Information on Heat Sensors

Infrared energy

• Heat sensors detect infrared radiation (IR). Every object in the universe emits IR, even ice cubes. However, the warmer an object is, the more IR it will emit.

Mechanism

• Transducers are devices that transform one type of energy to another. The pyroelectric transducer is the most important component of an infrared sensor, and it converts the energy of IR into a voltage signal.

Applications

• Many security systems use heat sensors to detect intruders. Smart buildings can use heat sensors to turn off lights and air conditioning in an empty room. Very sensitive IR sensors can be used to acquire information about the temperature of distant stars.

Capabilities

• The heat detectors commonly used to detect the presence of humans are sensitive enough to detect full body movement up to 12 meters. They can detect smaller movements, like the movement of a hand, at a distance of 3 meters.

Limitations

• Because glass is mostly opaque to infrared radiation, a heat sensor may fail to detect an intruder on the other side of a window. Also, a reflected sunbeam or a gust of cold air can cause a false alarm in an improperly placed sensor.