); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi Didier:
When just a diode is used the stretching is only at the bottom of the trailing edge and not enough to help. But when a little capacitance is added it works. The period is the same as what the SR620 reported, 1/ 32 Hz. Seems a strange number. 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 Didier Juges wrote: > 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 -- [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.
