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Correction For Cold-junction Errors
The voltage generated by a thermo-couple of an electric pyrom...

SULPHUR is another element (symbol S) which is always found i...

Knowing What Takes Place
How are we to know if we have given a piece of steel the ver...

Protective Screens For Furnaces
Workmen needlessly exposed to the flames, heat and glare from...

A Chromium-cobalt Steel
The Latrobe Steel Company make a high-speed steel without tun...

Mushet And Bessemer
That Mushet was "used" by Ebbw Vale against Bessemer is, perh...

Flange Shields For Furnaces
Such portable flame shields as the one illustrated in Fig. 1...

Rate Of Absorption
According to Guillet, the absorption of carbon is favored by ...

Judging The Heat Of Steel
While the use of a pyrometer is of course the only way to hav...

Introduction Of Carbon
The matter to which these notes are primarily directed is the...

A combination of the characteristics of nickel and the charac...

Rate Of Cooling
At the option of the manufacturer, the above treatment of gea...

Chrome-nickel Steel
Forging heat of chrome-nickel steel depends very largely on ...

Carburizing Low-carbon Sleeves
Low-carbon sleeves are carburized and pushed on malleable-ir...

Lathe And Planer Tools
FORGING.--Gently warm the steel to remove any chill, is parti...

The Theory Of Tempering
Steel that has been hardened is generally harder and more br...

Separating The Work From The Compound
During the pulling of the heat, the pots are dumped upon a ca...

Steel Before The 1850's
In spite of a rapid increase in the use of machines and the ...

Ebbw Vale And The Bessemer Process
After his British Association address in August 1856, Besseme...

Short Method Of Treatment
In the new method, the packed pots are run into the case-har...

Optical System And Electrical Circuit Of The Leeds & Northrup Optical Pyrometer


For extremely high temperature, the optical pyrometer is
largely used. This is a comparative method. By means of the rheostat
the current through the lamp is adjusted until the brightness of
the filament is just equal to the brightness of the image produced
by the lens L, Fig. 123, whereupon the filament blends with or
becomes indistinguishable in the background formed by the image
of the hot object. This adjustment can be made with great accuracy
and certainty, as the effect of radiation upon the eye varies some
twenty times faster than does the temperature at 1,600 deg.F., and some
fourteen times faster at 3,400 deg.F. When a balance has been obtained,
the observer notes the reading of the milliammeter. The temperature
corresponding to the current is then read from a calibration curve
supplied with the instrument.

As the intensity of the light emitted at the higher temperatures
becomes dazzling, it is found desirable to introduce a piece of red
glass in the eye piece at R. This also eliminates any question
of matching colors, or of the observer's ability to distinguish
colors. It is further of value in dealing with bodies which do
not radiate light of the same composition as that emitted by a
black body, since nevertheless the intensity of radiation of any
one color from such bodies increases progressively in a definite
manner as the temperature rises. The intensity of this one color
can therefore be used as a measure of temperature for the body
in question. Figures 124 to 126 show the way it is read.

Next: Correction For Cold-junction Errors

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