Electromagnetic compatibility

From Wikipedia, the free encyclopedia

Electromagnetic Compatibility (EMC) is the branch of electrical sciences which studies the unintentional generation, propagation and reception of electromagnetic energy and the unwanted effects of that energy. In particular, the aim of EMC is the correct operation, in the same environment, of different equipment which involve electromagnetic phenomena in their operation.

To achieve this objective EMC pursues different issues: emission issues, in particular, are related to the countermeasures necessary to reduce the unintentional generation and propagation of electromagnetic energy into the external environment; susceptibility or immunity issues, on the other hand, refer to the correct operation of electrical equipment in the presence of electromagnetic disturbances from that same environment.

When the propagation of electromagnetic disturbances in guiding structures, i.e. conductors, transmission lines, wires, cables, printed circuit board (PCB) traces, is by a conduction mechanism, conducted emission and susceptibility issues are considered, whereas, with open-space propagation of electromagnetic disturbances, the point of focus becomes radiated emission and susceptibility phenomena.

[edit] History

In the past, outside of the military field, there was a relaxed EMC regime and EMC was not of paramount concern to equipment manufacturers.

However, because of the proliferation of the clocks that synchronize modern digital circuits, the concomitant increase in their switching speeds, and the lower voltages these systems used, EMC increasingly became a source of concern. Many nations became aware of this growing problem and issued directives to the manufacturers of these digital electronic equipment, which set out the essential requirements which must be satisfied before such equipment may be sold. Organizations in each nation were set up to draw up and safeguard these directives.

Among the more well known national organizations are:

The FCC for the United States. CEN, CENELEC and ETSI for Europe and BSI for Britain.

There are also several international organizations who try "to promote international co-operation on all questions of standardization" (harmonisation), including EMC standards.

The most important international organisation is the International Electrotechnical Commission (IEC), which has several committees working full time on EMC issues.

These are "TC77" working on "electromagnetic compatibility between equipment including networks", and the International Special Committee on Radio Interference (CISPR).

Co-ordination of the IEC's work on EMC between these committees is the responsibility of the ACEC, the advisory committee on EMC.