Motion sensors and presence sensors have been confused with each other. Basic principle is that Motion sensors/detectors gets activated only when there are people moving in the specified range of the motion sensors. Presence sensors/detectors sense the presence of living objects in its vicinity.
Please click to see How motion sensors work?
The reason for use in both type is to save energy when people are not present in the range of its vision. The main difference how we select is whether the people are moving or idle in that area. If people are always moving in the area, we have to use motion sensor. If people are expected to sit idle, we have to use presence sensors. Please read on to understand what is difference between motion sensors and Presence sensors?
As an example in a class room if we use a motion sensor, it will get activated when students come into the class. However after starting the class, if all students sit motionless (as usually happen especially for subjects which are of less interest) for 30 seconds (or whatever time programmed), the sensors will be deactivated and lights will be switched off.
Whereas a presence sensors will remain in activated condition as long as there is someone present in its vicinity.
Typical applications for motion sensor/detector are : Corridors,staircases etc where people are not expected to remain idle for long time
Typical applications for Presence Sensor/detector are :Class room, toilet,office etc. where people may remain idle.
For both the sensors the time delay can be adjusted and the customer can decide the exact type to be used based on his exact needs.