Please click on the glossary link below to familiarize yourself with the industry’s Energy Efficiency Definitions and Terms.


5mm LED – Bullet type LED with flat or round (bullet) type shape. First type of LED used for acceptable channel letter illumination and is still in use by Agilight and others / aka Indicator type LED.

Accent Lighting – Directional lighting to emphasize a particular object or draw attention to a display item.
Active Component – A component that changes the amplitude of a signal between input and output.

Adaptation – The process by which the human eye adjusts to a change in light level.

Additive Color Model – A type of RGB color model that describes how different proportions of red, green, and blue light com- bine to create colors. In the additive color model, combining red, green, and blue light produces white light.

AlGaAs – One of the material systems for manufacturing LEDs that produce light in the red and amber portions of the visible light spectrum.

AllnGaP – The preferred LED (Light Emitting Diode) chip technology containing Aluminum, Indium, Gallium, and Phosphorous to produce red, orange and amber-colors.

Ambient Lighting – The general lighting present in an area –excluding task lighting and accent lighting but including general lighting and daylight streaming in.

Ambient Temperature (Ta) – 1. The air temperature surrounding the device. 2. The surrounding temperature within an environment.

American National Standards Institute (ANSI) – A non-profit organization that develops voluntary consensus standards and conformity assessment systems for products, services, processes, systems, and personnel in the United States.

Ampere (Amp) – The unit for measuring rate of flow of electrical current: Current (Amps) = Power (Watts) / Voltage (Volts)

Anode – The positively charged terminal or electrode toward which electrons flow.
ANSI Binning – The system defined by the American National Standards Institute for the binning specifications for light emit- ting diodes.

AWG – Abbreviation for “American Wire Gauge.” A gauge that assigns a number value to the diameter of a wire.

Backlit Sign – A sign where the sign face is illuminated from behind. Also called illuminated sign.

Backlighting – Use of an LED as a light source to illuminate a lens or legend from behind without protrusion through the panel.

Bezel – The faceted collar of a panel-mount LED indicator visible from the front.

Bi-Color LED – A single LED device containing two different colored LED dice. The different colored dice can be illuminated independently or together.

Bin (Binning) – The systematic dividing of distribution of performance parameters (Flux, Wavelength or CCT, and Vf) in to small finite groupings that may be selected to optimize assembly performance.

Black Body / Black Body Radiator – An object that absorbs all electromagnetic radiation falling on it. Because it reflects no light, a black body appears black. As a black body is heated to incandescence, it radiates light in a sequence of colors, from red to orange to yellow to white to blue, depending on its temperature. This color sequence describes a curve within a color space, known as the black-body curve.

Black Body Curve – A curve within a color space describing the sequence of colors emitted by a black-body radiator at different temperatures.

Bridge Rectifier – A circuit using four diodes to provide full wave rectification by converting an AC voltage to DC voltage.

Brightness – Often used incorrectly with respect to illumination as a synonym for luminous flux, an objective measurement of the visible power of a light source. The term is correctly used when describing screen brightness in a display or television. (see Nits).

Canadian Standards Association (CSA) – An organization that writes standards and tests lighting
equipment for performance as well as electrical and fire safety. Canadian provincial laws generally require that all products sold for consumer use in Canada must have CSA or equivalent approval.

Candela – 1. A unit of luminous intensity equal to 1/60th of the normal intensity of one square centimeter of a blackbody radiating at the temperature of solidification of platinum. 2. Unit of luminous intensity. One candela equals one lumen per steradian.

Candle Power – Luminous intensity expressed in candelas.

Case Temperature – The temperature measured at the LED package or case.

Cathode – The terminal or electrode that is negatively charged and from which electrons flow.

CCT – See Correlated Color Temperature.

Chip – See LED chip.

Chromaticity – An objective specification of the quality of a color, independent of its luminance, and as determined by its or saturation and hue.

CIE – See International Commission on Illumination.

CIE 1931 Color Space – A color space created by the International Commission on Illumination (CIE) in 1931 to define the entire

CIE Chromaticity Diagram – 1. A horseshoe shaped line connecting the chromaticities of the spectrum of colors. 2. In 1931 (Commission Internationale de l’Eclairage (CIE) established the X-Y-Z tristimulus system for measuring color properties, based on the assumption that every color is a combination of three primary colors: red, green and blue. The CIE Chromaticity Diagram is a two dimensional color space that defines all of the colors perceived by the human eye. Pure colors are located on the extreme outer edges of the diagram and white is located in the center.

Color Bin – LEDs are sorted according to their wavelength or CIE coordinates into different groupings or “bins.”

Color Definition – The color of uniformly illuminated objects described using three terms:
Hue: Describes the situation when the appearance of different colors is similar (e.g. matching blues and pinks). Lightness: Describes a range of grayness between black and white.
Chroma: Describes the degree of departure from gray of the same lightness and increasing color (e.g. red, redder, pure red).

