Electromagnetic compatibility

From Free net encyclopedia

Electromagnetic Compatibility (EMC) is the branch of electrical sciences which studies the unintentional generation, propagation and reception of electromagnetical energy with reference to the unwanted effects that such an energy may induce. In particular, the aim of EMC is the correct operation, in the same environment, of different equipments which involve electromagnetic phenomena in their operation.

In order to achieve such an objective, EMC pursues different issues: emission issues, in particular, are related to the reduction of unintentional generation of electromagnetical energy and to the countermeasures which should be taken in order to avoid the propagation of such an energy towards the external environment, susceptibility issues, instead, refer to the correct operation of electrical equipments in the presence of electromagnetic disturbances.

When the propagation of electromagnetic disturbances in guiding structures (i.e. wires, cables, printed circuit board (PCB) traces) is taken into account, conducted emission and susceptibility issues are considered, whereas, when the open-space propagation of electromagnetic disturbances is taken into account, radiated emission and suscebtibility issues are considered.

[edit]

History

In the past a relaxed EMC regime existed apart from in the military field, and equipment manufacturers did not care much about EMC issues. However, because of increases of clock speeds used in modern digital equipment coupled with the lower signal voltages these systems used, EMC became more and more an issue. Many nations became aware of this growing problem and issued directives to the manufacturers of these kind of 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.

[edit]