Electromagnetic compatibility (EMC) testing for information technology equipment (ITE) verifies that devices such as computers, network hardware, and multimedia products neither emit excessive electromagnetic interference nor fail when exposed to external disturbances. Governed by standards including CISPR 32/EN 55032, the IEC 61000 series, and GB 9254, EMC compliance is a mandatory requirement for market access in most regions. This article explains the scope, sample types, test items, methods, and practical applications of ITE electromagnetic compatibility testing.
Technical Overview
Electromagnetic compatibility (EMC) testing for information technology equipment (ITE) is a systematic evaluation process that ensures electronic devices can operate satisfactorily in their intended electromagnetic environment without introducing intolerable disturbances to other equipment or to themselves. With the rapid proliferation of digital devices operating at ever-higher clock frequencies and switching speeds, EMC performance has become a decisive factor in product design and regulatory approval.
EMC testing for ITE is generally divided into two complementary categories. Emission testing measures the electromagnetic energy a device unintentionally generates through conducted paths (such as the AC mains port and telecommunication ports) and through radiation into free space. Immunity testing, also called susceptibility testing, evaluates whether the device can continue to function acceptably when subjected to phenomena such as electrostatic discharge, radio-frequency fields, fast transients, surges, and power supply disturbances.
The principal standards framework for ITE and multimedia equipment includes CISPR 32 and CISPR 35 at the international level, adopted in Europe as EN 55032 and EN 55035, and in China as GB 9254 and GB/T 9383. Harmonic current and flicker limits are specified in IEC 61000-3-2 and IEC 61000-3-3, while immunity test methods are defined in the IEC 61000-4 series. In North America, the FCC Part 15 rules govern unintentional radiators, and in Japan, the VCCI voluntary scheme is widely applied alongside JIS-based methods.
Testing Samples
Electromagnetic compatibility testing applies to a broad family of information technology and multimedia equipment. Typical sample categories submitted to accredited third-party laboratories include:
Computing and Data Processing Equipment
Desktop and laptop computers, servers, workstations, tablet computers, point-of-sale terminals, and external storage drives. These samples are usually tested in a representative worst-case operating configuration, including all connected peripherals running simultaneously.
Network and Communication Equipment
Routers, Ethernet switches, wireless access points, modems, gateways, and network interface cards. Because these devices incorporate both wired telecommunication ports and radio transmitters, testing must address wired port emissions as well as coexistence with radio functions.
Peripherals and Imaging Equipment
Monitors, keyboards, printers, scanners, copiers, projectors, and multifunction devices. Motor-driven mechanisms and lamp or laser supplies in imaging equipment frequently introduce additional conducted disturbance sources that require careful evaluation.
Power Conversion Accessories
External power adapters, chargers, and DC power supplies intended for use with ITE. High-frequency switching converters in these accessories are among the most common sources of conducted emissions in the 150 kHz to 30 MHz range.
Combined Multimedia Equipment
Set-top boxes, digital media players, smart displays, soundbars, and broadcast receivers, which fall under the multimedia equipment scope that has merged the former ITE and audio/video standards into CISPR 32 and CISPR 35.
Testing Items
A complete EMC evaluation for information technology equipment typically comprises the following test items:
- Conducted emissions at the AC mains port, measured from 150 kHz to 30 MHz using an artificial mains network (LISN).
- Radiated emissions, measured from 30 MHz up to 6 GHz or above depending on the highest internal source frequency of the equipment.
- Conducted emissions at telecommunication/network ports, measured from 150 kHz to 30 MHz using an impedance stabilization network and a capacitive voltage probe.
- Harmonic current emissions, assessed against IEC 61000-3-2 for equipment with input current up to 16 A per phase.
- Voltage fluctuations and flicker, assessed against IEC 61000-3-3.
- Electrostatic discharge (ESD) immunity, typically at 4 kV contact and 8 kV air discharge levels.
- Radiated radio-frequency electromagnetic field immunity, typically 3 V/m or 10 V/m from 80 MHz to 1 GHz (and extended above 1 GHz where applicable).
- Electrical fast transient/burst (EFT) immunity, typically 1 kV on AC ports and 0.5 kV on signal and control lines.
- Surge immunity, typically 1 kV line-to-line and 2 kV line-to-earth on AC power ports.
- Conducted radio-frequency disturbances immunity, typically 3 V rms from 150 kHz to 80 MHz.
