[time-nuts] Scopes and 1 PPS signals?

Dave Brown tractorb at ihug.co.nz
Tue Oct 23 19:10:50 EDT 2007

----- Original Message ----- 
From: "Brooke Clarke" <brooke at pacific.net>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Wednesday, October 24, 2007 11:05 AM
Subject: [time-nuts] Scopes and 1 PPS signals?

> ); SAEximRunCond expanded to false
> Errors-To: time-nuts-bounces+tractorb=ihug.co.nz at febo.com RETRY
> 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?

 If your DSO has external triggering capability then using an external 
digital delay unit will do the trick.  Something as simple as a one 
shot driven from the preceding pulse to do the triggering?

This sort of thing is one of the reasons some analog scopes are still 
useful.  A tek 7K mainframe with a 7D11 delay unit is a good solution. 
That has up to 1 second precise low jitter delay available.

DaveB, NZ 

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