Glossary-I-J-K
Ignitor
An electronic device providing a high voltage pulse to initiate an electrical discharge. Typically, the ignitor is paired with or is a part of the ballast (See STARTER ).
Illuminance
The “density” of light (lumens/area) incident on a surface; i.e. the light level on a surface. Illuminance is measured in footcandles or lux .
Illuminance Meter
A device that measures the illuminance at a location calibrated either in footcandles or in lux. (Also know as a light meter — See COSINE CORRECTED )
Incandescent Lamp
A light source that generates light utilizing a thin filament wire (usually of tungsten) heated to white heat by an electric current passing through it.
Indirect Lighting
The method of lighting a space by directing the light from luminaires upwards towards the ceiling. The light scattered off the ceiling produces a soft, diffuse illumination for the entire area.
Induction Lighting
Gases can be excited directly by radio-frequency or microwaves from a coil that creates induced electromagnetic fields. This is called induction lighting and it differs from a conventional discharge, which uses electrodes to carry current into the arc. Induction lamps have no electrodes inside the chamber and generally, therefore, have longer life than standard lamps.
Infrared Radiation
Electromagnetic energy radiated in the wavelength range of about 770 to 1,000,000 nanometers . Energy in this range cannot be seen by the human eye, but can be sensed as heat by the skin.
Instant Start
A type of ballast designed to start fluorescent lamps as soon as the power is applied. Most T8 fluorescent lamps are being operated on electronic instant-start ballasts. Slimline fluorescent lamps operate only on instant start circuits (See RAPID START ).
Integral
A popular term for a compact fluorescent lamp which includes a built-in ballast (See CFL ).
Intensity Bin
LEDs are sorted according to their intensity values into different groupings or “bins.”
Inverse Sq uare Law
Formula stating that if you double the distance from the light source, the light level goes down by a factor of 4, if you triple the distance, it goes down by a factor of 9, and so on.
Isocandela Plot
A plot with lines connecting points of equal luminous intensity around a source.
Isolux Plot (or Isofootcandle Plot)
A line plotted to show points of equal illuminance (lux or footcandles) on a surface illuminated by a source or sources.
 |
 |
|
|
|
|
Kelvin
A unit of temperature starting from absolute zero, parallel to the Celsius (or Centigrade) scale. 0C is 273K.
Kilowatt (kW)
The measure of electrical power equal to 1000 watts .
Kilowatt Hour (kWh)
The standard measure of electrical energy and the typical billing unit used by electrical utilities for electricity use. A 100-watt lamp operated for 10 hours consumes 1000 watt-hours (100 x 10) or one kilowatt-hour. If the utility charges $.10/kWh, then the electricity cost for the 10 hours of operation would be 10 cents (1 x $.10)
Glossary-F
Federal Communications Commission (FCC)
The U. S. Federal agency that regulates emissions in the radio frequency portion of the electromagnetic spectrum. Part 18 of the FCC rules specifies electromagnetic interference (EMI) from lighting devices operating at frequencies greater than 9 kilohertz (kHz). Typical electronically-ballasted compact fluorescent lamps operate in the 24 – 100 kHz frequency range.
Field Angle
The angular dimension of the cone of light from reflectorized lamps (such as R and PAR types) encompassing the central part of the beam out to the angle where the intensity is 10% of maximum (See BEAM ANGLE ).
Filament Design
Filaments are designated by a letter combination in which C is a coiled wire filament, CC is a coiled wire that is itself wound into a larger coil, and SR is a straight ribbon filament. Numbers represent the type of filament-support arrangement.
Fixture Requirements
Describes fixture requirements for HID lamps.
O = Open or Enclosed Fixtures
E = Enclosed Fixtures Only
S = Lamps operated in a vertical position (Base Up or Down) ±15º, can be used in an open fixture. Lamps burned in any other orientation must be used in “enclosed fixtures only.” See additional details in the e-Catalog Help Menu under the HID category.
Flicker
The periodic variation in light level caused by AC operation that can lead to strobe effects.
Flood
Used to refer to the beam pattern of a reflector lamp, which disperses the light over a wide beam angle, typically 20 degrees or more. (“Flood” as opposed to “spot”)
Floodlight
A luminaire used to light a scene or object to a level much brighter than its surroundings. Usually floodlights can be aimed at the object or area of interest.
