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

Preventing Decarbonization Of Tool Steel
It is especially important to prevent decarbonization in such...

Blending The Compound
Essentially, this consists of the sturdy, power-driven separa...

Heat-treating Equipment And Methods For Mass Production
The heat-treating department of the Brown-Lipe-Chapin Company...

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

Rate Of Cooling
At the option of the manufacturer, the above treatment of gea...

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

Heat-treating Department
The heat-treating department occupies an L-shaped building. ...

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

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

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

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

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

Annealing Of Rifle Components At Springfield Armory
In general, all forgings of the components of the arms manufa...

Heat Treatment Of Punches And Dies Shears Taps Etc
HEATING.--The degree to which tools of the above classes shou...

Typical Oil-fired Furnaces
Several types of standard oil-fired furnaces are shown herew...

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

Drop Forging Dies
The kind of steel used in the die of course influences the he...

Crankshaft
The crankshaft was the most highly stressed part of the entir...

Tempering Colors On Carbon Steels
Opinions differ as to the temperature which is indicated by t...



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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