M&I 2marks,16marks,Problems

ASSIGNMENT QUESTIONS

MEASUREMENT AND INSTRUMENTATION

UNIT - I - INTRODUCTION

Part - A

1.1. Define an instrumentation system.

1.2. Classify the instruments.

1.3. What are the applications of a measuring system?

1.4. Distinguish between the direct and indirect methods of measurements. [AU,

Nov/Dec - 2007]

1.5. What are the functional elements of a generalised measurement system?

1.6. Explain the significance of negative feedback. [AU, April / May

- 2008]

1.7. List out the static characteristics.

1.8. When are static characteristics important? [AU, May/June - 2006, April /

May - 2008]

1.9. Define scale range and scale span. [AU, April / May

- 2010]

1.10. What do you mean by drift? Differentiate zero drift and span drift.

1.11. Define reproducibility.

1.12. Differentiate between accuracy and precision.

1.13. What is static sensitivity?

1.14. Define speed of response.

1.15. Define fidelity.

1.16. Define measuring lag.

1.17. What are the dynamic characteristics of a measurement system? Distinguish

between steady state response and transient response.

1.18. What is the importance of dynamic characteristics of systems? [AU, Nov/Dec

- 2008]

1.19. Define resolution.

1.20. Differentiate Resolution from Threshold. [AU, Nov/Dec -

2009]

1.21. What are the types of error?

1.22. Define static error. Classify the types of static error. [AU, Nov/Dec

- 2009]

1.23. Define dynamic error.

1.24. What are the three categories of systematic error?

1.25. How are the absolute and relative errors expressed mathematically?

[AU, Nov/Dec - 2009]

1.26. Define limiting error or guarantee error. [AU,

Nov/Dec - 2008]

1.27. Define relative limiting error.

1.28. What are the main reasons for instrumental errors? [AU, Nov/Dec -

2007]

1.29. List out the corrective measures to eliminate environmental errors.

1.30. What are random errors?

1.31. What is meant by quantization error? [AU,

Nov/Dec - 2008]

1.32. Define arithmetic mean, range, deviation and average deviation.

1.33. Define standard deviation. [AU, April/May -

2010]

1.34.. Define variance.

1.35. Define confidence interval and confidence level.

1.36. A set of independent current measurements was taken by observers and recorded as 12.8mA, 12.2mA, 12.5mA, 13.1mA, 12.9mA and 12.4mA. Calculate the (a) arithmetic mean (b) deviation from the mean.

1.37. What is a standard? What are the different types of standards? [AU,

May/June - 2006]

1.38. Classify the standards of measurement.

1.39. What is the difference between primary and secondary standards?

1.40. Give the advantages of atomic standard.

1.41. Define calibration.

1.42. What is the significance of calibration? [AU, April / May

- 2008]

1.43. Why is feedback necessary in instrumentation systems?1.44. Why must instruments be calibrated? [AU,

Nov/Dec - 2008]

Part - B

1.45. What are the basic blocks of a generalised instrumentation system? Draw the various blocks and explain their function with an example of Bourdon Tube pressure gauge. [AU, April / May - 2010,

May/June - 2009Nov/Dec - 2007,09]

1.46. Discuss in detail the various dynamic and static characteristics of a measuring system.

[AU, April / May - 2010, Nov/Dec - 2008,09]

1.47. Define and explain the following static characteristics of an instrument.

(a) accuracy (b) resolution (c) sensitivity (d) linearity

[AU, May/June -

2006]

1.48. Explain the different types of errors that occur in a measuring instrument and discuss the methods adopted to minimise these errors. [AU, April/may - 2010,

Nov/Dec - 2007,09]

1.49. Discuss briefly on the types of instrument errors and instrument faults.


1.50. Define and explain the types of static errors possible in an instrument

[AU, May/June - 2006]

1.51. Define the following terms in the context of normal frequency distribution of data.

a) mean value b) deviation c) average deviation d) variancee) standard deviation. [AU,

Nov/Dec - 2007]

1.52. Explain in detail Normal or Gaussian curve of errors and discuss the precision index. [AU, May / June -

2009]

1.53. Explain the method of treatment of single sample data with the help of uncertainty analysis by giving suitable example. [AU,

May / June - 2009]

1.54. Give the methods of using any three standard inputs being used for analysing the dynamic response of system with neat sketches. [AU, April / May -

2008]

1.55. Classify and explain the different types of standards of measurments.


1.56. Write briefly on instrument standards. [AU, April / May -

2008]

1.57. Explain in detail calibration technique and draw the calibration curve in general.

[AU, April / May - 2010, Nov/Dec -

2007]

PROBLEMS1.58. At the input an amplifier has a signal voltage of 3mV and a noise voltage

level of 1mV. What is the signal to noise ratio at the input?

a) If the voltage gain of an amplifier is 20, what is the S/N ratio at the output?

b) If the amplifier adds of noise, what is S/N ratio at the output? Calculate the noise factor and the noise figure.

1.59. A Wheatstone bridge requires a change of 7 in the unknown arm of the bridge to produce a change in deflection of 3mm of the galvanometer. Determine the sensitivity. Also determine the deflection factor.

1.60. The dead zone in a certain pyrometer is 0.125% of span. The calibration is 400oC to 1000oC. What temperature change might occur before it is detected?

1.61. A moving coil voltmeter has a uniform scale with 100 divisions, the full scale readings is 200V and 1/10 of a scale division can be estimated with a fair degree of certainty. Determine the resolution of the instrument in volt.

1.62. A digital voltmeter has a read - out range from 0 to 9,999 counts. Determine the resolution of the instrument in volt when the full scale reading is 9.999V.

1.63. The value of capacitance of a capacitor is specified as 1F + 5% by the manufacturer. Find the limits between which the value of the capacitance is guaranteed. The guaranteed value of the capacitance lie within the limits.

