Page:Popular Science Monthly Volume 89.djvu/345

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��mimmiini temperature it \vi 1200 (let;rees.

The i)rin(iiile upon whicli the opera- tion of tile sisiiit pyrometer is l)ased is the simple physical law that the intensity of light emitted by a heated body is 'iirectiy |)roportioiial to its temperature.

In iookiiiij throiiijh the pyrometer, two adjacent semicircular fields ol \isioi are obser\i'd, one beinsj; illuminated by the small standardized electric lamj) in the pyrometer and the other by the object whose temper- ature is to be measured. The red ray of the spectrum is used and very slight differen- ces in the intensity o f the heat in the object under in\ estigation produce (|uile perceptible differences in the shade.

In taking readings, the intensity of the field illuminated by the lamp is adjusted by turning the eye-piece until the line separating the two fields is eliminated, and the corresponding tem- perature is read directly from the dial. The matter of bringing both fields of \ision to correspond is not a jiersonal

���Measuring the White Heat of Molten Minerals. The Shield Protects the Hands of the Operator. The In- strument Also Measures the Heat of Moving Bodies

��one of matching colors. Then- is always a line between the two fields when they do not correspond ; therefore, it is simply u matter of eliminating this line, and any defects of \ision are cciualized.

The handling of the pyrometer re- Cjuires no special knowledge, and read- i n g s within ten degrees of each other can be made by any workman of a\erage intelli- g e n c e . I n making of),scr- \ations the tempera t u re <if the oliject itself is meas- ured. It is this tempera- ture and not I he heat (A the furnace that determines whether the object is being treated at the proper temperature to pro- duce the effect desired. For metallurgical operations the ideal pyrometer ne\er comes in contact with the heated ob- ject — in fact, no heating of the instru- ment is required, and the readings are taken almost instantanec»usl\'. It can also measure heated mo\ing bodies.

���The Intensity of Light Emitted by a Heated Body, Regardless of Size, Is Di- rectly Proportional to Its Temperature

���In Looking Through the Pyrometer Two Adjacent Semicircular Fields of Vision Are Observed with the Operator's Eye

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