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Thermocouple Types

Difference in Thermocouple Types
Each calibration has a different temperature range and environment, although the maximum temperature varies with the diameter of the wire used in the thermocouple. Although thermocouple calibration dictates the temperature range, the maximum range is also limited by the diameter of the thermocouple wire. That is, a very thin thermocouple may not reach the full temperature range.

What are the accuracies and temperature ranges of the various thermocouples?
It is important to remember that both accuracy and range depend on such things as the thermocouple alloys, the temperature being measured, the construction of the sensor, the material of the sheath, the media being measured, the state of the media (liquid, solid, or gas) and the diameter of either the thermocouple wire (if it is exposed) or the sheath diameter (if the thermocouple wire is not exposed but is sheathed).

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Type K Thermocouples

Thermocouple Grade

Temperature range °F/°C

-328/-200 2282/1250

Extension Grade

Temperature range °F/°C

32/0 392/200

International IEC 584-3

Alloy Combination

+ Lead : Nickel-Chromium Ni-Cr
- Lead : Nickel-Aluminum Ni-Al

Standard Limits of Error °C (whichever is greater)

2.2°C or 0.75% above 0°C

Special

1.1°C or 0.4%

Comments, Bare Wire Environment

Clean oxidizing and inert; limited use in vacuum or reducing;
wide temperature range; most popular calibration

Type J Thermocouples

Thermocouple Grade

Temperature range °F/°C

32/0 1382/750

Extension Grade

Temperature range °F/°C

32/0 392/200

International IEC 584-3

Alloy Combination

+ Lead : Iron Fe
- Lead : Copper-Nicket Cu-Ni

Standard Limits of Error °C (whichever is greater)

2.2°C or 0.75% above 0°C

Special

1.1°C or 0.4%

Comments, Bare Wire Environment

Reducing, Vacuum, Inert. Limited Use in Oxidizing at High Temperatures. Not Recommended for Low Temperatures.

Type T Thermocouples

Thermocouple Grade

Temperature range °F/°C

32/0 392/200

Extension Grade

Temperature range °F/°C

-328/-250 662/350

International IEC 584-3

Alloy Combination

+ Lead : Copper Cu
- Lead : Copper-Nickel Cu-Ni

Standard Limits of Error °C (whichever is greater)

1.0°C or 0.75% above 0°C

Special

0.5°C or 0.4%

Comments, Bare Wire Environment

Mild Oxidizing, Reducing Vacuum or Inert. Good Where Moisture Is Present. Low Temperature and Cryogenic Applications

Type R Thermocouples

Thermocouple Grade

Temperature range °F/°C

32/0 2642/1450

Extension Grade

Temperature range °F/°C

32/0 300/150

International IEC 584-3

Alloy Combination

+ Lead : Platinum-13% Rhodium Pt-13% Rh
- Lead : Platinum Pt

Standard Limits of Error °C (whichever is greater)

1.5°C or 0.25% above 0°C

Special

0.6°C or 0.1%

Comments, Bare Wire Environment

Oxidizing or Inert. Do Not Insert in Metal Tubes. Beware of Contamination. High Temperature

Type E Thermocouples

Thermocouple Grade

Temperature range °F/°C

-328/-200 1652/900

Extension Grade

Temperature range °F/°C

32/0 392/200

International IEC 584-3

Alloy Combination

+ Lead : Nickel-Chromium Ni-Cr
- Lead : Nickel-Aluminum Ni-Al

Standard Limits of Error °C (whichever is greater)

1.7°C or 0.5% above 0°C

Special

1.0°C or 0.4%

Oxidizing or Inert. Limited Use in Vacuum or Reducing. Highest EMF Change Per Degree

Type N Thermocouples

Thermocouple Grade

Temperature range °F/°C

-450/-270 2372/1300

Extension Grade

Temperature range °F/°C

32/0 392/200

International IEC 584-3

Alloy Combination

+ Lead : Nicrosil Ni-Cr-Si
- Lead : Nisil Ni-Si-Mg

Standard Limits of Error °C (whichever is greater)

2.2°C or 0.75% above 0°C

Special

1.1°C or 0.4%

Alternative to Type K. More Stable at High Temps

Type S Thermocouples

Thermocouple Grade

Temperature range °F/°C

32/0 2642/1400

Extension Grade

Temperature range °F/°C

32/0 300/150

International IEC 584-3

Alloy Combination

+ Lead : Platinum-10% Rhodium Pt-10% Rh
- Lead : Platinum Pt

Standard Limits of Error °C (whichever is greater)

1.5°C or 0.25% above 0°C

Special

0.6°C or 0.1%

Oxidizing or Inert. Do Not Insert in Metal Tubes. Beware of Contamination. High Temperature

Type C Thermocouples

Thermocouple Grade

Temperature range °F/°C

32/0 4208/2320

Extension Grade

Temperature range °F/°C

32/0 1600/870

Alloy Combination

+ Lead : TUNGSTEN-5% RHENIUM W-5% Re
- Lead : TUNGSTEN-26% RHENIUM W-26% Re

Standard Limits of Error °C (whichever is greater)

4.5°C or 1.0% above 0°C

Vacuum, Inert, Hydrogen. Beware of Embrittlement. Not Practical Below 399°C (750°F) Not for Oxidizing Atmosphere

Type B Thermocouples

Thermocouple Grade

Temperature range °F/°C

32/0 2642/1400

Extension Grade

Temperature range °F/°C

32/0 300/150

Alloy Combination

+ Lead : Platinum-30% Rhodium Pt-30% Rh
- Lead : Platinum-6% Rhodium Pt-6% Rh

Standard Limits of Error °C

0.5% over 800°C

Oxidizing or Inert. Do Not Insert in Metal Tubes. Beware of Contamination. High Temperature. Common Use in Glass Industry