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Restoring Overheated Steel
The effect of heat treatment on overheated steel is shown gra...

Impact Tests
Impact tests are of considerable importance as an indication ...

The Electric Process
The fourth method of manufacturing steel is by the electric f...

Hardness Testing
The word hardness is used to express various properties of me...

Silicon
SILICON is a very widespread element (symbol Si), being an es...

Manganese
MANGANESE is a metal much like iron. Its chemical symbol is M...

Quenching Tool Steel
To secure proper hardness, the cooling of quenching of steel ...

Preventing Decarbonization Of Tool Steel
It is especially important to prevent decarbonization in such...

Annealing Of High-speed Steel
For annealing high-speed steel, some makers recommend using g...

Nickel-chromium
A combination of the characteristics of nickel and the charac...

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

Standard Analysis
The selection of a standard analysis by the manufacturer is t...

William Kelly's Air-boiling Process
An account of Bessemer's address to the British Association w...

Carbon In Tool Steel
Carbon tool steel, or tool steel as it is commonly called, us...

Alloying Elements
Commercial steels of even the simplest types are therefore p...

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

Properties Of Alloy Steels
The following table shows the percentages of carbon, manganes...

Pyrometers For Molten Metal
Pyrometers for molten metal are connected to portable thermoc...

Optical System And Electrical Circuit Of The Leeds & Northrup Optical Pyrometer
For extremely high temperature, the optical pyrometer is lar...

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



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






Category: PYROMETRY AND PYROMETERS

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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