1.64. 0-15V voltmeter has a guaranteed accuracy of 1% of full scale reading. The voltage measured by this instrument is 75V. Calculate the limiting error in percentage.

1.65. The expected value of the voltage across a resistor is 80V. However the measurement gives a value of 79V. Calculate the (a) absolute error (b) % error (c) relative accuracy (d) % of accuracy.

1.66. A current passing through a resistor of 100 + 0.2V is 2 + 0.01A. Using the relationship I2R, calculate the limiting error in the computed power dissipation.

1.67. A 0 - 10A ammeter has a guaranteed accuracy of 1.5% of full scale reading. The current measured by the instrument is 2.5A. Calculate the limiting values of current and the percentage limiting error.

1.68. A meter reads 127.50V and the true value of the voltage is 127.43 V. Determine the (a) static error (b) static correction for the instrument.

1.69. The thermometer reads 95.45oC and the static correction given in the correction curve is - 0.08oC. Determine the true value of the temperature.

1.70. A voltage has a true value of 1.50V. An analog indicating instrument with a scale range of 0-2.50V shows a voltage of 1.46V. What are the values of absolute error and correction . Express the error as a fraction of the true value and the full scale deflection.

1.71. A thermometer is calibrated 150oC to 200oC. The accuracy is specified to be within + 0.25% of instrument span. What is the maximum static error?

1.72. A circuit was tuned for resonance by eight different students, and the values of resonant frequency in KHz were recorded as 532, 548, 543, 535, 546, 531, 543 and 536. Calculate the (a) arithmetic mean (b) deviations from the mean (c) average deviation (d) standard deviation.

1.73. If the rms value of reading in volts are observed in a digital CRO were 3.5, 3.452, 3.620,3.523, determine the (i) arithmetic mean (ii) average deviation (iii) standard deviation. [AU,

April / May - 2008]

1.74. If a set of six observations are as follows: 1.5 V, 3 V, 1 V, 5 V, 2 V, 4 V, calculate the arithmetic mean, average deviation and standard deviations. [AU, Nov/Dec - 2008]

1.75. A set of independent current measurements were recorded as 10.03, 10.10, 10.11 and 10.08. Calculate the (a) average current (b) range of error.

UNIT - II - ELECTRICAL AND ELECTRONIC INSTRUMENTS

Part - A

2.1. What are the types of analog ammeters and voltmeters?

2.2. How are the analog instruments classified on the basis of method used for comparing the unkown quantity? [AU,

May/June - 2009]

2.3. What are the advantages of digital instruments over analog instruments? [AU,

Nov/Dec - 2008]

2.4. What are the essential torque required for operating an instrument? [AU,

Nov/Dec - 2009]

2.5. What are the merits of PMMC instruments?

2.6. How can a PMMC meter be used as voltmeter and ammeter? [AU, Nov/Dec

- 2007]

2.7. Distinguish between an ammeter and a voltmeter. [AU, Nov/Dec -

2009]

2.8. What are the applications of induction type instruments?

2.9. What are the general requirements of a shunt?

2.10. What is Ayrton shunt (or) Universal shunt?

2.11. How will you convert a basic meter into a DC voltmeter?

2.12. How can the range of a voltmeter be extended?

2.13. What are the main sources of error in moving coil instruments?

2.14. Give the principle of working of a moving iron instrument. [AU,

Nov/Dec - 2007]

2.15. What are the advantages and disadvantages of moving iron instruments?

2.16. What is a transfer instrument?

2.17. What type of damping is employed in electrodynamometer types instruments?

2.18. How are electrothermic instruments classified?

2.19. What are the advantages of rectifier type instruments?

2.20. What are the considerations in choosing an analog voltmeter?

2.21. What is DVM?

2.22. List out the types of DVM.

2.23. List the advantages of digital voltmeter. [AU, April/May - 2010]

2.24. Explain the following terms as applied to digital displays 3 ½ digit and

4 ½ digit display. [AU, Nov/Dec -

2007]

2.25. How are resistors and diodes checked using digital multimeters? [AU,

Nov/Dec - 2008]

2.26. What are the types of wattmeters?

2.27. What is ampere-hour and watt-hour? [AU, April / May - 2008]

2.28. Why is an ordinary electrodynamometer wattmeter not suitable for measurement of power in low power factor circuits?

2.29. What are the errors caused in wattmeters?

2.30. What are the advantages and limitations of induction type wattmeters?

2.31. What are the types of energy meters?

2.32. What are the errors caused by the driving system in energy meters?

2.33. Which torque is absent in energy meter? Why? [AU, May/June - 2006]

2.34. What are the adjustments carried out in energy meters to correct the errors?


2.35. What is the principle of polyphase energy meters?

2.36. What are the types of tests on magnetic materials?

2.37. What are the principle requirements in magnetic measurement?

2.38. What are the reasons for inaccuracies in magnetic measurement?

2.39. What are the methods available to determine BH curve and hysteresis loop?

2.40. Explain the principle of permeameters.

2.41. Define leakage factor.

2.42. What are the methods of iron loss measurements?

2.43. What are the methods of measurement of air gap flux?

2.44. What is the important use of instrument transformers?

2.45. What are the advantages of instrument transformers?

2.46. What is the need to evaluate phase-angle error in instrument transformers?

[AU, April / May - 2008]

2.47. Define transformation ratio.

2.48. Define nominal ratio.

2.49. Define turns ratio.

2.50. What is meant by burden?

2.51. What are the characteristics of current transformers?

2.52. What are the causes of errors in current transformers?

2.53. Differentiate C.T. and P.T.

2.54. What are the possible errors in P.T.?

2.55. What are the modifications possible in the design, to reduce the errors?

2.56. What are the characteristics of P.T.?

2.57. What are methods of testing instrument transformers?

2.58. What are the types of power factor meters?

2.59. List out the advantages and disadvantages of moving iron power factor meter.

2.60. List out the different types of frequency meters.

2.61. Give the principle of working of vibrating reed type frequency meter.

2.62. What is phase meter? Mention the types of phase meter. [AU,

Nov/Dec - 2009]

2.63. Explain the principle of digital phase meter. [AU, April/May - 2010, May/June

- 2006]

2.64. Define synchronizing.

Part - B2.65. Describe the various operating forces needed for the proper operation of an

analog indicating instrument. [AU, Nov/Dec -

2008]2.66. Describe the construction and working of a PMMC instrument. Derive the

equation for deflection if the instrument is spring controlled.

