Equalizing the pressure in a sealed box

IP67

Thanks, those would be too big for us though. But it looks like there are smaller versions, as well as the "gore-tex" based solutions. The membrane under the lid idea in fact looks do-able too, and could also keep out water vapour.

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.

He has been dead a lot more than 17 years so his patents have probably run out!

Install a schraeder valve and fill with nitrogen!

Steve

Care to "expand" on this?

The aircraft industry uses nitrogen in the tires of planes because of its extremely low expansion in tires at altitude. The auto industry is using it in land vehicle tires now as well because of its low expansion rate due to heat. A schraeder valve is the type use in valve stems on tires and can be purchased in many different mounting styles for uses other than tires. This may be an option.

Steve

OK, I understand now - thanks for the clarification.

Nitrogen is used to prevent the tires from exploding if they overheat, it's true. However, this isn't because it's some magic gas whose P vs V curve is different from every other near-ideal gas, but rather because rubber doesn't burn in a nitrogen atmosphere. High partial pressures of oxygen make things burn *fast*--see the Apollo 1 fire for an appalling example.

Nitrogen won't help the OP's problem at all--it obeys PV=nRT just like every other nearly-ideal gas.

Cheers,

Phil Hobbs

Thread a nipple through the hole, the same size as a toggle switch barrel. (I think it's something like 1/2-32 or so.)

Cheers! Rich