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Placing The Thermo-couples
The following illustrations from the Taylor Instrument Compan...

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

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

Hardening Carbon Steel For Tools
For years the toolmaker had full sway in regard to make of st...

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

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

Correction For Cold-junction Errors
The voltage generated by a thermo-couple of an electric pyrom...

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

Double Annealing
Water annealing consists in heating the piece, allowing it to...

The Influence Of Size
The size of the piece influences the physical properties obta...

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

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

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

Heating Of Manganese Steel
Another form of heat-treating furnace is that which is used ...

The Packing Department
In Fig. 56 is shown the packing pots where the work is packe...

High-chromium Or Rust-proof Steel
High-chromium, or what is called stainless steel containing f...

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

Heat Treatment Of Milling Cutters Drills Reamers Etc
THE FIRE.--Gas and electric furnaces designed for high heats ...

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

Fatigue Tests
It has been known for fifty years that a beam or rod would fa...

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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