Monday, December 26, 2011

Ready-Made Connecting devices (cables) under EMC directive?

EMC test with stripline
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During the revision of the EMC directive 89/336/EEC, back in 2003, one of the most controversial proposals was the inclusion of “Ready-made connecting devices” within the scope of the EMC directive.

Ready-made connecting devices would encompass passive product, typically 3rd party in nature, designed to interconnect and be connected to apparatus covered within the scope of the directive, in effect classifying such connecting devices as apparatus themselves within the scope of the directive.

Products such as network cables, Audio / Video cables, and other interconnecting cables and adaptors would come under such classification and be subject to the protection requirements of the EMC directive (to paraphrase; must not interfere with others and must operate in the presence of interference without significant loss of performance) , thus requiring testing and marking as any other apparatus would.

It was argued that the term, “Ready-made connecting devices”, itself was ambiguous and unclear. Eventually it was decided that the devices represented no major interference potential, and because of the costs manufactures would incur for testing and marking, it was removed from the scope of the directive.

With the current revision and alignment of the EMC Directive with New Legislative Framework (NLF), the EMC directive 204/108/EC once again is subject to modification, and potential scope expansion. One such change being circulated for inclusion is that ready-made connecting devices be considered again and brought under the regime of the EMC directive.

In a proposal from the German Administration (BNetza), it is argued that in light of experience gained since 2003, the non interference claims argument cannot be maintained. The proposal claims there is no longer any serious doubt that insufficiently shielded connecting devices greatly increase the interference potential of TV and Cable networks in particular. The proposal cites several reports with data supporting this conclusion. One such report shows a  peak 30dB difference in screening effectiveness between two types tested, from most to least shielding, and notes that cable connectors can contribute around 10 dB of difference. See   ”The Concise Report of the CENELEC/ETSI Joint Working Group on the digital dividend" of 12 August 2010 (section 7.3)

The proposal suggests  that the following requirement be added to the new EMC directive;
Ready-made connecting devices, although incapable of generating electromagnetic disturbance in isolation, may generate or transmit electromagnetic disturbance when connected to an apparatus and should therefore be considered to be apparatus for the purposes of this Directive.

With ready-made connecting devices being defined as;
ready-made connecting devices' intended for connection to an apparatus by an end user for the transmission of signals, which are placed on the market separately from such apparatus, and which are liable to generate or transmit electromagnetic disturbance when connected to it.

This addition would then subject cables and connectors to the same technical requirements as any other product under the EMC directive, regardless of the component’s active or passive nature.

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