A
Amp
A measure of electrical current. In LED lights, the current is related to voltage and power as follows: Watts (power) = Volts x Amps (current).

ANSI
American National Standards Institute. The organization that develops voluntary guidelines and produces performance standards for the electrical and other industries.

AVERAGE RATED LIFE
An average rating, in hours, indicating when 50% of a large group of lamps have failed, when operated at nominal lamp voltage and current.

B
Brightness
Brightness can refer to any of several technical terms used in lighting and is, therefore, ambiguous (See LUMINANCE ).

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C
Chromaticity
Measure to identify the color of a light source, typically expressed as (x,y) coordinates on a chromaticity chart (See COLOR TEMPERATURE).

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 Rendering Index (CRI)
The ability of a light source to accurately render an object’s color in comparison with a natural light source. Measured on a scale of 1 -100 with 100 being the ideal. 

Color Temperature (Correlated Color Temperature - CCT)
A number indicating the degree of "yellowness" or "blueness" of a white light source. Measured in Kelvin’s, CCT represents the temperature an incandescent object (like a filament) must reach to mimic the color of the lamp. Yellowish-white ("warm") sources, like incandescent lamps , have lower color temperatures in the 2700K-3000K range; white and bluish-white ("cool") sources, such as cool white (4100K) and natural daylight (6000K), have higher color temperatures. The higher the color temperature the whiter, or bluer, the light will be (See CHROMATICITY).

Constant Current Technology (CCT)
Constant Current Technology (CCT), the heart of the SloanLED Line. CCT is the design backbone of the ChanneLED, ThinLED, FlexiBRITE and ColorLINE systems. CCT maintains consistent current levels, eliminating the line loss and voltage drop issues common in many LED lighting systems. CCT provides uniform light output throughout the entire installation, while also preventing damage from overdriving of the LEDs.

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.

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D
DAYLIGHT SENSOR
A device which senses the amount of daylight in a room and controls the luminaire accordingly.

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.

DIRECT
A direct source of light which is cast downwards from a fixture to provide lighting with uniform levels of illumination. Open, louvered, and lensed fixtures can all be “direct”. Also see Indirect and Direct/Indirect.

Direct/Indirect (DID)
A source of light in which light is cast both upwards and downwards from a fixture to provide a combination of direct and indirect illumination.

Dominant Wavelength
A quantitative measure of the color of an LED as perceived by the human eye. It is usually measured in nanometers (a billionth of a meter).

DOWNLIGHTING
Light which is cast downward from a fixture. The most common and direct form of lighting.

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E
Energy Conservation Measures (ECM)
A term commonly used by ESCOs in lighting audits/designs.

Efficacy
A measurement of how effective the light source is in converting electrical energy to LUMENS of visible light. Expressed in LUMENS-PER-WATT (LPW) this measure gives more weight to the yellow region of the spectrum and less weight to the blue and red region where the eye is not as sensitive.

Efficiency
The efficiency of a light source is simply the fraction of electrical energy converted to light, i.e. watts of visible light produced for each watt of electrical power with no concern about the wavelength where the energy is being radiated.

Energy Service Company (ESCO)
A company dedicated to helping commercial and industrial clients reduce their energy consumption.

Eye Sensitivity
A curve depicting the sensitivity of the human eye as a function of wavelength (or color). The peak of human eye sensitivity is in the yellow-green region of the spectrum. The normal curve refers to photopic vision or the response of the cones.

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F
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.

Flux
The sum of all the lumens (lm) emitted by a source (see lumen).

Footcandle (fc)
A unit of illuminance or light falling onto a surface. It stands for the light level on a surface one foot from a standard candle. One foot-candle is equal to one lumen per square foot. See also Lux.

Foot-candle Meter
(See ILLUMINANCE METER).

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

Forward Voltage (VF)
The voltage across a diode for a given forward current.

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G

H
HI-BAY
Lighting used in industrial applications where the ceiling height is greater than 20 feet. Common in big box retail, industrial, warehouse and manufacturing space

I
Illuminance
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.

Indirect Lighting
An indirect source of light which is cast upwards from a fixture and bounced down to provide lighting with minimal glare and more uniform levels of illumination.

NITIAL LUMENS
The lumens produced by a lamp after an initial burn in period (usually 100 hours).

