Hi The gotcha with translating ADEV directly to a measurement is the nature of ADEV. You are looking at a standard deviation measure, so the result will be some sort of “one sigma” kind of measure.
Bob > On Oct 30, 2014, at 6:32 PM, Adrian <rfn...@arcor.de> wrote: > > Karen, > > as by the datasheet, the time interval resolution of your counter is 50 ps. > This translates into an ADEV value of 5E-11 at tau = 1 sec, 5E-12 at tau > = 10 sec etc, and represents the theoretical measurement limit of the > counter. > It can be measured by feeding the same signal into both inputs (start > and stop) at the same time. A short delay (additional length of coaxial > cable) at the stop input keeps the counter from producing phase wraps > (jumping between a full input signal period and zero). > > A good MV89A can be below 1E-12. For measuring two good MV89A's against > each other, a TI resolution of 50 ps is insufficient because up to 100 > sec, to the most part of it, the actual ADEV of the oscillators can be > below the measurement limit of the counter. > > Adrian > > Karen Tadevosyan schrieb: >> Thanks again for your explanations and advices. >> I raised this question as a ADEV measurement result of my GPSDO/NEO-7M is >> about 1E-9 for tau = 1sec >> http://www.ra3apw.ru/wp-content/uploads/2014/10/NEO7M_OCXO_MV89A_10M_2h0_ADEV.jpg >> and it isn't meet my expectation. >> In my understanding (before I published my question here) the reason for >> this is not a good enough short range stability of my frequency counter's >> reference OCXO that's why I had an idea to use external rubidium source. >> Now I see that even my internal reference OCXO provides a good ADEV value >> 1E-10 for tau =1 sec (according Pendulum CNT-91 with opt.19 datasheet). >> If so what can be a reason of not a good ADEV result of GPSDO/NEO-7M? >> Karen, ra3apw >> >> _______________________________________________ >> 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.