Every electronic device generates electromagnetic radiation. It’s a byproduct of the electric current passing through a circuit. This energy is on the low-frequency, non-ionizing end of the electromagnetic spectrum. Unlike the ionizing radiation generated by the sun, X-ray machines, and radioactive elements, non-ionizing radiation is not harmful to living cells.
However, an electronic device’s electromagnetic fields (EMFs) can harm other devices around it. That’s why devices must meet specific regulatory requirements for electromagnetic compatibility (EMC).
What Is EMC?
EMC stands for “electromagnetic compatibility.” It examines a device’s ability to 1. function as expected in its electromagnetic environment and 2. not affect the other equipment in the environment’s ability to operate correctly.
In other words, EMC examines how well a device functions in the presence of electromagnetic energy and how much electromagnetic energy it produces that could potentially harm other devices in the environment. Electromagnetic compatibility can be achieved by limiting the unintentional creation and reception of potentially harmful electromagnetic energy (like EMI).
Difference Between EMI and EMC
“EMI” and “EMC” are often used interchangeably in device testing. Although related, they describe different things. EMI stands for “electromagnetic interference.” It describes electromagnetic energy that interferes with electronic devices.
Radio frequency interference is among the most common sources of interference seen today. Radio frequency interference (RFI) occurs when the electromagnetic energy in question is on the radio frequency spectrum.
EMC seeks to mitigate the impact of EMI through effective shielding of susceptible equipment. Mitigating electromagnetic interference (EMI) leads to electromagnetic compatibility (EMC).
Check out our blog entries to learn more about EMI RFI shielding and EMI shielding materials.
What Is EMC Testing, and Why Is It Important?
EMC testing determines how well a device can operate in the presence of electromagnetic energy in its environment and how much electromagnetic energy the device itself generates that could cause electromagnetic interference for other devices in its environment.
EMC testing focuses on two main issues. Emissions suppression and susceptibility hardening (mitigation).
EMC Emissions Testing
EMC emissions testing examines the amount of electromagnetic energy a device produces that could cause electromagnetic interference for other devices in its environment. It falls into two main categories.
- Radiated emissions – Measures the electromagnetic disturbance a device creates itself.
- Conducted emissions – Measures the amount of internal electromagnetic energy which can travel from this device via a conductor (typically wires) that could cause EMI on other devices or systems in the environment.
EMC Immunity and Susceptibility Testing
EMC immunity and susceptibility testing examine how well a device functions in the presence of outside electromagnetic energy. Similar to emissions testing, immunity and susceptibility testing fall into two main categories.
- Radiated immunity/susceptibility – Measures how well a device will perform when exposed to electromagnetic energy it will encounter in its common environment.
- Conducted immunity/susceptibility – Measures how a piece of equipment responds to electromagnetic energy generated from another source but is conducted (typically along a cable) to the device under test.
EMC testing labs and operators also consider coupling. This is the mechanism or pathway through which emitted interference reaches the impacted device.
EMC testing is essential because the generation of electromagnetic energy is ubiquitous throughout modern electronic devices. Any device that uses digital techniques and has timing pulses greater than 9000 cycles per second is a source of unintentional radiation. That includes every device with a microprocessor. Intentional radiation is generated by alarm systems, cordless phones, remote controls, and other devices that transmit radio signals.
EMC Compliance, Standards, and Certification
Virtually every country requires the testing and certification of devices to ensure they meet EMC standards. In the U.S., those standards are regulated by the Federal Communications Commission (FCC) according to FCC Rules and Regulations Title 47, Part 15.
EMC Class A vs. EMC Class B
Regulated devices generally fall into two categories. Devices for commercial or industrial use fall into Class A, and devices for consumer use fall into Class B. Class B devices have more stringent limitations on EMC than Class A devices. There are exemptions for appliances, automobiles, industrial, medical and scientific equipment, and a few other categories of devices.
United States vs. International EMC Standards
Regulated products sold in the U.S must be tested according to the procedures outlined in ANSI Standard C63.4. The objective is to ensure that they meet standards for RF emissions in the 9kHz to 40GHz frequency range. The rules may require a declaration of conformity, verification, or certification, depending on the type of device. The FCC regulates only emissions, not susceptibility/immunity of devices under test.
The E.U. regulates both emissions and susceptibility/immunity according to IEC 61000 standards. EMC Directive 2004/108/EC states that equipment must be tested for compliance and labeled accordingly. Many other countries require compliance with either the FCC or E.U. standards, although some countries have developed their own similar regulations. In some cases, testing must be performed by a certified lab.
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