Color (Dominant Wavelength) – LEDs are designed to give off a specific color emission. The dominant wavelength is a quantitative measure of an LED color as perceived by the human eye and is usually measured in nanometers (a billionth of a meter). In order to specify an LED, you must specify the color or dominant wavelength range required for your application. Some applications may have color constraints in order to meet specific government specifications or regulatory guidelines.

Color Gamut – The range of colors within the CIE Chromaticity Diagram included when combining different sources.

Color Model – An abstract mathematical model describing the way colors can be represented as groups of values or color components. RGB (Red-Green-Blue) is a color model with three color components, and CMYK (Cyan-Magenta-Yellow and Key (Black)) is a color model with four color components.

Color Rendering – A general expression for the effect of a light source on the color appearance of objects.

Color Rendering Index (CRI) – 1. A measure of the degree of color shift objects undergo when illuminated by the light source as compared with those same objects when illuminated by a reference source of comparable color temperature. The reference source has a CRI of 100. 2. Indicates how well a light source renders colors of people and objects, compared to a reference source.

Color Spectrum / Visible Spectrum – The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye, typically between 390nm and 750nm.

Color Temperature – 1. The description used to describe the effect of heating an object until it glows incandescently, the emit- ted radiation, and apparent color, changes proportional to the temperature; easily envisioned when considering hot metal in a forge that glows red, then orange, and then white as the temperature increases. 2. A measure of the color of a light source relative to a black body at a particular temperature expressed in degrees Kelvin (K). Incandescent lights have a low color temperature (approximately 2800K) and have a red-yellowish tone; daylight has a high color temperature (approximately 6000K) and appears bluish (the most popular fluorescent light, Cool White, is rated at 4100K). Lamps with color temperatures below 5000K tend to be more yellow/red, lamps rated between 5000 and 6000K are viewed as white, while lamps above 6000K tend to have a blue cast.

Conformal Phosphor Coating 
 – Phosphor application process that uniformly coats the LED chip with phosphor.
Continuous Forward Current – The maximum continuous operating current the LED can withstand without diminishing its operating life.

Controller – A device that controls the output of color-changing and tunable white lighting fixtures.

Controllers typically have software components for configuring fixtures and designing and editing light shows, and hardware components for sending control data to fixtures.

Cool Colors – 1. Refers to cool colors in the light spectrum – whites, blue, and green. 2. A description of a range of correlated color temperatures.

Cool White – A term loosely used to denote a color temperature of around 6500 K.

Correlated Color Temperature (CCT) – 1. The absolute temperature of a blackbody whose chromaticity most nearly resembles that of the light source. Usually specified in Kelvin (K). The lower the Kelvin temperature, the warmer the light feels, or appears.
2. The measure used to describe the relative color appearance of a white light source. CCT indicates whether a light source appears more yellow/gold/orange or more blue, in terms of the range of available shades of “white.” CCT is given in kelvins (unit of absolute temperature).

Cost of Light – Usually refers to the cost of operating and maintaining a lighting system on an ongoing basis. The 88-8-4 rule states that (typically) 88% is the cost of electricity, 8% is labor and only 4% is the cost of lamps.

CRI – The measure of a light source’s ability to render the color of objects “correctly,” as compared with a reference source with comparable color temperature – scale is from 1-100 – higher the number, richer the colors.

Current – Measured in amperes, it is the flow of electrons through a conductor. Also know as electron flow.

Current-Limiting Resistor – A resistor is added in series between the power source and the LED to regulate the current delivered to the device (see Ohm’s Law).

Current Type (AC/DC) – Whether the operational voltage is based on Alternating Current or Direct Current.

DALI – See Digital Addressable Lighting Interface

Delivered Light – The amount of light a lighting fixture or lighting installation delivers to a target area or task surface, measured in foot candles (fc) or lux (lx).

Die – 1. Chip: light emitting semiconductor. 2. The chip within the LED package; the plural form is dice.

Diffused Encapsulation – Glass particles are suspended within the epoxy lens of the LED diffusing the light over a wide viewing area. The encapsulation may be white or colored to match the LED output.

Diffuser – An object with irregularities on a surface causing scattered reflections.

Digital Addressable Lighting Interface (DALI) 
 – A digital communications protocol for controlling and dimming lighting fixtures, originally developed in Europe.

 – Whether or not the lamp lumens can be varied while maintaining reliability.

Dimmer, Dimming Control – A device used to lower the light output of a source, usually by reducing the wattage it is being operated at. Dimming controls are increasing in popularity as energy conserving devices.

Diode – A two terminal device that conducts in only one direction.

