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Phosphorus
PHOSPHORUS is an element (symbol P) which enters the metal fr...

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

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

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

Rate Of Cooling
At the option of the manufacturer, the above treatment of gea...

Annealing
ANNEALING can be done by heating to temperatures ranging from...

Highly Stressed Parts
The highly stressed parts on the Liberty engine consisted of ...

Annealing Work
With the exception of several of the higher types of alloy s...

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

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

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

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

Typical Oil-fired Furnaces
Several types of standard oil-fired furnaces are shown herew...

Heat Treatment Of Milling Cutters Drills Reamers Etc
THE FIRE.--Gas and electric furnaces designed for high heats ...

Quenching
It is considered good practice to quench alloy steels from th...

Manganese
MANGANESE is a metal much like iron. Its chemical symbol is M...

Annealing Alloy Steel
The term alloy steel, from the steel maker's point of view, r...

Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (...

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

Placing Of Pyrometers
When installing a pyrometer, care should be taken that it re...



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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