- Power frequency magnetic field immunity, typically 1 A/m for equipment containing magnetically sensitive components.
- Voltage dips and short interruptions on the AC power port, evaluated at multiple dip depths and durations.
Testing Methods
Emission measurements are performed in a normalized test environment. Radiated emission measurements below 1 GHz are conducted in a semi-anechoic chamber with a ground plane, or at an open-area test site (OATS), using calibrated broadband antennas and a conforming test receiver with quasi-peak and average detectors. Measurements above 1 GHz are performed in fully anechoic chambers using linearly polarized antennas. Conducted emissions use LISNs on each mains line, with the equipment placed on a non-conductive table at a defined height and operated in its worst-case mode.
Immunity tests follow the reproducible methods of the IEC 61000-4 series. ESD testing applies calibrated discharges from an ESD generator to all accessible surfaces and coupling planes. Radiated immunity testing exposes the equipment under test (EUT) to an amplitude-modulated field generated by power amplifiers and antennas inside an anechoic chamber. EFT and surge testing couples calibrated bursts and impulse waveforms into power and signal ports via coupling/decoupling networks. Voltage dips and interruptions are injected through programmable AC power sources. During each immunity test, the EUT is exercised in its most representative operating mode, and performance is judged against defined performance criteria A, B, or C, which specify whether the equipment must continue operating as intended, degrade temporarily and recover, or merely survive without damage.
Test planning requires careful definition of the worst-case configuration, including maximum load conditions, representative cables, and connected auxiliary equipment. Limits are selected based on equipment classification: Class B (residential environments) applies stricter limits than Class A (commercial and industrial environments), and the applicable class must be declared by the manufacturer and marked accordingly.
Applications
EMC test reports for information technology equipment support a wide range of regulatory and commercial objectives:
- CE marking for the European Union market, based on conformity with the EMC Directive via harmonized standards EN 55032, EN 55035, EN 61000-3-2, and EN 61000-3-3.
- FCC certification and verification for the United States market under 47 CFR Part 15, Subpart B for unintentional radiators.
- China Compulsory Certification (CCC), which requires conformity with GB 9254 and the GB/T 17626 immunity series for ITE within the certification catalog.
- Regulatory approval in markets applying national adoptions of CISPR and IEC standards, including Korea, Singapore, Australia, and the Gulf region.
- Voluntary schemes such as VCCI in Japan, which rely on testing against JIS-adopted CISPR limits.
- Product development support, including pre-compliance screening and diagnostic testing to identify emission hotspots and immunity weaknesses before formal certification.
- Purchase specifications and tender requirements, where EMC test reports from accredited third-party laboratories provide independent evidence of product quality.
FAQ
Which standard applies to my product: CISPR 22 or CISPR 32?
CISPR 32 has replaced CISPR 22 and CISPR 13, merging ITE and audio/video equipment into a single multimedia standard. New product assessments should be performed against CISPR 32/EN 55032 and CISPR 35/EN 55035, as the older standards have been withdrawn in most regulatory regimes.
What is the difference between Class A and Class B equipment?
Class B limits apply to equipment used in residential environments and are approximately 10 dB stricter than Class A limits, which apply to commercial and industrial settings. The manufacturer declares the class, and Class A devices sold to residential users generally require a warning notice in the user manual.
How should the equipment be configured during testing?
The EUT must be tested in a configuration that represents its worst-case emission and most susceptible operating state, including typical cable attachments, maximum processing load, and all intended peripheral connections. The laboratory and manufacturer jointly document the test configuration in the test report.
How long does a full EMC test sequence take?
For a typical ITE product with AC power and network ports, a complete emission and immunity evaluation usually requires several working days, depending on sample complexity, the number of ports, frequency extensions above 1 GHz, and whether any retesting after design modifications is needed.
What happens if the product fails a test item?
Failures are addressed through design remediation, such as improved shielding, filtering, grounding, or firmware changes. Many laboratories offer diagnostic support to localize the disturbance source, after which the affected items are retested to demonstrate compliance.
Do battery-powered devices need EMC testing?
Yes. Although battery-powered equipment without a mains connection is exempt from mains-port tests such as conducted emissions, harmonics, and voltage dips, it must still satisfy radiated emission limits and the applicable immunity requirements, particularly ESD and radiated RF immunity.