Ask Dr. Dave: June 2012
QUESTION: We manufacture an optical reader camera that attaches to gas, electric and water meter registers (digital display). We currently use a peel-off tape to bond the plastic reader to the plastic meter. The problem is that condensation sometimes builds up between our camera and the digital display, and we are looking for a solution.
ANSWER: There are two elements to your problem. Obviously, the moisture can come from two sources: atmospheric moisture can be trapped inside when you attach the camera to the meter, or moisture can enter the assembly during use. If your assembly is put together either indoors or outdoors at a relatively high temperature and humidity level, then any moisture in the enclosed air will condense on the coldest surface (the outside) when the temperature goes below the dew point. One possible solution to consider might involve putting a desiccant inside the enclosure to remove moisture. Beads of silica gel or molecular sieves should minimize any moisture being trapped inside, and these desiccants can be source packaged in small bags. Secondly, you need to attach the camera to the meter using an adhesive or sealant that prevents moisture from entering from the outside atmosphere. A good reactive acrylic adhesive is a favorable candidate, but a butyl sealant would be ideal. This combination of a desiccant and water-impermeable seal is used in the manufacturing of double-glazed windows to prevent condensation between the panes.