Hi Which approach are you using:
1) start with 1 pps, stop with 10 MHz (max period ~ 100 ns) 2) start with 1 pps stop with 1 pps (max period ~ 1 second) Each has it’s own set of issues. A 1% error on 100 ns is at the noise on a 5335. Both counters need a pretty accurate reference if they are running out in the half second or more region. The 10811 in the 5370 should be < 1x10^-11 at one second unless you have an unusual poor example. It should hold <3x10^-10 per day if it’s been on power for 30 days or more and not been abused. Bob > On Aug 1, 2015, at 2:57 PM, Bob Stewart <b...@evoria.net> wrote: > > Hi Poul, > "0) Make sure that the counter does not get its reference frequency > from any of the input signals." > Does your rule 0 hold if one of the input signals is a Cs standard? I > believe I've posted in the past that the ADEV from 1 tau to 100 tau is a bit > noisy if I use the internal 10811 to clock the 5370A. I noticed the same on > my 5335A. > Bob > > From: Poul-Henning Kamp <p...@phk.freebsd.dk> > To: Discussion of precise time and frequency measurement > <time-nuts@febo.com>; zzsili...@post.com > Sent: Saturday, August 1, 2015 4:19 AM > Subject: Re: [time-nuts] Data Collection for Allan Deviation > > -------- > In message > <trinity-fbe15ceb-78c6-4e04-a3e1-b9b5c2e20fd9-1438400665333@3capp-ma > ilcom-lxa02>, zzsili...@post.com writes: > >> If I have a GPS receiver with output pin of both 1pps & 10KHz, a >> Rubidium clock of 10MHz, and a signal generator. How can I determine >> their Allan Deviation? I know the math formula, but my problem is >> the data collection. > > Presuming you have a counter which can measure Time Interval between > two signals. > > 0) Make sure that the counter does not get its reference frequency > from any of the input signals. > > If one of your signals is 1PPS: > > 1) Connect 1PPS to START > > 2) Connect other signal to STOP > > 3) Collect TI measurements. > > else: > > 1) Connect signal with lowest frequency to START > > 2) Connect signal with highest frequency to STOP > > 3) Trigger measurements at 1Hz rate, either through EXT TRIG or GPIB > > For this to work, the signals must be sufficient "on-frequency" > that the phase-wrap-arounds (when the STOP signal slips past the > START signal) can be resolved afterwards. > > A good rule of thumb is that the flanks of the START/STOP signals > should not move more than 1/3 the period of the higher frequency > signal in the time between measurements (= 1sec above). > > I use my own home-grown program to calculate the MVAR. > > The Lady Heather program should be able to do it with data collected > this way. > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > p...@freebsd.org | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. > > > _______________________________________________ > 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.