"EMC" - THE BASICS

Electromagnetic compatibility (EMC) is the ability of equipment to operate as intended in its electromagnetic environment without causing unacceptable interference to other equipment.

Electromagnetic interference (EMI) is the unwanted disturbance that EMC design and testing aim to control. Understanding the difference helps you choose the right fix.

This guide explains emissions, immunity and the role of testing in bringing an electronic product to market.

What is EMC?

EMC considers both the electromagnetic noise a product produces and its ability to keep working when exposed to noise from other sources.

Design, measurement and testing help identify whether equipment meets the requirements for its intended use and destination market. Good EMC design reduces the risk of interference between products operating in the same environment.

Why is EMC important?

Unwanted electrical noise can cause communication errors, unexpected resets, unreliable measurements and interference with nearby equipment.

Controlling emissions and improving immunity helps equipment operate reliably. It also forms part of the regulatory assessment required for many electrical and electronic products.

How do you achieve EMC compliance?

Start with the intended environment and the requirements that apply to your product. Good PCB layout, grounding, shielding and filtering help reduce problems before testing begins.

Pre-compliance testing on early prototypes can reveal issues while changes are still manageable. Evaluate each modification on the complete system, including its power supply, cables and operating modes.

A practical fix may be an in-line filter, cable ferrite or improved enclosure shielding. Confirm the result by measurement, then record the change so it can be reproduced in production.

Relevant regulations and standards

The applicable requirements depend on the product, its intended environment and where it will be sold. Product and generic EMC standards define test methods, limits and performance criteria; there is no single test list for every electronic product.

Great Britain: equipment within the EMC regime must meet the applicable requirements of the Electromagnetic Compatibility Regulations 2016. Compliant CE-marked products continue to be recognised alongside the UKCA route. Northern Ireland has different marking arrangements. See the current GOV.UK EMC guidance.

European Union: products must meet the EU legislation that applies to them. For equipment within its scope, the EMC Directive 2014/30/EU is part of the CE-marking assessment. Applicable harmonised standards can provide a presumption of conformity for the requirements they cover.

United States: FCC rules, including relevant provisions of 47 CFR Part 15, apply to many electronic products. The required assessment depends on the equipment and its functions.

Useful standards and organisations include:

  • CISPR 11: radio-frequency disturbance requirements for equipment within its scope.
  • CISPR 32: emissions requirements for multimedia equipment.
  • CISPR 16 series: radio-disturbance measurement equipment and methods.
  • IEC 61000-4 series: common EMC immunity test methods.
  • CISPR: International Special Committee on Radio Interference.
  • IEC: International Electrotechnical Commission.
  • EN: the designation for European standards, developed through the relevant European standardisation organisations.

EMC is one part of the assessment. Safety, radio, environmental and other requirements may also apply. Contact us if you need help identifying the right route for your product.

COMMON ACRONYMS:

  • ANSI - American National Standards Institute
  • APLAC - former Asia Pacific Laboratory Accreditation Cooperation
  • BCI - Bulk Current Injection
  • CI - Conducted Immunity
  • CISPR - International Special Committee on Radio Interference
  • EFT - Electrical Fast Transients
  • EMC - Electromagnetic Compatibility
  • EMI - Electromagnetic Interference
  • ESD - Electrostatic Discharge
  • FCC - Federal Communications Commission
  • IEC - International Electrotechnical Commission
  • RFI - Radio Frequency Interference
  • RI - Radiated Immunity
  • RES - Radiated Electromagnetic Susceptibility

These abbreviations are commonly used in the field of EMC and are important to understand when working with electronic devices and systems. Knowing these abbreviations can help you understand the different types of electromagnetic disturbances and the regulations and standards that apply to them.

Putting it into practice

Identify whether the problem is unwanted emissions or reduced immunity, find the coupling path, and choose a fix suited to the frequency and interface involved.

Use the guides and product specifications to narrow your options, then verify the result on the complete equipment. A component that improves one setup does not automatically establish compliance for every installation.

STILL UNSURE?

Tell us about your product, the test result and the cables involved. We can help you choose a practical next step.

Contact Us