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What’s the LED general techical terms?

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

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

Color Rendering Index (CRI)
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.

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
The description used to describe the effect of heating an object until it glows incandescently, the emitted 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.

Correlated Color Temperature (CCT)
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.

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

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.

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

Flux / Luminous Flux
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.

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

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

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

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

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 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.

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).

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.

Infrared (Near)
Electromagnetic radiation with wavelength range from 700 nm – 3000 nm.

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

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

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.

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.

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.

A lighting fixture complete with installed lamps and other accessories.

Luminous Efficiency
The percentage of total lamp lumens that a lighting fixture, luminaire, or system emits, minus any blocked or wasted light.

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).

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.

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.

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.

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

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

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