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Active power the system input power (in watts) for a lamp-ballast combination.
Amalgam An alloy of mercury with other metals. Some CFL's use a mercury amalgam rather than standard mercury. An amalgam keeps mercury pressure in the discharge near its optimal value as lamp temperature changes. Amalgam lamps can produce more than 90 percent of maximum light output over a wide temperature range, but they can take longer to reach their full light output when started.
Ambient temperature The temperature of the surrounding air that comes into contact with the lamp and ballast. Ambient temperature affects the light output and active power of fluorescent lamp/ballast systems. Each fluorescent lamp-ballast system has an optimum ambient temperature at which it produces maximum light output. Higher or lower temperatures reduce light output. For purposes of lamp/ballast tests, ambient temperature is measured at a point no more than 1 meter (3.3 feet) from the lamp and at the same height as the lamp.
ANSI code American National Standards Institute (ANSI) code that indicates the electrical operating designation of the lamp, which must match that of the ballast.
Application The use to which a lighting system will be put; for example, a lamp may be intended for indoor residential applications.
Arc tube An envelope, usually quartz or ceramic that contains the arc of a discharge light source.
Average rated life The number of hours at which half of a large group of product samples fail under standard test conditions. Rated life is a median value; any lamp or group of lamps may vary from the published rated life.
Ballast A device required by electric-discharge light sources such as fluorescent or HID lamps to regulate voltage and current supplied to the lamp during start and throughout operation.
Ballast access The opening through which the ballast in a luminaire can be installed or replaced, either through the aperture or from above the luminaire.
Barn doors Typically, four adjustable shields that are attached to the face of the luminaire to reduce glare.
Beam angle The angle at which luminous intensity is 50 percent of the maximum intensity.
Beam appearance The description of a beam’s image on a wall as determined by subjective visual evaluations.
Beam spread The width of a light beam, expressed in degrees. The beam of light from a reflector-type lamp (PAR, R, ER, or MR) can be thought of as a cone. The beam spread is the angular width of the cone. Common beam spreads are known as spot, narrow, narrow flood, and flood.
Bin To sort or classify light sources (such as light emitting diodes) into groups according to their luminous intensity or color appearance.
Bulb designation An abbreviation of the shape and size of a lamp's outer envelope. The letter or letters indicate the shape and the numbers indicate the bulb's maximum diameter in eighths of an inch.
Bulb finish The coating, if any, that is applied to the inside surface of the bulb. Finishes are either clear, phosphor coated, or diffuse.
Candela The Systeme International d'Unities (SI) of luminous intensity. One candela is one lumen per steradian. Formerly, candle.
Capacitor A device used in electric circuitry to temporarily store electrical charge in the form of an electrostatic field. In lighting, a capacitor is used to smooth out alternating current from the power supply.
Compact fluorescent lamp (CFL) A family of single-ended fluorescent-discharge light sources with small-diameter [16-millimeter (5/8-inch) or less] tubes.
Dichroic coating (dichroic filter) A multi-layer coating that transmits certain wavelengths and reflects those not transmitted.
Diffuser material Diffusers scatter the light from a luminaire in all directions. Most diffusers in commodity residential-grade luminaires are made of plastic, usually acrylic or polycarbonate. Other materials include glass and alabaster.
Dimming ballast A device that provides the ability to adjust light levels by reducing the lamp current. Most dimming ballasts are electronic.
Direct light Light emitted by a luminaire in the general direction of the task to be illuminated. The term usually refers to light emitted in a downward direction.
Direct luminaire A luminaire that emits light in the general direction of the task to be illuminated. The term usually refers to luminaires that emit light in a downward direction.
Direct uplight Light emitted upward by a luminaire.
Driver For light emitting diodes, a device that regulates the voltage and current powering the source.
Efficacy The ratio of light output (in lumens) to input power (in watts), expressed as lumens per watt (LPW).
Electromagnetic interference (EMI) The interference of unwanted electromagnetic signals with desirable signals. Electromagnetic interference may be transmitted in two ways: radiated through space or conducted by wiring. The Federal Communications Commission (FCC) sets electromagnetic interference limits on fluorescent lighting systems in FCC Part 18.
Electromagnetic wave A wave composed of perpendicular electric and magnetic fields. The wave propagates in a direction perpendicular to both fields.
Electronic ballast A ballast that uses electronic components instead of a magnetic core and coil to operate fluorescent lamps. Electronic ballasts operate lamps at 20 to 60 kHz, which results in reduced flicker and noise and increased efficacy compared with ballasts that operate lamps at 60 Hz.