Fluorescence
A physical phenomenon whereby an atom of a material absorbs a photon of light an immediately emits a photon of longer wavelength. If there is a significant delay the phenomenon is called phosphorescence rather than fluorescence. It is interesting that “phosphors” used in lamps exhibit “fluorescence,” not “phosphorescence.” (See PHOSPHOR )
Fluorescent Lamp
A high efficiency lamp utilizing an electric discharge through low pressure mercury vapor to produce ultraviolet (UV) energy. The UV excites phosphor materials applied as a thin layer on the inside of a glass tube which makes up the structure of the lamp. The phosphors transform the UV to visible light.
Footcandle (fc)
A unit of illuminance or light falling onto a surface. It stands for the light level on a surface one foot from a standard candle. One footcandle is equal to one lumen per square foot. See also Lux .
Footcandle Meter
(See ILLUMINANCE METER ).
Footlambert
An obsolete term referring to a luminance of 1/? candelas per square foot.
Forward Current
Current through a diode in the direction of its greatest conduction.
Forward Voltage (VF)
The voltage across a diode for a given forward current.
Frequency (Nominal Operations)
The stated operating frequency in Hz of a discharge lamp.
Fovea, Foveal Vision
A small region of the retina corresponding to what an observer is looking straight at. This region is populated almost entirely with cones, while the peripheral region has increasing numbers of rods. Cones have a sensitivity peaking in the yellow and corresponding to the eye response curve (See PHOTOPIC , SCOTOPIC , EYE SENSITIVITY ).
Full Spectrum Lighting
A marketing term, typically associated with light sources that are similar to some forms of natural daylight (5000K and above, 90+ CRI), but sometimes more broadly used for lamps that have a smooth and continuous color spectrum.
Glossary-E
Eccentricity (Maximum)
In High Intensity Discharge lamps the Bulb to Arc Angle is the angle off of center between electrodes and bulb. The Bulb to Base Angle is the angle off of center that the bulb is from the base.
GE Edison Award
An annual competition where lighting designers submit their best projects. The entries are judged by an international panel and awards are presented at a banquet accompanying Light Fair, the North American trade show for the lighting industry.
Efficacy
A measurement of how effective the light source is in converting electrical energy to LUMENS of visible light. Expressed in LUMENS-PER-WATT (LPW) this measure gives more weight to the yellow region of the spectrum and less weight to the blue and red region where the eye is not as sensitive.
Efficiency
The efficiency of a light source is simply the fraction of electrical energy converted to light, i.e. watts of visible light produced for each watt of electrical power with no concern about the wavelength where the energy is being radiated. For example, a 100 watt incandescent lamp converts 7% of the electrical energy into light; discharge lamps convert 25% to 40% into light.
The efficiency of a luminaire or fixture is the percentage of the lamp lumens that actually comes out of the fixture (See LUMINOUS EFFICACY ).
Electrical Discharge
A condition under which a gas becomes electrically conducting and becomes capable of transmitting current, usually accompanied by the emission of visible and other radiation. An electric spark in air is an example of an electrical discharge, as is a welder’s arc and a lightning bolt. (See ARC , ELECTRODELESS LAMPS )
Electrodeless Lamps
Light sources where the discharge occurs in a chamber with no electrodes (no metal.) The energy for the discharge is supplied by radio frequency excitation, e.g. microwaves (See GENURA ).
Electromagnetic Ballast
A ballast used with discharge lamps that consists primarily of transformer-like copper windings on a steel or iron core (See ELECTRONIC BALLASTS ).
Electromagnetic Inference (EMI)
High frequency electronic ballasts and other electronic devices can produce a small amount of radio waves which can interfere with radio and TV. Federal mandated requirements must be met for EMI levels before an electronic device is considered FCC compliant. (FCC is the Federal Communications Commission.)
Electromagnetic Spectrum
A continuum of electric and magnetic radiation that can be characterized by wavelength or frequency. Visible light encompasses a small part of the electromagnetic spectrum in the region from about 380 nanometers (violet) to 770 nanometers (red) by wavelength.
