[ 24 103 ]

M.Tech. Degree Examination

Industrial Process Instrumentation

First Semester

COMPUTER CONTROL OF PROCESSES

(Effective from the Admitted Batch of2003 - 2004)

Time: 3 Hours Maximum marks: 100

Answer any FIVE questions.All questions carry equal marks.

1. a) Explain the concept of state variable feedback with a block diagramand an example.

b) The state equations of a linear time-invariant system are represented

dx(t) = A x (t) + B utt),by d{ _-=-=- ~j

Find the state transition matrix and characteristic equation when

A= [: ~5] andB= [:]

2. Explain with a block diagram a computer based data acquisitionsystem with alarm facility required for a process industry wherein120 analog signals (each 4 - 20 mA) have to be logged. Give thedetails of the signal conditioning circuits and interfacing circuitsalso.

3. a) It is required to start motor A 5 minutes after START, button ispressed, motor B 10 minutes after motor A is started, and motorC 8 minutes after motor B is started. After one hour of combinedoperation, all the motors should be switched off simultaneously.Give the details of the PLC for this problem including ladder diagram.

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6. a) Discuss the merits and demerits of distributed control system overcentralised control system.

b) Explain the various functions carried out at the following levels ofhierarchy in a Des: field level, area control level, plant controllevel and plant management level.

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b) Explain why it is necessary to design a digital controller with all ofits poles being positive.

4. a) Discuss the significance of (i) sampling time, and (ii) order ofhold circuit on the design of digital controllers.

b) Explain Kalman's digital control algorithm by means of an example.

5. a) Describe a method of tuning digital P+I+D controller.b) Explain with a block diagram a self tuning control system in which

on-line system identification is used.

7. a) What is an industrial computer? List a few industrial computersavailable in the market. Describe the processing capabilities andother features of industrial computers.

b) Explain how personal computers are used for quality control in aprocess industry.

8. Write short notes on the following:

a) Cascade control

b) Features of commercial DeS

c) Analog and digital subsystems for process control computers

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[ 24 - 107 1M.Tech. Degree Examination

Industrial Process Instrumentationf .

First Semester

PROCESS DYNAMICS AND CONTROL

(Effective from the admitted batch of2007-2008)

Time: 3 Hours Maximum marks: 70, Answer any FIVE question's.All questions carry equal marks.

I. ;y) Draw the block diagram of a generalized feedback control systemand explain the function of each block.

b) A steady heat flow occurs in 1/8 inch thick carbon steel plate witharea of 2.0 sq.ft. The temperature drop is from 300°F to 160°F.Calculate the resistance, if thermal conductivity is 29 Btu/ftdeg+hr". Derive the expression used to compute the resistance.

-2.-a) Describe in detail, the process characteristics of.atypical.vThermalprocess" and its associated variables.

b) Determine the effective time constant for a 2-tank inter-dependentsystem when the outlet from bottom of the first tank is connectedto the bottom of the second and latter discharges to atmosphere,when the tank diameters are 6 ft and the levels are 10ft and 6 ftfor a flow of3000 ftYhr.

Q) a). Show that a liquid level system can be effectively controlled byusing a proportional controller with zero effect for servo problem .

.l1) Draw schematic and describe how op-amps can be used toimplement the proportional, integral and derivative modes of analogcontro!.

{J a). Describe how do you arrive for optimum controller settings in arTAE system.

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[ 24 - 107 1~ n the Ziegler-Nichols method, the critical gain was found to be 4.2,

and the critical period 'was 2.21 min. Find the standard settings for(i)propOltiona! mode control, (ii) PI control and (iii) Pro control.

<i) a) Explain the constructional details and operation of any two control

valves.b) An equal percentage valve has a maximum flow of 50 cm

3/sec

and a minimum of2 cmt/sec. lfthe full travel is 3 em, find the flow

at a 1 em opening.

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6. a) Explain briefly the principJes of different types of pneumatic

actuators.b) Explain how the saturation ofthe actuator affects the performance

of a PID controller. Suggest one scheme for overcoming theproblem. Explain its operation.

7. a) Describe the typical dynamic response 6f a controlled variable inan uncompensated feed-forward system. How is lead-lagcompensation introduced into the system?

b) Are the outer loops in the ~1RAC and STR configurations, offeedforward or feedback nature?

4) Describe the basic controls necessary in distillation process as case

study.

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M.Tech. Degree Examination

Industrial Process Instrumentation

First Semester

INDUSTRIAL INSTRUMENTATION

(Effective from the admitted batch 0[2007-2008)

Time: 3 Hours Maximum marks: 70

Answer any FIVE questions .•All questions carry equal marks.

