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Sardar Vallabhbhai National Institute of Technology 2012 B.Tech Mechanical Engineering Instrumentation and control - Question Paper

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SARDAR VALLABHBHAI NATIONAL INSTITUTE OF TECHNOLOGY, SURAT Mechanical Engineering Department B.Tech. -IV (Mechanical Engg.) Sem-VIII, 2011-12 End Sem Examination Subject: Instrumentation & Control (ME 408)

Time: 2 Hrs. Max. Marks: 50

Date- 03 /05/ 2012

Instructions: l.Only minimum required number of answers in order will be examined.

Extra answers if any will be ignored.

2. Attempt all questions.

3. Draw neat sketches, wherever necessary.

Q* 1 Explain with neat sketches transducer actuating mechanisms.

OR

Explain working of L.V.D.T. and also write its advantages and applications.

Q.2 A linear resistance POT is 50 mm long and is uniformly wound with a wire having (05)

a resistance of 10,000 Cl. Under normal conditions the slider is at the centre of the POT.

(i.) Find the linear displacement when resistances of POT as measured by a Wheatstone bridge for two cases are : (A.) 3760 Cl (B.) 7450 2. .

(ii.) If is feasible to measure value of 15 Q resistance with the above arrangements: find the resolution of POT in mm.

OR

A steel cantilever is 0.25 m long, 20 mm wide and 4 mm thick .

(A.) Calculate the deflection at the free end for the cantilever when a force of 25 N is applied at this end. For Steel E = 200 GN/m².

(B.) An LVDT with a sensitivity of 0.5 V/ mm is used. The voltage is read on a 10 V voltmeter having 100 divisions . The 2/10 th of a division can be read with certainty.

(C.) Calculate the minimum and maximum value of force that can be measured with this arrangement.

Q. 3 Explain the working of Linear & Angular motion Potentiometers (POT) (05)

with suitable sketches.

OR

Explain briefly the following transducers -

I. Capacitive transducers,

II. Strain gauges.

Q. 4 Write short note on following (Any TWO) (05)

I. Transducers classification,

II. A.C & D.C. signal conditioning equipment,

III. R.T.D and its applications,

IV. Gauge factor of strain gauge,

V. Thermistors. ^P-^T0

(15)

Q.5 Answer the followings (Any THREE)

(A) Draw and explain block diagram of automatic controller, actuator and

measuring element.

(B) Explain proportional plus derivative control action.

(C) Obtain a transfer function of a electrical cascade system.

(D) Derive steady state error for ramp input for 0,1 and 2 order systems.

(E) Explain linearization of hydraulic servo systems.

(15)

Solve followings (Any THREE)

Q.6

(A) A system has G(s) = K/[S(1+TS)] with unity feed back when K and T are constants. Determine the factor by which K should be multiplied to reduce the overshoot from 85% to 35%.

(B) For a system having characteristic equation 2S⁴ + 4S¹ +1 = 0, by using Routh Hurwitz Criteria. Determine (1) No. of roots in the left half of S plane. (2) No. of roots in the right half of S plane. (3) No of roots in the imaginary axis.

(C) Use Mesons gain formula to find the overall gain of the systems shown in figure 1.

(D) Obtain the block diagram for the signal flow graph as shown in figure 2.

In Figure 3, Di = 8 N / (rad/s), F = 12 N, k = 169 Nm,m=l kg,

(E)