Hi, If you have a 1PPS the nominal rate is exactly 1 Hz. If your PRS-10 runs at +750 ns on every pulse then it has a frequency offset of 750E-9=7.5E-7 from the nominal frequency. You can expect jitter and wander on the PPS, as deviations from the frequency it has.
Cheers, Magnus <div>-------- Originalmeddelande --------</div><div>Från: mike cook <michael.c...@sfr.fr> </div><div>Datum:29-06-2014 09:58 (GMT+01:00) </div><div>Till: Discussion of precise time and frequency measurement <time-nuts@febo.com> </div><div>Rubrik: Re: [time-nuts] wander and jitter measurements </div><div> </div>Thanks for your responses and the links. My DQ3, Can I deduce offset from jitter comes from the following and while Bill's response was a succinct NO, I am still wondering. Maybe it's my interpretation of "nominal" and "ideal". Here is scenario : I have a 1PPS which is offset from a reference (PRS10 in this instance) by +750ns . If I take the wander about the "ideal" as per G.810 , it is systematically +ve by that figure, + or - some ps , so the offset is shown in these figures. However, if I take the DUT's signal as being "nominal" as per Magnus's statement, ie using the DUT's signal as reference, then of course I cannot see the offset. Mike Le 29 juin 2014 à 02:02, Magnus Danielson a écrit : > Mike, > > A frequency offset is just a long term shift from nominal rate. > > Wander is "slow" variations and jitter is "fast" variations of phase. > The separation between "slow" and "fast" is a bit arbitrary, but the 10 Hz > division-line is handy as it describes different sources, where wander is the > in-bandwidth noise accumulation where as jitter is usually damped pretty well > by being outside of the jitter bandwidth. > > See ITU-T G.810, G.813, G.823-825. > > Cheers, > Magnus > > On 06/27/2014 07:37 PM, bill wrote: >> On 6/26/2014 2:39 AM, mike cook wrote: >>> A few dumb questions: >>> >>> But first a quote from the ITU ( doc G.180 ) >>> >>> ""4.1.12 (timing) jitter: The short-term variations of the significant >>> instants of a timing signal from >>> their ideal positions in time (where short-term implies that these >>> variations are of frequency greater >>> than or equal to 10 Hz). >>> >> DQ1 yes >> >> DQ2 Frequency offset would come into the Wander category except it >> defined differently. >> >> DQ3 No >> >> >> That gives my take on your q questions. Its been 23 years since I had >> think about jitter and wander as chairman of T1X1.3 committee >> >> Bill >> K7NOM >>> 4.1.15 wander: The long-term variations of the significant instants of >>> a digital signal from their >>> ideal position in time (where long-term implies that these variations >>> are of frequency less than >>> 10 Hz). >>> NOTE – For the purposes of this Recommendation and related >>> Recommendations, this definition does >>> not include wander caused by frequency offsets and drifts."" >>> >>> DQ1. These both refer to phase variations, so with the exception of >>> the frequency range specified, are they mathematically equivalent? >>> >>> DQ2. The note on wander excludes frequency offsets, but that is not >>> specified for jitter, so do I have to include a frequency offset in >>> jitter measurements? It seems to me that it make no sense to do so. >>> >>> DQ3. Can I deduce an underlying frequency offset from jitter (wander) >>> by taking an RMS value over some window of values? >>> >>> >>> regards, >>> Mike >>> >>> _______________________________________________ >>> 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. _______________________________________________ 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.
