[time-nuts] Aging rate of crystals

Tom Van Baak tvb at LeapSecond.com
Mon Feb 18 06:36:20 EST 2008

> At the beginning of the E1938A project, I did some humidity
> tests on the 10811.  It was fairly sensitive to humidity.
> I think I remember being able to get parts in 10^8 shift.
> At the beginning of the E1938A project, I did a bunch of
> characterization of 10811 oscillators.  At the Santa Clara
> Division, we had first class environmental test chambers
> with heating, cooling, humidification, de-humidification,
> and nitrogen purge.  The nitrogen was also available for
> fast cooling.  The 10811 response to humidity was very rapid,
> like 10 or 15 minutes, almost as fast as the chamber
> itself could ramp.  This occurred whether going from
> dry to humid or the other way around.  I don't remember
> seeing any slow "tails" on the response.  The immediate
> humidity response was on the order of a month of aging,
> so any humidity related aging effects would be masked.
> Rick Karlquist N6RK


For these experiments did you remove the 10811 guts from the
outer case? I realize the case is not sealed, but the air gap is
very small; how could humidity get inside so rapidly?

Did you look into /why/ the 10811 was humidity sensitive? The
resonator and most individual board components are sealed, so
that doesn't leave too much. Maybe the coarse tuning variable
capacitor, which is exposed to air through its 2 mm hole?

Do you know if most modern high-end OCXO, which are solder
sealed, and which have no screwdriver tuning access hole, are
immune from all humidity variations?


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