Process Control and Instrumentation

141. Phase lag of the frequency response of a second order system to a sinusoidal forcing function

  1. Is 30°
  2. Is 90° at the most
  3. Approaches 180° asymptotically
  4. Is 120°

Correct answer: (C)
Approaches 180° asymptotically

142. Phase lag of the sinusoidal response of a first order system is

  1. 120°
  2. 30°
  3. 180°
  4. 90°

Correct answer: (D)
90°

143. Phase margin is equal to

  1. 180° - phase lag
  2. Phase lag - 180°
  3. Phase lag + 180°
  4. Phase lag + 90°

Correct answer: (A)
180° - phase lag

144. Photoelectric pyrometers are suitable in the temperature range of _________ °C.

  1. 400-1600
  2. 800-1600
  3. 800-2500
  4. 400-1000

Correct answer: (B)
800-1600

145. Pick out the first order system from among the following.

  1. Damped vibrator
  2. Mercury in glass thermometer kept in boiling water
  3. Interacting system of two tanks in series
  4. Non-interacting system of two tanks in series

Correct answer: (B)
Mercury in glass thermometer kept in boiling water

146. Pick out the most suitable instrument for measuring temperature in the range of-40 to 425°C.

  1. Mercury thermometer
  2. Bimetallic thermometer
  3. Radiation pyrometer
  4. None of these

Correct answer: (B)
Bimetallic thermometer

147. Pick out the one which is a first order instrument.

  1. Mercury in glass thermometer (without any covering or air gap)
  2. Bare metallic thermometer
  3. Bare vapor pressure thermometer
  4. All (A), (B) and (C)

Correct answer: (D)
All (A), (B) and (C)

148. Pick out the wrong statement

  1. Proportional controller is normally used for level control in industrial applications
  2. CSTR can be considered as a distributed parameter system
  3. Distributed parameter approach gives partial differential equation
  4. Non-linear behaviour is exemplified by an on-off controller

Correct answer: (B)
CSTR can be considered as a distributed parameter system

149. Pick out the wrong statement.

  1. There is no transfer lag for a single first order system
  2. Stirred tank with a water jacket exemplifies an interacting system
  3. Transfer lag is a characteristic of all higher order systems (other than first order systems)
  4. Transfer lag decreases as the number of stages decreases

Correct answer: (D)
Transfer lag decreases as the number of stages decreases

150. Pirani gauge is used for the measurement of

  1. Very high pressure
  2. High vacuum
  3. Liquid level under pressure
  4. Liquid level at atmospheric pressure

Correct answer: (B)
High vacuum

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