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Bessemer Process
The bessemer process consists of charging molten pig iron int...

The Quenching Tank
The quenching tank is an important feature of apparatus in c...

Compensating Leads
By the use of compensating leads, formed of the same materia...

Heat Treatment Of Steel
Heat treatment consists in heating and cooling metal at defin...

Preventing Carburizing By Copper-plating
Copper-plating has been found effective and must have a thick...

High Speed Steel
For centuries the secret art of making tool steel was handed ...

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

Manganese
Manganese adds considerably to the tensile strength of steel,...

Brown Automatic Signaling Pyrometer
In large heat-treating plants it has been customary to mainta...

Machineability
Reheating for machine ability was done at 100 deg. less than ...

The Care Of Carburizing Compounds
Of all the opportunities for practicing economy in the heat-t...

Testing And Inspection Of Heat Treatment
The hard parts of the gear must be so hard that a new mill f...

Preparing Parts For Local Case-hardening
At the works of the Dayton Engineering Laboratories Company, ...

Non-shrinking Oil-hardening Steels
Certain steels have a very low rate of expansion and contract...

Sulphur
Sulphur is another impurity and high sulphur is even a greate...

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

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

Highly Stressed Parts
The highly stressed parts on the Liberty engine consisted of ...

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

Calibration Of Pyrometer With Common Salt
An easy and convenient method for standardization and one whi...



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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