Thermocouple Types
Type J Thermocouple
Temperature Range
32 to 1382°F (0 to 750°C)
Accuracy
•Standard Limits: ± 2.2°C or ± 0.75% Tol.
•Special Limits: ± 1.1°C or ± 0.4% Tol.
Type J thermocouples are suitable for use in vacuum, in oxidising and reducing atmospheres or inert gas atmospheres. They are used for temperature measurements 760°C and below.
Type K Thermocouple
Temperature Range
–328 to 2282°F (–200 to 1250°C)
Accuracy
•Standard Limits: ± 2.2°C or ± 0.75% Tol.
•Special Limits: ± 1.1°C or ± 0.4% Tol.
Type K Thermocouples are the most common calibration for providing the widest operating range. Recommended for continuous oxidizing or inert atmospheres. Most commonly used for temperatures above 538°C. Not suitable for sulfur environments.
Type T Thermocouple
Temperature Range
-454 to 700F(-270 to 370C)
Accuracy
• Standard Limits: ± 2.2°C or ± 0.75% Tol.
• Special Limits: ± 1.1°C or ± 0.4% Tol.
Suitable in oxidizing, reducing, or inert atmospheres as well as vaccuum. Moisture resistant and very stable. This type is best suited for low temperature service. Because of its stability at lower temperatures, this is a superior thermocouple for a wide variety of applications in low and cryogenic
Type N Thermocouple
Temperature Range
–454 to 2,300F (–270 to 1260C)
Accuracy
•Standard Limits: ± 2.2°C or ± 0.75% Tol.
•Special Limits: ± 1.1°C or ± 0.4% Tol.
Type N thermocouples are suitable for use in oxidising atmospheres, in inert gas atmospheres or dry reduction atmospheres. They are very accurate at high temperatures. The source voltage(EMF) and the temperature range are almost the same as with type K.
Type E Thermocouple
Temperature Range
-454 to 1600F(-270 to 870C)
Accuracy
•Standard Limits: ± 2.2°C or ± 0.75% Tol.
•Special Limits: ± 1.1°C or ± 0.4% Tol.
The Type E thermocouple is suitable for use in vacuum, inert, mildly oxidizing or reducing atmosphere. Not subject to corrosion at cryogenic temperatures. This thermocouple has the highest EMF output per degree of all the only used thermocouples.
Type B Thermocouple
Temperature Range
1475 to 3270°F (800 to 1800°C)
Accuracy
•Standard Limits: ± 2.2°C or ± 0.75% Tol.
•Special Limits: ± 1.1°C or ± 0.4% Tol.
Type B thermocouples are recommended for use in clean air at temperatures from 870 to 1700°C (1600 to 3100°F). They may be used for brief periods in vacuum, but should not be used in reducing atmospheres nor where exposed to nonmetallic or metallic vapors.
Type R Thermocouple
Temperature Range
-58 to 2700F (-50 to 1480C))
Accuracy
•Standard Limits: ± 2.2°C or ± 0.75% Tol.
•Special Limits: ± 1.1°C or ± 0.4% Tol.
Type R thermocouple has superior mechanical properties to Type S and is recommended for continuous use in oxidizing and inert atmospheres around temperatures up to 1400°C and intermittently up to 1600°C. Reducing atmospheres may cause excessive grain growth and drifts in calibration.
Type S Thermocouple
Temperature Range
-58 to 2700F (-50 to 1480C)
Accuracy
•Standard Limits: ± 2.2°C or ± 0.75% Tol.
•Special Limits: ± 1.1°C or ± 0.4% Tol.
Type S thermocouples are suitable for continuous use in oxidizing or inert atmospheres at temperatures up to 1600 °C. They can not be inserted in a metallic protection tube. Beware of embrittlement due to contamination.
Thermocouple
Sensors
What is a Thermocouple?
A thermocouple (T/C) is a closed-circuit thermoelectric temperature sensing device consisting of two wires of dissimilar metals joined at both ends of temperature measurements.
