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Lighting Terminology

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0-10V: A dimming technology commonly used in commercial installations that controls the light level of the connected load through a separate, dedicated DC voltage signal that ranges from zero to 10 volts. Refer to our Dimming Technology guide for more information.

3-Way Dimmer: 3-way dimmers are designed to provide dimming control from one location, but can be installed in tandem with three-way on/off switches that allow you to turn the lights on to the preset dimmer level from a variety of different locations.

B

Beam Angle: This refers to the angle of distribution between two planes of light at which the light output is greater than or equal to 50% of the maximum center beam candlepower. This is a good measure of usable light.

C

Candela: The SI base unit of luminous intensity; the amount of light emitted from a light source in particular direction. Abbreviated "cd".

Center Beam Candlepower (CBCP): A measurement of the intensity of light at the center of a reflector lamp. Measured in candela.

Color Temperature: A measurement for determining the characteristics of a white light source, measured in degrees Kelvin (K). Lower values, such as 2000K-3000K, are considered "warmer" and give off a yellowish light. Higher values, such as 5000K-6000K, are considered "cooler" and give off a bluish light. Color temperature of the light source is an important consideration in every project and should be selected based on the application, tasks performed, and the environment of the project area. Also referred as Correlated Color Temperature (CCT).

Color Rendering Index (CRI): A measurement of how accurately a light source renders colors. It is measured on a scale of 0-100, with the higher the number indicating a "truer" representation of color. Color-critical applications should strive for a light source with a CRI of 85 or higher.

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DALI: Digital Addressable Lighting Interface is a two-way digital lighting control system protocol used in building automation in commercial applications.

Dark-Sky: A campaign to reduce light pollution in an effort to reduce energy use, reduce the harmful effects of unnatural lighting on ecosystems, and to increase the number of visible stars in the night sky. The use of full-cutoff fixtures is highly encouraged. International Dark-Sky Association

DesignLights Consortium (DLC): A voluntary utility-based certification initiative that promotes quality, performance and energy efficient commercial lighting solutions. www.designlights.org

DMX: A control technology commonly used in theatrical lighting and architectural accent lighting installations that controls the color, light level, and other aspects of the connected load through a dedicated low voltage digital communication signal. Refer to our Dimming Technology guide and DMX Hisotry article for more information.

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ELV: Electronic Low Voltage. A dimmer used for capacitive low voltage loads connected to a solid-state electronic transformer. Uses Reverse Phase dimming technology.

ENERGY STAR: A voluntary certification program from the U.S. Environmental Protection Agency and Department of Energy that helps consumers and businesses save money and protect the climate through energy efficiency. The ENERGY STAR program certifies products as well as homes and commercial buildings. www.energystar.gov

ETL: An independent testing and certification mark from Intertek Testing Services demonstrates compliance with nationally recognized safety standards. www.intertek.com/marks/etl/

F

Field Angle: This refers to the angle of distribution between two planes of light at which the light output has fallen to 10% of the maximum center beam candlepower. The difference between the Beam Angle (50% of max output) and the Field Angle is often referred to as "spill light" or "ghost light" and is an indicator of the point when the light's output essentially fades to nothing.

Foot-candle: The measurement of the intensity of light falling on a surface. One foot-candle is loosely defined as the amount of light coming from a one candela light source from one foot away. The foot-candle is commonly used in the United States, while the SI standard "lux" is used internationally. 1 foot-candle = 1 lumen/square foot, or 10.764 lux. Abbreviated "fc".

Forward Phase: A dimming technology that controls the light level of the connected load by phase cutting the leading edge of the AC power sine wave. Commonly called "incandescent dimming" or "Triac dimming". Refer to our Dimming Technology guide for more information.

Full-Cutoff Fixture: A light fixture designed to cast little or no upward light.

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IP Rating: The Ingress Protection (IP) rating is a standardized classification system that rates the degree to which a fixture or enclosure can be penetrated by solids or liquids. The first number indicates the protection against solid particles, ranging from 0 to 6. The second number indicates the protection against liquid, ranging from 0 to 9. Refer to this Wikipedia page for the complete number breakdown.

L

L70 Lifespan: The industry standard used to express the rated lifespan of an LED lamp or fixture. It indicates the number of hours before lumen output drops to 70% of the initial lumen output.

