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An IR pyrometer is an electronic device that is able to measure temperature from a distance. They operate using infrared light, and are able to detect thermal energy without being in direct contact with an object. These devices are also known as "infrared thermometers" or "spot thermometers," and are commonly used in industrial, medical, and security applications.
The name "pyrometer" comes from the Greek words for "fire" and "measure." An IR pyrometer consists of both an electronic detector and a lens. The lens is used to focus an object's thermal radiation onto the electronic sensor. This sensor converts infrared energy from a hot surface into an electronic signal. The higher the signal, the warmer the object. Most infrared pyrometers use a digital display to present the temperature value in Fahrenheit or Celsius degrees.
Not all objects and environments have the same thermal properties. This means that an IR pyrometer is not always perfectly accurate. If a surface is highly absorbent, much of its thermal radiation will not reach the detector and a false reading will occur. Dense atmospheres caused by fog or gas buildup can also cause an incorrect thermal reading. Infrared pyrometers are most accurate when measuring solid, flat surfaces such as walls.
Pyrometers can have different fields of view depending on the type of lens. Some lenses are designed to focus thermal radiation from a small area, while others are intended to view a wide area of heat. Ideally, a target object should fill the pyrometer's entire field of view. If it is not aimed properly, background radiation can influence the sensor reading. Most devices are intended to be used from a specific distance, or allow the operator to change lenses for different ranges.
Many handheld pyrometers employ a visible laser that is built into the unit. Devices with this feature are sometimes called "laser thermometers." The laser beam is intended to assist with the proper aiming of a pyrometer, however it is not a vital part of the actual temperature measurement process. Some IR pyrometers use an array of lasers to project a circle onto the target object. This projection is used to illustrate the viewing range of the thermal lense, and help users properly position the device.
These devices can be very useful in applications where traditional thermometers are not ideal. High-voltage electrical transformers, for instance, can be dangerous to touch. An IR pyrometer allows technicians to measure the temperature of the surface from a safe distance. Pyrometers can also be used to measure temperatures that are moving or too far away to reach with normal instruments.