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PI & C

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Process Control Question
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  2014 Asansol Engineering College M.Tech (EE) CAM-202 Process Instrumentation & Control Full Marks: 70 1.   a) How is PI action realized in pneumatic controllers? Explain with neat diagram. (5)  b) Why is integral control not used alone? (2) c) What do you mean by ‘reset time’ and ‘rate time’ of a PID controller? (2)  d) The transfer function of a PID controller is given as   ()(  )  Find the proportional gain, reset time and rate time of the controller. (5) 2.   a) What do you mean by tuning of controllers? (2)  b) What are the different methods of controller tuning? (3) c) What is process reaction curve? How is it obtained? Sketch it and show its various parameters that are used in controller tuning? (1+2+2) d) In the Ziegler-Nichols closed method of tuning, the critical gain was found to be 4.2, and the critical period was 2.21 mins. Find the standard settings for PID control. (4) 3.   a) Explain ratio control with example. (5)  b) Explain feed forward control technique with proper example. (7) c) What is the effect of differential gap or neutral zone on the performance of ON-OFF controller? (2) 4.   a) What is the function of a final control element in the process control loop? (2)  b) What do we mean by control valve sizing? Define valve coefficient? What is the necessity of control valve sizing? What are the factors taken care of while selecting a control valve? (1+2+2+3) c) Explain the principle of working of an I/P converter with a neat diagram. (4)  5.   a) Derive the expressions for position and velocity algorithm for implementation of a digital PID controller. (6)  b) What is integral windup? How can we overcome it? (3) c) A control valve regulates the liquid flow of a tank. The water level is controlled in the tank at a level of 8.3 m by regulating the outflow. The measured inflow varies from 0 to 300 c.c. /s. Calculate the value of valve coefficient. (5) 6.   a) Explain the working principle of a C-type bourdon tube with a neat diagram. (5)  b) Differentiate between RTD, thermocouple and thermistor on the basis of their various characteristics. (4) c) The current through an electric conductor is 1A when temperature of conductor is 0˚C and 0.7A when the temper  ature is 100˚C. Find the current when temperature of conductor is 1200˚C. (4) d) Define force summing devices. (1) 7.   a) Derive the Bernoulli’s equation for an incompressible fluid. (6)   b) Explain the principle of an ultrasonic level detector with a neat diagram. (5) c) In an ultrasonic transit time type flow meter, the b eat frequency is 805 Hz, the angle (θ)  between the transmitter and receiver is 45˚ and the sound path is 120 mm. Find the fluid velocity in m/s. (3) 8.   Write short notes on any two: (2x7=14) a)   Stepper Motor  b)   Ionization Gauge c)   Electromagnetic Flowmeter d)   Electronic PID Controller e)   DCS
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