AF - Audio Frequency
Components of a signal or noise having frequencies in the 15 Hz - 20 KHz range.
Air Filters, shielded
Used to permit ventilating shielded rooms and cabinets while removing dust and other air suspended particles. The filter also provides a shield to RF energy, which would otherwise leak in or out of an enclosure. Also see: honeycomb
A decrease in signal amplitude during its transmission from one point to another. If a signal attenuates too much, it becomes unintelligible,
Attenuation is measured in dB
A frequency range, usually limited by –3 dB
BeCu - Beryllium Copper
Among other applications, BeCu is used extensively for shielding finger stock gaskets because of its maximum spring properties of strength and fatigue resistance.
An elastomer containing metal powder or small flakes for bonding metal parts to achieve a defined shielding effectiveness.
The EMI that couples from the outside of equipment to the inside over the I/O cables, signal leads, or power lines.
dB - deciBel
the logarithm with the base of ten for the ratio between two power figures is called Bel
A unit of the logarithm of a ratio measurement X Bel = 10 log10 (P1/P2) = 20 log10 (V1/V2)-10 log10 (Z2/Z1).
A conductor that will connect electrical currents to the Earth.
A gasket used between two mating metal members to secure a low-impedance path. Gaskets are used to fill and electrically join and seal leaky apertures between these mating members in order to maintain a minimum shielding effectiveness over a defined frequency spectrum.
EMC - ElectroMagnetic Compatibility
Operations of equipment and systems in their installed environments which cause no unfavourable response to or by other equipment’s and systems in the same environment.
The capability of equipment to be operated in its intended operational environment at designed levels of efficiency without causing electromagnetic interference.
EME - Electromagnetic Environmental
The totality of electromagnetic phenomena’s existing at a given location
EMI - Electromagnetic interference
Any conducted, radiated or magnetically induced voltage which degrades, obstructs or repeatedly interrupts the desired performance of electronic equipment.
When an electrical disturbance from a natural phenomenon (e.g., lightning or ESD) or an electrical/electronic device or system causes an undesired conducted or radiated response in a victim. EMI is the opposite of EMC.
EMP - ElectroMagnetic Pulse
sometimes called a transient electromagnetic disturbance, is a short burst of electromagnetic energy. Such a pulse's origination may be a natural occurrence or man-made and can occur as a radiated, electric or magnetic field or a conducted electric current, depending on the source
ESD - ElectroStatic Discharge
the sudden flow of electricity between two electrically charged objects caused by contact, an electrical short or dielectric breakdown
Powered magnetic (permeable) material in the form of beads, rods, and blocks used to absorb conducted interference on wires, cables and harnesses.
Made by calcining a combination of metal oxides sintered into tiles. Material only a few millimetres thick absorbs low frequencies. Tiles may be used with dielectric materials or as a hybrid combination with dielectric pyramids.
A device for blocking the flow of EMI current while passing the desired 50/60/400-Hz current. In communications circuits, it suppresses unwanted frequencies, noise or separates channels.
Filters - EMI/RFI
Filters designed for power line and/ or signal line applications to pass a defined band and reject emissions above the cut-off frequency, containing series-inductive and/ or parallel-capacitive components.
A beryllium copper, electrical gasket used to bond metal panel members on doors, sills or covers designed to accommodate many openings and closings with limited aging effects.
The number of times a signal repeats in one second, measured in Hertz (cycles per second). The frequency equals 1/period.
Hertz (Hz): One cycle per second
Kilohertz (kHz): 1,000 Hertz; 103 Hz
Megahertz (MHz): 1,000,000 Hertz; 106 Hz
Gigahertz (GHz): 1,000,000,000 Hertz; 109 Hz
Gaskets are used to fill and electronically bond and seal leaky apertures between mating panel member parts in order to maintain a minimum shielding effectiveness over a defined frequency spectrum.
1. A conducting connection by which an electric circuit or equipment is connected to the earth to establish and maintain a reference voltage level.
