Temperature ThermocouplesSensors are best suited to high temperature, environmental extremes, or applications requiring microscopic size sensors. They are also recommended for high vibration environments. Sensors generating varying voltage signals are thermocouples. They combine dissimilar metallic elements or alloys to produce a voltage. Using specific combinations of metals and alloys in the thermocouple’s legs produces a predictable change in voltage based on a change in temperature. Frequently you will have a choice of thermocouple types. Make your selection carefully, based on factors such as operating temperature, accuracy and EMF output required, and the atmosphere in which you plan to install the thermocouple.
Thermocouples classified by calibration type are:
- Type k- Thermocouple usually works in most applications since they are Nickel based and have good corrosion resistance. It is the most common sensor calibration type providing the widest operating temperature up to 1260 oC. It’s a good practice to protect this type of TC with a suitable metal sheathing or ceramic protecting tube, especially in reducing atmospheres .in oxidizing atmosphere such as electric furnaces, type K will generally outlast Type J because the Jp(iron) will rapidly oxidizes, especially at higher temperatures.
- Type J- Thermocouple is the Second most common calibrated and is a good choice for general-purpose application where moisture is not present. This type may be used exposed or
- Un-exposed, where there is a deficiency of free oxygen, for longer life & clines protective sheathing is recommended. Since JP (iron) wire will oxidize rapidly at temperatures over 540 oC, it is recommended larger gauge wires be used to compensate.
- Other TC types include: Type B, Type R, Type S, and Type T.