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J


K
Kelvin Temperature
Term and symbol (K) used to indicate the comparative color appearance of a light source when compared to a theoretical blackbody. Light with a lower Kelvin rating will have a warmer, more yellow tint, while light with a higher kelvin rating will have a cooler, more blue tint.

Kilowatt (kW)
The measure of electrical power equal to 1000 watts.

Kilowatt Hour (kWh)
1000 Watts used continuously for one hour.

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L
Lamp Lumen Depreciation Factor (LLD)
The multiplier to be used in illumination calculations to relate the initial rated output of light sources to the anticipated minimum rated output based on the relamping program to be used. (See also Lumen Depreciation and Mean Lumens).

LED
A Light Emitting Diode (LED) is a solid-state semiconductor device that converts electrical energy directly into light.

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 Meter
A device that measures the illuminance at a location calibrated either in foot-candles or in lux.

LO-BAY
Lighting used in industrial applications where the ceiling height is 20 feet or less. Common in big box retail and industrial settings.

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. A 60-Watt Soft White incandescent lamp provides 840 lumens.

LUMEN DEPRECIATION
The decrease in lumen output of a light source over time; every lamp type has a unique lumen depreciation curve (sometimes called a lumen maintenance curve) depicting the pattern of decreasing light output.

Lumen Maintenance
A measure of how well a lamp maintains its light output over time. It may be expressed numerically or as a graph of light output vs. time.

Lumens Per Watt (LPW)
The number of lumens produced by a light source for each watt of electrical power supplied to the light source. See Efficacy.

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 Efficacy
(See EFFICACY)

Luminous Intensity
A measure of the visibility of a light source generally expressed in candelas. It is defined as luminous flux per unit solid angle (steradian) in a given direction.

Lux (lx)
A unit of illuminance or light falling onto a surface. One lux is equal to one lumen per square meter. Ten lux approximately equals one foot-candle. (See FOOT-CANDLE)

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M

N
Nits - Measurement of display screen brightness. 1 nit = 1 cd/m2. The more nits, the brighter the picture.

O
OCCUPANCY SENSOR
A device which activates a fixture upon sensing the presence of a person

P
Peak Wavelength
The maximum wavelength of an LED.

Phosphor
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.

Photometry
The measurement of light and related quantities.

PHOTOPIC LUMENS
A type of light measured in lumens that is generally detected by common light meters and accounts for part of the human eye’s perception of brightness.

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Q

R
Relative Light Output (RLO)
The ratio of light output between a fixture's potential light output at optimum ambient temperatures and actual light output at actual ambient temperatures. For example, if a fixture at its optimal temperature of 75°F produces 10,000 Lumens and 8,000 Lumens 50°F, that fixture's RLO at 50°F is 8,000 Lumens ÷ 10,000 Lumens, or 80%.

S
SCOTOPIC LUMENS
A type of light that is not generally detected by common light meters but which accounts for part of the human eye’s perception of brightness. 

SEMI-SPECULAR
A reflective but somewhat diffuse surface.

S/P RATIo
The ratio of scotopic to photopic lumens produced by a light source. An appropriate S/P ratio will provide for a more comfortable atmosphere and better perceived brightness. 

Solid-state lighting
A description of the devices that do not contain moving parts or parts that can break, rupture, shatter, leak or contaminate the environment.

SPECULAR
A highly polished or mirrored surface. 

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

Thermal resistance (C/W)
A measure of the heat transfer capacity of the LED. Lower resistance is preferred.

Total Harmonic Distortion (THD)
A measure of the distortion of an electrical wave form. Excessive THD (defined by ANSI as greater than 32%) may cause adverse effects to the electrical system.

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U
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.

UPLIGHTING
A source of light which is cast upwards to illuminate a ceiling cavity for aesthetic reasons. When combined with reflective ceiling materials, uplighting can function as a source of indirect lighting.

V
Viewing Angle
The maximum angle at which a display can be viewed with acceptable visual performance.

Volt
A measure of "electrical pressure" between two points. The higher the voltage, the more current will be pushed through a resistor connected across the points.

Voltage
A measurement of the electromotive force in an electrical circuit or device expressed in volts. Voltage can be thought of as being analogous to the pressure in a waterline.

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W
.Watt
A unit of electrical power. Lamps are rated in watts to indicate the rate at which they consume energy (See KILOWATT HOUR).

Wavelength
The distance between two neighboring crests of a traveling wave. The wavelength of light is between 400 and 700 nanometers. 

X

Y 

Z

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