Not only HP counters. I have never seen a TI counter that outputs negative values. I use the cable delay or user delay feature of GPSes to delay one PPS to the other so that the result is always positive. I have seen that only oscilloscopes can handle negative time interval values. Maybe that the Wavecrest counters can handle negative TI, I don't know.
On Wed, Jun 12, 2013 at 8:48 AM, Said Jackson <saidj...@aol.com> wrote: > Jim, > > Really annoying feature of HP counters. > > If you slowly drift from a positive period to a negative one, it will > indicate negative numbers for a while. > > Then almost sudden it will do the jump to 0.99999xxxx seconds. > > I found that adding a phase delay (long cable) helps keep the numbers > positive. > > Or trigger one on the rising, and one on the falling edge to add 50ns delay ( > for signals with good 50% duty cycle). > > Bye, > Said > > On Jun 11, 2013, at 21:13, Jim Palfreyman <jim77...@gmail.com> wrote: > >> Folks, >> >> I'm struggling to understand this button and how it reports intervals. It's >> supposed to show negative when the Stop is before the Start. >> >> When I connect up two clocks sending out 1PPS and say the one connected to >> Stop is ahead then sometimes I'd get -123.45 ns (say) and sometimes it >> flips to 999.999... ms. It can't seem to make up its mind which to use. >> >> Why is this inconsistent? >> >> If I flip it to + TI and make sure the leading clock is on Start - all >> works well. >> >> Thoughts? >> >> Jim Palfreyman >> _______________________________________________ >> 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.