2.67. Develop the torque equation for a PMMC instrument and show that its scale is linear

2.68. How is the current range of a PMMC instrument extended with the help of shunts?

2.69. Describe the working of the universal shunt which is used for multirange ammeters.

2.70. Explain the working of (i) an attraction type and (ii) a repulsion type of moving iron instruments with the help of neat diagrams. Explain why these meters can be used on both A.C and D.C [AU, April/May - 2010]

2.71. Describe the constructional details of an electrodynamometer type instrument. Derive the expression for the torque when the instrument is used on A.C. [AU, May/June - 2006]

2.72. Describe the errors in electro dynamometer type instuments.

2.73. Describe the working of a ramp type and integrating type digital voltmeter [AU, May/June - 2006]

2.74. Explain the functioning of a potentiometric type digital voltmeter and sucessive approximation type DVM. [AU,

April/May - 2010]

2.75. Write a note on analog multimeter. Draw and explain the basic block diagram of DMM.

2.76. Describe the constructional details of an electrodynamometer type wattmeter. Derive the expression for torque when the instrument is used on a.c. [AU, Nov/Dec - 2009]

2.77. With neat figures, explain the construction, working principle of a three phase wattmeter. What is the importance of deflection torque in these analog instruments?

[AU, April / May - 2008]

2.78. Describe the constructional details of a single phase induction type energymeter.

[AU, May/June - 2009, Nov/Dec -

2009]

2.79. Explain the sources of errors in a single phase induction type energymeters.

2.80. Describe the construction and working of a two element induction type energymeter.

2.81. Explain the working of a 3 phase wattmeter. Draw a neat sketch of the wattmeter and also its connection.

2.82. Describe the constructional details and working of a single phase electrodynamometer type of power factor meter.

2.83. Describe a method of experimental determination of flux density in a specimen of magnetic material using a ballistic galvanometer.

2.84. Explain the method for experimental measurement of magnetising force acting on a specimen of magnetic material.

2.85. Explain the construction and working of a magnetic potentiometer. 2.86. Explain the different methods of determination of a B-H curve.

[AU, April / May - 2010, May/June - 2006]

2.87. Write briefly with neat figures on (i) principle of operation of a current transformer.(ii) B.H. curve analysis of a magnetic circuit. [AU, Nov/Dec -

2008]

2.88. Write short notes on: (i) working of single phase energy meter. (ii) current transformer. [AU, April / May -

2008]2.89. Describe the different methods for the measurement of iron losses in a

specimen of lamination. 2.90. Explain with neat sketch the classification of Instrument Transformers. Write

a note on the errors affecting the characteristics of an Instrument Transformer. [AU, Nov/Dec - 2009]

2.91. Describe how high currents and voltages are measured with the help of instrument transformers.

2.92. Draw the equivalent circuit and phasor diagram of a current transformer. Derive the expressions for ratio and phase angle errors.

2.93. Describe the working of a capacitive type potential transformer.2.94. Describe the construction, principle of working and applications of synchro

transformers.


2.95. What are the different methods of measurement of frequency in the power frequency range ?

2.96. Explain the working of a mechanical resonance type frequencymeter.2.97. Explain in detail mechanical resonance type frequency meter and electrical

resonance type frequency meter. [AU,

Nov/Dec - 2009]

2.98. Describe the construction and functioning of a mechanical type (vibrating reed type) frequency meter. [AU,

May/June - 2009]

2.99. Explain the functioning of ferro-dynamic type electrical resonance frequency meter.

[AU, May/June -

2009]

2.100. With a neat block diagram, explain the working principle of a digital frequency meter.


2.101. Explain the phase meter principles empolyed in a measuring equipment. 2.102. Draw and explain digital phase meter. 2.103. Discuss why it is necessary to carry out frequency domain analysis of

measurement systems. What are the two plots obtained when the frequency response of a system is carried out?


PROBLEMS2.104. A permanent magnet moving coil instrument has a coil of dimensions 15mm

x 12mm. The flux density in the air gap is 1.8 x 10-3 Wb/m2 and the spring constant is 0.14 x 10-6 Nm/rad. Determine the number of turns required to produce an angular deflection of 90 degrees when a current of 5mA is flowing through the coil.

2.105. A moving coil voltmeter with a resistance of 20V gives a full scale deflection of 120o when a potential difference of 100mV is applied across it. The moving coil has dimensions of 30mm x 25mm and is wound with 100 turns. The control spring constant is 0.375 x 10-6 Nm/deg. Find the flux density in the air gap. Find also the diameter of copper wire of coil winding if 30% of instrument resistance is due to coil winding. The specific resistance for copper = 1.7x10-8Vm.

2.106. A 1mA meter d' Arsonval movement with an internal resistance of 100V is to be converted into a 0-100mA ammeter. Calculate the shunt resistance required. What particulars should be specified on the shunt?

2.107. Find the multiplying power of a shunt of 200V resistance used with a galvanometer of 1000 V resistance. Determine the value of shunt resistance to give a multiplying power of 50.

