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Understanding HID Light Technology

High Intensity Discharge (HID) lighting technology replaces the filament of the light bulb with a capsule of gas. The light is emitted from an arc discharge between two closely spaced electrodes hermetically sealed inside a small quartz glass tubular envelope capsule. To operate, they require ballasts, which supply proper voltage and control current. The amount of light produced is greater than a standard halogen bulb, while consuming less power, and more closely approximating the color temperature of natural daylight.

In all High Intensity Discharge lamps, light is produced by passing a current through a metal vapor. Free electrons colliding with an atom in the vapor momentarily knock an electron into a higher orbit of the atom. When the displaced electron falls back to its former level, a quantum of radiation is emitted. The wavelength of radiation depends on the energy zone of the disturbed electron and on the type of metal vapor used in the arc tube.

HID lighting has several advantages over conventional halogen primary lights:

  • More light output. The HID lamp’s lumens per watt (LPW) efficacy is roughly six to eight times that of an incandescent lamp.
  • Whiter light. The color temperature of HID lighting more closely approximates the color temperature of natural daylight than does a halogen system, which appears yellowish in comparison. We use the term \”correlated color temperature\” to indicate that the light appears as if the discharge lamp is operating at a given color temperature– traditional measurements of color temperature are drawn from the properties of the metal used in the bulb’s filament. Typical color temperatures are 2800K (incandescent), 3000K (halogen), 4100K (cool white or SP41 fluorescent), and 5000K (daylight-simulating fluorescent colors). A white light has a perceived brightness which may equate to the higher stated efficacies– ie., although an HID lamp might have equivalent lumens as a higher wattage halogen bulb, the HID will appear brighter and more pleasing to the eye than the output of a halogen lamp.
  • Longer Service Life. An HID lamp will last, on the average, 3 to 5 times as long as a halogen bulb. In normal use, an HID bulb should last beyond one thousand ignitions.

    The ballast in an HID lighting system generally has two purposes. It provides the proper starting voltage to strike and maintain the arc, and it regulates the proper current to the lamp once the arc is established.

    Ballasts are not interchangeable among different types of HID lamps. A ballast design incorporates electronic circuitry to provide specific lamp/ballast operating characteristics. As an example, the effects of line voltage variations on resultant changes of lamp wattage are a function of the ballast circuit design. Requirements for a circuit which will provide a finer degree of lamp regulation generally result in a higher ballast cost.


    About The Author:
    This article has been written by the staff of Magnalight. MagnaLight meets the high powered lighting needs for a variety of industries including the military. They also offer a number of lights for use by hunters, fishermen, and outdoor enthusiasts. The Magnalight website provides a wide-selection of Magnalight Spotlights, Boat Lights, 24 Volt Lights and more. http://www.magnalight.com

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    This entry was posted on Thursday, February 28th, 2008 at 11:02 pm and is filed under technology. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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