Glossary Terms

Amperes

("Amps.") A measure of electrical current. In incandescent lamps, the current is related to voltage and power as follows: Current (Amps) = Power (Watts) / Voltage (Volts).

American National Standards Institute (ANSI)

A consensus organization which coordinates voluntary standards for the physical, electrical and performance characteristics of lamps, ballasts, luminaries and other lighting and electrical equipment.

Ballast

An auxiliary piece of equipment designed to start and to properly control the flow of power to gas discharge light sources such as fluorescent and high intensity discharge lamps.

Beam Angle

The angular dimension of the cone of light from reflectorized lamps 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 reflectorized lamps.

Candela (cd)

The international unit (SI) of luminous intensity. The term has been retained from the early days of lighting when a standard candle of a fixed size and composition was used as a basis for evaluating the intensity of other light sources. Sometimes the term "candle power" is used to describe the relative intensity of a source.

Candlepower

Luminous intensity expressed in candelas. Plots of luminous intensity, called candlepower distribution curves, are used to indicate the intensity distribution characteristics of reflector-type lamps. A measure of intensity mathematically related to lumens. Candlepower is often to measure the intensity of lamps that project light.

Chromaticity

Also called Color Temperature.

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 better colors appear, CRI ratings of various lamps may be compared, but a numerical comparison is only valid if the lamps are also rated for the same chromaticity or color temperature. A measurement of the color shift an object undergoes when illuminated by the light source, as compared to a reference source at the same color temperature. Color rendering is measured on an index from 0-100, with natural daylight equal to 100.

Color Temperature

Originally, a term used to describe the "whiteness" of incandescent lamp light. Color temperature is directly related to the physical temperature of the filament in incandescent lamps so the Kelvin (absolute) temperature scale is used to describe color temperature. For discharge lamps where no hot filament is involved, the term "correlated color temperature" is used to indicate that the light appears as if the discharge lamp is operating at a given color temperature. More recently, the term "chromaticity" has been used in place of color temperature. Chromaticity" has been used in place of color temperature. Typical color temperatures are 2800K (incandescent), 3000K (halogen), 4100K (cool white or SP41 fluorescent), and 5000K (daylight-simulating fluorescent colors.

Compact Fluorescent Lamp (CFL)

The general term applied to families of smaller diameter fluorescent lamps, some of which have built in ballasts and medium screw bases for easy replacement of incandescent lamps.

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.

Efficacy

Efficacy is the rate at which a lamp is able to convert electrical power (Watts) into light (Lumens), expressed in terms of lumens per watt (LPW). Put simply, a watt or electricity is the amount of power in and a lumen or light is the amount of power out.

Efficacy is a critical consideration when evaluating a lamp because lighting represents 30 to 50% of the total operating cost of a typical installation and can affect related costs such as air conditioning. Secondly, energy accounts for 86% of the cost of an average lighting investment (maintenance accounts for 11%; the lighting itself, 3%) and has a major impact on operating costs. And finally, a lighting system that uses energy efficiently is beneficial to the environment.

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 lamps, but the circuits are quite different, there are few designs at present and only minor lamp efficacy improvements result.

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. Similar legislation is being proposed in Canada.

Federal Communications Commission

A U.S. Federal agency which is charged with regulating emissions in the radio frequency portion of the electromagnetic spectrum. For example, a regulation entitled, "Part 18" deals with electromagnetic interference (EMI) from all lighting devices operating at frequencies higher than 9 kilohertz (kHz.). Typical electronically-ballasted compact fluorescent lamps operate in the range of 24-100 kHz.

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.

Foot-candle (fc)

A unit of illuminance, or how much total light is reach onto a surface, such as a wall or table. One lumen falling on one square foot of surface produces illumination of one foot-candle. One foot-candle is equal to 1 lumen per square foot.

Halogen Lamp

A short name for the tungsten-halogen lamp. Halogen lamps are high pressure incandescent lamps containing halogen gases such as iodine or bromine which allow the filaments to be operated at higher temperatures and higher efficacies. At high-temperatures, chemical reaction involving tungsten and the halogen gas recycles evaporated particles of tungsten back onto the filament surface.

