Pyrometer
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A pyrometer, or radiation thermometer, is a type of remote sensing thermometer used to measure the temperature of distant objects. Various forms of pyrometers have historically existed. In the modern
An optical pyrometer
A sailor checking the temperature of a ventilation system
Technician measuring the temperature of molten silicon at 2,650 °F (1,450 °C) with a disappearing-filament pyrometer in Czochralski crystal growing equipment at Raytheon transistor plant in 1956
Measuring the combustion temperature of coke in a blast furnace using an optical pyrometer, Fixed Nitrogen Research Laboratory, 1930
Emissivity
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The emissivity of the surface of a material is its effectiveness in emitting energy as thermal radiation. Thermal radiation is electromagnetic radiation that most commonly includes both visible radiat
Pyrometer
…irradiance j ⋆ of the target object through the Stefan–Boltzmann law, the constant of proportionality σ, called the Stefan–Boltzmann constant and the emissivity ε of the object: This output is used to infer the object's temperature from a distance, with no need for the pyrometer to be in thermal contact with…
Blacksmiths work iron when it is hot enough to emit plainly visible thermal radiation.
Solar water heating system based on evacuated glass tube collectors. Sunlight is absorbed inside each tube by a selective surface. The surface absorbs sunlight nearly completely, but has a low thermal emissivity so that it loses very little heat. Ordinary black surfaces also absorb sunlight efficiently, but they emit thermal radiation copiously.