[time-nuts] Scopes and 1 PPS signals?

Brooke Clarke brooke at pacific.net
Tue Oct 23 20:08:45 EDT 2007


Hi Daun:

The previous message suggested using a 74123 one shot, and the FatPPS uses a 
74HC123.  But $45 seems a bit high for just this measurement.

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


Daun Yeagley wrote:
> ); SAEximRunCond expanded to false
> Errors-To: time-nuts-bounces+brooke=pacific.net at febo.com RETRY
> 
> What you need then is the FatPPS from TAPR.  Our own John Ackermann (N8UR)
> designed it primarily for use with time servers by stretching the 1PPS pulse out
> to several milliseconds so that the computer could see it.  I suspect the same
> principle would be useful for a scope.  Check out:
> http://www.tapr.org/kits_fatpps.html
> 
> Daun 
> 
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf
> Of WB6BNQ
> Sent: Tuesday, October 23, 2007 6:29 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Scopes and 1 PPS signals?
> 
> 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
>>http://www.PRC68.com
>>http://www.precisionclock.com
>>http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam
>>
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> 
> 
> 
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