To what extent can the diameter of the thermode be reduced to effectively reduce the thermal inertia of the thermocouple?

Generally speaking, under the premise of meeting the requirements of thermocouple strength and resistance, reducing the thermode diameter to about 1/2 to 1/3 of the original diameter can effectively reduce the thermal inertia of the thermocouple. For example, for the commonly used thermocouple with a diameter of 1.5mm, when it is reduced to about 0.5-0.8mm, the thermocouple's response speed to temperature changes will be significantly faster.
However, different application scenarios and thermocouple types have different requirements for thermode diameter. In some occasions where the temperature response speed is extremely high, such as the temperature measurement of the combustion chamber of an aircraft engine, it may be necessary to further reduce the thermode diameter to 0.3mm or even smaller. For some ordinary industrial temperature measurements, reducing the thermode diameter to 1.0-1.2mm can usually meet the needs of reducing thermal inertia, while also ensuring the reliability and service life of the thermocouple.