Re: Equalizing the pressure in a sealed box

On Tue, 16 Dec 2008 10:22:03 +0000, John Devereux <john@xxxxxxxxxxxxxx>
wrote:

Archimedes' Lever <OneBigLever@xxxxxxxxxxxxxxxxxx> writes:

On Sun, 14 Dec 2008 18:08:20 +0000, John Devereux <john@xxxxxxxxxxxxxx>
wrote:

Archimedes' Lever <OneBigLever@xxxxxxxxxxxxxxxxxx> writes:


[...]


Place the internal assembly in a clear ESD bag and remove practically
all the air from it, then there will not be much 'air' to regulate, and
the bezel/touchpad should remain as intentionally fixtured.

Sorry, I don't quite follow what you mean here.


An ESD bag because that keep static generating devices away from your
circuitry. A clear ESD bag, because they make them now.

Remove the air from it after you place your assembly in it, add a
desiccant bag, then seal it. What little air that remains will not
expand much. A test would be to simulate the pressure at 70,000 ft and
see how far the bag bloats, if at all. Place that assembly inside your
box, along with your desiccant bag. Your pressure sensitivities should
be dispersed.

Perhaps I'm being thick but I still can't visualise it.

We have a LCD, some circuit boards, a metal block, sealed external
connectors, and a keypad+window on the front. The internal components
take up maybe 1/3 the internal volume (in an irregular shape).

There's nothing we could reasonably put in a bag - apart from anything
else we would need to get the wires & fixings out etc!


I didn't know that it had I/O connectors on it.

You could put some space shuttle external tank foam in there...

Oh wait... that expands at altitude!
.

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