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Forty years ago, when Bell Labs researchers developed the first CCD camera, the technology was exclusively for the clean, climate-controlled lab. Today, vision operates in punishing applications ranging from inspecting steel castings straight out of the furnace to imaging Jupiter amid staggeringly strong radiation belts. Such performance doesn’t happen by accident, though; it takes careful design and testing to achieve systems capable of standing up to harsh conditions such as shock and vibration, extreme temperatures, contamination, and radiation.
In manufacturing environments that involve volatiles like propane, paint or adhesives, a spark in the camera electronics could conceivably ignite a conflagration. To protect the production floor and workers alike, integrators typically use explosion-proof housings. “An explosion-proof housing is designed such that if gases or dust get inside and the camera sets them off, the explosion won’t get out of the enclosure,” says Chris McGeary, president of the Allison Park Group (Allison Park, Pa.). “The enclosure is tested to ensure that external impacts would not damage it.”
Explosion-proof housings are typically 0.25-inch-to-0.5-inch-thick cast-aluminum cylinders without corners or seams that might be vulnerable to pressure. Housings can range from fitting only the camera to holding the camera, light source, and lens. The endcaps unscrew to allow access to hardware.
Users should be aware that housings are generally qualified for only a range of temperatures. Depending on whether the light source is included and how much heat it generates, not to mention the ambient conditions, it’s easy to exceed the temperature limit of an enclosure.
Sizing the enclosure can be another issue. The common mistake is to buy an enclosure that fits the camera and lens, without leaving additional space for filters and cabling. Thick camera cables, in particular, can require as much as three inches of space at the back of the enclosure to allow for the bending radius.