Direct-View Lighting Fixtures – Lighting fixtures intended for viewing, rather than for illumination. For example, arrays of direct view fixtures or nodes are used in large-scale video displays, traffic signals, and signage applications.

Directional Light Source 
 – A light source that emits light only in the direction it is pointed or oriented.

 – A digital communications protocol for controlling lighting fixtures, originally developed to control stage lighting.

Dominant Wavelength – A measure of the hue sensation perceived by the human eye. 
Driver – Electronics used to power illumination sources.

Efficacy – The light output of a light source divided by the total electrical power input to that
source, expressed in lumens per watt (lm/W).

Efficiency – See Luminous efficiency.

Electroluminescence – The conversion of electrical energy into light via non-thermal means.

Electrostatic Discharge (ESD) – A sudden redistribution of static charge which can be damaging to sensitive components.

ELV-type Dimmer – An electronic low voltage dimmer, used to dim LED lighting fixtures with electronic transformers.

Encapsulation – A hard rugged epoxy surrounding the LED die, provides diffusion & lensing of the LED light.

Epoxy – Organic polymer frequently used for a dome or lens, often prone to optical decay over time, resulting in poor lumen maintenance. High quality LEDs such as LUXEON contain no epoxy in the optical system and deliver superior lumen maintenance.

Eye-sensitivity Curve – See spectral luminous efficiency function.

Federal Communications Commission (FCC) – The U. S. Federal agency that regulates
emissions in the radio frequency portion of the electromagnetic spectrum. Part 18 of the FCC rules specifies electromagnetic interference (EMI) from lighting devices operating at frequencies greater than 9 kilohertz (kHz).

Flicker – The periodic variation in light level caused by AC operation that can lead to strobe effects.

Floodlight – A luminaire used to light a scene or object to a level much brighter than its surroundings.

Flow Soldering – Flow or wave soldering technique in large scale electronic assembly to solder all the connections on a printed circuit board by moving the board over a wave of molten solder.

Flux / Luminous Flux – 1. Luminous flux is the measure of the perceived power of light, adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light. 2. The total electromagnetic energy emitted by the light source into a sphere (360°) surrounding the light source.
3. The sum of all the lumens (lm) emitted by a source (see lumen).

Foot Candle (fc) – A measure of illumination in which one unit equals the amount of light delivered by a one-candela light source to a one square-foot surface one foot away.

Foot-lambert – An obsolete term referring to a luminance of 1/? Candelas per square foot.

Forward Bias – A P-N junction bias which allows current to flow through the junction. Forward bias decreases the resistance of the depletion layer.

Forward Current 
 – Current through a diode in the direction of its greatest conduction.

Forward Voltage (Vf) – The operating voltage of the LED. The typical rating is the voltage at which the LED will light. The maxi- mum rating is the voltage that, if exceeded, will diminish LED lifetime.

FR4 – A widely accepted printed circuit board (PCB) material which is fiberglass reinforced epoxy laminates that are flame retardant.

Freedom From Binning – Describes the case where the entire production of white LEDs can be described by a single CCT and within a declared number of MacAdam ellipses. No subdivision or color binning of the LEDs is required for use in the intended application.

Fresnel Lens – A thin optical lens consisting of concentric rings of segmental lenses and having a short focal length.

General illumination – A term used to distinguish between lighting that illuminates tasks, spaces,
or objects from lighting used in indicator or purely decorative applications. In most cases, general illumination is provided by white light sources, including incandescent, fluorescent, high-intensity discharge sources, and white LEDs. Lighting used for indication or decoration is often monochromatic, as in traffic lights, exit signs, vehicle brake lights, signage, and holiday lights.

Ghosting – An effect that occurs when lighting fixtures in the OFF state faintly glow as a result of residual voltage in the circuit.

Goniophotometer – A photometric device for testing the luminous intensity distribution, efficiency, and luminous flux of luminaires.

Halogen Lamp – An incandescent lamp with a filament that is surrounded by halogen gases.

Halogen gases allow the filaments to be operated at higher temperatures and higher efficacies.

Heat Sink – A part of the thermal system that conducts or convects heat away from sensitive components, such as LEDs and electronics.

HID Lamp (High Intensity Discharge) – A general term for mercury, metal halide and high-pressure sodium lamps. HID lamps contain compact arc tubes with enclose various gases and metal salts operating at relatively high pressures and temperatures.

High-Bay Lighting – Lighted designed for typically industrial locations with a ceiling height of 25 feet or above.

High Power LED – A high power LED, sometimes referred to as a power LED, is one that is driven at a current of 350 mA or higher.

High-Brightness – High-brightness is a term that is often applied to an LED but has no measured meaning and does not indicate any level of performance.

