Motion sensors are used to activate electrical circuits such as lights, cooling system etc. when some one moves in an area. When there is no movement in the vicinity, the circuit will be switched OFF and when some movement happens, the circuits will be Switched ON.
Major factors to be considered while selecting a motion sensor are detailed hereunder
1. Size of the room
This is the most important criteria for selection. The length, width and height of the room need to be considered need to be measured. Each model of sensor has a ‘visibility’ range which means the area which is visible to the sensor. The best performance of the sensor will be within this range. However it has to be noticed that the sensor will slightly detect outside this range also, but with reduced effectiveness. So care has to be taken while selecting motion sensors in wider areas with multiple circuits such as corridors, ware houses etc.
Motion sensors utilize different technologies available mainly infrared and ultrasound/microwave. Also dual technology sensors are available which use a combination of infrared and ultrasound. It may be noted that ultrasound sensors detect through glasses whereas infrared sensors do not detect through glasses.
3. Required sensitivity
The sensitivity of most of the models can be adjusted. Selecting the most sensitive setting means it will detect minutest movements. Selecting lesser sensitivity means minor movements will be ignored.
4. Time delay
Most of the models will have adjustable delay settings starting from 15 seconds to 10 or 15 minutes. If 15 seconds delay is selected, the sensors will switch OFF the circuits 15 seconds after the last detection of any movements.
5. The electrical load capacity
The total load to be connected to the sensor need to be calculated. This will include your total electrical load of lights, AC etc. Each model of sensors will have a current carrying capacity. However this need not be a major criteria, since you can add an auxiliary relay or contactor and increase the total loads
6. Ingress protection
There are models available upto IP 65 protection or explosion proof ratings. You may select different models for indoor and outdoor applications.
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