Emergency options Refers to options available when exit signs are operated on a non-utility power supply such as a generator, a central battery unit that operates several exit signs, or an individual rechargeable battery. Options include whether or not the exit sign increases the brightness of the light source if the utility-supplied power fails.
Field of view The area covered by an occupancy sensor, often reported (for wall-mounted sensors) as a horizontal field of view or (for ceiling-mounted sensors) as the solid angle of the cone-shaped coverage area.
Fixture A complete lighting unit consisting of lamp or lamps and the parts designed to distribute the light, position and protect the lamp(s), and connect the lamp(s) to the power supply. (Also referred to as luminaire.)
Flicker A rapid and continuous change in light levels caused by the modulation of the light output from fluorescent lamps.
Footcandle (fc) A measure of illuminance in lumens per square foot. One footcandle equals 10.76 lux, although for convenience 10 lux commonly is used as the equivalent.
Frequency The number of cycles completed by a periodic wave in a given unit of time. Frequency is commonly reported in cycles per second, or hertz (Hz).
Fully shielded luminaire A luminaire that emits no direct uplight, but which has no limitation on the intensity in the region between 80° and 90°.
Gas-discharge lamps An electric lamp that produces light from gas atoms excited by an electric current.
Glare The sensation produced by luminances within the visual field that are sufficiently greater than the luminance to which the eyes are adapted, which causes annoyance, discomfort, or loss in visual performance and visibility.
Grounded A circuit or metal object that is connected to the earth at one or more points. Done mostly for safety, grounding also reduces electromagnetic waves.
Halo-phosphors Also referred to as halophosphates. Phosphors are the white powder inside fluorescent lamps that fluoresces (emits visible light) when excited by the ultraviolet radiation produced by the mercury vapor that is energized by the electric arc sustained inside the lamp. Phosphors are used to achieve high efficacy, good color rendering, and low lamp lumen depreciation. Halo-phosphors, however, are limited in their ability to provide a high color rendering index without sacrificing light output and are often mixed with other phosphors.
Halogen cycle Halogen incandescent lamps are in the same family as standard incandescent lamps. The basic operating principle is the same, except that chemicals called halogens are introduced in the gas fill. When electricity passes through the lamp's filament, it is heated until it glows and emits light. In this process, tungsten from the filament evaporates and, over the life of the lamp, causes the glass bulb wall to slowly blacken and the filament to disintegrate until the lamp fails. Halogens remove evaporated tungsten from the glass wall and redeposit it back onto the filament. As a result, tungsten does not build up on the bulb, so the light output does not degrade as rapidly.
Halogen lamp An incandescent lamp that uses a halogen fill gas. Halogen lamps have higher rated efficacies and longer lives than standard incandescent A-lamps.
Halophosphates The class of phosphors commonly used in fluorescent lamps. Halophosphates are limited in their ability to provide a high color rendering index without sacrificing light output. Standard T12 lamps containing halophosphates are the most common and least expensive fluorescent lamps, but United States federal regulations require that all fluorescent lamps must meet minimum efficacy and CRI standards, and 40-watt T12 halophosphate lamps do not meet these standards. T8 lamps usually contain both halophosphates and rare-earth phosphors.
Heat sinking Adding a material, usually metal, adjacent to an object in order to cool it through conduction.
High-intensity discharge (HID) An electric lamp that produces light directly from an arc discharge under high pressure. Metal halide, high-pressure sodium, and mercury vapor are types of HID lamps.
High-pressure sodium (HPS) A high-intensity discharge lamp type that uses sodium under high pressure as the primary light-producing element. HPS lamps produce light with a correlated color temperature (CCT) of approximately 2000 kelvins, although CCTs for lamps having higher CRI values range from 2200 to 2700 kelvins. Standard lamps have a CRI value of 22; others have CRI values from 60 to 80. HPS lamps are among the most efficacious light sources, with efficacies as high as 150 lumens per watt, although those with higher CRI values have efficacies as low as 25 lumens per watt.
High-wattage compact fluorescent lamp Abbreviated as HW-CFL, sometimes called "high lumen CFLs", these lamps are a larger cousin to regular CFLs, usually much larger in size and with higher wattages and light output.
