Hi Nick,
Are you applying sawtooth correction to your phase measurement? If not, are
you merely seeing a hanging bridge that dissolves into at a normal sort of
tick-tock movement?
Bob
From: Nick Sayer via time-nuts <[email protected]>
To: Discussion of precise time and frequency measurement <[email protected]>
Sent: Wednesday, October 5, 2016 6:45 PM
Subject: [time-nuts] ADC sample voting algorithm?
This is tangentially on topic, I suppose. It’s for my GPSDO.
I notice periodically that the phase measurements seem “noisy.” You can see
that over the course of several seconds the value doesn’t change, then it jumps
a bunch and then comes right back.
My theory at the moment is that sampling the ADC multiple times in a row might
help, but then what’s the best way to (quickly) pick which sample to use?
The mean would allow a bad sample undue influence.
At the moment, I’ve coded taking 3 samples, averaging them and picking the
sample that is closest to the mean. If I’m right, and two of the samples happen
to be very close to each other and a third is an outlier, then that seems like
it would eliminate it.
I guess what I want is the mode, but with 3 samples, that’s going to be poorly
defined (if at all).
Anyone have any suggestions (besides a larger sample size)?
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