[time-nuts] Frequency Stability of Trimble Mini-T
SAIDJACK at aol.com
SAIDJACK at aol.com
Thu Oct 16 19:21:29 UTC 2008
exactly! What about units that jump only once every say 12 months or so?
I can't find much fundamental research on this at all; and if even Mr. Vig
says the phenomenon is not well understood.. But there are (propriatary) ways
to probe for the susceptibility of a particular unit to do this.
We have done some extensive research trying to correlate jumps to external
phenomena (radiation, vibration, thermal effects, etc). There is no straight
It's similar to asynchronous switching inside a digital computer. You can
add levels of flip flops to synchronize across two asynchronous time-domains,
but all you are doing is decreasing the possibility of a meta-stable failure to
make it through the flops. Statistically you can never guarantee that there
won't be a failure at all; even if the MTBF is 10 Million years by using five
levels of synchronization etc, a failure could actually happen after 10s of
The good news is: there are mitigating factors. Most jumps are in the E-011
or E-010 range, and most applications won't even be affected by such an
extremely small frequency change, and we have GPS to quickly correct the
I would not be surprised if your standard computer crystal has jumps in the
range of E-07 that happen all the time, and no one notices.
As Mike said, most specs that require performance of E-010 or better are
somewhat bogus, and don't have real-world requirements that come close to the
paper spec. So we try to improve the state of the art as best as we can.
In a message dated 10/16/2008 11:31:32 Pacific Daylight Time,
hmurray at megapathdsl.net writes:
> the problem is one of statistics. Not all crystals exhibit this, one
> may find only about 20% or so of a typical manufacturers OCXO will
> exhibit these jumps, and with varying intensity.
There is another dimension. How often do the jumps happen?
Do the other 80% make jumps if you wait longer?
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