A current is created when the temperature at one end or junction differs from the temperature at the other end. This phenomenon is known as the Seebeck effect, which is the basis for thermocouple temperature measurements.
One end is referred to as the hot junction whereas the other end is referred to as the cold junction. The hot junction measuring element is placed inside a sensor sheath and exposed to the process. The cold junction, or the reference junction, is the termination point outside of the process where the temperature is known and where the voltage is being measured. This cold junction is typically in a transmitter, control system input card or in a signal conditioner.
According to the Seebeck effect, a voltage measured at the cold junction is proportional to the difference in temperature between the hot junction and the cold junction. This voltage may be referred to as the Seebeck voltage, thermoelectric voltage, or thermoelectric EMF. As the temperature rises at the hot junction, the observed voltage at the cold junction also increases non-linearly with the rising temperature. The linearity of the temperature voltage relationship depends on the combination of metals used to make the T/C.
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Temperature Range
32 to 1382°F (0 to 750°C)
Accuracy
•Standard Limits: ± 2.2°C or ± 0.75% Tol.
•Special Limits: ± 1.1°C or ± 0.4% Tol.
Type J thermocouples are suitable for use in vacuum, in oxidising and reducing atmospheres or inert gas atmospheres. They are used for temperature measurements 760°C and below.
Type N Thermocouple
Temperature Range
–328 to 2282°F (–200 to 1250°C)
Accuracy
•Standard Limits: ± 2.2°C or ± 0.75% Tol.
•Special Limits: ± 1.1°C or ± 0.4% Tol.
Type K Thermocouples are the most common calibration for providing the widest operating range. Recommended for continuous oxidizing or inert atmospheres. Most commonly used for temperatures above 538°C. Not suitable for sulfur environments.
Type T Thermocouple
Temperature Range
-454 to 700F(-270 to 370C)
Accuracy
• Standard Limits: ± 2.2°C or ± 0.75% Tol.
• Special Limits: ± 1.1°C or ± 0.4% Tol.
Suitable in oxidizing, reducing, or inert atmospheres as well as vaccuum. Moisture resistant and very stable. This type is best suited for low temperature service. Because of its stability at lower temperatures, this is a superior thermocouple for a wide variety of applications in low and cryogenic
Type N Thermocouple
Temperature Range
–454 to 2,300F (–270 to 1260C)
Accuracy
•Standard Limits: ± 2.2°C or ± 0.75% Tol.
•Special Limits: ± 1.1°C or ± 0.4% Tol.
Type N thermocouples are suitable for use in oxidising atmospheres, in inert gas atmospheres or dry reduction atmospheres. They are very accurate at high temperatures. The source voltage(EMF) and the temperature range are almost the same as with type K.
Type E Thermocouple
Temperature Range
-454 to 1600F(-270 to 870C)
Accuracy
•Standard Limits: ± 2.2°C or ± 0.75% Tol.
•Special Limits: ± 1.1°C or ± 0.4% Tol.
The Type E thermocouple is suitable for use in vacuum, inert, mildly oxidizing or reducing atmosphere. Not subject to corrosion at cryogenic temperatures. This thermocouple has the highest EMF output per degree of all the only used thermocouples.
Type B Thermocouple
Temperature Range
1475 to 3270°F (800 to 1800°C)
Accuracy
•Standard Limits: ± 2.2°C or ± 0.75% Tol.
•Special Limits: ± 1.1°C or ± 0.4% Tol.
Type B thermocouples are recommended for use in clean air at temperatures from 870 to 1700°C (1600 to 3100°F). They may be used for brief periods in vacuum, but should not be used in reducing atmospheres nor where exposed to nonmetallic or metallic vapors.
Type R Thermocouple
Temperature Range
-58 to 2700F (-50 to 1480C))
Accuracy
•Standard Limits: ± 2.2°C or ± 0.75% Tol.
•Special Limits: ± 1.1°C or ± 0.4% Tol.
