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Introduction Of Carbon
The matter to which these notes are primarily directed is the...

The Effect Of Tempering On Water-quenched Gages
The following information has been supplied by Automatic and ...

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

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

Connecting Rods
The material used for all connecting rods on the Liberty engi...

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

Carbon-steel Forgings
Low-stressed, carbon-steel forgings include such parts as car...

Heavy Forging Practice
In heavy forging practice where the metal is being worked at...

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

Plant For Forging Rifle Barrels
The forging of rifle barrels in large quantities and heat-tre...

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

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

Affinity Of Nickel Steel For Carbon
The carbon- and nickel-steel gears are carburized separately...

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

Cyanide Bath For Tool Steels
All high-carbon tool steels are heated in a cyanide bath. Wi...

Shrinking And Enlarging Work
Steel can be shrunk or enlarged by proper heating and cooling...

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

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

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

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



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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