Thanks Bob. I was also thinking something similar but on the SRS pdf I mentioned (high res. freq. measurements), it also mentions Allan variance and as an example the noise floor data is collected also with a sample size of 1000. The setup is not like I mentioned but normal ChA/start ChB/stop driven from the same source but with REF OUT as EXT trigger and I guess because REF OUT is 1kHz, sample size is set to 1000 to get 1 sample per second.
I also wonder if there is no effect of converting 10MHz to 1 PPS in order to measure Allan variance (when the reference is GPSDO PPS). Isnt it at least conceptually the same thing if not exactly the same (that it eliminates the variations in a 10MHz signal) ? Mete >From the pdf mentioned: "(This data was collected by connecting one 10MHz out of an FS725 to the SR620 reference input. A second 10MHz output from the FS725 went to the input of an RF splitter (Minicircuits 15542 Splitter ZSCJ-2-1). The two splitter outputs were connected with identical 3 inch BNC cables to channel A and B of the SR620. The 1kHz REF out of the SR620 was connected to the EXT input of the SR620. The SR620 was set up for time interval measurements, starting on channel A using EXT +/-time gate/arm, with a sample size of 1000. 57600 1-second measurements were collected, starting on 3/2/04 4:15pm The modified root Allan variance was computed to give the graph shown above.)" On Thu, Mar 3, 2022 at 2:17 PM Bob kb8tq <[email protected]> wrote: > Hi > > The main disadvantage (if you are after ADEV) is the pre-processing > that takes out the noise you are trying to measure. Getting the repeat > rate so that you actually got samples once a second (after all the overhead > and processing) would be a challenge. > > Bob > > > On Mar 3, 2022, at 2:28 AM, Mete Balci <[email protected]> wrote: > > > > Hello, > > > > Is there any disadvantage of using SR620 with TimeLab as described in > high > > res freq. measurement document of SRS ? > > > > 1) DUT (10MHz) is connected to External Clock In > > 2) REF OUT (1kHz) is connected to ChA > > 3) GPS receiver PPS output configured as 1kHz and is connected to ChB. > > 4) Sample size 1000 > > > > Can this value be used in the same sense as in a (normal) single > > measurement (Ch A: GPS PPS vs. Ch B: DUT output converted to PPS) ? > > > > If not, is there still a benefit of maybe converting REF OUT (not DUT) to > > PPS and using it still like the above configuration but with sample size > 1 ? > > > > Mete > > _______________________________________________ > > time-nuts mailing list -- [email protected] -- To unsubscribe > send an email to [email protected] > > To unsubscribe, go to and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] -- To unsubscribe send > an email to [email protected] > To unsubscribe, go to and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
