Chassis Height
Basically all industrial equipment chassis define their height in Units 'U'. One 'U' [1U] is equal to 44.45mm. Rack panels and boards are defined the same way. Each unit increase grows by 44.45mm, so 2U is 88.90mm. 1U is normally the smallest blank panel in a rack and the smallest chassis height. A 1U chassis will normally hold one or two circuit boards mounted in the chassis horizontally. How ever vertical card mounting is more common and does not have the vibration issues of horizontally mounted cards.
Commercial PC cases are just classified as desk top or tower cases. An embedded PC is the exception and may use the modular unit measurement above.
Chassis width is given in Horizontal Pitch or HP. One HP [1HP] is equal to 5.08mm. There are three common rack widths; 465mm, 592mm, and 745mm [hole-to-hole]. Standard Rack depths are 17, 24, 29, and 36 inches.
Board Form factors; next page
Index page; How To Specify a Equipment Chassis
