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Separating The Work From The Compound
During the pulling of the heat, the pots are dumped upon a ca...

Optical System And Electrical Circuit Of The Leeds & Northrup Optical Pyrometer
For extremely high temperature, the optical pyrometer is lar...

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

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

Tensile Properties
Strength of a metal is usually expressed in the number of pou...

Heating Of Manganese Steel
Another form of heat-treating furnace is that which is used ...

Complete Calibration Of Pyrometers
For the complete calibration of a thermo-couple of unknown e...

Nickel
Nickel may be considered as the toughest among the non-rare a...

Protective Screens For Furnaces
Workmen needlessly exposed to the flames, heat and glare from...

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

Application Of Liberty Engine Materials To The Automotive Industry
The success of the Liberty engine program was an engineer...

The Forging Of Steel
So much depends upon the forging of steel that this operation...

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

Making Steel Balls
Steel balls are made from rods or coils according to size, st...

Annealing
There is no mystery or secret about the proper annealing of d...

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

Manganese
Manganese adds considerably to the tensile strength of steel,...

High-carbon Machinery Steel
The carbon content of this steel is above 30 points and is ha...

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

The Electric Process
The fourth method of manufacturing steel is by the electric f...



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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