An Infrared Sensor is an electronic device that emits and/or detects infrared radiation in order to sense some aspect of its surroundings. Infrared sensors can measure the heat of an object, as well as detect motion. Many of these types of sensors only measure infrared radiation, rather than emitting it, and thus are known as passive infrared (PIR) sensors. 

Why Use Infrared Measurement? 
 

• It is fast - time saved, allowing for more measurements and accumulation of data.
• It facilitates measurement of moving targets.
• Measurements can be taken of hazardous or physically inaccessible objects.
• There is no interference - no energy is lost from the target.
• There is no risk of contamination and no mechanical effect on the surface of the object.