Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

electromagnetic interference (EMI)
(1) any electromagnetic disturbance that interrupts, obstructs, or otherwise degrades or limits the effective performance of electronics/electrical equipment. It can be induced intentionally, as in some forms of electronic warfare, or unintentionally, as a result of a spurious emissions and responses, intermodulation products, and the like. Additionally, EMI may be caused by atmospheric phenomena, such as lightning and precipitation static and non-telecommunication equipment, such as vehicles and industry machinery.

(2) unwanted high-frequency electrical signals, also known as radio frequency interference (RFI), which can be generated by
power electronic circuits switching at high frequencies. The signals can be transmitted by conduction along cables (450 kHz to 30 MHz) or by radiation (30 MHz to 40 GHz) and can interfere with control or other electronic equipment.