2.108. A simple shunted ammeter using a basic meter movement with an internal resistance of 1800V and a full scale deflection current of 100mA is connected

in a circuit and gives a reading of 3.5mA on its 5mA scale. This reading is checked with a recently calibrated dc ammeter which gives a reading of 4.1mA. The implication is that the first ammeter has a faulty shunt on its 5mA range.

Calculate the (a) actual value of faulty shunt

(b) correct shunt for the 5mA range.

2.109. Design a multi - range dc milli - ammeter using a basic movement with an internal resistance R

m=50V and full scale deflection current I

m = 1mA. The

ranges required are 0-10mA ; 0-50mA; 0-100mA ; 0-500mA.

2.110. A moving coil instrument gives a full scale deflection of 10mA when the potential differences across its terminals is 100mV. Calculate the (a) shunt resistance for a full scale deflection corresponding to 100A (b) series resistance for full scale reading with 1000V. Calculate the power dissipation in each case.

2.111. What is the resolution of a 3½ digit display on the 1V and 10V ranges?

2.112. A 4½ digit voltmeter is used for voltage measurements. Find its resolution. How would 12.98V be displayed on a 10V range?

2.113. In a dynamometer watt meter, the moving coil has 500 turns of mean diameter 30mm. Estimate the torque if the axes of the field and the moving coils are at (a) 60o (b) 90o when the flux density produced by field coils is 15 x 10-3 Wb/m2, the current in moving coil is 0.05 A and the power factor is 0.866.

2.114. A wattmeter has a current coil of 0.03 V resistance and a pressure coil of 6000 V resistance. Calculate the percentage error if the wattmeter is so connected that the :

(a) current coil is on the load side

(b) pressure coil in on the load side

i) if the load takes 20A at a voltage of 220V and 0.6 power factor in each case.

ii) what load current would give equal errors with the two connections?

2.115. A 3 phase 500V motor load has a power factor of 0.4. Two wattmeters are connected to measure the input. They show the input to be 30KW. Find the reading of each instrument.

2.116. The meter constant of a 230V, 10A watthour meter is 1800 revolutions per KWh. The meter is tested at half load with rated voltage and unity power factor. The meter is found to make 80 revolutions in 138s. Determine the meter error at half load.

2.117. A constant of a given magnetic potentiometer is obtained by a coil of 300 turns in which a current of 0.6A is reversed. The resulting throw of the galvanometer is 157 scale divisions. It is then used to measure the magnetic

potential difference between two points and the throw is 304 divisions. Find the magnetic potential difference.

2.118. The name plate of a single phase energy meter installed in a house reads 1200 rev/KWh. If 6 lamps of 100W and 5 lamps of 60W are operated for one hour, the disc makes 1100 revolutions. State whether the meter reads correctly or not.

UNIT - III - COMPARISON METHODS OF MEASUREMENTS

Part - A3.1. What is a potentiometer?3.2. Describe the basic principle of operation of a d.c. potentiometer.3.3. Explain the term standardization of a potentiometer.3.4. What are the various types of potentiometers?3.5. What is an isolation amplifier? Where is it used? [AU, Nov/Dec -

2009]

3.6. Define true zero.3.7. What are the applications of DC potentiometers?3.8. What are the various types of AC potentiometers?3.9. Give the applications of AC potentiometers3.10. What is a standard cell dial?3.11. What is a volt-ratio box?3.12. What are active and passive bridge circuits? [AU, April /

May - 2008]

3.13. What are the uses of bridge circuits?3.14. Give the applications of Wheatstone bridge.3.15. What are the limitations of Wheatstone bridge?3.16. State the condition for balance in a Wheatstone bridge. [AU, Nov/Dec -

2009] 3.17. What is the use of Kelvin's bridge?3.18. What are the features of impedance measuring instruments?3.19. Mention any four types of A.C. bridges. [AU, Nov/Dec

- 2009]

3.20. Draw the circuit of Maxwell's bridge. [AU, Nov/Dec - 2007]

3.21. Compare Hay's bridge and Schering's bridge.3.22. What is the purpose of using Wien's bridge?3.23. What are the precautions to be taken when using a bridge?3.24. What is a transformer ratio bridge?3.25. What is the role of toroidal core in a trapped ratio transformer? [AU,

May/June - 2009]

3.26. What are the various parameters you can measure using the transformer ratio bridge?

3.27. Give the applications of ratio transformer.3.28. Give the features of ratio transformer.3.29. What is meant by self-balancing bridge? Give some example.3.30. Give the applications of self-balancing bridge.3.31. What is interference?3.32. What are the various types of interference?3.33. What is electromagnetic interference in instruments? [AU, Nov/Dec

- 2008]

3.34. What is screening?3.35. What is the use of electrostatic and electromagnetic screens?3.36. What are leakage current effects? [AU, April / May -

2008]

3.37. Define multiple earth.3.38. What are the main causes of earth loop current? [AU, Nov/Dec -

2009]

3.39. What is meant by grounding?

3.40. List the techniques to reduce the ground loop interference signals [AU,

April/May - 2010]

3.41. What are the various grounding techniques? [AU, Nov/Dec -

2007]

PART - B

3.42. Describe the basic principle of operation of a dc potentiometer.

3.43. Explain the term standardization of a potentiometer. Describe the procedure of standardization of a dc potentiometer.

3.44. Draw the circuit diagram of a Crompton's potentiometers or laboratory type dc potentiometer and explain its working.

3.45. Describe the working of a duo-range potentiometer by drawing its circuit diagram. Explain its advantages.

3.46. With fundamentals, distinguish between DC and AC potentiometers and give any two specific applications for each. [AU,

Nov/Dec - 2007]

3.47. What is a volt - ratio box? Explain its construction, working and applications.

3.48. Describe with the help of suitable diagrams, how a dc potentiometer can be used for

(i) calibration of a voltmeter (ii) calibration of an ammeter (iii) calibration of a wattmeter (iv) determination of an unknown resistance.


