4. Protection of equipment under test. Definition of a filter box

For certain tests, such as radiated emission measurements in accordance with MIL STD 461 E, a measurement noise level 6 dB below the limit is required. This noise level must be measured with the equipment switched off and the equipment outside the cage energized. Other tests, such as lightning injections (functional upset testing) or the electrical fast transient test (in accordance with EN 61000-4-4) are carried out with active control equipment. It seems obvious that the protection of checking fixtures must be provided for. These checking fixtures are often developed without regard for the rules of the art, and are highly sensitive and highly polluting pieces of equipment.

A filtering interface box is a solution that provides good decoupling between the inside and outside worlds of the cage. This box must be designed so that it can be positioned across the Faraday...