High-temperature thermocouples in oxidising atmospheres (~1600°C) Which thermocouple type is most suitable for measuring about 1600°C in an oxidising environment?

Introduction / Context: Selecting a thermocouple for very high temperatures demands attention to both temperature capability and atmosphere. Oxidising conditions quickly degrade base-metal thermocouples at extreme temperatures. Noble-metal combinations withstand oxidising atmospheres far better and maintain accuracy near 1600°C.

Given Data / Assumptions:

• Target temperature ≈ 1600°C.
• Atmosphere is oxidising (e.g., furnace air).
• Conventional industrial thermocouple types considered.

Concept / Approach: Platinum–platinum+rhodium (Types S or R) thermocouples are standard for high-temperature measurements in oxidising environments and are commonly used in ceramic kilns and metallurgical furnaces. Base-metal types like Iron–Constantan (Type J) and Copper–Constantan (Type T) have far lower temperature limits. Chromel–Alumel (Type K) handles moderately high temperatures but not reliably around 1600°C in oxidising atmospheres. Tungsten–rhenium requires inert or vacuum conditions; bare use in air is unsuitable due to oxidation.

Step-by-Step Solution:

Verification / Alternative check: Industry standards list Type S/R ranges up to around 1600–1700°C in oxidising atmospheres with proper protection tubes, confirming suitability.

Why Other Options Are Wrong:

Common Pitfalls: Choosing on maximum temperature alone without considering the atmospheric compatibility; atmosphere often dictates survivability.

Final Answer: Platinum–platinum + rhodium (noble metal type)