[time-nuts] Trimble T Lassen 2

[WarrenS]

That works when there is a trigger LED,
OR Just need to slow down the sweep rate to say 10ms / div or slower and 
then there will be a nice clear, easy to see, can't miss, white line, across 
ANY scope with each pulse when the scope is triggered by a short low rep 
input pulse.


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My old '465 will trigger on the 1pps, but it's far easier to see the
trigger LED flash than finesse the brightness/sweep to make it visible -
something possible only on a 'scope with a decently bright tube.
...
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Most scopes that I've used have some sort of indication if they are/aren't
getting triggered, so even if you can't see the pulse you can tell if there
is a pulse there.
...
 it helps to run in Triggered mode rather than Auto.
 Works fine in Triggered mode as long as you are happy without seeing
anything when the trigger doesn't happen.

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This can be done with ANY analog scope by using the "normal trigger mode"
and setting the trigger correctly.
An analog scope can detect the presents of any short pulse no matter how low
it's rep rate is,
so long as the pulse is wide enough that it is in the scope's (trigger)
bandwidth.  Under 5ns for a 100 MHz scope.
So detecting if there is a very short pulse even once every 10 or 100
seconds sec is NO problem.
Now measuring how wide the pulse really is, that is a problem for an analog
scope.

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Wow, that is indeed narrow. Only 1us out of a 1 second rep rate. That is one
millionth of the rep rate. No wonder analog scopes will not catch it. I'll
have to try it some time. Regards

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The pulse from my T-Bolt is on the order of 1uS wide. I captured it on the
digital scope for posterity and future reference.

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I was fooled by this too.  My analog scope does not sync on the 1Hz
pulse.  You have to breadboard something that will detect it, maybe a
flip flop and then look at the FF's output.

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...And don't forget that the PPS pulse is very narrow so you have to use a
'scope with memory, a digital 'scope or turn the brightness at max.