); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Some DSOs (my lowly Tek 210 does) have a peak detect acquisition mode where it will analyze the signal at the highest speed of the A/D converter regardless of sweep speed and report the min and max for each displayed pixel line. Main advantages are 1) to make aliasing obvious and 2) to be able to see very narrow pulses at low sweep speed. I can see 20nS wide pulses at 1 PPS easily. Of course, the precision of the measurement (if you use the period function) is limited to the display resolution, but at least you can get in the ballpark. My scope is in that mode all the time, little reason not to.
If you do not have such mode, put a diode (i.e. 1N4148) in series with the probe. The diode will charge the input capacitance of the probe, which will discharge exponentially in the 10 Mohm resistance and give you something you can see. Can't beat that for cost. Add some capacitance in parallel with the probe if needed to widen the pulse. Didier KO4BB > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Brooke Clarke > Sent: Tuesday, October 23, 2007 6:24 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Scopes and 1 PPS signals? > > Hi Bill: > > I'm sure that would work, but it's something else that needs > to be done sometime in the future. > > I checked the pulse coming from the M12+T and it's more like > 100 ms wide, probably for this reason. > > Have Fun, > > Brooke Clarke > http://www.PRC68.com > http://www.precisionclock.com > http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam > > > WB6BNQ wrote: > > Hi Brook, > > > > You could try using a 74123 (or newer variants) > retriggerable one shot > > to extend the pulse width to a level that would allow you > to see it on the scope. > > > > Bill....WB6BNQ > > > > Brooke Clarke wrote: > > > > > >>Hi: > >> > >>While trying to figure out the O-1814 Rb source I found a 1 > PPS signal > >>that's less than 10 us wide. But using an HP 54501A DSO > it's almost > >>impossible to determine the period. > >>http://www.prc68.com/I/O1814.shtml > >> > >>If the display is 1,000 dots wide: > >>at 2 us/sq the trace takes up about 4.5 squares or 450 dots, at 200 > >>us/sq the trace takes up about 0.045 squares or 4 dots but > the second > >>pulse is way off screen. At slower sweep speeds you can't > see the pulse. > >> > >>Are there scopes that allow the period of a narrow pulse to be > >>measured that don't cost an arm and leg? > >> > >>-- > >>Have Fun, > >> > >>Brooke Clarke _______________________________________________ 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.