High-Intensity Discharge (HID) Lamp

A general term for mercury, metal halide (GE Multi-Vapor, MXR or Arcstream) and high-pressure sodium lamps. HID lamps contain compact arc tubes which enclose various gases and metal salts operating at relatively high pressures and temperatures.

Incadescents

Incandescent lamps are the most familiar type of light source, with countless application in homes, stores and other commercial settings. Light is produced by passing electric current through a thin wire filament, usually a tungsten.

Illuminance

The "density" of light (lumens/area) incident on a surface. Illuminance is measured in foot-candles or lux.

Incandescent Lamp

A light source which generates light utilizing a thin filament wire (usually of tungsten) heated to white heat by an electric current passing through it.

Infrared radiation

Electromagnetic energy radiated in the wavelength range of about 770 to 1106 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 fluorescent lamp-ballast circuit designed to start fluorescent lamps as soon as the power is applied. Originally, instant-start circuits were developed to eliminate separate mechanical starter devices. Slimline fluorescent lamps operate only on instant start circuits.

Kilowatt (Kw)

A 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 (1-- x 10) or 1 kilowatt-hour. If the utility charge $.08/kWh, then the electricity cost for the 10 hours of operation would be 8 cents (1 x $.08).

Lamp

The term used to refer to the complete light source package including the inner parts as well as the outer bulb or tube. "Lamp", of course, is also commonly used to refer to a type of small light fixtures such as a table lamp.

Light

Radiant energy which can be sensed or seen by the human eye. Visible light is measured in lumens. The term generally applied to the visible energy from a source. Light is usually measured in lumens or candlepower. When light strikes a surface, it is either absorbed, reflected or transmitted. Light is said to travel in straight lines.

Lumen

The basic unit of measurement for light. A dinner candle shines at about 12 lumens. A 60-watt Soft White bulb is much more powerful: 855 lumens. If a uniform point source of 1 candela is at the center of a sphere of 1-foot radius which has an opening of 1 square foot area at its surface, the quantity of light that passes through is called a lumen. The sphere has a total surface area of 12.57 square feet. Since, by definition, a lumen flows to each square foot of surface area, a uniform point of 1 candela produces 12.57 lumens. The general term applied to families of smaller diameter fluorescent lamps, some of which have built in ballasts and medium screw bases for easy replacement of incandescent lamps.

Lux

The SI (International System) unit of illumination: one lumen uniformly distributed over an area of one square meter.

Specification Series (SP) Colors

Energy-efficient, all-purpose tri-phosphor fluorescent lamp colors that provide good color rendering (as measured by the Color Rendering Index or CRI). The CRI for SP colors is 70 or above and varies by specific lamp type. Available chromaticities (or "tones") within the SP group include SP30 (3000K) - a good match for the old standard "warm white" color and incandescent or halogen incandescent lamps; SP35 (3500K) - neutral all-purpose tone; SP41 (4100K) - cool in appearance and designed to match the old standard "cook white" color; SP50 - still cooler much like the combination of sun-skyclouds; SP65 - a color with a very cool appearance, much like north skylight, and designed to match the appearance of the old "daylight" color. SP fluorescent colors are available in most of the widely-used linear lamp types including the T8, T12, U-tube, and the high output.

Voltage

A measurement of the electromotive force in an electrical circuit or device expressed in volts. Voltage can be thought of as being analogous to the pressure in a waterline.

Watt

A unit of electrical power. Lamps are rated in watts to indicate their power consumption. Power consumed over time equals the electrical energy used.

Underwriter Laboratories (UL)

A private organization which tests and lists electrical (and other) equipment for electrical and fire safety according to recognized UL and other standards. A UL listing is not an indication of overall performance. Lamps are not UL listed except for compact fluorescent lamp assemblies - those with screw bases and built-in ballasts.

Ultraviolet (UV) Radiation

Radiant energy in the range of about 100-380 nanometer (NM). For practical applications, the UV band is broken down further as follows:

Ozone-producing	180-220nm
Bactericidal (germicidal)	220-300nm
erythermal (skin reddening)	280-320nm
"Black" light	320-400nm