Chassis EMI/RFI Issues:
As found in the links below, to each of the individual topics, this page serves more to re-map the issue to a more specific topic in chassis specification, rather than cover one. The picture is just an example of a Enclosed Chassis, in this case an ATR case. |  |
Front doors may be added to the front of the chassis to completely enclose and shield the cards held within the chassis. When chassis doors are used the card cage needs to be recessed to allow room for card panel connectors and any cable bend radius. Card front panels may be purchased with or with out EMI protection, usually in the form of copper fingers placed around the edge of the front panel [Front Panel Manufacturers]. Aluminum Air diverters may be used inside the chassis to help shield one card from another [Slot By-pass cards]. Air diverters are also normally supplied with a front panel, so separate front panels, or filler panels may not be required when an Air diverter is used in a slot. Of course metal and not plastic card guides would help with metal to metal contact of the Air diverters [Card Guide Manufacturers].
Metal dust caps can be placed on unused external connectors to shield their pins [and the signal lines] and provide EMI protection [Connector Dust Cap manufacturers].
EMI gaskets placed around all the connector cut-outs will reduce EMI leakage. This link provides manufacturers of Conductive Elastomer Plastic Gaskets, Beryllium Copper BeCu Metal Gaskets and a number of EMI shielding methods.
AC Power connectors can also be protected and filtered, cables can be shielded from RFI. This link provides a list of Power Connector Manufacturers. Ground the chassis to the Equipment Rack using a Ground Lug attached to the chassis.
Chassis Construction; Screws installed every two inches will insure a tight cover to case fit. When an equipment chassis is completely enclosed there is no way for EMI to enter the system other than the cabling and connector to chassis interfaces.
Chassis Grounding; next page in the series
Circuit Ground and Earth Ground
EMI/EMC Military Standards:
MIL-STD-461E Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment
MIL-STD-462 Measurement of Electromagnetic Interference Characteristics of Subsystems and Equipment
How To Specify a Equipment Chassis; Section Index page
Custom EMI and RFI Products