0f,l What is force-balance principle? Differentiate the principle andperformance of the following feedback methods in pressuremeasurement. (8)

i) Force-balance and ii) Electrostatic feedback.l1) Explain the functioning of variable gap and variable dielectric type

capacitive transducers. Explain suitable circuits for A.C. and D.C.operation. (6)

2. a) Mention the three pressure standards along with their pressureranges. Describe a method of calibrating a pressure gauge of 0-10kg/ern- range. . (6)

31 Explain with a neat sketch, the working principle of a piezo electricpressure meter. What are the environmental effects that mayintroduce errors in measurements and how do you OVercomethem?

(8),....

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(:0 M' Describe the constructio~ and working principle of a magnetic flowmeter. What are its limitations? . (7)

.9f Why is it recommended to have smaller taper angle for rotameters?Give the relative merits and demerits of variable lead and variablearea flow meters. (7) .

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r 24 - 1091o afExplain the installation detajl~ and working of a Doppler typeultrasonic flow meter. Mention its advantages over transit-time typeflow meter. . (8)

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Explain the principJe of operation and applications of a vortexshedding type flow meter. (6)

5. a) Discuss a scheme of monitoring the flow in an oil pipe-linetransporting different petroleum products along the same line at

=-different times. Choose an appropriate transducer and signalconditioning circuitry and indicate the design procedure in detailand explain its operation. (8)

b) Discuss the working principle of a Turbine type flow meter with aneat sketch. State its drawbacks. (6)

@).a1 Explain the basic principle of ultrasonic radiation and microwavesensors for the measurement of liquid leyels. Describe anyonemethod with a neat schematic diagram. '" ',';, (8)

b) Describe a capacitance method or-measurement of powder levelin a'pharmaceutical industry. (6)

7, a) What is a local cell? Explain how do you measure static and dynamicforces using load cell. (8)

b) Design a -strain gauge load cell of cantilever type capable ofmeasuring a force of 5 N with an accuracy of 5% given that thegauge factor is 2, battery voltage 6 V, the cantilever is made ofmild steel and the read out resolution is 10-2 V. (6)

8. Write short notes on the following:Ji1IC pressure sensors, (3)b) NMR mass flow meter. (4)c) Hydraulic loadcell. (3)

fiDiaphragms and bellows for the measurement of levels, (4)

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r 24 - 106 1M.Tech. Degree Examination

Industrial Process Instrumentation

!First Semester

TRANSDUCERS AND MEASUREMENTS

(Effective from the admitted batchof2007-2008)

Time: 3 Hours Maximum marks: 70Answer any FNE questions.

Allquestions carry equal marks.

1. a) Give the step response of a second order instrument and explain.(4)

b? Elaborate on the static and dynamic characteristics of instruments.(4)

c) A second order instrument is subjected to a sinusoidal input.Undamped natural frequency is 3 Hz and the damping ratio is 0.5.Caleulate the amplitude ratio and phase angle for an input frequencyof2 Hz. (6)

2. a1 What are the effects of temperature changes on a strain gauge?How do you compensate for the effects? (6)

b) Two active strain gauges are connected in series in one of thearms of a Wheatstone bridge network. The bridge is adjusted initiallyfor balance. Assuming both the strain gauges are to be identical,derive the sensitivity of the bridge. Discuss the salient features ofthis arrangement. (8)

3. ~ Explain the basic principle of temperature measurement usingthermocouple. What materials are used for construction ofthermocouples? Discuss their properties. (8)

b) A thermistor has a resistance of 3980 ohms at the ice point (O°C)and 794 ohms at 50°C. Calculate the constants 'a' and 'b'. Calculatethe range of resistance to be measured in case the temperaturevaries from 40°C to 100°C, (6)

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{ 24 - 106 14'. M What are piezo electric transducers? Explain the modes of operation

of a piezo electric force transducer with a neat sketch. (8). b) A quartz piezo electric crystal having a thickness of 2 mm and•~ voltage sensitivity 0[0.055 V-mfN is subjected to a pressure of 1.5

MN/m2• Calculate the voltage output. ffthe permittivity of quartzis 40.6 x J 0-12 Flm, calculate its charge sensitivity. (6)

5. a) Explain the pulse-cooling technique adopted in an industry tomeasure the temperature of a hot gas with necessary diagramsand equations. (8)

b) Derive the necessary expression for the dynamic response of amanometer for laminar flow case and discuss the result obtained.

(6)

6. a) Explain Hall effect and show how this effect may be used formeasurement of (i) magnetic fields, (ii) high currents and (iii)electrical power. . (8)

b) What is .meant· by magnetostriction? What are the merits ofmagnetostriction transducers? Outline the constructional featuresand principle of working of a magnetostrictive transducer for themeasurement of force. (6)

7'. a) What is the basic difference in the characteristics of ionizationchambers on one hand and radioactivd pulse counters on the other?Explain the principle of operation of an' ionization chamber. (6)

b) Distinguish clearly between photo emissive, photo conductive andphoto-voltaic phenomena and indicate one application of each andexplain their operation. (8)

8. Write short notes on the following:a) Frequency modulated and frequency generated transducers.

(5)..}I)) Digital transducers. . (4)o Bourdon tube and its applications. (5)

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