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Effect Of A Small Amount Of Copper In Medium-carbon Steel
This shows the result of tests by C. R. Hayward and A. B. Joh...

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

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

Annealing To Relieve Internal Stresses
Work quenched from a high temperature and not afterward tempe...

The Effect
The heating at 1,600 deg.F. gives the first heat treatment w...

High-carbon Machinery Steel
The carbon content of this steel is above 30 points and is ha...

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

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

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

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

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

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

Tensile Properties
Strength of a metal is usually expressed in the number of pou...

Correction By Zero Adjustment
Many pyrometers are supplied with a zero adjuster, by means ...

Effects Of Proper Annealing
Proper annealing of low-carbon steels causes a complete solu...

Robert Mushet
Robert (Forester) Mushet (1811-1891), born in the Forest of D...

Hardening
Steel is hardened by quenching from above the upper critical....

Annealing Method
Forgings which are too hard to machine are put in pots with ...

Detrimental Elements
Sulphur and phosphorus are two elements known to be detrimen...

Molybdenum
Molybdenum steels have been made commercially for twenty-five...



Correction For Cold-junction Errors






Category: PYROMETRY AND PYROMETERS

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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