Ignitor A device, either by itself or in association with other components, that generates voltage pulses to start discharge lamps
Illuminance The amount of light (luminous flux) incident on a surface area. Illuminance is measured in footcandles (lumens/square foot) or lux (lumens/square meter). One footcandle equals 10.76 lux, although for convenience 10 lux commonly is used as the equivalent
Indirect lighting Light arriving at a surface after reflecting from one or more surfaces (usually walls and/or ceilings) that are not part of the luminaire
Instant start A method of starting fluorescent lamps in which the voltage that is applied across the electrodes to strike the electric arc is up to twice as high as it is with other starting methods. The higher voltage is necessary because the electrodes are not heated prior to starting. This method starts the lamps without flashing. It is more energy efficient than rapid or preheat starting, but results in greater wear on the electrodes during starting. The life of instant-start lamps that are switched on and off frequently may be reduced by as much as 25 percent relative to rapid-start operation. However, for longer burning cycles (such as 12 hours per start), there may be no difference in lamp life for different starting methods
Kelvin Color temperature is measured in degrees Kelvin, which indicathe hue of a specific type of light source. Higher temperatures indicate whiter, "cooler" colors, while lower temperatures indicate yellower, "warmer" colors
Lamp A radiant light source
Lamp base position The location of the lamp socket, either in the center of the top of the ballast or on the side of the ballast. Modular ballasts for circular compact fluorescent lamps (CFLs) have a lamp socket located at the end of a wiring harness
Lamp current The current flowing between a lamp's electrodes during operation
Lamp efficacy The ratio of the light output of a lamp (lumens) to its active power (watts), expressed as lumens per watt (LPW)
Lamp life The median life span of a very large number of lamps (also known as the average rated life). Half of the lamps in a sample are likely to fail before the rated lamp life, and half are likely to survive beyond the rated lamp life. For discharge light sources, such as fluorescent and HID lamps, lamp life depends on the number of starts and the duration of the operating cycle each time the lamp is started
Lamp operating current Current flowing through a lamp during normal operation
Lamp rated life The number of operating hours at which half of a large group of product samples are expected to fail. The rated life is a median value of life expectancy; individual lamp life may vary considerably from the published rated life and operating conditions (e.g., temperature, hours per start) may affect actual life because rated life is based on standard test conditions. In addition, the way a product fails can vary by technology. For example, incandescent lamps abruptly stop producing any light while LEDs are considered to have failed when their light output drops below a certain fraction of the initial level
Lamp shield type The material used in a luminaire to shield the lamp from the environment. Lamp shields are required by Underwriters Laboratories for some lamp types
Light pollution An unwanted consequence of outdoor lighting that includes such effects as sky glow, light trespass, and glare
Load capacity The maximum total power that can be connected to an occupancy sensor
Load shedding The practice of turning off electrical devices during peak energy demand hours to reduce building energy use
Louver A fixed shield, usually divided into small cells, that is attached to the face of a luminaire to reduce direct glare
Lumen (lm) A unit measurement of the rate at which a lamp produces light. A lamp's light output rating expresses the total amount of light emitted in all directions per unit time. Ratings of initial light output provided by manufacturers express the total light output after 100 hours of operation
Luminaire A complete lighting unit consisting of a lamp or lamps and the parts designed to distribute the light, to position and protect the lamp(s), and to connect the lamp(s) to the power supply. (Also referred to as fixture.)
Lux (lx) A measure of illuminance in lumens per square meter. One lux equals 0.093 footcandle
Maximum ambient temperature The maximum ambient temperature for which a compact fluroescent lamp (CFL) product is warranted to achieve rated life
Maximum ballast case temperature The maximum temperature of the ballast case for which the manufacturer’s life rating is valid
Medium bi-pin A type of connector commonly used on T-8 and T-12 fluorescent lamps. Two small pins protrude from the lamp ends, which are inserted into a socket in the fixture
Mercury vapor (MV) lamp A high-intensity discharge lamp type that uses mercury as the primary light-producing element. Mercury vapor lamps produce light with a CCT from 3000 to 7000 K. Mercury vapor lamps with clear outer bulbs have CRI values from 15 to 25, whereas phosphor-coated lamps have CRI values from 40 to 55. Mercury vapor lamps are less efficacious than other HID lamp types, typically producing only 30 to 65 LPW, but they have longer lamp lives and lower initial costs than other HID lamp types
Metal halide (MH) lamp A high-intensity discharge lamp type that uses mercury and several halide additives as light-producing elements. Metal halide lamps have better color properties than other HID lamp types because the different additives produce more visible wavelengths, resulting in a more complete spectrum. Metal halide lamps are available with CCTs from 2300 to 5400 K and with CRI values from 60 to 93. Efficacies of metal halide lamps typically range from 75 to 125 LPW
