EMI and EMC: How They Are Differ?

EMI and EMC are the two terms that are related to each other and used for referring to the regulatory testing of electronic components and consumer goods. However, these two terms are different from each other.

All electronic devices or equipment produce electromagnetic radiation. We assume electronic devices as closed systems, however, the electricity flowing through the circuits and wires is never fully contained. The energy can travel through the air as electromagnetic radiation and/or conduct along interconnecting I/O or power cables, typically known as disturbance voltage.

Both EMI and EMC testing requirements can become complex with a wide variety of industry and application-specific implications that must be considered before bringing the product in the market.

Let’s understand the difference between EMI and EMC.

Electromagnetic Interference (or EMI)

The interference caused by an electromagnetic disturbance that affects the performance of an electrical/electronic device or equipment is known as EMI. EMI can occur naturally due to a variety of sources like dust storms and solar radiation. However, EMI usually occurs due to human-made sources like another electrical/electronic device.

The interference caused in the radio frequency spectrum is termed as radio frequency interference (or RFI).

Electromagnetic Compatibility (EMC)

EMC is a term that describes how a device can function in an environment of electromagnetic noise. There are two factors of electromagnetic compatibility — what is the device’s tolerance to noise and how much noise a device produces. A device must be able to operate in a shared operating environment without affecting the operation of other equipment in the same environment.

All electronic devices or products such as smartphones and smart refrigerators must pass compliance tests in a recognized test house. These products must be certified before bringing them to the market. The certificate indicates that the product will never electromagnetically interfere with any electronic products nearby. If you want your product to be certified, test houses are majorly concerned with ensuring that your product can pass four EMC tests: radiated emissions test, radiated immunity test, conducted emission test, and conducted immunity test.

The first two tests (radiated emissions test and radiated immunity test) refer to the electromagnetic energy released from the electronic product, and the last two tests (conducted emission test and conducted immunity test) refer to the internal electromagnetic emissions propagating along with signal/power cables, thus creating noise.

The emissions test is related to the amount of energy emitted from an electronic device, whereas the immunity test is related to how an electronic device is susceptible to electromagnetic energy emitted from surrounding devices.

The standards for testing electronic devices are set up by regulatory bodies such as FCC in the US. These standards vary with each product; for instance, the measurement of the amount of EMI on a smart refrigerator is different from that of military-grade avionic equipment. EMI is measured to ensure that there is no interference between devices during operation.

Conclusion

Electromagnetic Interference (EMI) and Electromagnetic Compatibility (EMC) are the most important design considerations. If you fail to consider these terms in the early stage of product development, you will need to redesign the product at a later stage to meet the EMI/EMC specification tests and prevent product failure or safety risk, which is an expensive and time-consuming process