Light Sources are also referred to as lamps in the industry and as bulbs by most people. The original lamp or artificial light source was the incandescent or standard bulb invented by Thomas Edison in the 1870’s. Since then a wide range of other lamps have been introduced from Halogen to HID to compact fluorescents and now LED bulbs. Below we cover some basic terminology.
Lamp Terminology
Arc Length: In High Intensity Discharge lamps, arc length is the distance between the electrode tips, which represents the physical length of the electrical
discharge.
Arc Tube: An envelope that contains the arc of a discharge light source; it is
usually made of quartz or ceramic.
Base: Refers to the end of a light source or lamp which connects into a socket
on a fixture. Various bases are used in lamps, with screw bases being
the most common. They are used in a wide range of incandescent, HID,
CFL and now LED lamps.
Bayonet: This is a less common type of bulb base which uses keyways instead
of threads to connect the bulb to the fixture base. The bulb is locked in
place by pushing it down and turning it clockwise.
Bi-Level Switching: A way to control of light source intensity at two discrete levels in addition to off.
Bi-Pin: A Bi-pin is a base with two metal pins for electrical contact. Bi-pins are
typically used in fluorescent tubes that are 1 to 4 feet long. It consists
of 2 prong contacts which connect into the fixture. Medium bi-pins are
used with type T-8 and T-12 tubular fluorescent lamps, and miniature
bi-pins are used for tubular T-5 fluorescent lamps.
Bulb: A common word used to describe a lamp or light source. The “bulb”
refers to the outer glass bulb containing the light source.
Bulb Finish
A coating that is applied to the inside surface of a bulb. Finishes are
either clear, phosphor coated, or diffuse.
Filament: Wire used in incandescent lamps, usually made of tungsten and often
coiled, that emits light when heated by an electrical current.
Lamp Current: The current flowing between a lamp’s electrodes during operation.
Lamp Life: Also known as the average rated life, is the number of hours at which
half of a large group of lamps have failed when operated under
standard testing conditions.
Socket: The socket is the receptacle connected to the electrical supply.
Starting Time: The time it takes the lamp to start from the point at which voltage is applied to the lamp until stable operation.
Starting Voltage: The voltage applied across the lamp during starting.
Warm-up Time: The time it takes for a High Intensity Discharge lamp to reach 90% of light output after being turned on.