Decoding EMC Testing: Common Terms and Their Meanings

Like many technical specialties, the field of electromagnetic compatibility (EMC) testing is chock-full of acronyms that can quickly confuse those who are new to the discipline. So, for those technical professionals who could use a helping hand in their journey to EMC mastery, I’ve assembled the following list of the acronyms and terms most frequently used in EMC testing, along with brief explanation of what they mean.

AAN - Asymmetric artificial network
An EMC testing device placed between the equipment under test (EUT) and auxiliary equipment (AE) to measure conducted common mode disturbances (often used interchangeably with “impedance stabilization network” (ISN). An AAN is typically used for measuring conducted emissions on Ethernet ports or other telecommunications lines.

AC - Alternating current
An electric current capable of flowing in alternating directions (see “direct current” (DC))

AE – Auxiliary equipment or associated equipment
An electronic device that can function independently of any main processing module. In EMC testing, auxiliary equipment typically consists of equipment, components, or parts that are separate from the equipment under test (EUT).

AF - Antenna factor
The ratio of the received field strength and the voltages measured at the receiving antenna terminals.

AM - Amplitude modulation
One of the earliest methods of information transmission over radio waves, amplitude modulation involves transmitting a radio signal by modulating the amplitude of the signal.

AMN - Artificial mains network
Used to supply the mains electrical voltage (either AC or DC) and current to the equipment under test (EUT). The AMN also established a measurement point for conducted emissions when stabilizing the impedance, inductance, and capacitance of the power supplied to the EUT

AN - Artificial network
A network that can used to simulate interaction between electrical systems and components

CDN - Coupling/decoupling network
Used in EMC conducted immunity testing to inject a disturbance into the equipment under test (EUT)

CE - Conducted emissions
Electromagnetic interference (EMI) generated by a device and transmitted through power lines, input/output lines, or control loads

CI - Conducted immunity
Applies to electromagnetic interference (EMI) entering an equipment under test (EUT) via conducted pathways. CI is a measurement of the extent to which a system or device can withstand or reject conducted EMI.

CP – Current probe
A sensor use to measure current flow through a conductor and convert it into a corresponding voltage

CS - Conducted susceptibility
The extent to which a system or device can withstand or reject electromagnetic interference (EMI) conducted into the system or device, as measured during testing.

CVP - Capacitive voltage probe
A testing device used to detect the presence of voltage in a wire or piece of equipment without making direct contact with the conductor or the energized part

DC - Direct current
An electric current that flows in one direction only (see “alternating current” (AC))

DUT – Device under test
The equipment, system, or components being tested for EMC (often used interchangeably with “equipment under test” (EUT))

EFT/B - Electrical fast transient/burst
A series of quick, high-frequency electrical pulses, typically caused by arching resulting from a disrupted AC/DC connection, an equipment power down, or a switch circuit breaker

EM – Electromagnetic
The interaction between electric currents or fields and magnetic fields

EMC - Electromagnetic compatibility
The ability of a device to be used in its intended environment without causing or receiving unintentional electromagnetic interference (EMI)

EMI - Electromagnetic interference
An electromagnetic disturbance that causes an undesirable response or degradation of performance in electrical or electronic equipment (often used interchangeable with “radio frequency interference” (RFI))

EMS - Electromagnetic susceptibility
The extent to which a system or device is susceptible to electromagnetic disturbances

EPS - External power supply
An external device or circuit that is used to convert household electric current into either direct current (DC) or lower voltage alternating current (AC)

ESD - Electrostatic discharge
The exchange or transfer of electrical charges between two products or components with different electrostatic potential, typically through direct contact

EUT - Equipment under test
The equipment, system, or components being tested for EMC (often used interchangeably with “device under test” (DUT))

FAR - Fully anechoic room
An EMC testing chamber fully enclosed with radio frequency (RF)-absorbent material to shield against radio frequency interference (RFI), and to remove all RF reflections from the metallic enclosure.

FSOATS - Free space open area test site
An environment for indoor EMC testing that is free of reflecting objects. Unlike an open area test site (OATS), a free space open area test site does not include a ground reference plane, allowing greater flexibility in emissions testing.

FCC - Federal Communications Commission
The U.S. regulatory body responsible for the implementation and enforcement of laws and regulations applicable to radio devices.

ICES - Interference-causing equipment standard
A standard specific to radio equipment marketed or sold in Canada that sets forth requirements for systems and devices, other than radio apparatus, that causes or is capable of causing interference to radio communications

ISM - Industrial, scientific, and medical
A class of specialized, interference-causing equipment that generates and/or uses localized radio frequency energy for industrial, scientific, medical, or domestic applications, excluding telecommunications and information technology equipment (ITE).

ISN - Impedance stabilization network
An EMC testing device placed between the equipment under test (EUT) and auxiliary equipment (AE) to measure conducted common mod disturbances (often used interchangeably with “asymmetrical artificial network” (AAN))

ITE - Information technology equipment
Represents a broad range of electrical and electronic equipment, including commercial and personal computers, telecommunications systems and devices, and multi-media equipment

LISN - Line impedance stabilization network
A measurement device positioned between a power supply and the power input of equipment under test (EUT) that provides a known impedance for testing

MI – Magnetic immunity
The extent to which a system or device can withstand or reject the effects of a nearby magnetic field

NSA - Normalized site attenuation
An assessment used to determine the suitability of an open area test site (OATS) or a semi anechoic chamber (SAC) for radiated emissions (RE) testing

OATS - Open area test site
An environment for outdoor EMC testing that is free of reflecting objects, except for a ground reference plane

PM – Pulse modulation
A type of modulation in which an analog or digital signal is transmitted in the form of pulses

RE - Radiated emissions
Electromagnetic energy that is propagated by or emitted from an electrical or electronic system or device

RF – Radio frequency
The frequency spectrum in which electromagnetic radiation can be used for radio or wireless communication

RFI – Radio frequency interference
Often used interchangeably with “electromagnetic interference” (EMI)

RI – Radiated immunity/Radiated susceptibility
The extent to which a system or device can withstand or reject EMI radiated in the vicinity of an EUT, as measured during testing.

SAC – Semi anechoic chamber
An enclosed EMC testing chamber consisting of a solid, reflective ground plane, with radio frequency (RF) absorber material on the walls and ceiling, and that provides a shield against radio frequency interference (RFI).

VSWR - Voltage standing wave ratio
The ratio of a voltage reading at the peak of a standing wave and the voltage reading at the lowest point of the standing wave

Although this list represents some of the most commonly used terms in EMC testing, it is by no means complete. So please feel free to share your additions to this list.

Remember that every journey begins with a single step. We hope that this list of EMC testing terms helps you to successfully navigate the complex but fascinating world of EMC. Good luck!