[ntp:questions] Loop Filter Gains vs. Polling Interval
david at ex.djwhome.demon.invalid
Mon May 16 07:01:12 UTC 2011
Mischanko, Edward T wrote:
> Can anyone tell me, does the sensitivity for frequency adjustment lessen
> as the polling interval increases? I ask because I'm observing that my
They are linked, but I have a feeling that the loop time constant is not
clamped, even though the poll interval is. The aim is to always achieve
a certain level of oversampling. At the very least, the intent is to
vary the time constant and then choose a poll interval that is
appropriate for that.
> offset increases and the frequency adjustment decreases to the point I
> fall out of sync at polling intervals above 256. What am I doing wrong?
The integral component should be retained. The effect of having too
long a loop time constant should be that the system fails to track clock
wander, so would be more vulnerable to temperature changes or forgetting
to disable power management of clock frequency.
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