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An infrared (IR) temperature sensor is a device that senses the IR radiation from a distant object and reports it back as a temperature. This device works by optically sensing the IR radiation, turning the radiation into electricity, and displaying the temperature of that electricity. The IR spectrum is generally considered to be between 0.7 and 1,000 microns, but an IR temperature sensor can only sense a portion of the full band. Most IR temperature sensor devices are made to detect a specific IR wavelength, so owners may need several devices at once; some models have adjustable sensors, but many do not. Primarily, the temperature sensor is used to safely determine the temperature of a surface, without having to be near the material.
Most objects, when they emit any amount of heat, also emit IR radiation; this is true for everything except a blackbody — an object that only absorbs energy and radiation and does not emit any. An IR temperature sensor uses an optical device that detects the amount of IR radiation. This radiation is then converted into electricity, which the device converts again into a temperature that is displayed to the user.
IR is typically measured in microns and rests between 0.7 to 1,000 microns. While this is a large spectrum, an IR temperature sensor only responds to between 0.7 and 14 microns, which ignores most of the IR spectrum. This is because the other sections of the spectrum are not responsible for emitting heat, making it unnecessary to respond to the rest of the spectrum.
The majority of IR temperature sensor units are specialized to respond to a certain number of microns, based on the material. For example, glass emits about 5 microns of IR radiation; using a sensor that responds to lower or higher micron counts would result in an inaccurate temperature assessment. Some sensors are adjustable, and can be set at different micron levels, but these are uncommon.
These temperature sensors are commonly used to ensure safety, because some surfaces can become dangerously hot. For example, the temperature of hot metal or glass cannot be measured directly without endangering someone. An IR temperature sensor can be used from a distance, however, so the user should be safe from the material while still receiving an accurate temperature assessment. Most IR temperature sensors are accurate and may be off by 1° or less from the actual temperature.