On 2/27/22 6:56 PM, Bob kb8tq wrote:
These are *all* compare to a reference measurements. The floor will always be
set by that, one way or another.
Bob just stated a great truth that explains why and how we become
time-nuts -- in order to characterize an oscillator, you need another
Hi
> On Feb 27, 2022, at 5:20 PM, Hal Murray wrote:
>
>
> kb...@n1k.org said:
>> Since there is a quick / simple / (near) zero cost solution ( look at a delta
>> to a second pps stream) crossing more sources of trouble off the list is
>> normally a pretty easy decision.
>
> I can see how
kb...@n1k.org said:
> Since there is a quick / simple / (near) zero cost solution ( look at a delta
> to a second pps stream) crossing more sources of trouble off the list is
> normally a pretty easy decision.
I can see how that works if the second PPS is high quality. What happens if
it is
Hi
*Could* it be perfect in some ideal device? Sure it could. In any real world
device I’ve ever used (and I think I’ve used just about everything on the market
…..) , it’s been far from perfect.
As you get out to even a modest tau ( say 1K sec) you are looking at something
in the 10,000 to
Bob
Would this rounding error be reduced if the phase is measured in a gapless
way, e.g. against a continuos running phase counter that is captured at the
moment of the PPS and the period is calculated as the delta between current
and previous capture. Any rounding in this delta calculation can
Erik,
> Does anyone know if it is possible with the U6200A to measure every
period of a PPS?
Yes, use time interval mode instead of period or frequency mode. TI mode
is a 2-channel measurement so one channel is your GPS/1PPS and the other
channel is your Rb/1PPS. The resulting readings
Hi
If your goal is an ADEV measurement, you will need to tag the
edges against a second “stable” PPS signal. A sequence of period
measures can get you into issues related to round off problems.
Bob
> On Feb 27, 2022, at 11:27 AM, Erik Kaashoek wrote:
>
> But why can't you measure the 1 s
But why can't you measure the 1 s period of a PPS?
If the counter would be able to do gapless measurement and you set the
gate to 0.9s it should be able to measure the period of a PPS, at least
my own build counter behaves that way so I was surprised the U76200A
could not do that.
On
Hi
If both signals arrive at the same time, many devices get a bit confused.
Many counters run into this same basic issue.
One work around is to “offset” one of the PPS signals. The cable delay
feature on the typical GPS module will let you do this over at least a
couple microseconds. For many
Without a reference? If the same PPS acts as start and as stop then
one (I suppose) rising edge is start and the next rising edge is stop,
so a measurement every second is not possible. Maybe a dedicated
hardware with two channels where one edge is the start for a channel
and stop for the other is
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