Type R thermocouple has superior mechanical properties to Type S and is recommended for continuous use in oxidizing and inert atmospheres around temperatures up to 1400°C and intermittently up to 1600°C. Reducing atmospheres may cause excessive grain growth and drifts in calibration.
Type S Thermocouple
Temperature Range
-58 to 2700F (-50 to 1480C)
Accuracy
•Standard Limits: ± 2.2°C or ± 0.75% Tol.
•Special Limits: ± 1.1°C or ± 0.4% Tol.
Type S thermocouples are suitable for continuous use in oxidizing or inert atmospheres at temperatures up to 1600 °C. They can not be inserted in a metallic protection tube. Beware of embrittlement due to contamination.
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[/ult_content_box]Popular Thermocouples
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Calibration types are designed to deliver as close to a straight line voltage curve inside their temperature application range as possible. This makes it easier for an instrument or temperature controller to correctly correlate the received voltage to a particular temperature.
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Thermocouple Wire
Thermocouple Grade Wire
| Calibration Type | Temperature Range | Tolerance Whichever is GREATER | ||||
|---|---|---|---|---|---|---|
| J | 32 to 1382°F | 0 to 750°C | ? 2.2°C or ? 0.75% | ? 1.1°C or ? 0.4% | ||
| K | 32 to 2282°F | 0 to 1250°C | ? 2.2°C or ? 0.75% | ? 1.1°C or ? 0.4% | ||
| E | 32 to 1652°F | 0 to 900°C | ? 1.7°C or ? 0.5% | ? 1.0°C or ? o.4% | ||
| T | 32 to 662°F | 0 to 350°C | ? 1.0°C or ? 0.75% | ? 0.5°C or ? 0.4% | ||
| R or S | 32 to 2642°F | 0 to 1450°C | ? 1.5° or ? 0.25% | ? 0.6°C or ? 0.4% | ||
| B | 1598 to 3092°F | 870 to 1700°C | ? 0.5% | |||
| N | 32 to 2282°F | 0 to 1250°C | ? 2.2°C or ? 0.75% | ? 1.1°C or ? 0.4% | ||
Thermocouple Extension Grade Wire
| Calibration Type | Temperature Range | Tolerance Whichever is GREATER | ||
|---|---|---|---|---|
| JX | 32 to 392°F | 0 to 200°C | ? 2.2°C | ? 1.1°C |
| KX | 32 to 392°F | 0 to 200°C | ? 2.2°C | ? 1.1°C |
| EX | 32 to 392°F | 0 to 200°C | ? 1.7°C | ? 1.0°C |
| TX | 32 to 212°F | 0 to 200°C | ? 1.0°C | ? 0.5°C |
| NX | 32 to 392°F | 0 to 200°C | ? 2.2° | ? 1.1°C |
Thermocouple Reference Tables
Thermocouple Type B
•Thermocouple Type B °C
•Thermocouple Type B °F
Thermocouple Type C
•Thermocouple Type C °C
•Thermocouple Type C °F
Thermocouple Type E
•Thermocouple Type E °C
•Thermocouple Type E °F
Thermocouple Type J
•Thermocouple Type J °C
•Thermocouple Type J °F
Thermocouple Type K
•Thermocouple Type K °C
•Thermocouple Type K °F
Thermocouple Type N
•Thermocouple Type N °C
•Thermocouple Type N °F
Thermocouple Type R
•Thermocouple Type R °C
•Thermocouple Type R °F
Thermocouple Type S
•Thermocouple Type S °C
•Thermocouple Type S °F
Thermocouple Type T
Thermocouple Color Codes
[vc_single_image image=”4860″ img_size=”full” alignment=”center”]Thermocouple Sheath Material
FEP Teflon Extruded– 204°C (400°F) / 260°C (500°F)
Conductor is FEP extruded Teflon. Overall jacket is FEP extruded Teflon. Abrasion resistance excellent. Moisture resistance is excellent. Color coded. Order Code TE/TE.
