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

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

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

Chrome-nickel Steel
Forging heat of chrome-nickel steel depends very largely on ...

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

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

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

Brown Automatic Signaling Pyrometer
In large heat-treating plants it has been customary to mainta...

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

Preparing Parts For Local Case-hardening
At the works of the Dayton Engineering Laboratories Company, ...

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

Carburizing By Gas
The process of carburizing by gas, briefly mentioned on page ...

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

Tool Or Crucible Steel
Crucible steel can be annealed either in muffled furnace or b...

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

Cutting-off Steel From Bar
To cut a piece from an annealed bar, cut off with a hack saw,...

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

Composition Of Transmission-gear Steel
If the nickel content of this steel is eliminated, and the pe...

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

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



Correction For Cold-junction Errors






Category: PYROMETRY AND PYROMETERS

The voltage generated by a thermo-couple of an electric pyrometer is
dependent on the difference in temperature between its hot junction,
inside the furnace, and the cold junction, or opposite end of the
thermo-couple to which the copper wires are connected. If the
temperature or this cold junction rises and falls, the indications
of the instrument will vary, although the hot junction in the furnace
may be at a constant temperature.

A cold-junction temperature of 75 deg.F., or 25 deg.C., is usually adopted
in commercial pyrometers, and the pointer on the pyrometer should
stand at this point on the scale when the hot junction is not heated.
If the cold-junction temperature rises about 75 deg.F., where base metal
thermo-couples are used, the pyrometer will read approximately 1 deg.
low for every 1 deg. rise in temperature above 75 deg.F. For example, if the
instrument is adjusted for a cold-junction temperature of 75 deg., and
the actual cold-junction temperature is 90 deg.F., the pyrometer will
read 15 deg. low. If, however, the cold-junction temperature falls below
75 deg.F., the pyrometer will read high instead of low, approximately
1 deg. for every 1 deg. drop in temperature below 75 deg.F.

With platinum thermo-couples, the error is approximately 1/2 deg. for
1 deg. change in temperature.





Next: Correction By Zero Adjustment

Previous: Optical System And Electrical Circuit Of The Leeds & Northrup Optical Pyrometer



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