Question

The devices which are used for the measurement of very high temperature are

• A. thermistors
• B. thermocouples
• C. pyrometers
• D. RTDs

Hint:

Whenever a temperature is too high for physical sensors to survive, non-contact optical/radiation methods like pyrometry are the only viable solution.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks to identify the class of temperature measurement devices suitable for very high temperatures (typically above $1500^\circ\text{C}$).

Step 2: Key Formula or Approach:
We evaluate the maximum operational temperature limits of each sensor type listed in the options.

Step 3: Detailed Explanation:

• Thermistors: High-sensitivity semiconductor devices, but their range is limited to low-to-medium temperatures (usually up to $300^\circ\text{C}$).

• RTDs (Resistance Temperature Detectors): Highly accurate platinum-based sensors, but typically limited to around $650^\circ\text{C}$ to $850^\circ\text{C}$.

• Thermocouples: Can measure higher temperatures up to around $1800^\circ\text{C}$ (using noble metal types like Type R or S). However, they require physical contact and degrade rapidly at very high temperatures.

• Pyrometers: These are non-contact temperature measurement devices that work on the principle of thermal radiation (Stefan-Boltzmann law). They can easily measure extremely high temperatures (up to $3000^\circ\text{C}$ or more) without physical contact with the hot object.

Step 4: Final Answer:
Pyrometers are used for the measurement of very high temperatures, which corresponds to Option (C).