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

Steel Can Be Worked Cold
As noted above, steel can be worked cold, as in the case of ...

Open Hearth Process
The open hearth furnace consists of a big brick room with a l...

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

Carburizing Material
The simplest carburizing substance is charcoal. It is also th...

Hardening High-speed Steel
In forging use coke for fuel in the forge. Heat steel slowly ...

High Speed Steel
For centuries the secret art of making tool steel was handed ...

Restoring Overheated Steel
The effect of heat treatment on overheated steel is shown gra...

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

Uses Of The Various Tempers Of Carbon Tool Steel
DIE TEMPER.--No. 3: All kinds of dies for deep stamping, pres...

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

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

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

Knowing What Takes Place
How are we to know if we have given a piece of steel the ver...

Temperature For Annealing
Theoretically, annealing should be accomplished at a tempera...

Heating
Although it is possible to work steels cold, to an extent de...

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

Carburizing By Gas
The process of carburizing by gas, briefly mentioned on page ...

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

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



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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