Hot / Cold Factor – The relative light output performance at a temperature compared to the light output at a nominal or test temperature. For LUXEON products this is the relative light output at 100C Tj compared to 25C Tj. For “Hot Tested” products like LUXEON A it is the relative light output at 100C Tj compared to 85C Tj.

Hot Testing – LED performance testing and specification at an elevated temperature of 85°C.

HPS Lamp (High Pressure Sodium) – HPS lamps are high intensity discharge light sources that produce light by an electrical discharge though sodium vapor operating at relatively high pressures and temperatures. HOT RESTART TIME: time it takes for a HID lamp to reach 9-% of light output after going from on to off to on.

IES / IESNA – Illuminated Engineering Society. Produce charts on where the light is. See Illuminating Engineering Society.

Illuminance – 1. The intensity of light falling on a surface area. If the area is measured in square feet, the unit of illuminance is footcandles (fc). If measured in square meters, the unit of illuminance is lux (lx). 2. The “density” of light (lumens/area) incident on a surface; i.e. the light level on a surface.

Illuminance is measured in foot-candles or lux.

Illuminating Engineering Society of North America (IES) – The recognized technical authority on illumination, communicating information on all aspects of good lighting practice to its members, to the lighting community, and to consumers through a variety of programs, publications, and services.

Inboard Power Integration – An approach to power management that integrates the power supply directly into a fixture’s circuitry, creating an efficient power stage that consolidates line voltage conversion and LED current regulation.

Incandescent Lamp – A light source where voltage passes through a filament to create heat which, in turn, creates light.

Indirect Lighting – The method of lighting a space by directing the light from luminaires upwards towards the ceiling. The light scattered off the ceiling produces a soft, diffuse illumination for the entire area.

Infrared (Near) – Gases can be excited directly by radio-frequency or microwaves from a coil that creates induced electromagnetic fields. This is called induction lighting and it differs from a conventional discharge, which uses electrodes to carry current into the arc. Induction lamps have no electrodes inside the chamber and generally, therefore, have longer life than standard lamps. Electromagnetic radiation with wavelength range from 700 nm – 3000 nm.

InGaN LED – The preferred LED (Light Emitting Diode) semiconductor material system containing Indium, Gallium, and Nitrogen to produce green, blue and white-colored LED light sources.

Integrating Sphere – A device used for a variety of optical, photometric, or radiometric measurements.

Intensity Bin – LEDs are sorted according to their intensity values into different groupings or “bins”.

Inverse Square Law – Formula stating that if you double the distance from the light source, the light level goes down by a factor of 4, if you triple the distance, it goes down by a factor of 9, and so on.

IP Rating – The IP Code (or International Protection Rating, sometimes also interpreted as Ingress Protection Rating)* consists of the letters IP followed by two digits and an optional letter. As defined in international standard IEC 60529, it classifies
the degrees of protection provided against the intrusion of solid objects (including body parts like hands and fingers), dust, accidental contact, and water in electrical enclosures. The standard aims to provide users more detailed information than vague marketing terms such as waterproof.

Junction Temperature – Junction temperature, noted as Tj, is the temperature of the LED’s active

Kelvin Temperature – Term and symbol (K) used to indicate the comparative color appearance of
a light source when compared to a theoretical blackbody. Yellowish incandescent lamps are 3000K. Fluorescent light sources range from 3000K to 7500K and higher. The color measurement for white light. The higher the number, the more blue (i.e. 7000K) the white will appear and the lower the number (i.e. 3200K) the warmer the light will appear. This is important if, as an example you have a set of halo / reverse channel letters mounted on a white background. A 5500K to 6500K is typically preferred and is the more common K color of most LED. On the other hand if you have the same letters on a wood background, a warmer LED chip in the 2800K to 3500K would give a nice warm illumination making the wood background look very nice.

Kerning – The act of moving letters further apart or closer together in order to achieve a desired effect.

Kilowatt (kW) – The measure of electrical power equal to 1000 watts.
Kilowatt Hour (kWh) – The standard measure of electrical energy and the typical billing unit used by electrical utilities for electricity use. A 100-watt lamp operated for 10 hours consumes 1000 watthours (100 x 10) or one kilowatt-hour. If the utility charges $.10/kWh, then the electricity cost for the 10 hours of operation would be 10 cents (1 x $.10)

Lambertian – Radiation pattern where the brightest spot is in the middle and it drops off at a
constant rate from the middle. This pattern is only used when we cover the Qube with another lens (i.e. we leave the lens on from the existing wall-pack because the customer wants a glass lens and we use a plastic lens on the Qube).

Lamp Size – Industry standard classifications for lamps sizes are based on descriptive designators referring to the diameter of the lamp. “T-1” is the base designation for a 1/8” diameter lamp. Other designations are based on the T-1 standard, i.e., T-13⁄4 is 13⁄4 multiplied by 1/8, or .219”.
Lead Frame – A metallic frame used for mounting and connecting LED chips. The leadframe functions as the electrical leads of the device.
Leading Edge Dimmer – A type of dimmer that regulates power to lamps by delaying the leading edge of each half-cycle of AC power. Compatible with many LED fixtures.

LED – See Light Emitting Diode.

LED Array – An assembly of LED packages or dies on a printed circuit board or substrate, possibly with optical elements and additional thermal, mechanical, and electrical interfaces that are intended to connect to the load side of an LED driver.

LED Chip (Chip) – The light producing semiconductor device that may or may not be incorporated into an LED.

LED Driver – An electronic circuit that converts input power into a current source — a source in which current remains constant despite fluctuations in voltage. An LED driver protects LEDs from normal voltage fluctuations, overvoltages, and voltage spikes.

LED Light Engine – An integrated assembly comprised of LEDs or LED arrays, LED driver, and other optical, thermal, mechani- cal, and electrical components.

LED Luminaire – A complete lighting unit consisting of LED-based light emitting elements and a matched driver together with parts to distribute light, to position and protect the light emitting elements, and to connect the unit to a branch circuit. The LED based light emitting elements may take the form of LED packages, (components), LED arrays (modules) LED Light Engine, or LED lamps. The LED luminaire is intended to connect directly to a branch circuit.

LED Module – See LED array.

Lens – A transparent or semi-transparent element which controls the distribution of light by redirecting individual rays. Luminaires often have lenses in addition to reflectors.

Light – Radiant energy that can be sensed or seen by the human eye. Visible light is measured in lumens.

Light Emitting Diode (LED) – 1. A Light Emitting Diode (LED) is a solid-state semiconductor device that converts electrical energy directly into light. On its most basic level, the semiconductor is comprised of two regions. The p-region contains positive electrical charges while the n-region contains negative electrical charges. When voltage is applied and current begins to flow, the electrons move across the n region into the p region. The process of an electron moving through the p-n junction releases energy. The dispersion of this energy produces photons with visible wavelengths. 2. Based on inorganic (non-carbon based) materials. An LED is a semi-conducting device that produces light when an electrical current flows through it. LEDs were first developed in the 1960s but were used only in indicator applications until recently.

Light Meter – A device that measures the illuminance at a location calibrated either in foot-candles or in lux. When you find the footcandles for a certain application (i.e. parking lot light – stand directly under it, measure the light, then walk 5’, 10’, 15’ and 20’ in all directions and measure the light at each point).

Light Output – See luminous flux.

LM79 – Verifies the IES files are correct, lens losses, etc.

LM80 – Light depreciation over time – test LED chip at 6,000 hours.

L70 – 30% light loss in 70,000 hours (shorthand for lumen depreciation to 70% of initial lumen output, it indicates 70% of lumen maintenance).

Lumen (lm) – The international (SI) unit of luminous flux or quantity of light and equals the amount of light that is spread over a square foot of surface by one candle power when all parts of the surface are exactly one foot from the light source. For example, a dinner candle provides about 12 lumens.

Lumens per Watt – In SI, luminous efficacy has units of lumens per watt (lm/W). Photopic luminous efficacy has a maximum possible value of 683 lm/W, for the case of monochromatic light at a wavelength of 555 nm (green).

Lumen Depreciation – Describes the percentage of light lost relative to the initial lumen output. See lumen maintenance for more information.

Lumen Maintenance – The luminous flux at a give time in the life of the LED. This is expressed as a percentage of the intial luminous flux.

Lumen Maintenance Curve – A graph illustrating the predicted average light output behavior over time of a single LED or solution.

Lumen Output – The total lumens emitted of a light source, system, or solution.

Luminaire – A lighting fixture complete with installed lamps and other accessories.

Luminance – A measure of “surface brightness” when an observer is looking in the direction of the surface. It is measured in candelas per square meter (or per square foot) and was formerly referred to as “photometric brightness”.

Luminous Efficiency – 1.The percentage of total lamp lumens that a lighting fixture, luminaire, or system emits, minus any blocked or wasted light. 2. The most commonly used measure of the energy efficiency of a light source. It is stated in lumens per watt (lm/W), indicating the amount of light a light source produces for each watt of electricity consumed. For white high- brightness LEDs, luminous efficacy published by LED manufacturers typically refers to the LED chip only, and doesn’t include driver losses.

Luminous Flux – See Flux.

Luminous Intensity (Iv) – Luminous Intensity is equal to the amount of luminous flux emitted into a very small solid angle at a
defined angular orientation from the light source. The measurement for luminous intensity is the lumen or candela.

Lumiramic – This Philips proprietary phosphor system embeds phosphor in a ceramic platelet that can be mass manufactured with very high degrees of uniformity and consistency.