3.49. Describe the working of a self balancing potentiometer with the help of a diagram for the measurement of temperature using a thermocouple.

3.50. Describe the construction and working of a polar type potentiometer. How is its standardized? What are the functions of the transfer instrument and the phase shifting transformer?

3.51. Describe the construction and working of a co-ordinate type ac potentiometer.

3.52. Explain with suitable diagrams, how ac potentiometers can be used for

(i) calibration of voltmeters (ii) calibration of ammeters (iii) calibration of wattmeters and energymeters (iv) measurement of reactance of a coil.

3.53. Derive the expression for bridge sensitivity for a Wheatstone bridge with equal arms. Find also the expression for current through the galvanometer for a small imbalance. [AU, May/June -

2009]

3.54. Explain the principle of working of a Kelvin's double bridge and explain how the effect of contact resistance and resistance of leads are eliminated.

3.55. Derive the general equations for balance for an A.C. bridge and describe the sources and null detectors that are used for A.C. bridge.

3.56. Derive the bridge balance condition for the Maxwell bridge and Schering bridge. [AU, Nov/Dec - 2008,09]

3.57. Describe the working of a low voltage Schering bridge. Derive the equations for capacitance and dissipation factor. [AU, April/May - 2010]

3.58. Derive the equations of balance for an Anderson's bridge Draw the phasor diagram for conditions under balance.

3.59. Explain how Wein's bridge can be used for experimental determination of frequency. Derive the expression for frequency in terms of bridge parameters.

3.60. Explain the purpose of a Hay's bridge. Draw the necessary phasor diagram.3.61. Describe what do you understand by the term ratio transformer. Explain the

construction of a ratio transformer and describe its uses.3.62. Explain how a ratio transformer bridge can be used for the measurement of (i) resistance ii) capacitance (iii) phase angle. 3.63. With a neat sketch explain the construction and working principle of self-

balancing bridge. [AU, Nov/Dec - 2007]

3.64. Explain the classification of external interference signals. 3.65. Explain in detail about electrostatic and electromagnetic interference. [AU,

Nov/Dec - 2007]

3.66. Explain the various types of earth loops. 3.67. Discuss the multiple earth and earth loops in detail. [AU,

April/May - 2010]

3.68. Explain in detail about grounding techniques. 3.69. Explain the grounding techniques in detail to reduce the ground loop

interference signal. [AU, Nov/Dec - 2009]

3.70. Discuss in detail : (i) bridge to measure low - Q of a coil. (ii) cause and effects of poor grounding in instruments. [AU, April / May - 2008]

3.71. With a neat figure, explain the need of WAGNER'S earth (ground) connection in bridge circuit. [AU, Nov/Dec

- 2008]

PROBLEMS3.72. A basic slide wire potentiometer has a working battery voltage of 3.0V with

negligible internal resistance. The resistance of the slide wire is 400 and its length is 200 cm. A 200 cm scale is placed along the slide wire. The slide wire has 1 mm scale division and it is possible to read upto 1/5 of a division. The instrument is standardized with a 1.018 V standard cell with sliding contact of 101.8 cm mark on the scale. Calculate the (i) working current (ii) resistance of the series rheostat. (iii) measurement range and (iv) resolution of the instrument.

3.73. A simple slide wire is used for measurement of current in a circuit. The voltage drop across a standard resistor of 0.1 Ohm is balanced at 75 cm. Find the magnitude of the current if the standard cell emf of 1.45 V is balanced at 50 cm. [AU, May / June - 2009]

3.74. During the measurement of low resistance using a potentiometer, the following readings were obtained. Voltage drop across the low resistance under test = 0.4221 V, voltage drop across a 0.1 ohm standard resistance = 1.0235 V. Calculate the value of unkown resistance, current and power lost in it. [AU, May/June - 2009]

3.75. A volt ratio box should be designed such that when an unknown voltage of 100 V is applied to the input terminals, an output voltage of 2 V is available at the box output terminals. An additional. requirement is that the total input resistance (R

1+R

2) of the box is 10 M . Determine the volt - box ratio

and the relationship between R1 and R

2.

3.76. Calculate the inductance of a coil from the following measurement on an ac potentiometer. The voltage drop across a 0.1 standard resistor connected in series with the coil = 0.613 . The voltage across the test coil through a 100/1 volt - ratio box = 0.781 V . The frequency is 50 Hz

3.77. A resistance bridge has the configuration shown in figure below :in which R

1 = 120. 4, R

2 = 119.0 and R

3 = 119.7.

a) What resistance must R4 have for resistance balance?

b) If R4 has a valve of 121.2, and if the input voltage is 12Vdc, what is the

output voltage of the bridge, assuming it to be voltage sensitive bridge?

3.78. In a Wheatstone bridge three out of four resistors have a value of 1K each, and the fourth resistor equals 1010. If the battery voltage is 100V, what is the approximate value of the open circuit voltage? If the output of the bridge is connected to a 4K resistor, how much current would flow through the resistor?

3.79. The four arm bridge ABCD, supplied with a sinusoid voltage, have the following values:

AB = 330 ohm resistance in parallel with 1.5 F capacitor

BC = 400 ohm resistance

CD = 800 ohm resistance; DA resistance R in series with a 0. 2 F capacitor. Determine the (i) value of R and (ii) supply frequency at which the bridge will be balanced.

