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Instrument for measuring relatively high temperatures, as in furnaces. Most pyrometers work by measuring radiation from the body whose temperature is to be measured (radiation devices have the advantage of not having to touch the material being measured). Optical pyrometers measure the temperature of glowing bodies by comparing them visually with an incandescent filament of known temperature whose temperature can be adjusted. In resistance pyrometers, a fine wire is put in contact with the object; the instrument converts the change in electrical resistance caused by heat to a reading of the temperature of the object.
This entry comes from Encyclopædia Britannica Concise. For the full entry on pyrometer, visit Britannica.com.