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

The Quenching Tank
The quenching tank is an important feature of apparatus in c...

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

Double Annealing
Water annealing consists in heating the piece, allowing it to...

Heat Treatment Of Axles
Parts of this general type should be heat-treated to show the...

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

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

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

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

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

Detrimental Elements
Sulphur and phosphorus are two elements known to be detrimen...

Phosphorus
Phosphorus is one of the impurities in steel, and it has been...

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

Quenching Tool Steel
To secure proper hardness, the cooling of quenching of steel ...

Affinity Of Nickel Steel For Carbon
The carbon- and nickel-steel gears are carburized separately...

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

Critical Points
One of the most important means of investigating the properti...

Leeds And Northrup Optical Pyrometer
The principles of this very popular method of measuring tempe...

Gas Consumption For Carburizing
Although the advantages offered by the gas-fired furnace for ...

Quenching The Work
In some operations case-hardened work is quenched from the bo...



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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