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:
“We have not passed that subtle line between childhood and adulthood until we move from the passive voice to the active voice—that is, until we have stopped saying “It got lost,” and say, “I lost it.””
—Sydney J. Harris (b. 1917)