[time-nuts] Trimble T Lassen 2

WarrenS warrensjmail-one at yahoo.com
Mon Jul 23 17:44:58 UTC 2012


And here it goes again for about the umpteenth time, how to detect the 
presents of a short low rep rate pulse.

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.

******************

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

********************
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.

***************
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.

*****************
...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.





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