Electromagnetic interference (EMI) and electromagnetic compatibility (EMC) are two common terms you’ll see if you’re in the process of developing an electronic device.
Electronic devices are tested for both EMI and EMC before going to market. While these terms are similar, they refer to different things. Understanding the differences between EMI and EMC is important for designing your device correctly and complying with regulations.
Put simply, EMI refers to interference caused by electromagnetic emissions from an electronic device or natural source.
EMC refers to how effectively a device can operate when exposed to emissions, as well as its ability to operate in a shared environment without affecting other devices.
You can find more information about the differences between EMI and EMC below. For expert help with EMC testing and compliance for your device, please contact us online or call us at 866-540-5287 to talk to our engineering team.
What is Electromagnetic Interference (EMI)?
Electromagnetic interference, or EMI, refers to disruptions in an electronic device caused by an external source of electromagnetic energy. EMI is typically caused by electronic devices, which can release radiated emissions and conducted emissions, as well as certain natural events.
Radiated emissions are electromagnetic emissions produced by electronic devices that spread via the air. A device that uses poor design practices may radiate a lot of electromagnetic energy, causing interference that affects other devices.
Conducted emissions are electromagnetic emissions that spread via power or signal lines. This type of electromagnetic energy can produce interference that affects other devices on the same signal or power line as the emissions-producing device.
When emissions are released from a device, they can cause interference that may affect other devices in the surrounding area.
Examples of electromagnetic interference include:
- Speakers or headphones not functioning correctly when exposed to radio frequency emissions from another device.
- A TV losing its signal when power tools or other construction equipment are used in surrounding areas.
Electronic devices vary in electromagnetic immunity, or immunity to the effects of radiated or conducted emissions. A device with a high level of electromagnetic immunity will continue to function normally even when it’s exposed to significant electromagnetic emissions.
Sources of Electromagnetic Interference
Artificial sources of electromagnetic interference include:
- Cellphones and tablets
- Wi-FI routers and other equipment
- Baby monitors and home communications devices
- Bluetooth headphones, watches and other devices
- X-ray machines, MRI machines and other lab equipment
- Cellular networks and radio transmitters
- Devices that contain motors
- Electrical generators
- Electrical transformers
- Microwaves
Natural sources of electromagnetic interference include:
- Lightning
- Dust and snow storms
- Solar flares and radiation
- Aurora borealis/australis
What is Electromagnetic Compatibility (EMC)?
Electromagnetic compatibility, or EMC, refers to how well a device can operate without causing electromagnetic interference, or being affected by electromagnetic emissions released by other devices.
Put simply, EMC refers to how well a device blocks emissions from other devices, and stops its own electromagnetic energy from being released into the surrounding environment.
A device with a high level of electromagnetic compatibility is less susceptible to interference. It also has a lower chance of causing interference that may affect other devices.
Devices vary in their electromagnetic compatibility. A device with a poor PCB layout and choice of components is likely to be less electromagnetically compatible than a device with smart PCB design and proper component selection.
Additional factors that can improve a device’s EMC performance include the use of EMC filters, shielding, grounding and changes to its design. Our guide to reducing EMI shares a longer list of techniques commonly used to improve devices’ EMC performance.
Electromagnetic compatibility is a critical aspect of compliance with regulations for electronic devices. In the United States, FCC Part 15 sets electromagnetic compatibility standards that apply to almost all electronic devices.
Similar EMC regulations, such as the Electromagnetic Compatibility Directive in the EU, also apply to electronic devices and set minimum standards for electromagnetic compatibility.
Compliance with these regulations is required for market access. To receive FCC certification and/or CE certification, your device will need to demonstrate that its emissions and immunity match those required under these regulations.
How EMI & EMC Testing Works
In order to verify that a device has a sufficient level of electromagnetic compatibility for market access, testing is performed in a laboratory environment. The device, referred to as the device under test (DUT), is measured for radiated emissions, conducted emissions and immunity.
These tests are often performed in an anechoic chamber, or EMC chamber — a special testing room that is designed to absorb electromagnetic energy and sound waves, allowing for precise testing.
Different types and classes of devices may require distinct tests. If you are planning to market your electronic device and need help understanding the testing and compliance requirements, you can contact us to talk to our engineers about the required tests.
Learn More About EMI and EMC
- EMI and EMC Testing Basics
- Types of Electromagnetic Interference
- FCC Certification Process for Electronic Devices
