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Steel Making

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

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

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

Composition And Properties Of Steel
It is a remarkable fact that one can look through a dozen tex...

An Automatic Temperature Control Pyrometer
Automatic temperature control instruments are similar to the ...

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

Non-shrinking Oil-hardening Steels
Certain steels have a very low rate of expansion and contract...

The Pyrometer And Its Use
In the heat treatment of steel, it has become absolutely nece...

Annealing Method
Forgings which are too hard to machine are put in pots with ...

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

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

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

Composition Of Transmission-gear Steel
If the nickel content of this steel is eliminated, and the pe...

Suggestions For Handling High-speed Steels
The following suggestions for handling high-speed steels are ...

For Milling Cutters And Formed Tools
FORGING.--Forge as before.--ANNEALING.--Place the steel in a ...

Piston Pin
The piston pin on an aviation engine must possess maximum res...

Properties Of Alloy Steels
The following table shows the percentages of carbon, manganes...

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

Hardening High-speed Steels
We will now take up the matter of hardening high-speed steels...

Process Of Carburizing
Carburizing imparts a shell of high-carbon content to a low-...



Compensating Leads






Category: PYROMETRY AND PYROMETERS

By the use of compensating leads, formed of
the same material as the thermo-couple, the cold junction can be
removed from the head of the thermo-couple to a point 10, 20 or 50
ft. distant from the furnace, where the temperature is reasonably
constant. Where greater accuracy is desired, a common method is
to drive a 2-in. pipe, with a pointed closed end, some 10 to 20
ft. into the ground, as shown in Fig. 128. The compensating leads
are joined to the copper leads, and the junction forced down to
the bottom of the pipe. The cold junction is now in the ground,
beneath the building, at a depth at which the temperature is very
constant, about 70 deg.F., throughout the year. This method will usually
control the cold-junction temperature within 5 deg.F.

Where the greatest accuracy is desired a compensating box will
overcome cold-junction errors entirely. It consists of a case enclosing
a lamp and thermostat, which can be adjusted to maintain any desired
temperature, from 50 to 150 deg.F. The compensating leads enter the box
and copper leads run from the compensating box to the instrument,
so that the cold junction is within the box. Figure 129 shows a
Brown compensating box.



If it is desired to maintain the cold junction at 100 deg.: the thermostat
is set at this point, and the lamp, being wired to the 110- or
220-volt lighting circuit, will light and heat the box until 100 deg.
is reached, when the thermostat will open the circuit and the light
is extinguished. The box will now cool down to 98 deg., when the circuit
is again closed, the lamp lights, the box heats up, and the operation
is repeated.





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Previous: Correction By Zero Adjustment



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