Thanks to everyone who responded to my post. I put in a 5 minute DAC value
averager and saved that once every 15 minutes to a 12 hour circular queue last
night. It just started giving me responses, and I've gotten -139 seconds,
-4800, -7200, and -2400. The -139 is probably because I started the thing up
too early in the lock process. I'm going to have to give some thought to this
as I get more results. I expected to get values around -3600, and actually,
the last three fit that criteria with a dividend of only 43,200 (12 hours). I
notice that I had an OCXO burp in the middle of the night. So, I'll have to
give some thought about saving a number of the most recent values and throwing
away any that don't seem to fit in with the rest. Once I'm satisfied with the
code, I'll increase the queue size to at least 48 hours. I'm not sure if more
than that is really useful, but a multiple of 24 may bias it toward
environmental conditions at startup, so perhaps 64 hours would b
e better.
Bob
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GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
From: Bob Stewart <[email protected]>
To: Discussion of Precise Time and Frequency Measurement <[email protected]>
Sent: Wednesday, October 5, 2016 12:37 PM
Subject: [time-nuts] Measure GPSDO stability with minimum resources?
For my GPSDO, I need to calculate the OCXO aging for holdover projection
purposes as well as get some figure of merit for the recent past of the OCXO
stability. The latter is so that I can determine that the PLL has (or soon
will have) a good lock. I'm developing on a dfPIC33FJ128MC802, and I've used
about 70% of the code space, I could probably set aside 4K bytes of data space
for this calculation.
I have a rather primitive way of doing part of this, but I was hoping someone
would steer me to something a bit better.
Bob
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