Motion Sensors Don’t Sense Motion

Home Security Alarm Systems

Home Security Alarm SystemsInfrared Motion Sensors are Heat Sensors

What? Did I hear correctly? Infrared Motion Sensors don’t detect Motion?

Infrared Motion Sensors, sometimes called Infra-reds, IR’s, or PIR’s (Passive Infra-reds) are alarm sensors that are a common component on business and home security alarm systems.  They are installed inside the room, typically wall-mounted in a corner, and detect an intruder.  They do not, however, detect motion.  They are Passive Infra-red detectors.  They pick up subtle changes in the temperature inside a room.  They are passive, because they do not transmit anything.  They “watch” the room for changes in heat.  There are no “beams” to break.  When an intruder walks through the detection area, the sensor sees a change from the ambient background temperature of the room, and triggers an alarm.  They are sensitive enough to pick up as little as 1-2 degrees temperature difference.  PIR’s are most sensitive when the room is either relatively cool or hot, then the change of temperature is more pronounced, and therefore, the sensor trips quicker.

Even though PIR’s are heat sensors, they ARE NOT designed to detect fires.  They ARE intrusion sensors.  If you want fire detection, then you need appropriate Smoke or Heat sensors that are suitable for fire detection.  Most alarm systems can have fire detection sensors, but I’ll save that for another post…

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One Response to “Motion Sensors Don’t Sense Motion”

  1. Amedar Says:

    Amedar Consulting Group…

    Magnificent site. Lots of helpful info here. I’m sending it to some friends ans also sharing in delicious. And certainly, thank you for your sweat!…