Crestron electronic IPAC-GL1, GLPS-SW Appendix E Glossary of Lighting Terminology, Doc. 4775A

Commercial Lighting Design Guide Appendix E

Appendix E: Glossary of Lighting Terminology

A

AMPERE: The standard unit of measurement for electric current that is equal to one coulomb per second. It defines the quantity of electrons moving past a given point in a circuit during a specific period, abbreviated amp.

ANSI: Abbreviation for American National Standards Institute

ARC TUBE: A tube enclosed by the outer glass envelope of a HID lamp and made of clear quartz or ceramic that contains the arc stream

ASHRAE: American Society of Heating, Refrigerating and Air-Conditioning Engineers

B

BAFFLE: A single opaque or translucent element used to control light distribution at certain angles

BALLAST: A device used to operate fluorescent and HID lamps. The ballast provides the necessary starting voltage, while limiting and regulating the lamp current during operation

BALLAST CYCLING: Undesirable condition under which the ballast turns lamps on and off (cycles) due to the overheating of the thermal switch inside the ballast. This may be due to incorrect lamps, improper voltage being supplied, high ambient temperature around the fixture, or the early stage of ballast failure

BALLAST EFFICIENCY FACTOR: The ballast efficiency factor (BEF) is the ballast factor (see below) divided by the input power of the ballast. The higher the BEF (within the same lamp-ballast type) the more efficient the ballast.

BALLAST FACTOR: The ballast factor (BF) for a specific lamp-ballast combination represents the percentage of the rated lamp lumens that will be produced by the combination

C

CANDELA: Unit of luminous intensity, describing the intensity of a light source in a specific direction

CANDELA DISTRIBUTION: A curve, often on polar coordinates, illustrating the variation of luminous intensity of a lamp or luminaire in a plane through the light center

CANDLEPOWER: A measure of luminous intensity of a light source in a specific direction, measured in candelas (see above)

CBM: Abbreviation for Certified Ballast Manufacturers Association.

CEC: Abbreviation for California Energy Commission

COEFFICIENT OF UTILIZATION: The ratio of lumens from a luminaire received on the work plane to the lumens produced by the lamps alone. (Also called "CU")

COLOR RENDERING INDEX (CRI): A scale of the effect of a light source on the color appearance of an object compared to its color appearance under a reference light source. Expressed on a scale of 1 to 100, where 100 indicates no color shift. A low CRI rating suggests that the colors of objects will appear unnatural under that particular light source

COLOR TEMPERATURE: The color temperature is a specification of the color appearance of a light source, relating the color to a reference source heated to a particular temperature, measured by the thermal unit Kelvin. The measurement can also be described as the "warmth" or "coolness" of a light source. Generally, sources below 3200K are considered "warm;" while those above 4000K are considered "cool" sources

COMPACT FLUORESCENT: A small fluorescent lamp that is often used as an alternative to incandescent lighting. The lamp life is about 10 times longer than incandescent lamps and is 3-4 times more efficacious. Also called PL, Twin-Tube, CFL, or BIAX lamps

CONSTANT WATTAGE (CW) BALLAST: A premium type of HID ballast in which the primary and secondary coils are isolated. It is considered a high performance, high loss ballast featuring excellent output regulation

CONSTANT WATTAGE AUTOTRANSFORMER (CWA) BALLAST: A popular type of HID ballast in which the primary and secondary coils are electrically connected. Considered an appropriate balance between cost and performance

CONTRAST: The relationship between the luminance of an object and its background

CRI: (SEE COLOR RENDERING INDEX)

CUT-OFF ANGLE: The angle from a fixture's vertical axis at which a reflector, louver, or other shielding device cuts off direct visibility of a lamp. It is the complementary angle of the shielding angle

D

DALI: Digital Addressable Lighting Interface is a protocol set out in the technical standard IEC 60929. A DALI system is self-contained. A ballast and a multi-sensor, offer benefits such as constant light control, PIR movement-detection and IR remote operation. Multiple DALI systems can be connected together using gateways to building management systems. Software programs offer more sophisticated programming functionality for grouped systems, such as scene setting, time clock, and partition control

DAYLIGHT COMPENSATION: A dimming system controlled by a photocell that reduces the output of the lamps when daylight is present. As daylight levels increase, lamp intensity decreases. An energy-saving technique used in areas with significant daylight contribution

DERATING: Components can be treated in such a way as to enhance their life expectancy. Derating is the name normally given to operating a component well inside its normal operating limits to extend the life of a component, and is a practical means of reducing failures. The National Electrical Code and local electrical codes determine the amount of available current based on a derating factor. A derating factor improves reliability by reducing the upper limit of current carrying capacity to compensate for electrical, mechanical and thermal stress

DIFFUSE: Term describing dispersed light distribution. Refers to the scattering or softening of light

DIFFUSER: A translucent piece of glass or plastic sheet that shields the light source in a fixture. The light transmitted throughout the diffuser will be redirected and scattered

DIRECT GLARE: Glare produced by a direct view of light sources. Often the result of insufficiently shielded light sources. (See GLARE)

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