[time-nuts] Looking for off-the-shelf device to timestampmultiple PPS inputs
albertson.chris at gmail.com
Wed Sep 28 23:46:28 UTC 2011
On Wed, Sep 28, 2011 at 4:20 PM, Kevin Rosenberg <kevin at rosenberg.net> wrote:
> Hi Bob,
> That's a fine solution that wins on re-use of old PC's and scalability of inputs.
> Obviously over the course of days, NTP is superior to an Rb clock, but my son
> really wants to use the Rb for reference time. I suppose we could read the PPS
> from the Rb to compare to the other two PPS lines, though. Could be a winner.
> In fact, if don't use NTP to discipline the local clock, we can use the local clock
> as a measurement of a the stability of a quartz oscillator for his project.
> Not having used counters much, I'm a little surprised they can't do continuous
> logging. I suppose their strengths, though, are in triggering and gating.
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.
A Thunderbolt will do as well as Rb.
Redondo Beach, California
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