[AU, April / May -

2008]

3.80. Find the equivalent parallel resistance and capacitance that causes a Wein bridge to null if the following components are given:R

1 = 8 , C

1 = 6 , R

2 = 30 , f = 2.5 KHz. R

3 = 1

[AU, Nov/Dec

- 2008]

UNIT - IV - STORAGE AND DISPLAY DEVICES

Part - A

4.1. Explain briefly on magnetic tape. [AU, Nov/Dec -

2008]

4.2. What is the magnetic principle used in computer data storage? [AU, May /

June - 2009]

4.3. What are the basic components of a tape recorder?4.4. Mention the methods used for magnetic tape recording used for

instrumentation purposes. [AU,

Nov/Dec - 2009]

4.5. Draw a neat diagram on xy recorder. [AU, April / May -

2008]

4.6 What you mean by X-Y recorders? [AU, April/May -

2010]

4.7. What are the methods of recording?4.8. What are the advantages of direct recording?4.9. What are the limitations of direct recording?4.10. What are the advantages of FM recording?4.11. What are the disadvantages of PDM recording?4.12. What are the features of digital plotters?4.13. Write briefly on pink plotter. [AU,

Nov/Dec - 2008]

4.14. What are the major types of printers? [AU, Nov/Dec -

2009]

4.15. Give the features of dot matrix printer.4.16. State the featurers of ink-jet printers. [AU, May / June -

2006]

4.17. What are the sizes of matrix available in dot matrix printers? Which is used frequently?

4.18. How are the displays classified?4.19. Give the list of active displays.4.20. List out the passive displays.4.21. Classify the displays according to display format.4.22. Give the classification of displays according to the display size and

dimensions.4.23. What are the advantages of LED display?4.24. What are the materials used for doping to give different colours?4.25. Give the principle of LCD type display device. [AU, April / May

- 2008]

4.26. What are the characteristics of LCD display? [AU,

Nov/Dec - 2007]

4.27. Give the important features of LCDs.4.28. What are the types of LCDs?4.29. Differentiate between LED and LCD. [AU, May / June -

2006]

4.30. In what respect LCD displays are advantageous over LED displays. [AU,

April/May - 2010]

4.31. Explain briefly about dot matrix display.4.32. Explain briefly about CRT display.4.33. What are the main parts of the cathode ray tube? [AU, Nov/Dec -

2009]

4.34. Give the block diagram of a liquid crystal switch used with a CRT.4.35. What are the main parts of a digital CRO?4.36. What is meant by strobing?

4.37. Describe the principle and working of nixie tubes.

Part - B

4.38. Explain the basic mechanism of recording and reproduction of an analog voltage signal by means of a magnetic tape

4.39. Describe the important stages that make up a magnetic tape recorder.

[AU, April / May -

2010]

4.40. Explain with a suitable circuit diagram, the working of an XY recorder. Describe its applications [AU,

Nov/Dec - 2007]

4.41. Explain the functioning of a basic type of strip chart recorder. Explain the different types of marking mechanisms used in it.

4.42. Describe the working of a galvanometric type strip chart recorder. What are the different types of tracing systems used in it?

4.43. Explain with the help of a diagram, the working of a null type recorder. Distinguish between single point and multipoint recorders.

4.44. Explain the working of an ultraviolet recorder.

4.45. What are the different types of magnetic recording? Write the advantages and disadvantages of each type of magnetic recording. [AU,

Nov/Dec - 2008]

4.46. Describe the pulse duration modulation (PDM) as used in magnetic tape recording and explain its merits and demerits.


4.47. Describe the direct and frequency modulation magnetic tape recording types. Give its merits and demerits. [AU,

Nov/Dec - 2009]

4.48. Describe the different methods used for digital tape recording. Explain its advantages and disadvantages.

4.49. Explain in detail with suitable diagram

i) magnetic tape ii) digital printers. [AU, April / May -

2008]

4.50. Explain with a neat sketch

i) digital plotters ii) printers

4.51. Explain various types of printers in detail giving all the important aspects of them. [AU,

Nov/Dec - 2009]

4.52. Draw the block diagram of a general purpose CRO and explain the functions of the following controls :

i) intensity ii) focus iii) horizontal and vertical positioning iv) synchronization

4.53. With neat figures, explain how frequency of a signal is measued using CRO. [AU, Nov/Dec -

2008]

4.54. Describe the basic components of a CRT. [AU, May / June -

2006]

4.55. Explain the two methods of deflecting the electron beam in a CRT.

[AU, April/May - 2010]

4.56. Derive an expression for the vertical deflection of an electron beam in a CRT

4.57. Draw and explain the block diagram of a sampling oscilloscope.

4.58. Describe the mesh storage technique used in storage oscilloscopes.

4.59. Describe the following types of oscilloscopes

i) dual trace type ii) dual beam type

4.60. Describe with a block diagram the principle of working of a digital storage oscilloscope. What is its advantages over analog CRO? [AU, May/June -

2006, April / May - 2008]

4.61. Explain the modes of operation of digital storage oscilloscope. [AU, April/May

- 2010]

4.62. Explain the theory and working of an LED. What are the advantages and applications of LEDs ? [AU,

May / June - 2006, May/June - 2009]

4.63. Explain the theory and working of LCDs. What is the difference between light scattering and field effect types of LCDs ? [AU, Nov/Dec -

2007, May / June - 2006]

4.64. Describe the principle of operation of LED and LCD display devices.


4.65. Write a note on [AU, April / May -2010, May/June - 2009]

i) Gas discharge plasma display

ii) Segmented gas discharge display

iii) Dot matrix display

iv) Bar graph display

v) Electro - luminescent display

vi) Liquid vapour display

4.66. Write a note on data loggers.

4.67. Write briefly on

i) Dot matrix display.

ii) Advantages and principles of LCD display.

iii) Digital data loggers. [AU, Nov/Dec -

2008]

PROBLEMS4.68. a) What is the resolution of a 3½ digital display?

b) Find the resolution of a 3½ digit meter in case its range is 1V.c) Find the resolution of the meter for 10V range.