Miniature bi-pin A type of connector commonly used on T-5 lamps. Similar in design to but smaller than medium bi-pin connectors, it uses two small pins that protrude from the lamp ends and are inserted into a fixture socket
Minimum ambient temperature The minimum temperature at which a compact fluorescent lamp (CFL) product is warranted to start
Operating cycle The frequency with which lamps are cycled on and off
Operating voltage The voltage a ballast supplies to a lamp's electrodes
PAR lamp An incandescent or tungsten-halogen incandescent lamp with a hard glass bulb and an interior reflecting surface, a precisely placed filament, and a lens to control beam spread. The lens is hermetically sealed to the reflector. Metal halide PAR-lamps are also now available
Pendant mounting A suspension device between a mount and a luminaire
Phosphors Materials used in a light source to produce or modify its spectral emission distribution. In fluorescent and high intensity discharge lamps, the phosphors fluoresce (emit visible light) when excited by ultraviolet radiation produced by mercury vapor inside the lamp when energized by an electric arc. In a light emitting diode, phosphors convert short-wavelength light or ultraviolet radiation produced by a semiconductor die into longer-wavelength light, usually with the goal of producing white illumination
Power The power used by a device to produce useful work (also called input power or active power). In lighting, it is the system input power for a lamp and ballast or driver combination. Power is typically reported in the SI units of watts
Power factor (PF) The ratio of active power (in watts) to apparent power (in rms volt-amperes), power factor is a measure of how effectively an electric load converts power into useful work. Power factor (PF) is calculated using the equation PF = (active power) / [(rms voltage) x (rms current)]. Phase displacement and current distortion both reduce power factor. A power factor of 0.9 or greater indicates a high power factor ballast
Prismatic lens An optical component of a luminaire that is used to distribute the emitted light. It is usually a sheet of plastic with a pattern of pyramid-shaped refracting prisms on one side. Most ceiling-mounted luminaires in commercial buildings use prismatic lenses
R lamp A common reflector lamp. An incandescent filament or electric discharge lamp in which the sides of the outer blown-glass bulb are coated with a reflecting material so as to direct the light. The light-transmitting region may be clear, frosted, or patterned
Rapid start A method of starting fluorescent lamps in which the electrodes are heated prior to starting, using a starter that is an integral part of the ballast. Heating the electrodes before starting the lamps reduces the voltage required to strike the electric arc between the electrodes. A rapid-start system starts smoothly, without flashing
Rated light output The sum of the initial rated lamp lumens of the lamp(s) that were supplied with the luminaire
Rated lght output from lamp(s) The sum of the initial rated lamp lumens of the lamp(s) that were supplied with the luminaire
Rms current Root-mean-square current, a value that quantifies the magnitude of a current that varies with time (as in ac circuits). Rms current is calculated as the square root of the squared values of current over one complete cycle. Rms current delivers the same power to a resistive load as an equivalent steady dc current
Root-mean-square (rms) The effective average value of a periodic quantity such as an alternating current or voltage wave, calculated by averaging the squared values of the amplitude over one period and taking the square root of that average
Semiconductor A material whose electrical conductivity is between that of a conductor and an insulator; the conductivity of most semiconductors is temperature dependent
Shielding Blocking an electric or magnetic field with a metallic substance. The incident field induces currents in the metallic substance, and these currents induce a field that opposes the incident field. Shielding reduces radiated electromagnetic waves. Electronic components, wires, lamps, and devices can all be shielded
Time delay range For motion sensors, the range of time that may be set for the interval between the last detected motion and the turning off of the lamps
Track luminaire options Accessories available for track luminaires
Track mounting For track luminaires, the method by which the track is attached to the ceiling
Transformer Transformers are electrical devices with no moving parts, which change distribution voltages to higher or lower levels. When used with incandescent or halogen lamps, they typically step 120-V distribution downward to 12V, although 5.5V and 24-V models are also offered
Tri-phosphor A mixture of three phosphors to convert ultraviolet radiation to visible light in fluorescent lamps; each of the phosphors emits light that is blue, green or red in appearance with the combination producing white light
Ultraviolet Any radiant energy within the wavelength range 100 to 400 nanometers is considered ultraviolet radiation (1 nanometer = 1 billionth of a meter, or 1 X 10-9 m)
Uplight Light directed upward at greater than 90° above nadir. The source of uplight can be from a combination of direct uplight and reflected light
Venting Holes in the reflector assembly of a downlight
Wall-washing The practice of illuminating vertical surfaces, such as walls. Wall-washer luminaries are designed to illuminate vertical surfaces
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