Process Control and Instrumentation Questions and Answers - Set 05 - ObjectiveBooks
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# Practice Test: Question Set - 05

1. According to Bode stability criterion, a system is unstable, if the open loop frequency response exhibits an amplitude ratio exceeding unity at frequency for which phase lag is
(A) 0°
(B) 45°
(C) 90°
(D) 180°

2. Find the ultimate gain and frequency for a proportional controller in the case of a process having the transfer function Gp(s) = 1/(4s + 1)(2s + 1)(s + 1).
(A) w = 1/√14, Kc = 45/7 √14
(B) w = √(7/6), Kc = 46/3
(C) w = 1, Kc = 13
(D) w = √(7/8), Kc = 45/4

3. The transfer function of a first order system is
(A) 1/(Ts + 1)
(B) 1/Ts
(C) s/(Ts + 1)
(D) None of these

4. Ordinary mercury in glass thermometer is used for measuring temperature upto 120°C. However, for measuring higher temperature upto _________ °C, thermometer is made by filling nitrogen under pressure above the mercury, which stops the evaporation of mercury and reduces the chance of broken thread of mercury.
(A) 250
(B) 350
(C) 550
(D) 700

5. Identify an unbounded input from inputs whose transfer functions are given below
(A) 1
(B) 1/S
(C) 1/S2
(D) 1/(S2 + 1)

6. Pyrometry refers to the measurement of temperature
(A) With the mercurial thermometer upto 350°C
(B) Directly
(C) Which is of higher magnitude
(D) All (a), (b) & (c)

7. Which of the following does not figure in the list of seven substances selected for international temperature scale?
(A) Ice (F.P) and steam (B.P)
(B) Oxygen and sulphur (B.P)
(C) Antimony and silver (F.P)
(D) Zinc (B.P) and mercury (F.P)

8. Which of the following is not suitable for measuring the temperature of a red hot object in the range of 800 - 1600°C?
(A) Optical pyrometer
(C) Photoelectric pyrometer
(D) Thermocouples

9. In a single tank system, the transfer function of _________ to inlet flow rate is 1/(TS+1).
(A) Outlet flow rate
(B) Level
(C) Both (a) & (b)
(D) Neither (a) nor (b)

10. Water is flowing through a series of four tanks and getting heated as shown in figure. It is desired to design a cascade control scheme for controlling the temperature of water leaving the tank 4 as there is a disturbance in the temperature of a second stream entering the tank 2. Select the best place to take the secondary measurement for the second loop.
(A) Tank 1
(B) Tank 2
(C) Tank 3
(D) Tank 4

11. Bode diagram are generated from output response of the system subjected to which of the following input?
(A) Impulse
(B) Step
(C) Ramp
(D) Sinusoidal

12. A first order system with unity gain and time constant τ is subjected to a sinusoidal input of frequency w = 1/τ. The amplitude ratio for this system is
(A) 1
(B) 0.5
(C) 1/√2
(D) 0.25

13. The frequency response of a first order system, has a phase shift with lower and upper bounds given by
(A) - ∞, π/2
(B) -π/2, π/2
(C) -π/2, 0
(D) 0, π/2

14. Silver point temperature is ________ °C.
(A) 760.5
(B) 860.5
(C) 960.5
(D) 1060.5

15. A photo electric device in which the resistance of the metal is directly proportional to the light striking on it, is known as photo-conductive cell. Photoelectric transducers are used for the measurement of those parameters, which can be used to produce variation in
(A) Light intensity
(B) Current
(C) Flux density
(D) Voltage

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