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Pulse-Start Metal Halide Lighting

Definitions

Ballast – A device required to provide the electrical conditions needed to start and operate a discharge lamp.

Colour rendering – The colour rendering index (CRI) describes the effect of a light source on the colour appearance of objects, compared with a reference source of the same colour temperature. It serves to distinguish quality differences between light sources that emit light of the same colour.

The highest CRI value attainable is 100. Typical cool white fluorescent lamps have a CRI of 62. A value of 85 or higher is preferable where people work with colours, such as when people must identify products by colour and work with pigments or colour-coded wiring.

Colour temperature – Any very dark material reflects almost no light. But when heated to high temperatures, even these materials glow – or burn, giving off light. At a certain temperature, they glow a certain colour. For example, the yellowish light of a tungsten incandescent bulb has the colour temperature of about 2,800 degrees Kelvin – about 2,600 degrees Celsius. This means that when electricity heats the lamp's tungsten filament to 2,600 degrees Celsius, it glows this yellowish colour.

High-bay space – Generally, these are spaces that have at least five metres and, more often, at least seven metres of clear height. High-bay spaces are widely used in warehousing, big box retail and manufacturing.

HID (high-intensity discharge) lamp – This class of lamps includes high-pressure sodium, mercury vapour and metal halide lamps. All HID lamps have an inner arc tube within another tube. Of these three types, metal halide lamps are the most common choice for interior lighting because they have the best colour rendering. Low-intensity discharge lamps are better known as fluorescent lamps.

High-pressure sodium lamp – A type of HID lamp that is filled with sodium vapour. Sodium lamps are more efficient than metal halide lamps but have poorer colour rendering.

Incandescent lamp – A lamp that generates light by heating a filament.

Lumen – The flux of light being produced by a light source or received by a surface. The intensity of a light source is measured in candelas. One lumen represents the total flux of light emitted, equal to the intensity in candelas multiplied by the solid angle in steradians [1/(4·π) of a sphere] into which the light is emitted.

Luminaire – A complete lighting unit, comprising lamps, ballasts and components required to distribute the light and to connect the lamps to the power supply.

Mean lumens – The lumen is a unit of light output. Mean lumens are the number of lumens produced at 40 to 50 percent of rated lamp life.

Metal halide lamps – A type of HID lamp that is filled with metal halides in addition to the argon and mercury used in mercury vapour lamps. Metal halide lamps are more efficient and have better colour rendering than mercury lamps.

Probe-start lamp – An HID lamp that uses a starting probe to start the lamp. No igniter is used.

Pulse-start lamp – An HID lamp that uses an igniter located inside the ballast pod to start the lamp.

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