Artifact Spotlight-Optical Pyrometer

With temperatures reaching into the thousands of degrees in the steelmaking process, CF&I employees found it much safer to regulate and record accurate temperatures using a tool known as an optical pyrometer. This pyrometer, which dates to the 1940s or 1950s, measures temperature by means of calculating the intensity of the light of a particular wavelength emitted by a hot substance, such as steel. The pyrometer makes it calculations by comparing the radiation of the hot object produced with the radiation produced by a hot filament (such as a thin wire through which electricity flows, such as the wire in an old-fashioned incandescent light bulb, which glows white when it gets hot). Accurate temperatures are important in the steelmaking process to allow for scientific processes, such as carbonization, to occur.


To use the tool, the operator would look through the telescopic eyepiece, through a red filter (to protect his or her eyes) at the object they were measuring, such as a ladle full of steel.  What they would see is a dull red glow from the hot object with a line of brighter light from the filament and superimposed on top of the image of the steel. The knob on the side could be turned to adjust the electric current passing through the filament. This makes the filament a bit hotter or colder and alters the light it gives off. When the filament was exactly the same brightness as the hot object they were measuring, it effectively would disappear because the radiation produced would be the same color. At that point, the operator would stop looking through the eyepiece and read the temperature on the side of the meter, recording it on a chart.

Donated to the Steelworks Center of the West by EVRAZ Rocky Mountain Steel in 2004.

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