Hmmm... Magnus thank you for your comments. The 5 ns figure is certainly helpful. My 1980 manual from HP just says "Time Interval" A -> B = 0 ns to 10E7 seconds. Not very helpful.
May I ask where you found your 1992 reference? Perhaps you have a link? Many thanks, Jim... N5SPE On Feb 22, 2014, at 5:20 PM, Magnus Danielson <mag...@rubidium.dyndns.org> wrote: > Hi Jim, > > On 22/02/14 14:17, Jimmy Burrell wrote: >> I need some help with a 'noob' question regarding some practical examples in >> some of the NIST literature. When attempting to compare two clocks, I'm a >> bit confused on the subject of exactly how to use my counter to compare a >> delayed clock relative to another. Or perhaps I should just say 'comparing >> two clocks'. Let's take some concrete examples. >> >> Let's say I want to characterize my Morion MV89 ocxo using my HP5335a. >> Obviously, I can tune the MV89's 10MHz by +/- 1Hz and feed it to the >> counter's input 'A'. Obviously, I can feed in a second, external reference >> clock at 10MHz into input 'B'. Suppose, however, I didn't have an external >> reference clock. Can I compare against the counter's internal time base by >> hooking a line from the rear jack time base output to channel 'B' input? Or >> am I making it too complicated? Do I simply plug into input 'A' and go? >> >> In a somewhat related question, in this article >> (http://www.wriley.com/Examples%20of%201%20PPS%20Clock%20Measuring%20Systems.pdf) >> where two clocks, both divided to 1PPS, were compared, W.Riley makes the >> following statement, "The two 1 PPS outputs were connected to a Racal Dana >> 1992 time internal counter having 1 nanosecond resolution, and the start and >> stop signals were separated sufficiently in time for the counter to function >> properly". I wonder what exactly is meant by "separated sufficiently in >> time for the counter to function properly" and how one would go about doing >> this? For example, is inverting one of the signals sufficient separation? If >> not, how is this typically done? Delay line? > > The problem is that the start trigger (Channel A) will arm the measurement on > the stop channel (Channel B). For this process to operate properly, allow 5 > ns. If you look into the 1992 spec-sheet it says that TI interval is from 5 > ns. > > If you have a 10 MHz or 5 MHz signal, you only have 100 ns or 200 ns periods > to play with. Dividing them down to say 10 Hz gives you plenty of time such > that you can boot-strap one of the dividers such that you don't go through > zero within the measurement period. > > Adding a delay doesn't help, as frequency error will get the phase into > through zero condition pretty quick I would guess. > > The SR620 counter has a coax delay-line to give trigger look-ahead. > > Cheers, > Magnus > _______________________________________________ > 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.
