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EMC GENERAL INFORMATION

1 EMI AND EMS

Almost every electronic device emits some electromagnetic interference (EMI). These

emissions can be transmitted as electromagnetic radiation or conducted through cables

such as power cords. At the same time, most electronic devices are susceptible to emissions

generated either internally or by other devices.

Receptors susceptible to electromagnetic radiation include communication receivers such as

radio and television, radar and navigation devices or computing devices. The effect of the in-

terference on the receptor depends on several parameters: strength of the source, transmis-

sion medium, distance from the source, coupling mechanisms and degree of susceptibility of

the medium.

Figure 2. EMC Contents: EMI and EMS

Electromagnetic interference (EMI) tests involve measuring the frequency and amplitude of

undesirable signals emitted by the tested equipment. Signal radiated into free space are

called radiated emissions, whereas signals travelling along power cords or other intercon-

necting cables are called conducted emissions.

Electromagnetic susceptibility (EMS) testing is a way to determine the ability of the device

to operate properly in an undesirable electromagnetic environment. These tests use signal

sources and power amplifiers to generate high level fields around a device. Conducted sus-

ceptibility measurements are performed by coupling an offending signal of a specified level

onto cables to try to induce a malfunction into the tested device. Other forms of susceptibility

tests include electrostatic discharge (ESD), transient burst and voltage surge testing.

VR02102B

Electromagnetic

Susceptibility

EMS

EMI

Electromagnetic

Interference

Radiated

Conducted

Radiated

Conducted

EMC

Electromagnetic Compatibility

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