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

Furnace Data
In order to give definite information concerning furnaces, fu...

Quenching The Work
In some operations case-hardened work is quenched from the bo...

Heat Treatment Of Lathe Planer And Similar Tools
FIRE.--For these tools a good fire is one made of hard foundr...

Using Illuminating Gas
The choice of a carburizing furnace depends greatly on the fa...

Composition Of Transmission-gear Steel
If the nickel content of this steel is eliminated, and the pe...

Liberty Motor Connecting Rods
The requirements for materials for the Liberty motor connecti...

Effect Of Different Carburizing Material
[Illustrations: FIGS. 33 to 37.] Each of these different p...

Forging High-speed Steel
Heat very slowly and carefully to from 1,800 to 2,000 deg.F....

Suggestions For Handling High-speed Steels
The following suggestions for handling high-speed steels are ...

Placing Of Pyrometers
When installing a pyrometer, care should be taken that it re...

Temperature For Annealing
Theoretically, annealing should be accomplished at a tempera...

Affinity Of Nickel Steel For Carbon
The carbon- and nickel-steel gears are carburized separately...

Silicon prevents, to a large extent, defects such as gas bubb...

Tool Or Crucible Steel
Crucible steel can be annealed either in muffled furnace or b...

The crankshaft was the most highly stressed part of the entir...

Quality And Structure
The quality of high-speed steel is dependent to a very great ...

High-chromium Or Rust-proof Steel
High-chromium, or what is called stainless steel containing f...

Heating Of Manganese Steel
Another form of heat-treating furnace is that which is used ...

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

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

Previous: Leeds And Northrup Optical Pyrometer

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