I recommend the differential pair: here the trigger have to sense the crossing of the two signals and this crossing is well definite.
On Thu, Feb 23, 2012 at 3:36 PM, Jim Lux <[email protected]> wrote: > On 2/23/12 6:24 AM, Alberto di Bene wrote: > >> On 2/23/2012 1:04 AM, Poul-Henning Kamp wrote: >> >> I simply don't buy the story that tightening the connector makes >> a consistent 60 nanoseconds difference on a signal. >> >> I spoke with a physicist of Cern, friend of the leader of the team that >> performed the Opera experiment. >> He told me that the badly seated connector caused the amplitude of the >> signal to be lower, and for this reason the trigger point, which was >> set at a specific level, was reached 60ns later. >> 73 Alberto I2PHD >> > > > > Darn those finite rise times<grin> > I've been bitten more than once by this very phenomenon (which I admit > doesn't say a lot for me.. being bitten once is ok, but since I've had > multiple bites...) > > But this brings up an interesting time-nut problem for the hive mind.. > > If you had to design some scheme for interconnecting "boxes" and wanted to > transmit an accurate time sync, what should it look like, so that you're > insensitive to things like rise time. > > (maybe this harkens back to the discussion about 10 MHz, why sine vs > square wave distribution) > > It has to be a single signal (maybe a differential pair), because > otherwise, don't you have potential for skew between the multiple signals. > > Zerocrossing sort of works, if you take only one direction, but does > asymmetry of the waveform screw you up? (e.g. what's "zero".. is it half > way between peak values + and -?) > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
