A passive infrared sensor (PIR sensor) is an electronic sensor that measures infrared (IR) light radiating from objects in its field of view. They are most often used in PIR-based motion detectors.
Read more about Passive Infrared Sensor: Operating Principles, Construction, PIR-based Motion Detector, PIR-based Remote Thermometer
Famous quotes containing the word passive:
“The best emotions to write out of are anger and fear or dread.... The least energizing emotion to write out of is admiration. It is very difficult to write out of because the basic feeling that goes with admiration is a passive contemplative mood.”
—Susan Sontag (b. 1933)