[time-nuts] Aging rate of crystals
iovane at inwind.it
iovane at inwind.it
Mon Feb 18 23:02:33 UTC 2008
I learn from this discussion that the aging rate claimed by manufacturers would refer to the
aging of the whole assembly, not the crystal alone. And for practical purposes that is correct.
And even in the case of sealed assemblies, components other than the crystal itself may affect
the overall measured drift.
So my original question on this subject seems to lose any sense, because we will never be able
to measure the aging of the crystal alone (if any, at this point) and hence variations in the
aging rate either.
Anyway some doubts of mine are not yet fully answered by this discussion, and I would appreciate
your opinions.
Given a good quality sealed OCXO running in constant ambient temperature, what kind of aging
curve should one expect, a fluctuating one? (I understand that this might be the case, due
to the interaction of known "intrinsic" aging factors having different timescales, as I've just
learnt on this list. A "regular" curve would be hard to get).
May it happen that fluctuations in frequency due to "external" causes such as tides, geomagnetic
storms, or so, and not actually affecting the "aging rate", are interpreted as fluctuations
in the aging rate?
I'm running a simple test comparing an OCXO (option 04E on a military Racal 1992 counter) to
rubidium (LPRO), the counter being counting the LPRO. The test is running since about two weeks,
and I started recording three days after power up. In the first days the OCXO showed a decreasing
drift starting with some 3x10e-10 per day until it reached a stability within +/- 1x10e-10 in the
last 5 days (that is, since 5 days back, the counters reads always the same value +/- the occasional
uncertainty of the rightmost (11th) digit (10 seconds gate time). The OCXO specs are <= 5x10e-10
per day. I didn't notice whether it is sealed, and won't check right now. I don't expect that the
counter will always stay there, and I don't know what to think when the drift (aging rate?) will
change.
Thanks,
Antonio I8IOV
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