Description

Electronic and instrument enclosures are structures that house electronic components and instruments. They are usually designed for handheld or desktop applications. Example applications include calculators, cash registers, remote controls, and data acquisition instruments.

Selection Considerations

When selecting enclosures, correct size and adequate protection are the priorities. When considering quality of protection, material type and professional rating systems are the deciding factors. Additional features such as ventilated sections or insulation may be important depending on the application.

Sizes and Shapes

Electronic enclosures and instrument enclosures are typically rectangular, slanted, t-shape, or readout style.  The top and bottom surfaces of a rectangular enclosure are parallel while the sides may be angled. Slanted enclosures are also generally rectangular in shape with the top surface angled relative to bottom surface.  T-shaped enclosures are generally used in handheld applications. The "handle” or lower portion of the enclosure is narrower than the upper portion of the enclosure. A readout style enclosure is a rectangular enclosure with a section of top surface sloped, typically for LCD readout.

The size of an enclosure depends on what is being encapsulated. Enclosures may come in standardized dimensions or shapes which can be stacked for assembly, or they can be custom built to particular specifications.

Material Types

The amount of protection and durability an enclosure depends largely on its material composition. Most electronic and instrument enclosures are made from materials classified as either metals or polymers.

• Metals generally exhibit higher conductivity to both heat and electricity than other material types. Steel is widely used to form enclosures because of its strength and malleability. Stainless steel is used rather than standard steel in environments requiring corrosion resistance and lightweight materials. Aluminum is a less expensive, lightweight, and more conductive metal that exhibits good resistance to oxidation.
• Polymers are nonmetal materials with varying properties. ABS is a hard, rigid, inexpensive thermoplastic polymer that has good chemical and creep resistance, but is prone to cracking under stress. Fiberglass is a strong, durable, reinforced polymer that is resistant to many caustics and extreme temperatures. Polycarbonate exhibits excellent impact strength and can be molded to tight tolerances, but has only moderate resistance to chemical corrosion. Polystyrene is used for its rigidity, hardness, heat, and dimensional stability and because of its ease of fabrication.

Rating Systems

NEMA ratings indicate whether electronic and instrument enclosures are suitable for hazardous or non-hazardous locations and designed for indoor or outdoor use. All NEMA enclosures protect personnel against incidental contact with the enclosed equipment.

The Ingress Protection (IP) ratings system from the International Electrotechnical Commission (IEC) describes the degree to which electronic and instrument enclosures provide protection against the ingress of foreign objects and moisture. There are six IP ratings that describe protection against foreign objects and vary from >50mm particle protection to completely dust-tight protection. There are eight IP ratings for protection against moisture which vary from dripping water protection to protection when completely submersed.