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Steel Making

Classifications Of Steel
Among makers and sellers, carbon tool-steels are classed by g...

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

Vanadium
Vanadium has a very marked effect upon alloy steels rich in c...

Carbon Steels For Different Tools
All users of tool steels should carefully study the different...

Pickling The Forgings
The forgings were then pickled in a hot solution of either ni...

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

Process Of Carburizing
Carburizing imparts a shell of high-carbon content to a low-...

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

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

Annealing
ANNEALING can be done by heating to temperatures ranging from...

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

Instructions For Working High-speed Steel
Owing to the wide variations in the composition of high-speed...

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

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

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

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

A Chromium-cobalt Steel
The Latrobe Steel Company make a high-speed steel without tun...

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

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

Leeds And Northrup Optical Pyrometer
The principles of this very popular method of measuring tempe...



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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