High Temperature Sheathed Thermocouples

Sheathed thermocouples feature fast response, high pressure resistance, vibration resistance, and flexibility. With a measurement range from -200℃ to +1300℃, they are designed for demanding applications. WINNERS supplies thermocouple types K, N, E, J, T, and S, capable of meeting the requirements of various harsh industrial conditions such as high temperature and high pressure.

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Product Description

Sheathed Thermocouples (also known as Mineral-Insulated (MI) Thermocouples) are high-performance industrial temperature sensors designed for demanding applications. Key thermocouple types include K-type, N-type, E-type, J-type, T-type, and S-type, covering a broad temperature measurement range from -200°C to 1300°C.

Sheathed thermocouples are widely used across industries such as petroleum, chemical, power generation, metallurgy, and aerospace.

A sheathed thermocouple is a temperature sensor manufactured through a mechanical compaction process, integrating thermocouple wires, insulating material, and a metal sheath. It features flexibility, high-temperature resistance, and high-pressure tolerance. Compared with conventional thermocouples, the sheathed type has a smaller diameter and superior bendability, making it suitable for temperature measurement in narrow, hard-to-reach spaces, while also offering a rapid response.

Working Principle of Sheathed Thermocouples

The temperature measurement principle of a sheathed thermocouple is the same as that of a standard thermocouple, based on the Seebeck effect. When a temperature difference exists between the measuring junction (hot end) and the reference junction (cold end/connection end), a thermal electromotive force (EMF) is generated in the circuit formed by two dissimilar conductors. By measuring this thermal EMF, the temperature at the measuring junction can be determined.

Features of Sheathed Thermocouples

• Fast thermal response time and low dynamic error

• High mechanical strength, resistant to pressure, impact, and vibration

• Flexible installation due to bendability

• Resistant to high temperatures and corrosion

Applications of Sheathed Thermocouples

• Industrial process control: Temperature monitoring and control in pipelines, reactors, and other equipment in the petroleum, chemical, and power industries.

• High-temperature and metallurgical applications: Temperature measurement in high-temperature equipment such as kilns and blast furnaces in the steel and cement industries.

• Special environments: Fast-response or confined-space temperature measurement in aerospace engine testing and scientific research experiments.

• Demanding conditions: Complex working environments involving vibration, high pressure, requirements for bent installation, or the need for rapid response.

Types of Thermocouple Measuring Junction

Grounded type: The measuring junction is welded to the sheath, providing the fastest response. However, it is not suitable for conductive or corrosive media.

Ungrounded type: The measuring junction is electrically insulated from the sheath. It offers slightly slower response but strong noise immunity, is the most commonly used type, and has a long service life.

Exposed type: The measuring junction is exposed outside the sheath, delivering extremely fast response. However, the wires are prone to damage, limiting its use to dry, non-corrosive media.

Types of Thermocouples

Thermocouple Type	Measurement Range	Accuracy Class I	Accuracy Class II
K	-40 to 1200℃	±1.5℃	±2.5℃
N	-40 to 1200℃	±1.5℃	±2.5℃
E	-40 to 900℃	±1.5℃	±2.5℃
J	-40 to 750℃	±1.5℃	±2.5℃
T	-40 to 1000℃	±0.5℃	±1.0℃
S	0 to 1600℃	±1.0℃	±1.5℃