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Annealing Alloy Steel
The term alloy steel, from the steel maker's point of view, r...

The Forging Of Steel
So much depends upon the forging of steel that this operation...

Heat Treatment Of Axles
Parts of this general type should be heat-treated to show the...

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

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

The Leeds And Northrup Potentiometer System
The potentiometer pyrometer system is both flexible and subst...

Annealing Work
With the exception of several of the higher types of alloy s...

Complete Calibration Of Pyrometers
For the complete calibration of a thermo-couple of unknown e...

Pyrometry And Pyrometers
A knowledge of the fundamental principles of pyrometry, or th...

A Satisfactory Luting Mixture
A mixture of fireclay and sand will be found very satisfactor...

Application To The Automotive Industry
The information given on the various parts of the Liberty eng...

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

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

Crucible Steel
Crucible steel is still made by melting material in a clay or...

Case-hardening Treatments For Various Steels
Plain water, salt water and linseed oil are the three most co...

The Pyrometer And Its Use
In the heat treatment of steel, it has become absolutely nece...

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

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

Application Of Liberty Engine Materials To The Automotive Industry
The success of the Liberty engine program was an engineer...

Annealing In Bone
Steel and cast iron may both be annealed in granulated bone. ...

Correction For Cold-junction Errors


The voltage generated by a thermo-couple of an electric pyrometer is
dependent on the difference in temperature between its hot junction,
inside the furnace, and the cold junction, or opposite end of the
thermo-couple to which the copper wires are connected. If the
temperature or this cold junction rises and falls, the indications
of the instrument will vary, although the hot junction in the furnace
may be at a constant temperature.

A cold-junction temperature of 75 deg.F., or 25 deg.C., is usually adopted
in commercial pyrometers, and the pointer on the pyrometer should
stand at this point on the scale when the hot junction is not heated.
If the cold-junction temperature rises about 75 deg.F., where base metal
thermo-couples are used, the pyrometer will read approximately 1 deg.
low for every 1 deg. rise in temperature above 75 deg.F. For example, if the
instrument is adjusted for a cold-junction temperature of 75 deg., and
the actual cold-junction temperature is 90 deg.F., the pyrometer will
read 15 deg. low. If, however, the cold-junction temperature falls below
75 deg.F., the pyrometer will read high instead of low, approximately
1 deg. for every 1 deg. drop in temperature below 75 deg.F.

With platinum thermo-couples, the error is approximately 1/2 deg. for
1 deg. change in temperature.

Next: Correction By Zero Adjustment

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

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