Thermocouple sensors differ from a conventional thermocouple types because of their smaller construction and their ability to be bent. Because of these features, they can be used in places that are difficult to access.
Assembly of a thermocouple sensor
This thermocouple type consists of an outer metallic sheath, which contains insulated internal leads that are embedded within a high-density ceramic compound (mineral-insulated cable, also called MI cable). Sheathed thermocouples may be bent to a minimum radius of five times the sheath diameter, and this thermocouple type is resistant to extreme vibration.
Inconel 600 or stainless steel are the sheath materials primarily used for this thermocouple type. Inconel 600 (2.4816 Ni alloy) is the standard material for high temperature applications requiring corrosion-resistance; and for applications requiring resistance to induced stress corrosion cracking and pitting when the media contains chloride. Thermocouple sensors constructed from Inconel 600 are resistant to halogens, chlorine, hydrogen chloride and ammonia in aqueous solutions. Thermocouple sensors constructed with 316 stainless steel provide strong resistance against aggressive media, and against vapor and combustion gases in chemical media.
In our extensive range of thermocouple types, you can find a suitable version for every application.
Frequently used thermocouple types:
Type K: NiCr-NiAl thermocouples are suitable for use in oxidizing or inert gas atmospheres up to 1200 °C (ASTM E230: 1260 °C) with the largest wire size.
Type J: Fe-CuNi thermocouples are suitable for use in vacuum; in oxidizing and reducing atmospheres; or inert gas atmospheres. They are used for temperature measurements up to 750 °C (ASTM E230: 760 °C) with the largest wire size.
Type N: NiCrSi-NiSi thermocouples are suitable for use in oxidizing atmospheres; in inert gas atmospheres; or dry reduction atmospheres up to 1200 °C (ASTM E230: 1260 °C). They must be protected from sulphurous atmospheres. They are very accurate at high temperatures. The source voltage (EMF) and the temperature range are almost the same as with type K. thermocouple. They are used in applications where a longer service life and greater stability are required.
Type E: NiCr-CuNi thermocouples are suitable for use in oxidizing or inert gas atmospheres up to 900 °C (ASTM E230: 870 °C) with the largest wire size.
Type T: Cu-CuNi thermocouples are suitable for temperatures below 0 °C with an upper temperature limit of 350 °C (ASTM E230: 370 °C) and can be used in oxidizing, reducing or inert gas atmospheres. They do not corrode in moist atmospheres.
To determine the thermocouple type for an application, consider the direct contact with the medium.
Type R, S and B thermocouples are also available with an embedded in MI cable. For assistance with temperature range, accuracy class and dimensions for these noble sheathed thermocouples, contact WIKA's techical support team at 1-888-431-1559 (press 1).
Tip designs of thermocouple sensors