[time-nuts] Double ovened 10811-60158 on ebay

Chuck Harris cfharris at erols.com
Sun Jul 20 19:13:32 EDT 2008


Hi Rick,

Rick Karlquist wrote:

> 
> My tests showed that epoxy has no effect whatsoever on humidity.
> Goes right through it, right away.

That is not generally possible.  Some epoxies will hold a vacuum
for an extended period of time.  I know of no mechanism whereby epoxy
could hold back both nitrogen and oxygen molecules, and not be able
to hold back H2O vapor molecules.  Epoxy is even a pretty good seal
for helium as was shown by its successful use in HeNe lasers.

Either your epoxy seals were not properly done (very likely), or
there is another mechanism in play.  If you did not pressure test
your epoxy seals, you really gained no useful information from your
tests.... Well, other than the knowledge that you didn't make a
successful epoxy hermetic seal.

I presume that you saw different behavior with solder seals?

If you didn't, then maybe what you were seeing was the difference
in thermal resistance between humid air and dry air.

-Chuck Harris







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