Electronic Ballast
A short name for a fluorescent high frequency electronic ballast. Electronic ballasts use solid state electronic components and typically operate fluorescent lamps at frequencies in the range of 25-35 kHz. The benefits are: increased lamp efficacy , reduced ballast losses and lighter, smaller ballasts compared to electromagnetic ballasts. Electronic ballasts may also be used with HID (high intensity discharge) lamps (See ELECTROMAGNETIC BALLAST ).
Elliptical Reflector (ER) Lamp
An incandescent lamp with a built-in elliptically-shaped reflecting surface. This shape produces a focal point directly in front of the lamp which reduces the light absorption in some types of luminaires . It is particularly effective at increasing the efficacy of baffled downlights.
Encapsulant Finish
GE Lumination offers products with several types of encapsulant finishes. An encapsulant finish may have some effect to the photometric output of the device. The unique encapsulant finish of GE Lumination product is identified in the 11th position of the part number, i.e., GERD5R015-CC.
Available Encapsulant Finishes:
Water Clear: Colorless in appearance.
Diffused: A diffuser scatters the light emitted and widens the viewing angle, resulting in a more even distribution of light. Diffusing the encapsulant may also reduce the intensity of the device. Diffused LEDs are ideal for applications where the LED acts as an indicator, rather than an illuminator. Diffused LEDs are also usually tinted.
Tint: Tinting an LED can be accomplished by adding a dye to the encapsulant encapsulant similar in color to the light emitted. This allows identification of the LED color in the OFF state, as well as offering color filtering of direct sunlight. Tinting may also reduce the intensity of the device.
GE Lumination can provide both the tinting and diffusing of the LED encapsulant.
Enclosed Fixtures
(See OPEN FIXTURE RATED )
Energy Policy Act (EPACT)
Comprehensive energy legislation passed by the U. S. Congress in 1992. The lighting portion includes lamp labeling and minimum energy efficacy (lumens/watt) requirements for many commonly used incandescent and fluorescent lamp types. Federal Canadian legislation sets similar minimum energy efficacy requirements for incandescent reflector lamps and common linear fluorescent lamps.
Energy Policy Act (EPACT) Indicator
Means this lamp is Federally regulated for Energy Efficiency (See ENERGY POLICY ACT ).
Eye Sensitivity
A curve depicting the sensitivity of the human eye as a function of wavelength (or color). The peak of human eye sensitivity is in the yellow-green region of the spectrum. The normal curve refers to photopic vision or the response of the cones. (See Photopic , Scotopic , Fovea, Foveal vision )
Glossary-D
Daylight Harvesting
Lighting design for building interiors that makes of daylight as a way of reducing energy consumption.
Daylight Lamp
A lamp resembling the color of daylight, typically with a color temperature of 5500 K to 6500K
Dichroic Reflector (or Filter)
A reflector (or filter) that reflects one region of the spectrum while allowing the other region(s) to pass through. A reflector lamp with a dichroic reflector will have a “cool beam” i.e. most of the heat has been removed from the beam by allowing it to pass through the reflector while the light has been reflected.
Die
See Chip.
Dimmable
Whether or not the lamp lumens can be varied while maintaining reliability.
Dimmer, Dimming Control
A device used to lower the light output of a source, usually by reducing the wattage it is being operated at. Dimming controls are increasing in popularity as energy conserving devices.
Dominant Wavelength
A quantitative measure of the color of an LED as perceived by the human eye. It is usually measured in nanometers (a billionth of a meter).
Glossary-C
Canadian Standards Association (CSA)
An organization that writes standards and tests lighting equipment for performance as well as electrical and fire safety. Canadian provincial laws generally require that all products sold for consumer use in Canada must have CSA or equivalent approval.
Candela (cd)
The measure of luminous intensity of a source in a given direction. The term has been retained from the early days of lighting when a standard candle of a fixed size and composition was defined as producing one candela in every direction. A plot of intensity versus direction is called a candela distribution curve and is often provided for reflectorized lamps and for luminaires with a lamp operating in them.
Candlepower
An obsolete term for luminous intensity; current practice is to refer to this simply as candelas.
Candlepower (Mean Spherical)
Initial mean spherical candlepower at the design voltage. Mean spherical candlepower is the generally accepted method of rating the total light output of miniature lamps. To convert this rating to lumens, multiply it by 12.57 (4 pi).
Candlepower Distribution Curve
A graphical presentation of the distribution of light intensity of a light source, usually a reflector lamp or luminaire.