4.69. A 4½ digit voltmeter is used for voltage measurement.a) Find its resolutionb) How would 12.98 V be displayed on 10V range?c) How would 0.6973 be displayed on 1V range?d) How would 0.6973 be displayed on 10 V range?

4.70. A 3½ digit DVM has a accuracy specification of + 0.5 percent of reading 11 digit. a) What is the possible error in the voltmeter, when the instrument is reading 5.00 V on the 10V range?b) What is the possible error in the voltmeter, when reading 0.10 V on the 10 V range?c) What percentage of the reading is the possible error in the case of (b)?

UNIT - V - TRANSDUCERS AND DATA ACQUISITION SYSTEMSPart - A

5.1. Define a transducer.5.2. What are the advantages of electrical transducers?5.3. What are the types of transducers?5.4. What is Transducer and an Inverse transducer. [AU, Nov/Dec -

2009]

5.5. What are the main parts of a transducer?5.6. Define the primary and secondary transducers. [AU, April/May -

2010]

5.7. What are the factors that influence the selection of a transducer?5.8. What is a resistive transducer?5.9. Differentiate sensor from transducer. [AU,

Nov/Dec - 2009]

5.10. What are the types of strain gauges?5.11. Define gauge factor.5.12. What are the desirable characteristics of a resistance wire strain gauge?

5.13. What are the advantages of a semiconductor strain gauge?5.14. How are strain guages used for pressure measurement? [AU, Nov/Dec -

2008]

5.15. What are the limitations of a resistance thermometer?5.16. What are thermistors?5.17. Give the various configurations of thermistors.5.18. What are the advantages and limitations of thermistors?5.19. What is the principle of working of inductive transducers?5.20. What is a LVDT?5.21. Give the advantages of LVDT.5.22. What are the limitations of LVDT?5.23. What is the output expected out of an LVDT provided with unidirectional

excitation, while measuring a displacement of 3 cm?. [AU,

April / May - 2008]

5.24. Give the principle of working of capacitive transducers.

5.25. State Piezoelectric effect. [AU, April / May -

2008]

5.26. What is the principle of operation of Piezo electric transducers? [AU,

Nov/Dec - 2007]

5.27. Which are the materials used in Piezo electric transducers? [AU, May / June -

2006]

5.28. Give the properties of Piezo electric crystals.

5.29. Name the transducers used for sensing acceleration. [AU, May / June - 2006]

5.30. What are the categories of temperature transducers?

5.31. What are the various types of RTDs?

5.32. What are the electrodes used for pH measurement?

5.33. Give the advantages of differential input pH amplifier.

5.34. What are the transducers used for the measurement of linear displacement?

5.35. List out the rotary displacement transducers.

5.36. What are the elements of load cell?

5.37. What is the principle of magnetostrictive transducers?

5.38. Classify the electromagnetic transducers.

5.39. What is an optical transducer?

5.40. What is an digital transducer?

5.41. Define inverse transducer with example. [AU, Nov/Dec - 2007]

5.42. What are the various types of digital encoders?

5.43. What are the various components of analog data-acquisition system?

5.44. What are the various components available in digital data-acquisition system?

5.45. List the uses of data-acquistion system.

5.46. What is a multiplexer?

5.47. What are the applications of multiplexer?

5.48. What are the two types of multiplexing?

5.49. What is a data converter?

5.50. What are the major components of a data converter?

5.51. What are the methods used for analog to digital conversion?

5.52. Find the successive approximation AID output for a 4 bit converter to a 3.217V input if the reference is 5 V.

5.53. Give the principle of V-I ADC.

5.54. State the performance parameters of ADC. [AU, April/May -

2010]

5.55. Draw the block diagram of voltage to frequency converter.

5.56. Draw the block diagram for 4 bit Analog to Digital Converter. [AU,

Nov/Dec - 2009]

5.57. Find the resolution of an eight bit A/D converter having an input voltage of -5V to +5 V.

5.58. What are the advantages of a dual slope integration type ADC?

5.59. A 10 bit DAC has a step size of 10 mA. Find its maximum full scale input current and the percentage of resolution.

PART - B

5.60. Describe the different criteria for selection of transducers for a particular application.

[AU, Nov/Dec -

2007]

5.61. Explain the construction and working principle of

(i) resistive transducer (ii) inductive transducer.

5.62. Explain the construction of wire wound strain guages and derive the expression for guage factor.

5.63. Explain with diagrams, the bonded and unbonded types of strain guages.

5.64. Describe the working and construction of resistance thermometers.

5.65. What are thermistors? Explain their different forms of construction. Describe the following for thermistors. i) resistance - temperature characteristics ii) voltage - current characteristics iii) current - time characteristics.

5.66. Write briefly on thermocouples and thermistors as temperature transducer


5.67. With neat diagram explain potentiometer resistance transducer. List advantages and disadvantages. [AU,

April/May - 2010]

5.68. Explain pressure capactive transducer with neat diagram. [AU,

April/May - 2010]

5.69. How is a differential output taken from an inductive transducers? Explain the advantages when inductive transducers are used in push-pull configuration.


5.70. Explain how using a differenctial arrangement, a capacitative transducer which works on the principle of variation of capacitance with displacement between two plates, the respeonse can be made linear.

[AU, May / June - 2009]

5.71. Describe the constructional features of the linear variable differential transformer. [AU,

Nov/Dec - 2009]

5.72. With neat figure, explain LVDT for velocity measurement. [AU,

Nov/Dec - 2008]

5.73. Describe the methods of measurement of pressure using [AU,

Nov/Dec - 2007]

(i) capacitive transducers (ii) photo - electric transducers.

5.74. Describe the different modes of operation of Piezo-electric transducers. Explain the applications of Piezo electric transducers [AU,

Nov/Dec - 2009]

5.75. Derive the expressions for frequency response characteristics of Piezo-electric transducers.

5.76. Write a note on

i) vaccuum type photo tube ii) photo multiplier tube.

iii) photo diode iv) photo transistor

v) photo conductive cell vi) photo voltaic cell.

