Lighting Glossary
Definitions of key terms used in modern lighting.
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. Amp is an abbreviation.
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
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.
Candela: Unit of luminous intensity, describing the intensity of a light source in a specific direction.