Cathode
The “negative” terminal of a diode.
Cathode Resistance
Resistance of the cathode in a Fluorescent lamp. It is measured “cold” before the lamp is turned on (Rc) or “hot” after the lamp is turned on (Rh). The ratio of the hot resistance to the cold resistance is also measured (Rh/Rc).
Center Beam Candlepower (CBCP)
Refers to the luminous intensity at the center of the beam of a blown or pressed reflector lamp (such a s a PAR lamp). Measured in candelas.
Chip
A very small square of semi-conducting material. Also known as a “die,” it is the “active” light-emitting component of an LED.
Chromaticity
Measure to identify the color of a light source, typically expressed as (x,y) coordinates on a chromaticity chart (See COLOR TEMPERATURE ).
Chromaticity Coordinates
A system for measuring the color of the light emitted from a light source–either a primary source like a lamp or a secondary source like an illuminated object. Usually two numbers, x and y coordinates ranging from 0 to 1 specify the chromaticity.
Coefficient of Utilization (CU)
In general lighting calculations, the fraction of initial lamp lumens that reach the work plane. CU is a function of luminaire efficiency , room surface reflectances and room shape.
Color (Dominant Wavelength)
LEDs are designed to give off a specific color emission. The dominant wavelength is a quantitative measure of an LED color as perceived by the human eye and is usually measured in nanometers (a billionth of a meter). In order to specify an LED, you must specify the color or dominant wavelength range required for your application. Some applications may have color constraints in order to meet specific government specifications or regulatory guidelines.
Color Bin
LEDs are sorted according to their wavelength or CIE coordinates into different groupings or “bins.”
Color Rendering Index (CRI)
An international system used to rate a lamp’s ability to render object colors. The higher the CRI (based upon a 0-100 scale) the richer colors generally appear. CRI ratings of various lamps may be compared, but a numerical comparison is only valid if the lamps are close in color temperature. CRI differences among lamps are not usually significant (visible to the eye) unless the difference is more than 3-5 points.
Color Rendering Indicator
Draws attention to the fact that this is a lamp with high color rendering, which helps objects and persons illuminated to appear more true to life.
Compact Fluorescent Lamp (CFL)
The general term applied to fluorescent lamps that are single-ended and that have smaller diameter tubes that are bent to form a compact shape. Some CFLs have integral ballasts and medium or candelabra screw bases for easy replacement of incandescent lamps.
Color Temperature (Correlated Color Temperature – CCT)
A number indicating the degree of “yellowness” or “blueness” of a white light source. Measured in kelvins, CCT represents the temperature an incandescent object (like a filament) must reach to mimic the color of the lamp. Yellowish-white (“warm”) sources, like incandescent lamps , have lower color temperatures in the 2700K-3000K range; white and bluish-white (“cool”) sources, such as cool white (4100K) and natural daylight (6000K), have higher color temperatures. The higher the color temperature the whiter, or bluer, the light will be (See CHROMATICITY ).
Coolbeam
(See DICHROIC REFLECTOR )
Cool White
A term loosely used to denote a color temperature of around 4100 K. The Cool White (CW) designation is used specifically for T12 and other fluorescent lamps using halophosphors and having a CRI of 62.
Cosine-Corrected
An illuminance meter that measures the light level correctly irrespective of the angle the light is coming from. (See ILLUMINANCE METER )
Cost of Light
Usually refers to the cost of operating and maintaining a lighting system on an ongoing basis. The 88-8-4 rule states that (typically) 88% is the cost of electricity, 8% is labor and only 4% is the cost of lamps.
Crest Factor (Max Current)
The ratio of the peak lamp current to average lamp operating current (RMS). The lower the current crest factor is, the gentler the ballast is on the lamp.
Current Type (AC/DC)
Whether the operational voltage is based on Alternating Current or Direct Current.
Glossary-B
Ballast
An auxiliary piece of equipment required to start and to properly control the flow of current to gas discharge light sources such as fluorescent and high intensity discharge (HID) lamps.
Ballast Factor (BF)
This is the percentage of a lamp’s rated lumen output that can be expected when operated on a specific, commercially available ballast. For example, a ballast with a ballast factor of 0.93 will result in the lamp’s emitting 93% of its rated lumen output. A ballast with a lower BF results in less light output and also generally consumes less power.
