It looks like the "winding stem" is the GPS antenna? If that is the
case, then it could get calibrated when ever it can see some satellites
and sit still for awhile. The next thing it needs is solar cells to
recharge the battery. The WWVB watches are doing that now.
Tom
On 10/1/2013 4:28 PM, Bob Camp wrote:
Hi
…. also don't forget that it's got a magnetic field susceptibility. Rotate it
in the earth's magnetic field and you get something very similar to a 2 G tip
on a crystal oscillator. That alone is enough to nuke the average error budget
for 1,000 years.
Of course there's also that pesky and oh so obvious 0.2 wander in the second
hand. Can't see at all how a *real* Time Nut could put up with that. :)
It is indeed a marvelous device. Packing all that into a tiny package wasn't
easy at all.
Bob
On Oct 1, 2013, at 6:59 PM, [email protected] wrote:
Guys,
there is only one problem: there is just no way they can claim only 1
second error in a 1000 years unless they also have a GPS receiver for
calibration in there, which kind of mutes the point as that has been done using
wwvb
etc. Let's do the math:
1/ (1000 * 365 * 24 *3600) = 3.171E-011 average error required over 1000
years.
The CSAC has a thermal spec of +/-0.5ppb for -20C to +70C, meaning 5.6E-012
per Degree C sensitivity.
So the temperature would have to stay stable within a couple degrees C,
hardly possible in a wrist watch.
Also, initial CSAC aging is 0.3ppb per month, about 100x worse than they
claimed 1000 year per second accuracy. It gets better over time, but still
around a ppb per year or so of aging is expected, far off from the 0.032ppb
claim.
They did a great job integrating that together, and its novel, but the
marketing department is off by many orders in magnitude in their accuracy
claims.
I know CSAC applications that would be very happy to get around 0.1 second
error per year consistently without external re-calibration in a stable
environment.
bye,
Said
In a message dated 10/1/2013 15:32:27 Pacific Daylight Time,
[email protected] writes:
That's the first time I have seen a practical explanation and working
example of a CASC in operation.
Can I say "Awesome"?
--marki
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