R5221303 Electrical And Electronic Measurements

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Code No: R5221303

II B.Tech. II Semester (R05) Supplementary Examinations, April/May 2009 ELECTRICAL AND ELECTRONIC MEASUREMENTS (Electronics & Control Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) The coil of a moving coil galvanometer is wound on a non-magnetic former whose height and width are both 20 mm. It moves in a constant field of 0.12 wb/m2 . The M-I of its moving parts 0.25 × 10−6 kg − m2 , and the control spring constant is 30 × 10−6 NM / rad. Calculate i. the number of turns that must be wound on the coil to produce a deflection of 1500 with a current of 10 milli Amperes. ii. the resistance of the coil to produce critical damping, all damping being assumed as electromagnetic. (b) Explain the constructional details of d’Arsonval galvanometer.

[8+8]

2. (a) Explain the working principle of shunt type ohm meter. (b) A shunt type ohmmeter uses a basic meter with a full scale current of 2mA and an internal resistance of 25Ω. The battery has an e.m.f of 1.5V. Find i. the value of resistance R1 . ii. At what point (in percentage of full scale) will 100Ω be marked on scale? [6+10] 3. (a) Explain the construction and working principle of single phase moving iron power factor meter? (b) State the advantages and dis-advantages of moving iron power factor meters. [10+6] 4. (a) Explain the importance of thermocouples in the construction of true RMS type of Voltmeter. (b) What is the necessity of electronic voltmeter? Explain. (c) What is multimeter? What are the parameters that can be measured with multimeter? [6+6+4] 5. (a) Draw the block diagram of a Q meter and mention the parameters that can be measured with Q meter. (b) Give the construction details of power meter and explain principle and operation of it

[8+8]

6. (a) Derive an equation for magneto static deflection sensitivity of a CRT. (b) Find the electro static deflection sensitivity of a CRT if the applied deflecting voltage of 500V deflects the electron on the screen by 1cm. [10+6] 7. (a) With a neat sketch explain the Digital FFT Spectrum analyzer . (b) Discuss the different applications of spectrum analyzer.

[8+8]

8. (a) To what accuracy can a frequency counter determine an unknown frequency of 500KHz using a 1.2 Sec time base and a time base accuracy of 0.02% ? (b) Explain the method of multiple period averaging scheme using suitable block diagram. ?????

[8+8]

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Code No: R5221303

II B.Tech. II Semester (R05) Supplementary Examinations, April/May 2009 ELECTRICAL AND ELECTRONIC MEASUREMENTS (Electronics & Control Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) Explain the constructional details of PMMC instruments with a neat sketch. (b) Explain different errors of PMMC instruments.

[10+6]

2. Explain the working of a rectifier type of voltmeter. Explain sensitivity of these instruments in measuring a.c. quantities? How does the a.c. sensitivity of rectifier type of instruments compare with their d.c. Sensitivity. [16] 3. Derive the expression for deflecting torque in single phase induction type energy meter. Show that the deflection is maximum when the phase angle between two fluxes is 900 and when the disc is purely non-inductive. [10+6] 4. With a neat sketch explain the Ramp type Digital Voltmeter in detail. Mention its merits and demerits. [16] 5. (a) The self capacitance of a coil is to be measure by Q meter. The first measurement result is f1 = 2MHz and C1=600 pF. The second measurement result is f2 = 5 MHz and new value of tuning capacitor is 130 pF. Find the distributed capacitance and the inductance. (b) Compare Analog and digital RF power and voltage measurement.

[10+6]

6. (a) Why attenuators and amplifiers are required in vertical and horizontal sections of a CRO. (b) Discuss A & B chopped and alternate display modes of a dual trace CRO. [6+10] 7. (a) Discuss the merits and demerits of RF generator. (b) Discuss the merits and demerits of AF generator.

[8+8]

8. (a) With a neat sketch explain the ratio and multiple ratio measurement for frequencies. (b) Explain the basic principle behind the extension of frequency range of counters. [10+6] ?????

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Code No: R5221303

II B.Tech. II Semester (R05) Supplementary Examinations, April/May 2009 ELECTRICAL AND ELECTRONIC MEASUREMENTS (Electronics & Control Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) Explain the effect of temperature changes in D.C. voltmeters? (b) A moving coil instrument whose resistance is 25 Ω gives a full scale deflection with a voltage of 25 mV. This instrument is to be used with a series multiplier to extend its range to 10 V. Calculate the error caused by 100 C rise in temperature. [6+10] 2. Draw the circuit diagram of series type ohmmeter. Explain its working principle? What is significance of half scale value? How are the adjustments done in case the battery runs down? How are the zero adjustments made? [16] 3. Draw the equivalent circuit and phasor diagram of a current transformer. Derive the expressions for phase angle error. [8+8] 4. (a) Explain the importance of thermocouples in the construction of true RMS type of Voltmeter. (b) What is the necessity of electronic voltmeter? Explain. (c) What is multimeter? What are the parameters that can be measured with multimeter? [6+6+4] 5. (a) Briefly discuss the various source of errors that affect the accuracy in Q- meter based measurement. (b) Discuss how a Q-meter can be employed to determine the distributed capacitance. [9+7] 6. (a) How an electron beam is focused to a fine spot on the face of the CRT using Electric field? (b) Compare the performance characteristics of different types of CRO probes. [8+8] 7. (a) Discuss in detail about Audio frequency wave generator. (b) What are the precautionary measures to be considered in a signal generator? Explain how they can be achieved. [9+7] 8. (a) List the application of frequency synthesizer. Discuss in brief. (b) Explain the standard time base generator with a neat sketch. ?????

[8+8]

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Code No: R5221303

II B.Tech. II Semester (R05) Supplementary Examinations, April/May 2009 ELECTRICAL AND ELECTRONIC MEASUREMENTS (Electronics & Control Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) Explain happens when a permanent magnet moving coil instrument is connected to a.c. supply? (b) Explain how is damping attained in D’Arsonval galvanometer? (c) Comment upon the shape of scale if spring control is used in PMMC instrument?

[6+6+4]

2. Explain the circuit of a multimeter for measurement of A.C. voltages. Why are multimeters provided with a separate scale for low voltage a.c. range? [16] 3. (a) Draw the possible methods of connecting the pressure coil of a wattmeter and compare the errors. Explain the meaning of compensating winding in wattmeter? (b) An electrodynamometer type wattmeter is employed to measure power in a single phase circuit. The load voltage is 200 volts and the load current is 5 A at a lagging p.f. of 0.1. The wattmeter potential coil has a resistance of 12,000Ω and inductance of 120 mH. Determine the percentage error in wattmeter reading? [10+6] 4. (a) With a neat sketch explain the Electronic AC voltmeter.

[8+8]

(b) Compare AC & DC Voltmeter. 5. (a) What the merits and demerits of Vector impedance meter. (b) What are the merits and demerits of Phase angle meter. (c) What are the merits and demerits of Q - meter.

[5+6+5]

6. (a) What is probe? What are the advantages of an active voltage probe? (b) Why an attenuator probe is used in oscilloscope . (c) What is delayed sweep? when it used?

[8+4+4]

7. (a) With a neat sketch explain the Digital FFT Spectrum analyzer . (b) Discuss the different applications of spectrum analyzer.

[8+8]

8. (a) Explain the measurement of frequency with the help of a basic frequency counter. (b) Explain the display technique used frequency counter with an example. ?????

[8+8]