Blackbody The socket is the receptacle connected to the electrical supply; the base is the end of the lamp that fits into the socket. There are many types of bases used in lamps, screw bases being the most common for incandescent and HID lamps, while bipin bases are common for linear fluorescent lamps. Sample Base Types
Base Temperature (Maximum)
The maximum operating temperature permitted for the base in Celsius. Fixture manufacturers need to ensure that these conditions are satisfied in their fixture.
Bayonet
A style 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.
Beam Angle
The angular dimension of the cone of light from reflectorized lamps (such as R and PAR types) encompassing the central part of the beam out to the angle where the intensity is 50% of maximum. The beam angle sometimes called “beam spread” is often part of the ordering code for the reflectorized lamps. Example: The 50PAR30/HIR/NFL25 is a 50 watt PAR30 narrow flood lamp with a beam angle of 25 degrees (See FIELD ANGLE ).
Beam Lumens
The total lumens present within the portion of the beam contained in the beam angle.
Beam Spread (Approximate)
For reflector type lamps. The total angle of the directed beam (in degrees horizontal or vertical) to where the intensity of the beam falls to 50% or 10% of the maximum candlepower value as indicated.
Bi-Pin
Any base with two metal pins for electrical contact. This is the typical base for a fluorescent tube of 1 to 4 feet in length. 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.
Blackbody
A hot body with an incandescent black surface at a certain temperature used as a standard for comparison. Note that a black surface is the best radiator possible. A tungsten filament will emit slightly less radiation than a blackbody at the same temperature.
Black Light
A popular term referring to a light source emitting mostly near UV (320 to 400 nm) and very little visible light.
Blacktop
Whether or not the top of the miniature lamp has a blacktop coating. The coating is used to control unwanted brightness or glare.
Bollard
A short, thick post with a light at its top, used for grounds and outdoor walkway lighting.
Bulb
A loose way of referring to a lamp. “Bulb” refers to the outer glass bulb containing the light source.
Bulb Material or Coating
The type of glass (or quartz) used in the glass envelope surrounding the light source. The material can also have coatings applied to achieve particular performances.
Brightness
Brightness can refer to any of several technical terms used in lighting and is, therefore, ambiguous (See LUMINANCE ).
Glossary-A
Accent Lighting
Directional lighting to emphasize a particular object or draw attention to a display item.
Adaptation
The process by which the human eye adjusts to a change in light level.
Ambient Lighting
The general lighting present in an area –excluding task lighting and accent lighting but including general lighting and daylight streaming in.
Ambient Temperature
The surrounding temperature within an environment.
Amperes
(“Amps.”) A measure of electrical current. In incandescent lamps, the current is related to voltage and power as follows: Watts (power) = Volts x Amps (current).
American National Standards Institute (ANSI)
A consensus-based organization which coordinates voluntary standards for the physical, electrical and performance characteristics of lamps, ballasts, luminaires and other lighting and electrical equipment.
Anode
The “positive” terminal of a diode.
ANSI Ballast Type
Ballast type used to operate lamp in accordance with ASNI standard.
ANSI Codes
These are 3-letter codes assigned by the American National Standards Institute. They provide a system of assuring mechanical and electrical interchangeability among similarly coded lamps from various manufacturers. General Electric uses the assigned ANSI Codes as Lamp Ordering Codes for most Projection Lamps.
Application
Also called “lighting application,” it refers to the particular use the lamp is being put to. (e.g. high-bay industrial application or retail lighting application.) The term can also refer in a general way to “application engineering” which deals with specific paramters and usage of light sources. (e.g. how to do a lighting layout, where to place fixtures and so on.)
Arc
A general term for a high intensity electrical discharge occurring between two electrodes in a gaseous medium, usually accompanied by the generation of heat and the emission of light (See ELECTRICAL DISCHARGE ).
Arc Lamp
A light source containing an arc (see above). Also called a discharge lamp, or an arc discharge lamp (See ELECTRICAL DISCHARGE ).
Arc Length
In High Intensity Discharge lamps this is the distance between the electrode tips, which represents the physical length of the electrical discharge.
Atmosphere
This field designates the type of gas or vacuum filling a volume or chamber of the lamp. This chamber might contain a filament or it might refer to the bulb which contains the arc tube.