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Light meters or light detectors are used in to
measure the amount of ambient light or illumination. Their purpose is to
measure the illumination level in the interior and to switch off or
reduce the output level of luminaires. This can greatly reduce the
energy burden of the building by significantly increasing the efficiency
of its lighting system.
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It is estimated that between 20 and 60 percent of all electrical power
in a building is consumed by illumination. It is therefore recommended
to use light meters in lighting systems, especially in rooms where one
cannot expect users to pay attention to manually switching off the
lights. Examples include hallways, stairs, and big halls.
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However, there are certain obstacles to overcome in order to
achieve a successful implementation of light meters in lighting systems;
where obtaining user acceptance is by far the most difficult.
Unexpected or too frequent switching and too bright/ dark rooms are very
annoying and disturbing for users of the rooms. As a result, a couple
of different switching algorithms have been developed:
- difference algorithm, where light switch on lower light level than
they switch off, thus taking care that the difference between the
light level of the 'on' state and 'off' state is not too big
- time delay algorithms:
- certain amount of time must pass since the last switch
- certain amount of time of sufficient illumination.
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