Chemical Engineering - Process Control and Instrumentation - Discussion

3. 

Pick out the one which is a first order instrument.

[A]. Mercury in glass thermometer (without any covering or air gap).
[B]. Bare metallic thermometer.
[C]. Bare vapor pressure thermometer.
[D]. All (a), (b) and (c).

Answer: Option D

Explanation:

No answer description available for this question.

Bala Chandar said: (Nov 3, 2012)  
Thermometers for measuring temperature are first-order instruments. The time constant of a measurement of temperature is determined by the thermal capacity of the thermometer and the thermal contact between the thermometer and the body whose temperature is being measured.

A cup anemometer for measuring wind speed is also a first order instrument. The time constant depends on the anemometer's moment of inertia.

Madeshwaran said: (May 31, 2013)  
How to find out first order, second order instrument?

Parth said: (Sep 6, 2013)  
Up to I know if the mechanical parts of the system or fluid are subjected to acceleration, the dynamic behavior is described by second order system.

Chandru said: (Nov 20, 2018)  
Can anyone briefly explain how to find the first order and second order system?

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