EMI & EMC

EMI & EMC

(1) What's the difference between EMI and EMC?

When it comes to regulatory testing of electronic components and consumer goods, the terms electromagnetic interference (EMI) and electromagnetic compatibility (EMC) are generally used interchangeably. Because they are related in many ways, it's easy to confuse the two. In this article, we try to uncover the mystery of EMI and EMC, and provide a basic overview of the types of test equipment used, as well as the corresponding requirements of each field.

Any electronic equipment will produce a certain amount of electromagnetic radiation. We think of electronic equipment as a closed system, but the current flowing through circuits and wires will never be fully controlled. This energy can be transmitted by air as electromagnetic radiation and / or along (or coupled to) interconnected I / O or power cables, which is often referred to as "interference voltage.".

EMI and EMC's testing requirements can become very complex, and a wide range of industry and application specific impacts must be considered when bringing products to market.

(2) What is EMI?

EMI can be defined as the electromagnetic wave energy that affects the function of electronic equipment. Sometimes, the source of EMI may be natural environmental events, such as electric storms and solar radiation; but generally, the source of EMI is another electronic equipment or electrical system. Although EMI can be generated from any electronic device, some devices and components (such as mobile phones, welding machines, motors and LED screens) are more prone to interference than others.

Because electronic products rarely operate independently, they are usually designed to operate in the presence of a certain amount of EMI, which is particularly important in military level and avionics equipment, as well as equipment requiring high reliability in all cases.

(3) What is EMC?

EMC measures the ability of a device to operate as expected in its shared operating environment without affecting the ability of other devices in the same environment to operate as expected. Evaluating how the device reacts when exposed to electromagnetic energy is an integral part of this process, which is called immune (or sensitivity) testing. Measure the amount of EMI generated by the electrical system inside the device - another process called emission testing.

Both aspects of EMC are important design and engineering considerations in any system. Failure to correctly predict the EMC of equipment may have many negative consequences, including security risk, product failure and data loss. As a result, a variety of test equipment for EMC and EMI has been developed, enabling engineers to have a clearer understanding of how the equipment operates in real conditions.

(4) Measure and monitor EMC?

Radiation testing requires the use of EMI measuring equipment, such as receiving antennas, amplifiers and spectrum analyzers. By working together, these tools can accurately measure the amount and type of noise produced by the equipment. This can be done in an open area test site or in a shielded, silenced (or semi silenced) test room.

Immunity (or sensitivity) testing involves determining the ability of the device to tolerate noise from external sources, for which it is necessary to use tools that can simulate and measure specific frequencies of electromagnetic energy. EMC test equipment can be used to make equipment subject to electromagnetic noise of various frequencies, simulate power surge or evaluate the effectiveness of equipment power supply. Finally, the nature of the equipment, its intended application and any regulatory requirements will determine the type of test equipment required.

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