[time-nuts] Looking for off-the-shelf device to timestampmultiple PPS inputs

Kevin Rosenberg kevin at rosenberg.net
Thu Sep 29 00:10:18 UTC 2011


On Sep 28, 2011, at 5:46 PM, Chris Albertson wrote:
> Counters will not log the time of a pulse but they will continuously
> measure time intervals.    And the interval might be "time from the
> last tick ofthe second."  So you 'd use the  Rb's PPS to trigger the
> "start" channel and the device under test to trigger the "stop"
> channel.  the counter measures the time difference.  You don't care
> what the difference is but only how it changes over time. If the
> pulses are going at different rates you will see the times get longer
> and long and then very short.   later you figure out the "beat
> frequency" and then you have the rate of the DUT.

Thanks, Chris, that makes sense. I considered recommending my DTS-2077 
using a phase difference method like that. But, one of the goals is 
to count all PPS cycles, not just the rate of the DUT, especially if one 
of the oscillators is less stable than expected.

> A Thunderbolt will do as well as Rb.

For timing purposes, sure. In the thread, also talked about the benefits 
of NTP. Nonetheless, my son wants to use the Rb and (more importantly) 
understand some of the physics of the Rb. So, while the Rb as a long-term
reference isn't as good as NTP +/- Thunderbolt, it intrigues him. 
That's good enough for me to help him with his goal.

Kevin




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