Lumen: The SI base unit of luminous flux; the amount of visible light emitted by a light source, without regard to direction. Abbreviated "lm". Lumens do not measure the amount of light falling on a surface - see "Foot-candle".

Luminous Efficacy: The measurement of how well a light source produces light, measured in lumens of output per watts of energy used. In effect, it tells you how efficient the light source is in converting power used to visible light. Expressed in "lm/W".

Lux: The SI base unit of illuminance measuring the intensity of light falling on a surface. 1 lux = 1 lumen/square meter. Abbreviated "lx".

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Maximum Overall Length (MOL): Indicates the overall end-to-end measurement of a bulb/lamp, including the base.

MLV: Magnetic Low Voltage. A dimmer used for inductive low voltage loads connected to a magnetic transformer. Uses Forward Phase dimming technology.

Multi-location Dimmer: Multi-location dimmers are designed to be paired with other accessory dimmers in order to provide dimming control of a light source from many locations.

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NEMA Beam Type: This is a standardized method for classifying the light output distribution of directional light fixtures, such as floodlights, established by the National Electrical Manufacturers Association (NEMA). Numbers are assigned in both the horizontal and vertical direction based on a fixture's field angle. See our article on NEMA Beam Angle Types for a more complete breakdown.

NEMA Rating: This is a rating system for heavy duty enclosures that will house electrical components established by the National Electrical Manufacturers Association (NEMA). The ratings identify performance requirements of an enclosure at each classification level, such as protection from moisture, dust, gases, and other factors. See our article on NEMA Enclosure Type Ratings for a more complete breakdown.

O

Ohm's Law: A fundamental electrical law that says that the electrical current between two points is directional proportional to the voltage across those points. It is often expressed as I = V / R, where "I" is the electrical current in amperes, "V" is voltage, and "R" is the resistance of the conductor in ohms. In other words, "amps = volts / ohms".

A derivative of this law, called "Watt's Law" describes the relationship between electrical current, voltage, and power (measured in watts). It is often expressed as I = P / V. In other words, "amps = watts / volts".

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Reverse Phase: A dimming technology that controls the light level of the connected load by phase cutting the trailing edge of the AC power sine wave. Usually used for low voltage fixtures and commonly called "ELV dimming". Refer to our Dimming Technology guide for more information.

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Single Pole Dimmer: Single-pole dimmers are designed to provide dimming control from only one location.

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Title 24: Created by the California Building Standards Commission in 1977, the California Title 24 Building Energy Efficiency Standards are designed to reduce California's energy consumption by providing requirements for energy efficiency and indoor and outdoor environmental air quality in residential and non-residential buildings. As part of the building code, it applies to new construction and remodel projects in the state. It is generally considered one of the most progressive building codes in the United States, and often serves as a trailblazer for standards and requirements that influence manufacturer product designs, as well as other building codes such as the International Code Council's International Energy Conservation Code (IECC) and ANSI/ASHRAE/IES Standard 90.1.

Triac Dimming: Common term for Forward Phase dimming technology.

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UL: An independent safety company that provides standards, certification, testing, and inspection for a range of disciplines, products, fixtures, and components. www.ul.com

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Voltage: The difference in electric potential energy measured in volts.

Voltage Drop: The amount of voltage lost in a circuit due to impedance, or resistance. The more resistance is encountered, the more voltage is lost, or drops. Wires carrying electrical current have some form of inherent resistance to them. The diameter, or gauge, of the wire is a primary factor that determines its impedance. Larger wires have less resistance and allow more electrical current to flow through, while smaller wires have more resistance. Another primary factor of voltage drop is the length of the wire. The longer the run of wire, the more resistance the electrical current is encountering. The result of all this is a difference in voltage from the start of the wire to the end of the wire. In practice with lighting, it often means the voltage of your supply power is not the same voltage that will be supplied to your light fixtures after the electrical current runs through the electrical wiring. Voltage drop is present in all voltages, and some degree of voltage drop is expected and acceptable. But most people encounter it directly with low voltage lights. This is why you usually cannot place a low voltage light too far away from its power source, as the voltage will have changed too much for the light to operate properly.

W

Watt: The SI unit for power defined as joules per second. Watt describe how much energy a light bulb or light fixture is consuming.