)
Is the slope value for the phase difference shown in TimeLab an average of the overall data sample duration? The reason I ask is that my service manual for my RFS says: /"//A faster way to make the comparison between the reference frequency and the DUT is to use the time interval measurement mode of the counters. In this case, the time intervals between the 10MHz zero crossings of the reference frequency and the DUT are measured and averaged. If this time interval changes by less than 10ps per second, then the DUT is within 1 part in //10^11 of the frequency reference."/ I'm just curious if the phase difference slope value can be plugged in to this equation. Regards, Chris ___ 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.
