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Steel Making

A Satisfactory Luting Mixture
A mixture of fireclay and sand will be found very satisfactor...

Preventing Carburizing By Copper-plating
Copper-plating has been found effective and must have a thick...

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

The material used for all gears on the Liberty engine was sel...

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

Sulphur is another impurity and high sulphur is even a greate...

Silicon prevents, to a large extent, defects such as gas bubb...

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

Quenching Tool Steel
To secure proper hardness, the cooling of quenching of steel ...

William Kelly's Air-boiling Process
An account of Bessemer's address to the British Association w...

Lathe And Planer Tools
TO FORGE.--Gently warm the steel to remove any chill is parti...

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

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

Impact Tests
Impact tests are of considerable importance as an indication ...

Annealing Of High-speed Steel
For annealing high-speed steel, some makers recommend using g...

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

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

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

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

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

Compensating Leads


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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