Light sensors are used to switch electrical circuits depending on the required light levels in an occupied area. These devices constantly monitor the surrounding lights and decide whether required lux level is available. The required lux level can be set on the device.If the surrounding area is dark, the switching circuit will be automatically switched ON, for lighting circuits or any other loads.
There are other type of models which combine motion and light sensing. CI-355 Passive Infrared Line Voltage Ceiling Sensor of Watt stopper is one such sensor which combines motion and light sensing.The lights will be switched off automatically if there is no motion in the area and if there is no sufficient light available in the area. The required light level can be automatically set by pressing a button on this device. The device has to be exposed to the desired light level and thereafter press the set button briefly. This will program the sensor to the desired lux level.
Similarly Steinel has a model in which we can adjust the Lux level by selecting the desired lighting requirement. There are lighting design calculations which specify the required lux levels. As an example if you desire 300 Lux in a corridor you can program the sensor to 300Lux. At any point when the natural available light goes below 300 lux, the lights will be switched ON automatically.
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