Instrumentation and Process Control GATE-2015

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Q 1. Match the output signals as obtained from four measuring devices in response to a unit step change in the input signal.





Ans is C)

Explanation:

Q 2. The transfer function for the disturbance response in an open-loop process is given by G_d^{open}\left(s\right) . The corresponding transfer function for the disturbance response in a closed-loop feedback control system with proportional controlled is given by G_d^{closed}\left(s\right) . Select the option that is ALWAYS correct {O[G(s)] represents order of transfer function G(s)}:





Ans is D)

Explanation:

Q 3. Which one of the following transfer functions, upon a unit step change in the disturbance at t = 0, will show a stable time domain response with a negative initial slope (i.e., slope t = 0):





Ans is A)

Explanation:

Q 4. The block diagram for a process with feedback control for output deviation variable h is shown in the figure below. All transfer functions are given with pre-factor of s in minutes. A unit step change is made in the set-point at t = 0. The time required for h to reach 50% of its ultimate value, in minutes (up to two decimal places), is: __________________

Ans is 0.86 to 0.9)

Explanation:

Q 5. Consider a control system with the open loop transfer function given by:

G_{OL}\left(s\right)=\frac{K_ce^{-0.3s}}{1.5s+1}

In the above function, pre-factor of s is in minutes and Kc­is the gain of proportional controller. The frequency for phase margin of 30o is 4.04 rad/min. The value of Kc for a gain margin of 1.7 (up to one decimal place) is _______________.

Ans is 3.5 to 3.7)

Explanation: