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Glossary

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A Lamp
General Service Incandescent bulbs of less than 200 Watts.
AC
Alternating Current.
Accent Lighting
Directional lighting emphasizing a particular object or area.
AllnGaP (Aluminum Gallium Indium Phosphide)
Active materials used to produce red, amber, and yellow LEDs.
AlGaAs (Aluminum Gallium Arsenide)
Active material used to produce infrared emitting diodes (IREDs).
Ambient Lighting
Lighting available in area absent of sources inside that area.
Ambient Light Sensor
An ambient light sensor is an electronic component found in some devices that detects the amount of light around the object. They are used to automatically adjust the output of a fixture to compensate for ambient lighting conditions.
Ambient Temperature
The temperature of the air around a fixture.
Amperes (A)
The unit of measurement of current.
Anode
The positive terminal of an electrical device.
ANSI
A private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States.
Aperture
The opening which determines how much light is allowed to enter or exit a source or fixture.
Ballast
An enclosed device that regulates electrical power to a specific type of light source; also known as a driver module.
Black Body Curve or Planckian Locus
The curve on the CIE chart representing the colors of a blackbody radiator at a specified temperature. Low temperature radiators begin at the red edge of human vision and move through white toward blue, though the curve ends well before reaching saturated blue.
Bond Wire
A method of connecting integrated-circuit chips to their substrate, using ultrasonic energy to weld very fine wires mechanically from metalized terminal pads along the periphery of the chip to corresponding bonding pads on the substrate.
Candela (cd)
The measure of luminous intensity of a source in a given direction. The unit is equivalent to lumens per steradian (lm/sr).
Cathode
The negative terminal of an electrical device.
Candlepower
An obsolete term for luminous intensity; current practice is to refer to this simply as candelas.
CCT (Correlated Color Temperature)
A measurement of color that maps spectral output to the apparent color of a heated object (black body) at the specified temperature.
Chromaticity
The color of light as mapped to the CIE 1931 color chart, expressed as x and y coordinates.
Color Bin
The region of the CIE 1931 chart that an individual LED fits into; the bin boundaries may vary between suppliers.
Color Temperature
See CCT (Correlated Color Temperature).
Cool White
A general term for higher CCT, bluer white light sources; typically indicates CCTs from 5,000°K up to 10,000°K.
CRI (Color Rendering Index)
A scale from 0-100 that indicates the similarity of reflected light off select colors in comparison to a pure black body at the same CCT.
Current
Electrical charge through a device, measured in Amperes.
Damp location
A designation for fixtures suitable to be installed in damp locations, ie: shower.
Daylight White
5,000°K to 7,500°K; CIE defines daylight over a range, CCT:5,000°K (CIE D50) is Equal Energy Daylight White, 5500°K(CIE D55) is Direct Sunlight, (Noon Sky sunlight), 6,500°K (CIED65) is Average Daylight, 7,500°K (CIE D75) is Northern SkyDaylight.
DC
Direct Current.
Die
The light emitting chip contained in the LED package. The chemical composition of the die determines the output color.
Dielectric
An electrical insulator or insulation layer.
Diffuser
A filter or film which disperses light uniformly.
DMX (Digital MultipleXing)
A digital lighting control standard employed primarily by the theater industry, frequently used to color control LED fixtures.
Dominant Wavelength
The apparent wavelength of an LED to the human eye.
Duty Cycle
the fraction of time that a system is in an "active" state as the system oscillates between activity and inactivity (on and off).
Efficacy
A measurement of a light source’s effectiveness in converting electrical energy to lumens of visible light; expressed in lumens per watt (LPW).
Efficiency
The percent of electrical energy converted to light, i.e. watts of visible light produced for each watt of electrical power.
Eye Sensitivity
The response of the human eye to light with respect to wavelength; peak response is at 555 nm.
Fill Light
Lighting throughout an area that produces general illumination.
Flood Light
A fixture designed to emit usable light over a wide beam angle.
Footcandle (fc)
A unit of illuminance equivalent to the illumination produced by a source of one candle, at a distance of one foot; equal to one lumenincident per square foot; can be written as lm/ft^2 (see Lux).
Forward Current
Current through an LED in the direction that will produce light.
Forward Voltage (VF )
The voltage across an LED for a given forward current.
GaAs (Gallium Arsenide)
Active material used to produce IREDs.
GAN (Gallium Nitride)
Active materials used to produce low intensity blue, green, and white LEDs.
GaP (Gallium Phosphide)
Active materials used to produce low intensity red, amber, and yellow LEDs.
General Lighting
Lamps designed to produce ambient light, as a replacement or supplement to natural sunlight.
Glare
A form of light pollution making vision difficult caused by reflected light.
I2C
Two-wire, serial protocol developed by Philips in the early 1980s; used in today’s mobile applications.
Illuminance (E)
The amount of light arriving on a surface, measured in lux or footcandles.
Infrared Light
Electromagnetic waves with a wavelength of 1 mm to 700 nm.
InGaN (Indium Gallium Nitride)
Active material used to produce blue, green, and white LEDs.
Intensity Bin
A group of LEDs defined by pre-established upper and lower brightness bounds.
IRED
Infrared emitting diode.
Kelvin (K)
A temperature scale starting with 0°K (= -273.16°C) at the absolute zero temperature; a difference in temperature of one Kelvin (K) is equal to the difference in temperature in degrees Celsius.
Key Light
Directional lighting used to highlight an object in order to draw attention.
Leadframe
A metal frame used to mount and connect to LED chips; the leadframe channels current and often heat to and from the LED.
Lens
an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam.
Light Distribution
Pattern of light produced by a fixture, or created in a room.
Light Trespass (Spill Light)
Light that escapes the optical system that contains the light source.
Lumen
The SI unit of measurement that represents the total output of a light source measured in all directions.
Lumen Maintenance
A measure of how the light output of a light source degrades over time.
Luminaire
A fixture with power requirements and light sources included.
Luminaire Efficiency
Percentage of lumens emitted by the lamp that escapes the luminaire.
Luminance (L)
The amount of visible light leaving a point in a given direction; the light can be reflected, transmitted, or emitted; luminance is measured in nits, equivalent to one candela per square meter (cd/m2).
Luminous Flux
A measure of total emitted light weighted by the human eye’s sensitivity expressed in lumens (lm); peak lumens per watt of radiated light occurs at 555 nm and 683 lm for 1W radiated.
Luminous Intensity
Luminous flux emitted per unit solid angle in a particular direction; standard unit of luminous intensity is a candela (cd).
Lux (lx)
A unit of illuminance or light incident on a surface, one lux is one lumen per square meter; ten lux approximately equals one footcandle (see footcandle).