Radiation thermometer can not measure the temperature
A. Inside a pressure vessel
B. Of an object without coming in contact with it
C. Of liquid oxygen
D. Of moving objects at high temperature
Answer: Option C
Solution (By Examveda Team)
The correct answer is A: Inside a pressure vessel.Here's why:
A radiation thermometer works by detecting the infrared radiation emitted by an object.
This radiation travels through the air (or a vacuum) to the thermometer.
Option A: Inside a pressure vessel, the radiation thermometer cannot directly "see" the object whose temperature it needs to measure.
The vessel walls would block the radiation.
Think of it like trying to see something behind a solid wall – you can't!
Option B: Of an object without coming in contact with it is a key advantage of radiation thermometers; they measure temperature remotely.
Option C: Of liquid oxygen - Radiation thermometers *can* measure the temperature of liquid oxygen, even though it's very cold.
Everything emits some radiation.
Option D: Of moving objects at high temperature - Radiation thermometers are well-suited for measuring the temperature of hot, moving objects because they don't require physical contact.
This Question Belongs to Chemical Engineering >> Process Control And Instrumentation
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Related Questions on Process Control and Instrumentation
Phase lag of the frequency response of a second order system to a sinusoidal forcing function
A. Is 30°
B. Is 90° at the most
C. Approaches 180° asymptotically
D. Is 120°
Which of the following is not classified as a thermo electric pyrometer?
A. Resistance thermometer
B. Thermocouple
C. Optical pyrometer (disappearing filament type)
D. Radiation pyrometer
A. Chromel-alumel
B. Iron-constantan
C. Platinum-platinum/rhodium
D. None of these
The correct answer is:
A. Inside a pressure vessel
✅ Explanation:
A radiation thermometer (also called a pyrometer) measures temperature based on the thermal radiation (infrared or visible) emitted by a body. It does not require physical contact, making it ideal for:
Measuring moving objects (✔ D is incorrect)
Measuring objects from a distance (✔ B is incorrect)
Measuring cryogenic liquids like liquid oxygen, if emissivity is accounted for (✔ C is incorrect)
However:
Inside a pressure vessel, direct optical access is generally not possible due to the enclosed and pressurized environment, preventing the thermometer from “seeing” the object inside.
🧠 So:
Radiation thermometers cannot measure temperature inside a pressure vessel, unless there's a specially designed optical window that can withstand the pressure and still allow IR radiation to pass through — which is not common in standard setups.
👉 Hence, the correct answer is:
✅ A. Inside a pressure vessel.