05212201 C A L I B R A T I O N A N D E L E C T R O N I C M E A S U R E M E N T S

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Code No: R05212201
Set No. 1
II B.Tech I Semester Supplimentary Examinations, November 2008
CALIBRATION AND ELECTRONIC MEASUREMENTS
(Instrumentation & Control Engineering)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks

1. The following 10 observations were recorded when measuring a voltage: 41.7, 42.0,
41.8, 42.0, 42.1, 41.9, 42.0, 41.9, 42.5 and 41.8 volt Calculate

(a) the arithmetic mean
(b) the deviation from the mean

(c) the average deviations
(d) Standard deviation
(e) Variance
(f ) Probable error of one reading
(g) Probable error of mean
(h) Range
[16]

2. (a) State the SI units, unit symbols and de ne each unit for the following
i. Conductance
ii. Magnetic ux
iii. Flux density
iv. Inductance

(b) A bar magnet with a one inch square cross section is said to have a total
magnetic ux of 500 Maxwell. Determine the ux density in tesla? [8+8]

3. Write short notes on any of the :

(a) Testing
(b) Calibration

(c) Reliability
(d) Traceability [16]

4. (a) A 10mA meter movement with an internal resistance of 100 is to be converted
into a 0-100mA. Calculate the value of shunt resistance required?
(b) State di erent types of thermocouples and explain the e ect of frequency on
thermocouples? [12+4]

5. (a) Explain how a Kelvin’s double bridge can accurately measure low resistances.
Also derive the condition for balance.

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Code No: R05212201
Set No. 1
(b) In the Kelvin’s Bridge shown in gure 5b the ratio of Ra to Rb is 2000 ,R1
is 10 and R1=0.2 R2. Calculate the value of Rx . [10+6]

Figure 5b
6. (a) With a neat sketch explain the operation of a co-axial wave meter.
(b) What are various synthesis techniques which generate di erent frequencies
from a given reference frequency? [8+8]

7. (a) Explain the operation of 10 to 1 probe .
(b) A given oscilloscope has an input resistance of 10 M ohm shunted by 20 pf.
Design a 10 to 1 probe. [8+8]

8. (a) Compare the selectivity characteristics of the spectrum analyzer and wave
analyzer.
(b) Explain the following terms associated with spectrum analyzer.
i. Sensitivity
ii. Dynamic Range
iii. Harmonic mixing [7+3+3+3]

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Code No: R05212201
Set No. 2

1. Write short notes on any of the :

(a) Gross errors
(b) Instrument errors

(c) Environmental errors
(d) Observational errors [16]

2. (a) Determine the dimensions of charge, power and voltage.
(b) Describe the international standard of length and volume? [12+4]

3. (a) Write short notes on the concept of traceability?
(b)
SCALE READING PRECISION VOLTAGE CORRECTION
100 103 +3
90 93 +3
80 82.5 +2.5
70 72.5 +2.5
60 62 +2
50 51.7 +1.7
40 41.5 +1.5
30 31 +1
20 19.7 -0.3
10 9.5 -0.5
0 0 0

For the 30 and 70 readings in the calibration chart shown above determine the
instrument accuracy as a percentage of the reading and as a percentage of full
scale? [8+8]
4. Draw the block diagram of multimeters and explain its operation? [16]

5. (a) Find the series inductance, resistance and Q of an inductive element using
Maxwell bridge .Given Z1=parallel combination of a resistor of value 470
and a capacitor of value 0.5 F, Z2=Z3=2K . The bridge is driven by a 3
KHz sinusoidal source.
(b) Explain the principle and working of Q meter? [8+8]

6. (a) Distinguish between time and phase measurements?

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Code No: R05212201
Set No. 2
(b) Explain any two metho ds generally used to extend the frequency range of a
frequency counter? [6+5+5]

7. (a) Name the various types of probes with their applications
(b) Write short notes on time base generators used in oscilloscopes [8+8]

8. (a) Compare the selectivity characteristics of the spectrum analyzer and wave
analyzer.
(b) Explain the following terms associated with spectrum analyzer.
i. Sensitivity
ii. Dynamic Range
iii. Harmonic mixing [7+3+3+3]

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Code No: R05212201
Set No. 3

1. (a) Explain the following terms
i. Instrumental error
ii. Limiting error
iii. Random error
iv. Probable error
(b) The current passing through a resistor of 100 ± 0.2 is 2.00 ± 0.5A. Using
the relationship P = 2R, Calculate the limiting error in the computed value
of power dissipation? [8+8]
2. Write short notes on any of the THREE:
(a) International standards
(b) Primary standards
(c) Secondary standards
(d) Working standards [16]
3. (a) Explain the concept of traceability?
(b) Explain the concept of primary and secondary calibration? [8+8]
4. (a) Write short notes on the principle of RMS voltmeter?
(b) Explain with a neat block diagram dual slope type DVM? [8+8]

Figure 5b

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Code No: R05212201
Set No. 3
6. (a) When is period measurement preferred over frequency measurement and ob-
tain the condition ?
(b) With a suitable block diagram explain the operation of a pre scaled frequency
counter. [4+4+8]

7. (a) Describe the electrostatic focusing system of a CRT.
(b) What is the minimum distance L, that will allow full de ection of 4 cm at the
oscilloscope screen with a de ection factor of 100 V/cm and with an acceler-
ating potential of 2000 V ? [8+8]

8. (a) Explain the di erent applications of spectrum analyzer.
(b) Explain the F M recording method. [8+8]

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Code No: R05212201
Set No. 4

1. (a) De ne the following terms:
i. Absolute error
ii. %Error
iii. Precision
iv. % of accuracy
(b) What are the four sources of possible errors in instruments and explain each
of them brie y? [8+8]

2. (a) Explain the concept of capacitance standards?
(b) De ne the seven base units of SI system? [8+8]

3. (a) What is reliability and explain the concept of measurement reliability?
(b) Explain the calibration of DC and AC instruments? [8+8]

4. (a) For the circuit shown ( gure 4a) calculate the AC and DC sensitivity?

Figure 4a
(b) Sketch a neat block diagram of microprocessor based ramp type DVM and
explain brie y? [8+8]


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Code No: R05212201
Set No. 4

Figure 5b
6. (a) With the help of a block diagram explain the multiplexed display technique
used in a frequency counter.
(b) Explain in detail about frequency mo de errors and period mode errors. [4+6+6]

7. (a) Draw the block diagram of a catho de ray oscilloscope and describe the oper-
ation of each blo ck.
(b) Explain the method of nding phase, frequency relationship of two waveforms
using Lissa jous gures. [2+6+4+4]

8. (a) With a neat sketch explain the operation of a strip chart recorder.
(b) Explain di erent applications of spectrum analyzer. [2+6+8]

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05212201 C A L I B R A T I O N A N D E L E C T R O N I C M E A S U R E M E N T S

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