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The Thermo-couple
With the application of the thermo-couple, the measurement of...

Case-hardening Treatments For Various Steels
Plain water, salt water and linseed oil are the three most co...

The Effect Of Tempering On Water-quenched Gages
The following information has been supplied by Automatic and ...

Annealing In Bone
Steel and cast iron may both be annealed in granulated bone. ...

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

Pyrometers For Molten Metal
Pyrometers for molten metal are connected to portable thermoc...

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

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

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

Cyanide Bath For Tool Steels
All high-carbon tool steels are heated in a cyanide bath. Wi...

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

Heat Treatment Of Gear Blanks
This section is based on a paper read before the American Gea...

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

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

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

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

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

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

Heat Treatment Of Steel
Heat treatment consists in heating and cooling metal at defin...

Steel Can Be Worked Cold
As noted above, steel can be worked cold, as in the case of ...



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.





Next: Brown Automatic Signaling Pyrometer

Previous: Correction By Zero Adjustment



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