Residential Lighting Design Guide | Appendix D |
Appendix D: 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
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
BALLAST FACTOR: The ballast factor (BF) for a specific
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
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)
D
DALI: Digital Addressable Lighting Interface is a protocol set out in the technical standard IEC 60929. A DALI system is
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
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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