[time-nuts] HP 10811 Response I Replies

[ws at Yahoo]

>Within minutes the frequency changed more than the spec

For humidity to get thru something like that it takes weeks or more it does 
it at all.
That fast of reaction, Sure sounds like some other effect like blowing a 
little air on the case or loading the osc output with water in the output 
cable etc, etc.
I think it is safe to say the effect was not due to water inside, unless 
there was a hole.

ws

*****************
Chuck Harris cfharris at erols.com

You had a leak.  If epoxy was really as bad as you indicate,
it would not be usable for holding pressure, or mild vacuum,
and yet it is.  Somehow, someway you left a big hole in the
bucket.

-Chuck Harris

************
Rick Karlquist wrote:
> Perry Sandeen wrote:
>
>> Wrote: Doing what you describe will result in a very sensitive humidity
>> sensor, having eliminated the thermometer effect.
>>
>> I do not understand.  I believed that since the OCXO temperature will be
>> substationally higher than the surrounding temps, any residual moisture
>> would migrate to a lower temperature.  The fiberglass insulation inside
>
> Heating up a space does not change the absolute humidity AFAIK.
> It only changes the relative humidity.  We did tests where we
> "sealed" a 10811 inside a box that was held together with so-called
> "hermetic" epoxy.  We put it in an environmental chamber at a
> constant temperature and constant low humidity and let it stabilize.
> We then increased the humidity to something like 80%,
> while holding the temperature constant.  Within
> minutes the frequency changed more than the spec for the entire
> temperature range.  Therefore, you should do your experiment with
> the hermetic version of the 10811.  The hermetic version is soldered
> shut, rather than using epoxy, which turns out not to be hermetic,
> no matter what they claim.
>
> Rick Karlquist
>
>