On 2012-01-11, David J Taylor <[email protected]> wrote: > "unruh" <[email protected]> wrote in message > news:[email protected]... > [] >> No, I was talking about the width of the edge transition. Neither the >> accuracy of that transition, nor the width of the pulse. the former one >> cannot know unless one has another gps whose accuracy one knows, and the >> latter is irrelevant to timekeeping. However the post I was replying to >> almost certainly was talking about the width of the pulse, not the width >> of the transition. Note that the gamin has a pulse width that is quite a >> bit less than 1usec. What its accuracy is I do not know. > > Please be more careful in your terminology. The width of the Garmin GPS > 18(x) LVC pulse is nominally 100 milliseconds, not "bit less than 1usec". > You will be confusing people who haven't worked with this kit. You almost > had me believing that the Oncore had a pulse with of 1 microsecond (which > sounded wrong, but....). > > The Garmin 18x is specified: "1 microsecond accuracy [under normal > conditions]"
Just like the rs232 specs say at least -3V to +3 V for the signals, when most rs232 cards will accept +.5V to +2 V for the transition levels. What the specs say and what the card does need not be the same. People have claimed that the Garmin 18x actually does significantly better than 1us but I have not tested it. If I had you believing that the Oncore had a width of 1us, I appologise. That is certainly wrong. I have not measured it, so cannot say what its width actually is. I have looked at the Sure, and its pulse width is about 5ns. > > Cheers, > David > > _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
