On 3/22/17 4:28 AM, Bob Camp wrote:
Hi
In this case, the vacuum might work against you. You change the pressure outside
the package and you get a flex. Flex translates to dimensional changes. That
gives you
a frequency shift. People make absolute pressure sensors this way :) Rb’s are
by no
means the only frequency standard impacted by this effect. Precision OCXO’s
have the
same issue.
If you had enough room inside the package, you could do a “can in a can” sort
of approach.
The outer vacuum sealed can flexes. The inner vacuum sealed can does not see
anything.
You don’t eliminate the sensitivity this way, you do attenuate it quite a bit
with each layer.
The question then becomes - is is worth the increase in size? Since the
pressure sensitivity
is well below many other environmental factors …. probably not.
The CSAC is a can within a can (or more properly, the physics package is
inside a sealed can) but I don't know if there's vacuum inside the can.
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