5.77. Explain the construction and working of digital transducer.

5.78. With a neat block diagram, explain single and multichannel data acquistion system. Give example for each block. [AU,

April / May - 2008,2010]

5.79. Explain the generalized diagram of a digital data acquisition system. Give the uses of data acquisition system. [AU,

May/June - 2009]

5.80. Draw the basic schemes of the analog and digital type multiplexers and explain their operation

5.81. Explain the binary weighted resistor technique of D/A conversion.

[AU, May / June - 2006]

5.82. Describe one method of digital to analog converter.

5.83. Define the following terms for D/A converter.

(i) resolution (ii) accuracy (iii) monotonicity (iv) conversion time

[AU, May / June - 2006]

5.84. Write short notes:

(i) integral type analog to digital converter.

(ii) thermocouple. [AU, April / May -

2008]

5.85. Explain in detail the various conversion techniques of A/D converter.

[AU, Nov/Dec - 2007,09]

5.86. How are A/D converters classified? With a neat diagram, explain the construction and principles of successive approximation type ADC. [AU, Nov/Dec - 2008]

5.87. What are the performance parameters of Analog to Digital Converter? Explain any two basic A/D conversion techniques in detail. [AU,

Nov/Dec - 2009]

5.88. Write a short notes on smart sensors.

5.89. Discuss optical fiber displacement sensors. [AU, April/May - 2010]

PROBLEMS

5.90. The output voltage of a LVDT is 1.5V at maximum displacement. At a load of 0.5M, the deviation from linearity is maximum and it is + 0.003 V from a straight line through origin. Find the linearity at the given load.

5.91. The output of an LVDT is connected to a 5V voltmeter through an amplifier whose amplification factor is 250. An output of 2mV appears at the terminals of the LVDT when the core moves through a distance of 0.5mm. Calculate the sensitivity of the LVDT and that of the whole set up. The millivoltmeter scale

has 1000 divisions. The scale can be read to 1/5 of a division. Calculate the resolution of the instrument in mm.

5.92. A capacitive transducer uses two quartz diaphragms of area 750mm2, separated by a distance of 3.5mm. A pressure of 900 KN/m2 when applied to the top diaphragm produces a deflection of 0.6mm. The capacitance is 370pF when no pressure is applied to the diaphragms. Find the value of capacitance after the application of a pressure of 900KN/m2.

5.93. A pressure measuring instrument uses a capacitive transducer having a spacing of 4mm between its diaphragms. A pressure of 600 KN/m2 produces an average deflection of 0.3mm of the diaphragm of the transducer. The transducer which has a capacitance of 300 pF before application of pressure and is connected in an oscillator circuit having a frequency of 100KHz. Determine the change in frequency of the oscilator after the pressure is applied to the transducer.

5.94. A capacitive transducer is made up of two concentric cylindrical electrodes. The outer diameter of the inner cylindrical electrode is 3mm and the dielectric medium is air. The inner diameter of the outer electrode is 3.1mm. Calculate the dielectric stress when a voltage of 100V is applied across the electrodes. Is it within safe limit? The length of electrode is 20mm. Calculate the change in capacitance if the inner electrode is moved through a distance of 2mm. The breakdown strength of air is 3KV/mm.

5.95. A quartz Piezo - electric crystal having a thickness of 2mm and voltage sensitivity of 0.055V-m/N is subjected to a pressure of 1.5MN/m2. Calculate the voltage output. If the permittivity of quartz is 40.6 x 10-72 F/m, calculate its charge sensitivity.

5.96. A Piezo - electric crystal having dimensions of 5mm x 5mm x 1.5mm and a voltage sensitivity of 0.055 V - m/N is used for force measurement. Calculate the force if the voltage developed is 100 V.

5.97. a) An analog transducer with 0-10V input is able to distinguish a change of 10mV in its input signal. Calculate its resolution.

b) Calculate the number of bits of an A/D converter so that the digital output has almost the same resolution as the tranducer. The A/D converter uses a binary code. Calculate also i) the quantization error ii) the number of decision level (Comment upon the result)

5.98. A 5 bit converter is used for a dc voltage range of 0-10V. Find the weight of MSB and LSB and also the exact range of the converter and the error. Find the error if a 10 bit converter is used.

5.99. A control valve has a linear variation of opening as the input voltage varies from 0 to 10V. A microcomputer output uses an 8 bit output word to control valve opening using 8 bit D/A converter to generate the valve voltage (a) Find the reference voltage required to obtain full valve opening 10V, (b) Find the percentage of valve opening for all bit change in the input word.

5.100. An analog voltage signal whose highest significant frequency is 1KHz is to be digitally coded with a resolution of 0.01% covering a voltage range of 0-10V. Determine the (a) minimum number of bits in the digital code (b) analog value of LSB (c) rms value of the quantization error (d) minimum sampling rate (e) aperture time required for the A/D converter (f) dynamic range of converter in dB.

5.101. A D/A converter has 6 bits and a reference voltage of 10V. Calculate the minimum value of R such that the maximum value of output current does not exceed 10mA. Find also the smallest quantized value of output current.

5.102. Consider a 6 bit D/A converter with a resistance of 320K in LSB position. The converter is designed with weighted resistive network. The reference voltage is 10V. The output of the resistive network is connected to an op amp with a feedback resistance of 5K. What is the output voltage for a binary input of 111.010?

5.103. Find the successive approximation A/D output for a 4 bit converter to a 8.217 V input if the reference is 5V.

*********

M&I 2marks,16marks,Problems

Documents

dot matrix

moving iron

full scale

digital storage

magnetic tape

independent

full scale

write short