Equipment Chassis Definitions

'A' to 'E' Chassis Terms, 'F' to 'Z'

Form Factor. The size and shape of a board or chassis. Dimensions may be provided as a measurement in mm, or a letter code that indicates a particular size [size 'A'], or in some other unit system [1U]. Circuit Card Assembly Board Form Factors

Fuse. A device that has as its critical component a metal wire or strip that will melt when heated by a prescribed (design) amperage, creating an open in the circuit of which it is a part, thereby protecting the circuit from an over-current condition. Also refer to How to Derate a Fuse, or Fuse Manufacturers

Ground Lug. A ground connection point on the outside of an equipment chassis. Refer to Chassis Grounding Issues. [Ground Lug Manufacturers]

Military Specifications. [MIL-SPEC] Technical requirements and standards adopted by the Department of Defense that must be met by vendors selling materials to DOD.

Military Standards. [MIL STD] Standards of performance for components or equipment that must be met to be acceptable for military systems. Military Specifications

Panel Mount. Any component that attaches to a side panel of a chassis. Normally a panel mount component will use the chassis wall as an attachment point as it protrudes through the chassis wall allowing connections or interaction to either side of the component. Panel-mount components could be switches, Fault Indicators, connectors, Fuse Holders, LEDs and so on.

Panel mount LEDs are a bit less common these days, as many designers may just select a lighted switch or lighted fuse holder to indicate power reaching the chassis or boards. Why add in an additional LED and the wiring associated with it when a lighted power switch will do the same thing. However if there is a requirement to indicate a particular power supply, than a separate LED may be required.

Printed Circuit Board. [PCB] See PWB.

Printed Wiring Board. [PWB] The circuit card used as the backplane within the chassis. Also refer to Terms used with PCBs.

SBC. Single Board Computer. Either a stand-alone computer board which does not require another board to function, or a computer board which requires a backplane or motherboard connection to receive power and pass data.

Subrack. A Sub-rack is not a complete electronic enclosure and may only include a metal frame and a card cage. When a Sub-rack is included as part of a chassis to hold the cards the Sub-rack may be Flush mounted, or Recessed mounted to the front of the chassis. A Flush-Mounted Sub-rack does not require a chassis front door. While a Recessed-Mounted Sub-rack may allow the addition of a front door to the chassis and may also allow panel to panel cabling behind the door, depending on the amount of Recess.

VME. An industrial board standard developed by the IEEE that uses the Euro board format/size. The IEEE 1014 defines board sizes, chassis, and electrical interfaces.

VXI. VME Extension for Instrumentation. An industrial board standard developed by the IEEE that uses the Euro board format/size. The VXI standard uses the VME spec as a base, but adds enhancements to cover Heat dissipation, and EMI radiation.

PC motherboard

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