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

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

Forging High-speed Steel
Heat very slowly and carefully to from 1,800 to 2,000 deg.F....

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

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

Machineability
Reheating for machine ability was done at 100 deg. less than ...

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

The Care Of Carburizing Compounds
Of all the opportunities for practicing economy in the heat-t...

Carbon Steels For Different Tools
All users of tool steels should carefully study the different...

The Theory Of Tempering
Steel that has been hardened is generally harder and more br...

Using Illuminating Gas
The choice of a carburizing furnace depends greatly on the fa...

Pyrometers
Armor plate makers sometimes use the copper ball or Siemens' ...

Steel Worked In Austenitic State
As a general rule steel should be worked when it is in the a...

Fatigue Tests
It has been known for fifty years that a beam or rod would fa...

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

The Modern Hardening Room
A hardening room of today means a very different place from ...

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

Silicon
SILICON is a very widespread element (symbol Si), being an es...

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

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



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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