Instrument enclosures protect electronic devices inside metal or plastic housing. Because of their sensitive circuitry, the components must be protected from dirt, water and accidental contact. Being kept in an enclosure prevents the intrusion of solid foreign objects as well as liquids to a certain extent. Instrument enclosures are made from aluminum, acrylonitrile butadiene styrene (ABS) plastic, stainless steel and, for certain models, polyester with fiberglass reinforcing.
Instrument enclosures come in many varieties to accommodate the wide array of electronic instruments. For small handheld instruments, enclosures may be custom-contoured to the shape of the device and designed to provide long-lasting protection and shock absorption. Desktop instruments can generally be housed in a box-like enclosure that is manageable in size and durability, protecting against spills and accidental contact. Wall mounted enclosures keep their contents close to the electronic equipment the instruments control while shielding them from dust, dirt, splashing water and other undesirable contact. Electronic instruments are used in many applications, especially for precision work in scientific, engineering, medical and technological fields. Possible instrument uses include control panels, operation switches, measuring devices and more. New ways of making enclosures safe and effective are constantly being researched due to the demand for and critical nature of electronic instruments.
The parts of an instrument enclosure vary depending on the application. Hand held enclosures may have slide-on covers or a knockout for a LCD screen. Desktop enclosures may have vents, handles, locking mechanisms and membrane keyboards while wall mounted enclosures are frequently hung on DIN rail with the ability to slide into position. Other options incorporate neoprene seals or watertight gaskets, transparent lids or covers, recessed areas for labels or keypads, cylinder catches, lock covers, thermometers, drains, air dyers and special coatings to shield the contents from static electricity or EMI/RFI (electromagnetic and radio frequency interference). Metal enclosures can be constructed of cold rolled sheet metal that is welded for a smooth seam; aluminum is usually extruded. Plastics, fiberglass and composite materials are gaining favor in certain situations because of their corrosion resistance, durability and weight. No matter what the material is, however, there are certain standards to which all enclosures must adhere. NEMA, the National Electrical Manufacturers Association, UL, the Underwriters Laboratories and the IP Code, or the International Protection Rating are all used to identify the enclosure's strengths and applicable functions as determined by the conditions they can withstand. For example, the common NEMA Type 4X enclosure can be used indoors or outdoors to protect its contents against corrosion, windblown dust, rain, sleet, snow, splashing or hose-directed water and the external formation of ice.