What is an ideal high temperature sensor setup with Type D and Type C wires inside?

There is in fact no standard ideal high temperature sensor setup, there is only the ideal setup for a particular environment and situation.

When designing a Type C and Type D thermocouple set up, the first step is to consider both what the (working) temperature will be and whether the atmosphere is oxidizing, reducing, inert or a vacuum?

The second step is to choose the appropriate sheath material and back fill gas according to the influencing factors in the first step. The sheath material needs to be able to protect the thermocouple wires from the effects of the temperature and atmosphere. Some considerations with regard to the sheath include:

• In a vacuum it is better for the sheath to be metallic than ceramic
• Some sheath materials are porous, does this affect the particular setup?
• Is the sheath compatible with the thermocouple wires?
• Sheath vaporization can occur at certain temperatures and can result in deposits on the thermocouple wires causing contamination and failures.
• If your setup is at risk of vaporization due to very high temperatures then you can consider a tungsten tube for the thermocouples. However, the tungsten tube will itself need a sheath of ceramic materials to protect it from the application environment.

These are a few examples of what needs to be considered in designing an ideal high temperature Type C or Type D thermocouple set up. Kamet is well equipped with knowledge and extensive experience with which to assist your engineers in choosing which thermocouples and sheaths have the specs that will match your specific situation. Please feel free to contact us for advice.