Hello. Um, I am not sure how it works. Thanks
In: Engineering
Pressure sensors I would think are relatively rare, unless you’re referring toa physical switch that is triggered by a door or window, but not sure those are ever used for alarms.
Alarms generally have 3 types of sensors:
Motion – usually infrared based, they shoot out an IR signal and monitor the return for changes. Really good at detecting side to side movement. An object moving slowly directly at them can fool cheaper ones.
Contact – these are magnetic sensors. Usually there will be a wire run to the door/window frame where a small magnetic sensor resides. The part that opens has a hole drilled into it and a magnet shoved in so that the contact and the magnet are next to each other in a closed position.
Sound – I have never seen one like in the movies where it is monitoring the overall sound levels in a room for variation. The more standard ones are called glass breaks, which are tuned, not surprisingly, to the frequency glass makes when it shatters with a reasonable SPL requirement. That way dogs barking doesn’t set it off.
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