We have a custom enclosure that houses electronics. We have a humidity sensor installed and can read that via wireless. We want to know if air trapped inside the housing will condense under any circumstances. How do we test for this? We have put the housing into a freezer and then brought it out and read the sensor. Are there other tests that we can do?
Fasemex Toys
Fasemex Toys And Games
3 Comments
February 8, 2010 in Electronics Tagged condensing, determine, Electronics, enclosure, inside, test, water
3 Responses
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sciquest
Unless you have a perfect air tight box and have some type of bellows indide to reduce the pressure differential, over time the seal will leak and will exchange air with the ambient.
The worst case test would be to condition the box to suck in air at relatively high humidity and high temp to have a max possible absolute amount of water inside the box. One such scenario may be as follows:
(1) Bake and soak the box at its hottest storage/operational temp to let the air inside expand and bleed to the environment
(2) Cool the box down, may be to room temp and always with near 100% relative humidity surrounding air, soak the box at the cool temp to let the external air, with the water, get in due do to equate the pressure inside the box to that of the ambient air
(3) Repeat Steps 1 and 2 few times–each air exchange cycle, due to dilution of the air inside the box, nets out more water inside the box
(4) Further freeze the box down to its mininum storage/operational temp, always maintain 100% surrouding air ambient relative humidity. At the lowest temperature you have conditioned the box to the worst internal condensing condition: your sensor inside should report a 100% RH.
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You could put a glass window at the lowest point and look at that, either visually or with a beam set at a glancing angle and going to a photosensor. You could also put an glass plate in there and deposit two electrodes on the glass. Measure the current between the electrodes and it will increase dramatically with moisture in there.
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What I will do is to first put this module in high humidity chamber for 1 hr, then move it freezer and keep it there for 1/2 hr. Take the unit out, open it up and take a look.
To help yourself in identifying condensation more easily, you may want to paint interior of the unit with some sort of watersoluble ink (e.g. you can draw long lines and break in lines will signify condensation).