Hi One of the simplest justifications I can think of for a dirt cheap “Chinese” digital ’scope is to capture short burst stuff like narrow pps pulses.
10 us / non-adjustable is a *very* common spec for a 1 PPS. Bob > On Apr 21, 2020, at 4:56 AM, Chris Burford <[email protected]> wrote: > > I reached out to SRS several months ago to inquire if the pulse width could > be configured from the default of 10 micro second. Their responses was no. > > Chris > > -----Original Message----- > From: time-nuts <[email protected]> On Behalf Of Taka Kamiya > via time-nuts > Sent: Monday, April 20, 2020 22:35 > To: Discussion of precise time and frequency measurement > <[email protected]> > Cc: Taka Kamiya <[email protected]> > Subject: Re: [time-nuts] Using speaker / earphone for PPS testing (not a > question) > > Out of all signal source, the shortest 1 pps is PRS-10 at 10 micro second. > T-bolt is quite short as well but I don't have a definite data. > For those, speaker method worked just fine. I'm just sharing what I learned > on happenstance. > > --------------------------------------- > (Mr.) Taka Kamiya > KB4EMF / ex JF2DKG > > > On Monday, April 20, 2020, 11:05:02 PM EDT, Bill Byrom > <[email protected]> wrote: > > It's easy to trigger on short pulses on most oscilloscopes if you follow > these steps: > (1) Do NOT use Auto Trigger mode. Instead use Normal trigger mode. > (2) Set the vertical coupling mode to DC. > (3) Set the vertical gain (volts/div) and offset so that the baseline (OFF > voltage between pulses) and pulse ON voltage should both be visible on the > vertical scale. > (4) Set the trigger coupling mode to DC and the trigger source to the proper > channel. > (5) Set the trigger voltage to the midpoint between the pulse OFF and ON > voltage. > (6) Set the trigger slope appropriately, depending on the polarity of the 1 > PPS pulse. > (7) Many oscilloscopes have a trigger indicator LED. It should flash visibly > on each 1 PPS signal. > (8) If you are using an analog scope which does NOT have a microchannel plate > (which was used on the Tektronix 2467 family and a few other models), the > pulse ON signal may be difficult to see at a fast time/div setting, even with > a high scope intensity setting. But you can slow down the time/div of an > analog scope to something easy to see, such as 10 ms/div. This will allow you > to see a bright sweep each time the scope triggers, even if a short pulse > can't be seen. > (9) When using a digital oscilloscope, turn on the peak detect display mode. > This allows the oscilloscope to keep a high sampling rate even if the > time/div is set for a moderately slow sweep. > > If the 1 PPS signal is very short, you won't be able to hear it on a speaker > with a direct connection as you describe. But you can use a pulse stretcher > circuit (such as a 555 timer IC) to drive a LED or speaker with a long output > pulse (such as 10 ms). If you use two 555 IC's (or a 556 dual timer IC), you > can even configure one section as a one-shot and the other as a tone > generator so that a beep is produced for each pulse. The 555 and 556 may be > sold as LM555/LM556 or NE555/NE556. > -- > Bill Byrom N5BB > Retired Tektronix Application Engineer > > On Mon, Apr 20, 2020, at 9:25 PM, Taka Kamiya via time-nuts wrote: >> Maybe everyone but I knew, but I just did this and found it useful. >> 1 pps signal from some GPS are notoriously narrow and difficult to sync >> on and see on scopes. LED will barely light if some kind of stretcher >> is not used. If your purpose is ONLY to see if it's there or not, hook >> up a small speaker, earphone, amplified or not, and you can hear the >> tick-tick sound. >> >> I like DIYing and many times, I wonder if pps distribution circuit is >> working. I can tell a very short pulse that will barely register on >> LED is clearly audible. >> I thought I'd share. >> >> --------------------------------------- >> (Mr.) Taka Kamiya >> KB4EMF / ex JF2DKG >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > <1PPS - 1MΩ.png>_______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
