Bruce Griffiths wrote:
Skip Withrow wrote:
Hello time-nuts,
I'm looking for the group expertise to tell me what would be the best
test setup for looking at ADEV of several oscillators.
I have severa crystal, rubidium, and GPSDO oscillators that I would
like to characterize. I have a 5370B and cesium that has 1, 5, and
10 MHz output. The question is what is the best configuration of
internal/external oscillator, start input, and stop input of the
5370B (and do I use an external 1pps trigger)?
Then there is the issue of whether to use the cesium as the reference
in all cases. Seems the GPSDO would have better long term stability
for very long tau. Any insight appreciated.
Regards,
Skip Withrow
One setup that works well is to divide down one of the oscillators
being compared to 1Hz (or 10Hz, 100Hz) and use this to arm the 5370B.
Use the input signal for the divider to Start the 5370B and use the
other source to stop the 5370B.
This setup minimises the effect of divider jitter so that the
technology employed in the divider isnt critical.
Then one has to unwrap the phase of the measured time intervals, a
fairly straightforward task.
This method also ensures that the 5370B time base accuracy isn't
critical as the 5370B only measures time intervals of around 1 period
of the STOP input frequency.
For quiet sources the measurement noise of the 5370B will dominate for
tau less than 100sec or so (depends on the source ADEV vs tau).
Bruce
For most caesium standards and for some GPSDOs the jitter of the PPS
output exceeds the jitter of the 5370B so using the PPS output to arm
the 5370B reduces the measurement noise over the setup where the PPS
output is used to start (or stop) the 5370B.
Bruce
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