[time-nuts] ADEV interpretation

[Marek Dorsic]

Hello,

I would like to ask your knowledge to help me interpret this basic ADEV result.
Assume following measurement setup:
PPS output of Ublox RCB-F9T connected to channel 1 of a HP53131A counter.
10MHz output of the counter's internal oscillator (opt. 010, medium stability oven) divided with PICDIV to 1 PPS connected to channel 2 of the counter.
Counter set to measure time interval from channel 1 to channel 2.
After processing the readings, the floor of ADEV is 5x10^-10 at about 30-100 seconds interval.
Which of the following is true?
a) ADEV shows the real performance of the internal oscillator,
b) ADEV floor is 5x10^-10 because of the restricted counter time interval resolution (500ps),
c) ADEV floor is 5x10^-10 because of the ZED-F9T PPS jitter (after saw correction) of the gate start input channel.



Thanks in advance
     .marek