The standard deviation is good and consistent with others measurements which seem to be in the range 10 to 15 psecs.
I think the channel skew is one half of 112psecs = 56 psecs (as it adds one way and subtracts the other) and this is close to the Keysight datasheet claim of 50 psecs typically. It is interesting to get some practical readings - when I was trying to decide on my counter it was very hard to get information - different datasheets give different parameters eg Pendulum CNT91/Tek fca 3100 has skew as < 500 psecs whilst Keysight put 50 psecs typical. I ended up getting an fca3100 as I got a very good discount and I found that the skew I actually measured was (5.1282 nsecs - 5.0972 nsecs)/2 = 15psecs which is very good. The std dev for the fca3100 on my unit was 30psecs which is 2 to 3 times worse than the 53230A which is consistent with the ratio of 50 psecs (fca3100) and 20 psecs (53230A). It seems that the typical one-shot resolution is around 2.5 times better than the datasheet (your measurement of 12psecs/sqrt(2) is 2.4 times better than the nominal 20 psecs whilst my fca 3100 measurement of 30psecs/sqrt(2) is also 2.4 times better than the nominal 50 psecs. Interestingly, the SR620 data sheet says the one shot is typically 20 psecs and is 50 psecs max which is also a similar ratio. Perhaps there is some sort of industry standard that states datasheet one shot resolution should be expressed as 2.5 times the typical one shot resolution :). James -----Original Message----- From: Anders Wallin <anders.e.e.wal...@gmail.com> To: Discussion <time-nuts@febo.com> Sent: Fri, 3 Apr 2015 12:04 Subject: [time-nuts] 53230A noise floor Hi all, I ran some tests on a new 53230A counter that just arrived: http://www.anderswallin.net/2015/04/keysight-53230a-noise-floor-test/ The time-interval single-shot noise and resulting ADEV seems easy enough to explain. I didn't yet have time to look closely at Enrico Rubiola's notes over here: http://rubiola.org/pdf-slides/2012T-IFCS-Counters.pdf There is probably a good explanation for the ADEV-level in standard (pi-counting?) reciprocal frequency counter mode as well as the roughly 1/sqrt(10) enhancement in ADEV when increasing the gate-time 10-fold. on another note: The discussion on phase-noise <-> ADEV calculations earlier was interesting. Datasets (synthetic or real) with known correct ADEVs and phase-noise-spectra would be a good addition to allantools and a motivation to add code for the phase-noise <-> ADEV conversion. cheers, Anders _______________________________________________ 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.
