What Are EMC and EMI?

Electromagnetic compatibility (EMC) and electromagnetic interference (EMI) are frequently referred to when discussing the regulatory testing and compliance of electronic and electrical products.

Electromagnetic compatibility and interference are extremely important design considerations. Failing to consider them in the early stages of product development can result in the time-consuming and costly need to redesign the product at a later stage or that your product can’t pass governmental certifications which means you won’t be allowed to sell it until those issues are resolved.

What is EMI?

EMI is the interference caused by an electromagnetic disturbance that affects the performance of a device. Sources of EMI can be environmental, such as electrical storms and solar radiation, but more usually will be another electronic device or electrical system. If the interference is in the radio frequency spectrum, it is also known as radio frequency interference or RFI.

Electromagnetic interference often manifests as undesirable noise and may lead to disrupted function of electrical, electronic, and RF systems. There are four types of EMI:

  • Conducted EMI EMI that flows through wires and is caused by physical contact with the source of EMI.
  • Common Mode EMIA high-frequency EMI that flows in the same direction through one or more conductors.
  • Differential Mode EMIA low-frequency EMI that flows in an opposite direction through adjacent wires.
  • Radiated EMIThe most common type of EMI, caused by radiating electromagnetic fields. Common manifestations of radiated EMI include static noise on AM/FM radio receivers and “snow” on TV monitors.

Common sources of EMI include:

  • Power generating equipment and peripherals such as; generators, power supplies, voltage regulators, switches and relays, battery chargers, and high voltage electrical transmission lines.
  • Devices operating at high frequencies like oscillators, computing devices, radios, radar, and sonar equipment.
  • Machines that use both high voltage and high frequencies, including motors and ignition systems.

What is EMC?

EMC is a measure of a device's ability to operate as intended in its shared operating environment while, at the same time, not affecting the ability of other equipment within the same environment to operate as intended.

Electromagnetic compatibility of an electrical, electronic, or RF device has two facets:

  • The ability to work properly in the presence of electromagnetic radiation.
  • The ability to not generate additional EMI that affects the operation of other devices in its vicinity.

Even though EMC testing can be expensive, it is essential to ensure that a design will function properly and won’t generate disruptive electromagnetic interference.

Help for Designers

How can you help ensure that your design will pass EMI/EMC testing? F3 Wireless is one option. They offer a schematics review service that will help designers understand the potential risks associated with their design and offer solutions to mitigate any possible unintentional RF spurious emissions or receiver interference. This could save the designer a lot of time and expense later in the product development process, speed up time-to-market, and ensure the product works as intended. Something designers should seriously consider.

About this author

Image of Kelsie McMillin

Kelsie McMillin, Partnership Marketing Manager – Strategic Programs at Digi-Key, has been with the company since 2015. She works with all products and services related to the IoT and earned her Associate of Applied Science degree in Electronics Technology & Automated Systems from Northland Community & Technical College through the Digi-Key scholarship program. In her free time, she enjoys going on adventures with her family.

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