Jawaharlal Nehru Technological University Hyderabad 2005-1st Sem B.Tech Applied Electronics and Instrumentation Code No: RR311004 Set No.3 IIIRegular s,- PROCESS CONTROL INSTRUMENTATIO

Code No: RR311004 Set No.3
III B.Tech. I Semester Regular Examinations, November -2005
PROCESS CONTROL INSTRUMENTATION
( Common to Electronics & Instrumentation Engineering and
Instrumentation & Control Engineering)
Time: three hours Max Marks: 80
ans any 5 ques.
All ques. carry equal marks
1. (a) Derive the transfer function H(S)/Q(S) for the liquid level system shown beneath
figure2. The resistances are linear. H and Q are deviation variables. Derive
the transfer function of the system.
(b) What modification you have to make in the transfer function if a disturbance
U occurs in inflow.
(c) Write the expression for the response if the above system experiences a step
change in Q. [6+5+5]
2. (a) provide 1 example for non-interacting 1st order elements in series.
(b) Write the dierential formula for this combination and determine the transfer
function.
(c) Comment on the transfer function. [3+10+3]
3. (a) Determine the controller actions current in the controllers provided beneath figure3.
Also obtain the proportional gain, derivative and integral time if they exist.
(b) A PI controller has Kp=5 and KI=6 sec. obtain the controller output for an
fault provided by ep =4 sin(t). Also obtain the phase shift ranging from fault and
controller output. [8+8]
4. (a) discuss with a neat sketch, the working principle of a displacement kind pneu-
matic proportional controller. explain the eect of adding the negative feed-
back.
(b) With necessary diagrams, define a hydraulic integral controller. discuss
how integral time can be adjusted.
5. (a) What is a optimum - tuning control? elaborate its dierent approaches?
(b) How are the interactions in control being channelized to optimize the control
action in a boiler? [8+8]
6. discuss the principle of a direct and reverse pneumatic actuator. [16]
7. A heating furnace requires a control valve passing 10gpm preheated light fuel oil
(SP.gr. = 0.8) at full load and only two gpm at the smallest heating load. The source
pressure constant at 50psi gage, but there is 10psi drop in the oil pre heater and
20 psi drop at the furnace burner nozzles. Remaining pressure drop occurs only at
control valve when it is fully opened.
(a) obtain out control valve size needed for the above application.
(b) obtain out needed rangeability of the valve
(c) obtain out characteristic coecient (). [6+4+6]
8. Draw the feed forward and feed back control systems that regulate the flow through
the pipe? explain about both the control systems and provide reasons to choose any of
the 2 systems in maintaining the desired flow?

Earning:   Approval pending.