Lux (lx) – The SI (International) unit of illuminance, or luminous flux incident on a unit area, frequently defined as one lumen per square meter (lm/m2).
acAdam Ellipse – A MacAdam ellipse is the region on a chromaticity diagram which contains all
colors which are indistinguishable, to the average human eye, from the color at the center of the ellipse.

Material System – The material, such as aluminum indium gallium phosphide (AlInGaP) and indium gallium nitride (InGaN), used within an LED to produce light of a specific color.

MCPCB – A widely accepted Printed Circuit Board (PCB) material with a Metal Core (MC) for better thermal performance.

Mean Spherical Candle Power (MSCP) – The average luminous intensity of a lamp illuminating in all directions. The measurement is made by placing the lamp in the center of a sphere.

Mercury Lamp – A high-intensity discharge light source operating at a relatively high pressure (about 1 atmosphere) and temperature in which most of the light is produced by radiation from excited mercury vapor. Phosphor coatings on some lamp types add additional light and improve color rendering.

Metal Halide Lamp – A high intensity discharge light source in which the light is produced by the radiation from mercury, plus halides of metals such as sodium, scandium, indium and dysprosium. Some lamp types may also utilize phosphor coatings.

Metal Halide Lamp – A high intensity discharge light source in which the light is produced by the radiation from mercury, plus halides of metals such as sodium, scandium, indium and dysprosium. Some lamp types may also utilize phosphor coatings.

Milliamp / mA – The current any given LED module needs for efficient operation. The higher mA number, the brighter the LED will be, however this higher mA also (typically) reduces LED life. Higher ma also causes more heat that the PN Junction and if not cooled properly will lead to premature failure. Thus for long term benefits, you want the lowest mA you can effectively get, while not affecting the brightness. This is partially accomplished by using first quality “chips” as we do at US LED.

Monument Sign – A freestanding sign that stands directly on the ground or ground level foundation. A monument sign is often used to mark a place of significance or the entrance to a location.

Nanometer (nm) – The nanometer (one-billionth of a meter) is the measurement unit for peak
wavelength. Visible light falls in the range of 380 to 700nm.

NITS – Measurement of display screen brightness. 1 nit = 1 cd/m2. The more nits, the brighter the picture.

NTSC Color Space – The range of colors within the CIE Chromaticity Diagram included when combining phosphor based RGB sources in CRTs such a televisions and computer monitors.

Ohm – Unit of resistance symbolized by the Greek capital letter omega (O).

Ohm’s Law – Relationship between voltage, current and resistance. Ohm’s law states that current in a resistance varies in direct proportion to voltage applied and inversely proportional to resistance.

Onboard Power Integration – An approach to power management that integrates the power supply into a fixture’s housing, eliminating the need for an external power supply.

Open Channel Letter – A channel letter with returns that project forward from face of letter such that the neon tubing is visible.

Operating Current – The amount of current an LED is designed to draw from the power source.

Operating Temperature – The temperature range over which an LED is designed to operate safely.

Organic Light-Emitting Diodes (OLED) – Organic light-emitting diodes (OLEDs) are based on organic (carbon based) materials. In contrast to LEDs, which are small point sources, OLEDs are made in sheets which provide a diffuse area light source. OLED technology is developing rapidly and is increasingly used in display applications such as cell phones and PDA screens. However, OLEDs are still some years away from becoming a practical general illumination source. Additional advancements are needed in light output, color, efficiency, cost, and lifetime.

P-N Junction – Area on an LED chip where the positively and negatively charged regions meet. When current is applied, the electrons move across the n region into the p region. The process of an electron moving through the p-n junction releases energy. The dispersion of this energy produces photons with visible wavelengths. In short, the area on a chip where light is produced.

P-type Material – In a diode’s p-n semiconductor junction, p-type material is positively charged. Atoms in the p-type material have electron holes, electrons missing from their outer rings.

Passive Component – A Component that does not amplify a signal. Resistors and capacitors are examples.
PC Amber (Phosphor Converted) – PC amber is a method of making amber colored LEDs from royal blue LED chips. It requires the use of special phosphors and results in a more reliable, less temperature sensitive, and more consistent amber LED.

Peak Forward Current – Forward current driven during pulse operation.

Peak Wavelength – 1. Peak Wavelength is defined as the single wavelength of saturated color at the peak of the radiated spectrum. 2. The maximum wavelength of an LED

Phosphor – 1. A coating of phosphorescent material which photons from a royal blue LED pass through causing those photons to exit with a different color property. 2. An inorganic chemical compound processed into a powder and deposited on the inner glass surface of fluorescent tubes and some mercury and metal-halide lamp bulbs. Phosphors are designed to absorb short wavelength ultraviolet radiation and to transform and emit it as visible light.

Phosphor Conversion – 1. This is the process by which photons from an LED chip are converted to a different color. White LEDs and some colored LEDs are made using phosphor conversion. 2. A method used to generate white light with LEDs. A blue or near-ultraviolet LED is coated with a yellow or multichromatic phosphor, resulting in white light.

Photometer – An instrument for measuring a property of light, especially luminous intensity or flux. A photometer uses special colored filters to replicate the response of the human eye. Light intensity is measured in candle power, usually by comparison with a standard source.

Photometry – The measurement of light and related quantities.

Planckian Black Body Locus – The line on the CIE Chromaticity Diagram that describes the color temperature of an object when heated from approximately 1,000K to more than 10,000K.

Point of Purchase (POP) Sign – In-store advertising designed to stimulate impulse purchases by shoppers inside a store. Also known as “point-of-sale advertising”.

Power Dissipation – Amount of heat energy generated by a device in one second when current flows through it.

Power Factor – The active power divided by the apparent power (i.e., product of the rms input voltage and rms input current of a driver).

Power Factor Correction – In an electronic device, such as an LED lighting fixture, a system of inductors, capacitors, or voltage converters to adjust the power factor of electronic devices toward the ideal power factor of 1.0.

Printed Circuit Board – Insulating board containing conductive tracks for circuit connections.

Pulse Width Modulation (PWM) 
 – A method, used by LED drivers, to regulate the amount of energy to the LEDs.

PWM turns LEDs on and off at high frequency, reducing total ON time to achieve a desired dimming level.

Pylon sign – A freestanding sign that is not a pole or ground sign.

Raceway – It is an enclosed conduit that forms a physical pathway for electrical wiring. Channel Letters are mounted to the front of the Raceway. It protects wires and cables from heat, humidity, corrosion, water intrusion and general physical threats. The raceway itself is attached to the wall with lag bolts, through bolts or toggle bolts, depending on your type of wall.

Radiant Flux – The total energy emitted by a light source across all wavelengths, measured in watts.

Radiometry – The measurement of radiant energy (including light) in terms of absolute power. Compare photometry.

Remote Phosphor – A phosphor conversion technique in which photons from a royal blue LED pass through a phosphor material that is not attached to the LED chip.

Resistance – Symbolized “R” and measured in ohms. Opposition to current flow and dissipation of energy in the form of heat.

Resistor – Component made of material that opposes flow of current and therefore has some value of resistance.

Reverse Breakdown Voltage – Amount of reverse bias that will cause a P-N junction to break down and conduct in the reverse direction.

Reverse Channel Letter – A channel letter that has a face and sides but no back, and is pinned out from a background surface. When the neon tube inside the letter is illuminated, it produces a halo effect around the letter.

Return – The sides of a channel letter.

RGB – Stands for red, green, and blue, the three primary colors of light. When the primaries are mixed, the resulting light appears white to the human eye. Mixing the light from red, green, and blue LEDs is one way to produce white light.

RGB Color Model – An additive color model in which red, green, and blue light are added together in different proportions to produce a broad range of colors, including white.
RGB White – A method of producing white light by combining the output from red, green, and blue LEDs.


SDCM – See standard deviation of color matching.

SMDs – Surface-mount LEDs.

Solder Point Temperature (Ts) – Solder point temperature as specified by ENERGY STAR® and Philips Lumileds Application Brief 33.

Solid-state lighting (SSL) – 1. A description of the devices that do not contain moving parts or parts that can break, rupture, shatter, leak or contaminate the environment. 2. Technology uses semiconducting materials to convert electricity into light. SSL is an umbrella term encompassing both light-emitting diodes (LEDs) and organic light emitting diodes (OLEDs).

Spectral Luminous Efficiency Function – A bell-shaped curve describing the sensitivity of a human eye with normal vision to the spectrum of visible light. Also known as the eye-sensitivity curve.

sRGB – A Standard Default Color Space for the Internet created by Hewlett-Packard and Microsoft to support a standard color space within the Microsoft operating systems, HP products, and others.

Standard Deviation of Color Matching (SDCM) – Describes the difference between two colors. A difference of one to three SDCM “steps” is virtually imperceptible, a difference of four SDCM steps is just noticeable, and a difference of more than four SDCM steps is readily visible.

Starting Temperature (Minimum) – The minimum ambient temperature at which the lamp will start reliably.

Steradian – The standard unit of solid angle. Describes two-dimensional angular spans in threedimensional space.

Storage Temperature – The temperature range over which an LED is designed to be stored safely in the off-state.

Stroke Width – The width of the lines comprising a letterform.

Substrate – The material out of which the face is made. Wood, metal sheeting, paper and acrylic are some examples of sign substrates.

Subtractive Color Model – A color model that applies to reflective surfaces such as paints, dyes, and inks. Combining red, green, and blue in equal amounts produces black.

Superflux LED – The type of LED used by US LED, GE and Sloan / 2.5 to 3X better performance than traditional 5mm indicator type LED.

Surface-Mount (SMT) LED – SMT LEDs are soldered to the surface of the circuit board. The LED die is integrated into the pack- age design. SMT components can be assembled faster and with better quality than through-hole components.


Ta – See Ambient Temperature.

Tc – See Case Temperature.

Temperature Sensor – Heat sensing device – like a thermostat – sends a signal to the power source that LED’s are getting too hot, will dim down to save LED’s (on the Qube there are 2 black dots, one on each end, these are the thermisters).

Thermal Management – Controlling the operating temperature of the product through design, examples includes heat sinks and improved airflow.

Thermal Pad Temperature – The measured temperature of the thermal pad during tesing. The thermal pad aides in the conduction of heat away from the component being cooled and into the heatsink. For more information refer to LUXEON® Rebel and LUXEON® Rebel ES Assemby and Handling Guide application brief 32.

Thermal Resistance (K/W) – The property of a material’s ability to conduct heat.

Through-Hole LED – This kind of package is soldered “through holes” to the circuit board. The LED chip is seated in a reflector and light is emitted by a lens integrated into the package. Different radiation characteristics are produced as a function of chip-to-lens spacing and the shape of the lens.

Tinted Encapsulation – Color added to the LED epoxy lens to identify the LED color when it is in the off-state. The tint does not affect the luminous intensity or viewing angle.

Tj – See Junction Temperature.

Tp – See Thermal Pad Temperature.

Trailing Edge Dimmer – A type of dimmer that regulates power to lamps by delaying the end of each half-cycle of AC power. Compatible with many LED fixtures.

Tri-Color LED – A single LED device containing two different colored LED dice and three leads. The different colored dice can be illuminated independently or together with a common anode or cathode.

Troffer – A long, recessed lighting unit, usually installed in an opening in the ceiling.

Ts – See Solder Point Temperature.

Tunable White Light – White-light LED fixtures that combine channels of warm white and cool white LEDs to produce a range of color temperatures.

Ultraviolet (UV) – Electromagnetic radiation with wavelength shorter than that of visible light.

Underwriters Laboratories (UL) 
 – A private organization which tests and lists electrical (and other) equipment for electrical and fire safety according to recognized UL and other standards. A UL listing is not an indication of overall performance.

Useful Life – The amount of light a lighting fixture delivers in an application, minus any wasted light.

Viewing Angle – The maximum angle at which a display can be viewed with acceptable visual

Volt – The term used to describe the electrical potential difference between oppositely charged conductors, for example there is a 1.5V potential between the top and bottom of an AAA battery. 
Voltage (V) – Term used to designate electrical pressure or force that causes current to flow.

Voltage Drop – Voltage or difference in potential developed across a component due to current flow.

Wall Plug Efficiency – This typically refers to the effectiveness of converting electrical power to
light output. It is defined as the ratio of the radiant flux to the input electrical power.

Warm Colors – Refers to the warmer colors in the light spectrum – red, orange and yellow.

Warm White – A description of light with a correlated color temperature between 3000K and 3500K, usually perceived a slightly yellow.

Waterclear Encapsulation – An LED lens without tint or color. The LED color cannot be determined in the off state.

Waterproof – Meaning the LED product can be submerged into calm water but there is a limited depth as stated for each specific product. Most aluminum bodied LED products will not do well in salt or acidic water.

Watt – 1. The unit of electrical power as used by an electrical device during its operation. Many lamps come with rating in watts to indicate their power consumption. 2. The unit for measurement od Metrical power; the energy required to light the product. The lower the wattage, the less energy is used. It defines the rate of energy consumption by an electrical device when it is in operation. The energy cost of operating an electncal device is calculated as its wattage times the hours of use. In single phase circuits, it is related to volts and amps by the formula: Volts x Amps x PowerFactor = Watts.

Watt per LED – It can be confusing when two watt numbers are used in product specifications. For the application to smd hiqh powered LEDs, the 1 watt, 3 watt, 5 watt, etc, refers to the power consumption of that specific LED installed in that product The watt numbers expressed as light output are a comparison to an incandescent light bulb light output, for example- a 60 watt light output is equal to a 60 watt incandescent light bulb.

Wavelength – Distance between two points of corresponding phase and is equal to waveform velocity divided by frequency.

White – White is defined by Kelvin Temperature or Degrees Kelvin. Kelvin Temperature of 6000K plus is white with a bluish tint.

White Point – The Coordinated Color Temperature (CCT) defined by a line perpendicular to the Planckian Black Body Curve and intersecting the measured chromaticity.




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