[time-nuts] oscillators

Dennis Ferguson dennis.c.ferguson at gmail.com
Thu Aug 30 20:36:32 UTC 2012

On 30 Aug, 2012, at 13:14 , Rick Karlquist wrote:
>> The other area where a uP is useful is in an environment with high
>> vibration.  It can correct for acceleration as well as temperature.  There
> I've never heard of this being done.  Do you have a reference?

I'm not sure how that would be done with a single crystal but I heard
a talk by David Allan about a (carefully oriented) array of 6 crystals
for which that was done.  A Kalman filter which understood the physics
of acceleration effects was applied to the output of the 6 crystals
to produce a composite clock and, as a side effect, inertial navigation
information.  This allowed the composite clock to be corrected for
g-effects as well as providing the same data that would be output by
a conventional, mechanical inertial navigation unit.

I think the target application was a drone aircraft, with the clock
output ending up at a GPS receiver while the inertial data was used
as a fallback if the GPS was jammed and as a sanity check to detect
GPS spoofing.  This seemed like a nice one-stone-several-birds solution.
I have a copy of the powerpoint somewhere, but I've not seen this
written down anywhere else.

Dennis Ferguson

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