How Lamps Produce Light zIncandescentzFluorescent zHIDzLow Pressure Sodium
Relative Performance of Lamp Types Compare: yRelative Light Output yRange of Wattages yRange of Light Output yEfficiency or Efficacy yRange of Rated Life
Relative Light Output
Range of Lamp Wattages zThe range of lamp wattages, and hence light output, is an indication of the scope of applications of each lamp type.
Range of Light Output zThe range of light output is also an indication of the scope of applications.
Lamp Efficacy (1) zThe ability of a lamp to convert watts into lumens is its efficacy zEfficacy is expressed in Lumens Per Watt zOne comparison of efficacy is made by comparing the highest wattage rating of each lamp type.
Lamp Efficacy (2)
Range of Rated Life
Range of Rated Life (2) zFluorescent, mercury vapor and high pressure sodium lamps have the longest expected life. zIncandescent have the shortest.
Common Lamp & Lighting Terms zCurrent (Amp or I): The flow of electricity through a lamp or circuit. It is measured in amperes, abbreviated A or I zDirect Current: In direct current, the flow of electricity is in a single direction. Batteries produce DC current.
Common Lamp & Lighting Terms (2) zAlternating Current: In alternating current, the flow of electricity alternates direction. The current flowing in the circuit goes on and off twice in one cycle. zThe number of cycles completed in one second is called the frequency of the AC voltage and is designated by Hertz (Hz). The most common frequency is 60 Hz (60 Hertz).
Common Lamp & Lighting Terms (3) zVoltage (V or E): A measurement of the electrical force or pressure. It is analogous to the pressure in a water line. Measured in volts, abbreviated as V or E zResistance (R): The resistance to the flow of electricity. Measured in ohms, abbreviated R. It is analogous to the resistance of water flow by a sprinkler at the end of a hose.
Common Lamp & Lighting Terms (4) zOhms Law: The relationship of voltage & resistance. The current that will flow in a circuit is dependent on the voltage applied to the circuit and the resistance in the circuit. Use I =E/R. zWatt (W): The power used or consumed by a lamp. It is the product of voltage applied to the lamp or circuit and the current flowing through it, where the power factor is unity or 1.0.
Common Lamp & Lighting Terms (5) zPower Factor: The ratio of the actual power being consumed by the lamp or circuit to the apparent power being consumed. zPower Factor = Actual/Apparent zThe apparent power is the product of the voltage and the current (V x I). Therefore, the actual power equals the apparent power times the power factor zActual = V x I x PF
Common Lamp & Lighting Terms (6) zKilowatt: A kilowatt equals 1000 watts. zKW = W/1000 zKilowatt Hour: The unit of energy. Energy use is determined by Energy = Power x Time. Utilities charge for energy used not power consumed.
Common Lamp & Lighting Terms (7) zTransformer: An AC device that transforms the voltage from the supply side to the load side. It can be designed to raise or lower the secondary voltage. zReactor: A device to limit the current flow to a fluorescent, HID or sodium lamp. It is sometimes called a choke. zCapacitor: A device used to correct power factor.
Light Terms zLumen: Defines the total quantity of light produced by a lamp regardless of direction. zCandlepower (CP): Defines the quantity of light emitted by a lamp in one direction, or the intensity of light in that direction. zCandlepower Distribution Curve: A representation of how light is distributed by a fixture or by a reflector and PAR lamps. zIllumination: The quantity of light falling on a surface. Measured in footcandles.
Light Terms (2) zFootcandle (FC): The amount of lumens falling on an area with the area expressed in square feet. zLux: The metric equivalent of the footcandle with the area expressed in square meters.
Lamp Color Terms zThe color of a lamp is described by two independent characteristics: yColor Temperature: The color appearance of the lighted lamp yColor Rendition: How colors appear when lighted by the lamp.
Lamp Color Terms (2) zColor Temperature (Kelvins, K): The color temperature of a lamp is based on a theoretical object called a black body which when heated, emits light. zAt a given temperature, the black body has a distinct color appearance. The heated temperature is measured and the value of that temperature is designated its color temperature.
Lamp Color Terms (3) zColor Rendition: An evaluation of how colors appear when lighted by the lamp. The color rendering ability of a lamp is indicated by its color rendering index rating zColor Rendering Index (CRI): Expresses the relative ability of a lamp to match the color rendering of a standard illuminant. A scale of 100 is used to measure CRI.