Technical Data and Definitions

Active Component: A component capable of voltage or current gain or switching.

Ambient: Associated with a given environment.

Ampere: A unit of electrical current or rate of flow of electrons. One volt across one ohm equals one ampere.

Anode: Positive electrode.

Ballast: The electrical device required for all discharge lamps that limits lamp current. Additional functions maybe incorporated in the basic unit such as starting circuits and dimming control.

Ballast Capacitor: Limits lamp current and isolates lamps from each other and the power inverter (transformer), typically a 3KVDC ceramic disc capacitor in the 15 to lOOpF range for CCFL lamps.

Ballast Resistor: A series resistance used to maintain a constant lamp current.

CCFL: Cold cathode fluorescent lamp acronym. Also called CCFT for cold cathode fluorescent tube.

Candela: A unit of luminous intensity of 1/60th sq. cm of a blackbody radiator operating at the temperature of the solidification of platinum. (historically- the amount of light emitted by one candle)

Candelas per Square Metre (Cd/m2) Also called NIT: The term for luminous (surface) intensity of a light source. This can be converted to foot-lambert by dividing Cd/m2 by Pi (3.246).

Cathode: Negative electrode.

Chromaticity: The color of light, as defined by its chromatic coordinates, generally using the CIE diagram.

CIE: The Commission Internationale d’Eclairage (CIE) is the international commission on illumination, devoted to international cooperation in the field of lighting.

CIE Chromaticity Coordinates: The Cartesian coordinates used to define a color in the 1931 CIE color space. They are designated as s, y and z and are the ratios of each of the tristimulus values X, Y and Z in relation to the sum of the above.

Cold Spot: The area of the lamp which is coldest, where excess mercury may condense. Condensed mercury inside the lamp usually appears as small dark specks.

Correlated Color Temperature: Term used to describe the color of white light sources. It is usually expressed in degrees Kelvin (0K).

Filter Photometer: A photometer that incorporates a filter with a response trimmed to match the 1931 CIE photopic function. Photopic quantities are obtained directly by measuring the light after it passes through a photopic filter.

Fluorescence: Emission of light or other electromagnetic radiation by a substance when exposed to radiation.

Foot Candle: A unit of luminance on a surface one square foot in area, on which there is a uniformly distributed flux of one lumen, or the illuminance at a surface all points of which are at a distance of one foot from a uniform source of one candela.

Foot Lambert: A unit of luminance equal to 1ft candle per square foot.

Fuse: A protective device that opens a circuit on overcurrent.

Harmonic: A sinusoid having a frequency that is an integral multiple of the fundamental frequency.

Hue: The attribute of color by which a color is perceived to be red, green, blue, yellow etc. Achromatic colors like black, white and gray do not exhibit hue.

Illuminance: Luminous flux incident on a surface per unit area. The SI of Illuminance is the Lux (lumen/m2), and the English unit of illuminance is the foot-candle (lumen/ft2). One lux = 0.0929 foot-candle, and reciprocally one foot-candle = 10.76 lux.

Incandescence: The emission of light by raising a material to a high temperature.

Inverse Square Law: The intensity of light varies inversely to the square of distance from the source.

Inverter: A device for converting DC to AC by switching DC alternately in inverted polarity

Lamp Ionization: The state of the lamp in which the fill gasses and evaporated mercury are stimulated to emission of ultraviolet energy by the electrical potential applied to the lamp (i.e., start-up).

LED (light emitting diode): The LED is the semiconductor die itself, which sits in a reflective cup that acts as a heat sink and reflector. When voltage is applied to the LED, electrons and holes in the two semiconductor layers are attracted to each other at the junction. When they combine, they create photons.

Life Hours: The time required for the lamp to reach 50% of its initial or rated luminance, and/or total output flux.

Life Test: The test of a component or unit under the conditions which approximate, or stimulate by acceleration, a normal lifetime of use.

Light Pipe (or Tube): A transparent material that transmits light from one end to the other, whether rigid or flexible, straight or bent.

Lumen: A unit of “luminous flux”, defined as the amount of light which falls on one square metre of a surface at a constant distance of one metre from a source of one candela. Convert to MSCP (mean spherical candle power) by dividing lumens by 12.56 (4Pir).

