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Steel Making

Tungsten
Tungsten, as an alloy in steel, has been known and used for a...

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

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

Carbon In Tool Steel
Carbon tool steel, or tool steel as it is commonly called, us...

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

Liberty Motor Connecting Rods
The requirements for materials for the Liberty motor connecti...

Hints For Tool Steel Users
Do not hesitate to ask for information from the maker as to t...

Testing And Inspection Of Heat Treatment
The hard parts of the gear must be so hard that a new mill f...

Cutting-off Steel From Bar
To cut a piece from an annealed bar, cut off with a hack saw,...

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

Temperature Recording And Regulation
Each furnace is equipped with pyrometers, but the reading an...

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

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

Surface Carburizing
Carburizing, commonly called case-hardening, is the art of pr...

Correction By Zero Adjustment
Many pyrometers are supplied with a zero adjuster, by means ...

Air-hardening Steels
These steels are recommended for boring, turning and planing...

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

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

Hardening
The forgings can be hardened by cooling in still air or quen...

Protectors For Thermo-couples
Thermo-couples must be protected from the danger of mechanica...



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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