TFE Teflon Fused Tape– 260°C (500°F) / 316°C (600°F)
Conductor is TFE Teflon fused tape. Overall jacket is TFE Teflon fused tape. Abrasion resistance is good. Moisture resistance is excellent. Color coded. Order Code TF/TF.
TFE Teflon Tape– 482°C (900°F) / 538°C (1000°
Conductor is TFE Teflon tape, (not fused), with TFE coated glass. Overall jacket is Teflon coated glass braid. Abrasion resistance is good. Moisture resistance is excellent. Color coded. Order Code TFB/TFB.
Glass Braid– 482°C (900°F) / 538°C (1000°F)
Conductor is glass braid. Overall jacket is glass braid. No color coding. Abrasion resistance is fair. Moisture resistance is fair. Order Code FBN/FBN.
Glass Braid with Silicon Resin– 482°C (900°F) / 538°C (1000°)
Conductor Glass Braid with Silicone Resin Impregnation. Overall Jacket Glass Braid with Silicone Impregnation. Impregnation retained to 204°C (400°F). Abrasion Resistance Fair. Moisture Resistance Good. Color coded. Order Code FB/FB
Double Glass Braid– 482°C (900°F) / 538°C (1000°F)
Conductor Double Glass Braid with Silicone Resin Impregnation. Overall Jacket Glass Braid with Silicone Impregnation. Impregnation retained to 204°C (400°F) Abrasion Resistance Good. Moisture Resistance Good. Color coded. Order Code FB2/FB.
Double Glass Wrap– 482°C (900°F) / 538°C (1000°F)
Conductor is double glass wrap with high temperature varnish. Overall jacket of glass braid with silicone resin impregnation. Impregantion retained to 204°C (400°F). Abrasion resistance is fair. Moisture resistance is good. Color coded. Order Code FW2/FB.
High Temp Glass Braid– 704°C (1300°F) / 871°C (1600°F)
Conductor is hi-temp glass braid. Overall jacket of hi-temp glass braid with light laquer coating impregnation. Impregantion retained to 204°C (400°F). Abrasion resistance is fair. Moisture resistance is fair. Not color coded. Order Code HGN/HG .
Ceramic Fiber– 1204°C (2200°F) / 1427°C (2600°F)
Conductor is ceramic fiber. Overall jacket is ceramic fiber.Abrasion resistance is good. Moisture resistance is Fair. Not color coded. Order Code CF/CF.
PVC– -29°C (-20°F) / 105°C (221°F)
Conductor is PVC. Overall jacket is PVC. Abrasion resistance is good. Mositure resistance is excellent. Color coded.Order Code PC/PC.
Kapton Fused Tape– 316°C (600°F) / 427°C (800°F)
Conductor is kapton fused tape. No overall jacket. Wires are twisted. Both legs have a tracer. Abrasion resistance is good. Mositure resistance is excellent. Color coded. Order Code KF/TW.
Thermocouple Junctions
Grounded Thermocouples: This is the most common junction style. A thermocouple is grounded when both thermocouple wires and the sheath are all welded together to form one junction at the probe tip. Grounded thermocouples have a very good response time because the thermocouple is making direct contact with the sheath, allowing heat to transfer easily. A drawback of the grounded thermocouple is that the thermocouple is more susceptible to electrical interference. This is because the sheath often comes into contact with the surrounding area, providing a path for interference.
Ungrounded Thermocouples: A thermocouple is ungrounded when the thermocouple wires are welded together but they are insulated from the sheath. The wires are often separated by mineral insulation.
Exposed Thermocouples (or “bare wire thermocouples”): A thermocouple is exposed when the thermocouple wires are welded together and directly inserted into the process. The response time is very quick, but exposed thermocouple wires are more prone to corrosion and degradation. Unless your application requires exposed junctions, this style is not recommended.
Ungrounded Uncommon: An ungrounded uncommon thermocouple consists of a dual thermocouple that is insulated from the sheath and each of the elements are insulated from one other.
Thermocouple Order Process
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