Lumens per Watt: The measurement of efficiency –EFICACY- of a light source, determined by dividing total visible output power (lumens) by total input power (electrical watts).

Luminance: Luminous flux emitted from a surface; per surface, per unit area in a given direction. The SI unit is the Nit (cd/m2) and the English unit is the foot-lambert. 1 cd/m2 = 0.2919 foot-lambert and, reciprocally, 1 foot-lambert = 3.426 cd/rn2.

Luminous Flux: Radiant flux weighed by the 1931 CJE photopic V (1) function. The SI unit of luminous flux is the lumen. The lumi¬nous flux per steradian from a source whose luminous intensity is one candela is one lumen.

Lux: A unit of illumination (luminance) equal to one lumen per square meter. One foot-candle equals 10.4 lux.

Mean Spherical Candle Power (MSCP): A measurement of luminance attained by dividing lumens by 12.56 (4xPi).

Neon Bulb: A glass envelope filled with neon gas and containing two or more insulated electrodes. The tube will not conduct until the potential difference between two electrodes reaches the firing, or ionization, potential, and will remain conductive until the voltage is reduced to less than excitation.

NITS: See Candelas per square metre (Cd/m2).

Passive Component: A component that is not capable of amplification or switching action.

Phosphors: Chemical substances that exhibit fluorescence when excited by ultraviolet radi¬ation, x-rays or an electron beam. The amount of visible light is proportional to the amount of excitation energy. If fluorescence decays slowly after the exciting source is removed, the substance is said to be phosphorescent.

Photometer: An instrument used to measure photometric qualities such as luminance, illuminance, luminous flux and luminous intensity.

Photometry: The technology of generating and harnessing light and other forms of radiant energy whose quantum unit is the photon.

Photopic Function: The spectral response of the average human observer defined by CIE and called the Standard Observer Function. The response for a 20 visual field defined in 1931 is more commonly used than the 10deg function defined in 1964.

Photovoltaic: Voltage generation as a result of light radiation.

Potting: A rubber or plastic insulating compound in which an assembly may be encapsulated for protection from vibration, moisture, etc.

Radiometry: The measurement of radiation in the infrared, visible and ultraviolet portions of the spectrum.

Remote Ballast Capacitor: Used when a lamp is positioned away from the inverter, typically at a distance of one to three feet via shielded cable.

Ringing: A damped oscillation in the output of a system as a result of a sudden change in the input signal.

Saturation: The point at which increasing one quantity no longer has an effect on the second quantity. The attribute of color perception that expresses the degree of departure from gray of the same brightness.

Spectroradiometer: An instrument to measure the spectral energy radiated by a source. The energy in the visible region of the spectrum can be used to calculate photometric and colorimetric parameters.

Standard Illuminant: A series of spectral power distribution curves recommended by CIE as standard light sources for light measurement.

Steradian: The solid angle of a sphere. The area of a spherical surface equal to the square of its radius. The total solid angle at a point in space is 4Pi steradian.

Strobe: To gate on and off at a regular rate.

Thermionics: Producing emission of electrons by heating.

Transducer: A device that converts energy from one form to another, especially one that converts some physical quantity to electric current or voltage for the purposes of measurement or control.

Trimmer: A small capacitor or resistor adjustable by screwdriver or thumbwheel for purposes of alignment.

Tristimulus Values: The amounts of each of the three primary colors that must be combined to match a sample.

Ultraviolet: The invisible region of the spectrum; those radiant energy rays that lie immediately beyond the violet ends of of the spectrum, and between the wavelengths of approximately 100 to 380nm.

Ultraviolet A: The region of the electromagnetic spectrum from 320-400nm.

Ultraviolet B: The region of the electromagnetic spectrum from 280-320nm.

Ultraviolet C: The region of the electro¬magnetic spectrum that is less than 280nm.

Virtual Ground: Not actually grounded, but at ground potential for purposes of most calculations.

Visible Light: Electromagnetic radiation in the spectral range from 380 to 780 nanometres that is visible to the human eye.