Operating Principles
All objects above absolute zero emit heat energy in the form of optical radiation (light). Usually this light is invisible to the human eye because body temperature radiates at infrared wavelengths, but it can be detected by electronic devices designed for such a purpose.
The term passive in this instance refers to the fact that PIR devices do not generate or radiate any energy for detection purposes. They work entirely by detecting the energy given off by other objects.
Read more about this topic: Passive Infrared Sensor
Famous quotes containing the words operating and/or principles:
“Go on then in doing with your pen what in other times was done with the sword; shew that reformation is more practicable by operating on the mind than on the body of man.”
—Thomas Jefferson (1743–1826)
“Every political system is an accumulation of habits, customs, prejudices, and principles that have survived a long process of trial and error and of ceaseless response to changing circumstances. If the system works well on the whole, it is a lucky accident—the luckiest, indeed, that can befall a society.”
—Edward C. Banfield (b. 1916)