2. The voltage reference point in a circuit.
Honeycomb, EMC Airflow
A hexagonal cell configuration (honeycomb) to permit smooth airflow into and out of shielded enclosures while also blocking electromagnetic radiation leakage.
The ratio between the power received at a specified load before and after the insertion of a filter at a given frequency. It is an indication of the attenuation provided by a filter.
The degree of protection conferred by the enclosures of electrical equipment are defined by the French standard NF C 20-010 and DIN 40050. To symbolise degrees of protection the letters IP followed by three numbers are used
First number: protection against solid objects
Second number: protection against liquids
Third number: protection against mechanical impact
An unwanted voltage or current in an electrical circuit.
The mathematical relationship between current (I), voltage (V), and resistance (R) where
V=I x R. If any of the two variables are known, the third can be calculated.
The capacitive leakage across a component such as a resistor, inductor, filter, isolation transformer or optical isolator that adversely affects high-frequency performance.
The maximum voltage level measured from a zero reference point
The voltage measured from the maximum point of a signal to its minimum point.
The amount of time it takes a wave to complete one cycle. The period equals 1/frequency.
The amount of time that passes from the beginning of a cycle to the beginning of the next cycle, measured in degrees.
A common waveform shape that has a fast rising edge, a width and a fast falling edge.
A collection of pulses traveling together.
The amount of time the pulse takes to go from low to high and back to low again, conventionally measured at 50% of full voltage.
RE - Radiated Emission
The potential EMI, which radiates from escape-coupling paths such as cables, leaky apertures or inadequately shielded housings.
Undesirable EMI radiated into equipment from outside electromagnetic sources.
The outward flow of energy from any source in the form of electromagnetic energy.
RF - Radio Frequency
A frequency at which coherent electromagnetic radiation of energy is useful for communications. Radio frequencies are designated as very low: <30 kHz,
low: 30 to 300 kHz
medium: 300 to 3,000 kHz
high: 3 to 30 MHz
very high: 30 to 300 MHz
ultrahigh: 300 to 3,000 MHz
superhigh: 3 to 30 GHz
extremely high: 30 to 300 GHz
RFI - Radio Frequency Interference
A high frequency, cyclic series of spikes or noise injected onto an electrical line by means of radio wave energy or by a piece of equipment connected to the line. Exists when either the transmitter or receiver is carrier operated (has an antenna), causing undesired responses to or from other electronic equipment or systems.
To protect EMI from entering or exiting a cable, shield(s) may be added. Braids, mesh and foils are the most common shields.
The relative capability of a shield to screen out undesirable electric and magnetic fields and plane waves. The measurement is the ratio of the signal received without the shield to the signal received inside the shield.
A material that maintains shielding effectiveness across a seam or gap in an electronic enclosure. Electrical gaskets used to bond to pieces of metal or to fill voids between mating metal members to block aperture leaks. It is made from a variety of materials including fabric over foam, wire mesh, stamped metal and elastomer.
A room made free from EMI by applying shielding to the floor, walls and ceiling, and by suppressing interference entering through the power lines. Typical construction shields from 70 dB to 140 dB from 10 kHz to 10 GHz.
Shielding accomplished by using a thin conducted film, a fine mesh or metalized open-mesh on the window
Metal mesh screen or thin films deposited on a substrate used to cover displays to block RF radiation while permitting optical viewing.
A process of preventing radiation from coupling into or out of defined areas or regions. Shielding materials are always metals, metalized plastics (conductive coatings) or conductive composites.
Fabrics made of metal threads or yarn, or conductive-coated yarn, woven to form a shielded fabric.
Shielding Foils and Sheets
Thin sheets of metallic foil are used for both shielding and grounding. Foil sheets are usually adhesive backed to line nonconductive boxes, cabinets, and walls. They also make low-impedance ground plates.
Used for HVAC or simple ventilation of shielded products, cabinets, enclosures and rooms. Some provide high shielding, such as honeycomb, while others provide air filtering, as well.