EMC Testing Explained

Electromagnetic Compatibility (EMC) testing and compliance is a subject we deal with often.  However, depending on the system being designed and the region it is being used in, the standards and processes can be different.  This article was written to help clarify the purpose, scope, terminology, and importance of this testing.

EMC testing is a process to ensure that electronic devices operate as intended in their electromagnetic environment and do not emit levels of electromagnetic interference (EMI) that could cause malfunction of other devices. EMC testing encompasses two main aspects: emissions and immunity.

Key Concepts in EMC Testing

  1. Emissions Testing:

    • Purpose: To measure the amount of electromagnetic interference a device emits. The goal is to ensure that the device does not exceed the prescribed EMI limits.
    • Types of Emissions:
      • Radiated Emissions: These are EMI that the device emits through the air.
      • Conducted Emissions: These are EMI that the device emits through power or signal lines.

  2. Immunity Testing:

    • Purpose: To determine a device's ability to operate correctly in the presence of electromagnetic disturbances.
    • Types of Immunity Tests:
      • Radiated Immunity: Ensures the device can function correctly when exposed to electromagnetic fields.
      • Conducted Immunity: Ensures the device can operate correctly when exposed to EMI conducted through power or signal lines.
      • Electrostatic Discharge (ESD) Immunity: Tests the device’s resilience to static discharges.
      • Surge Immunity: Ensures the device can withstand high-energy surges typically caused by lightning strikes or power system faults.
      • Electrical Fast Transient (EFT) Immunity: Tests the device’s resistance to fast, repetitive bursts of energy typically caused by inductive loads switching.

EMC Testing Standards

Different regions and countries have their own EMC standards that products must meet before they can be marketed and sold. Some of the commonly referenced standards include:

  • CISPR (International Special Committee on Radio Interference): Develops international standards for controlling EMI.
  • IEC (International Electrotechnical Commission): Provides international standards for electronic devices, including EMC.
  • FCC (Federal Communications Commission, USA): Regulates EMI for electronic devices sold in the United States.
  • EN (European Norms): Standards used in the European Union for EMC compliance.

EMC Testing Process

  1. Pre-Compliance Testing:

    • Preliminary tests performed during the design and development stages to identify and rectify potential EMC issues early in the product lifecycle.

  2. Compliance Testing:

    • Formal testing performed in accredited laboratories to ensure the product meets the required EMC standards.
    • Includes both emissions and immunity testing.

  3. Documentation and Certification:

    • Detailed test reports and documentation are prepared, demonstrating compliance with the relevant standards.
    • Certification marks (such as CE in Europe or FCC in the USA) are applied to the product to indicate compliance.

EMC Testing Environments

  • Anechoic Chambers: Specially designed rooms that absorb reflections of electromagnetic waves, providing a controlled environment for radiated emissions and immunity testing.
  • Shielded Rooms: Enclosures that block external electromagnetic fields, used for conducted emissions and immunity testing.

Importance of EMC Testing

  • Ensures Device Reliability: Helps in verifying that devices operate reliably in their intended electromagnetic environment.
  • Prevents Interference: Minimizes the risk of devices interfering with each other, ensuring they can coexist without performance degradation.
  • Regulatory Compliance: Necessary for meeting legal and regulatory requirements for market access.
  • Safety: Reduces the risk of electromagnetic disturbances causing dangerous malfunctions in critical systems such as medical devices, automotive electronics, and industrial controls.

EMC testing is a critical part of the product development cycle, ensuring that electronic devices function correctly and safely within their electromagnetic environment while complying with regulatory standards. 

The engineering team at Zippertubing has many years of experience assisting with designing and recommending proper EMI shielding, especially on cables and harnesses.  For assistance early in the design process or to remedy issues discovered during the testing phase, we are happy to provide support.

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Matt Hesselbacher - Principal Engineer

Written by Matt Hesselbacher - Principal Engineer