Equipment Chassis Form Factors

The size and shape of an electronic equipment chassis is dictated by a number of factors. The type of card used within the chassis plays a large role, but many of the Board configurations result in the same size case. This discussion covers the form factor of the equipment chassis, and not the board form factor which is a separate issue.

Equipment enclosures can be sub-divided into four main categories; Rack-Mount, Wall-mount, Tower, or table-top. Portable is another chassis style, but normally a Portable chassis is also a Desk-Top chassis. Any of these types of chassis may be further categorized into either of these sub-categories; Commercial, Industrial, Rugged, or Military.

Additional configurations include a Sub-rack which is not a complete electronic enclosure and may only include a metal frame and a card cage. A Card Cage has no enclosure at all and is just a frame [with card guides] to support the particular CCA form factor used [CCA; Circuit Card Assembly].

Rack-Mount chassis are designed to fit inside an equipment rack. The physical size of the rack sets the maximum width of the chassis. The most common rack width is 19", and there are a number of commonly used depths.

Wall-Mount chassis are not that common. Normally Wall Mounted Enclosures are more equipment cases than chassis. Because of weight issues a wall mount chassis will not support many cards, if any cards at all. A Wall-Mount chassis could be no more than a Mother-Board, a read-out and some I/O.

Table-top chassis are designed to rest on a table. A table top chassis can be any size or shape, but will almost always have large rubber feet to support the chassis on the table. Chassis's designed for table-tops could be a normal chassis or used with Automatic Test Equipment [ATE] or as a Test Bed to design and develop embedded cards used within the same chassis style. When used as a development chassis this style may be purchased with out sides or top panels so the developmental cards can be worked on.

Portable chassis are smaller in size and weight and normally designed with a rigid handle on the top of the chassis so that the case can be carried. Portable chassis may be used for demonstration purposes for presentations, but other than that a portable chassis does not seem to be that common.

Developmental Chassis is any style chassis that is designed to allow testing and debug of prototype circuit boards. Sometimes the side and top panel of the chassis is detachable to make it easier to work on the circuit boards under development. In some cases a Developmental Chassis may also be a Table-top chassis.


Next section on how to design a chassis:
Chassis Height Specifications

When designing a rack mount chassis remember to leave room for any cable bend radius within the rack. The larger the cable, the greater the bend radius. Reference the page on Cable Carriers.

PC motherboard

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