EC-302 Electronic Measurements and Instrumentation - Dec 2023 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aList various static and dynamic characteristics of measurement system and briefly explain each one of them.
   How to answer

   • List static characteristics: accuracy, precision, sensitivity, linearity, resolution, threshold, drift, stability
   • List dynamic characteristics: speed of response, fidelity, lag, dynamic error, bandwidth
   • Brief explanation of each term with definition/formula
2. 7 Marks
   bExplain the working principle of chopper type DC voltmeter along with a suitable block diagram.
   How to answer

   • Need for DC voltmeter and chopper modulation concept
   • Block diagram: input attenuator, chopper modulator, AC amplifier, demodulator, filter/meter
   • Working: DC to AC conversion, amplification, synchronous demodulation
3. 7 Marks
   aDifferentiate between dual beam and dual trace CROs, also draw block diagram of each.
   How to answer

   • Construction difference: two electron guns vs single gun with electronic switching
   • Comparison table: operation, modes alternate/chopped, cost, speed, applications
   • Block diagrams of dual beam and dual trace CRO
4. 7 Marks
   bWhy Maxwell's inductance capacitance bridge cannot be used, for high Q coils, to find unknown inductance?
   How to answer

   • Balance equations of Maxwell inductance-capacitance bridge
   • Q-factor expression and requirement of large variable standard capacitor
   • Unsuitability for high Q: very large capacitor value, impractical and costly
5. 7 Marks
   aDiscuss about the various types of optical transducers Photoemissive, photoconductive and photovoltaic.
   How to answer

   • Principle of optical transducers
   • Photoemissive: photoelectric emission, phototube, photomultiplier
   • Photoconductive: LDR, photodiode in photoconductive mode; Photovoltaic: solar cell, photodiode in photovoltaic mode
6. 7 Marks
   bList the different ways to classify transducers.
   How to answer

   • Basis of classification: transduction principle, active/passive, analog/digital, primary/secondary
   • Classification by measurand, energy source, output
   • Examples for each class
7. 7 Marks
   aExplain the working principle of sweep frequency generator along with block diagram.
   How to answer

   • Need for sweep frequency and wobbulator concept
   • Block diagram: sweep oscillator, marker generator, detector, CRO display
   • Working: frequency swept over band, response displayed vs frequency
8. 7 Marks
   bClassify various display devices: LED, LCD. List their advantages and disadvantages.
   How to answer

   • Classification of displays: LED, LCD, CRT, seven segment
   • LED advantages/disadvantages: brightness, power, life
   • LCD advantages/disadvantages: low power, flat, viewing angle, speed
9. 7 Marks
   aList the advantages and disadvantages of digital instrument over analog instrument.
   How to answer

   • Advantages of digital: accuracy, resolution, no parallax, storage, automation
   • Disadvantages: cost, complexity, sampling/aliasing, power
   • Comparison table with analog instruments
10. 7 Marks
    bExplain the working principle of R-2R ladder type DAC, along with circuit diagram.
    How to answer

    • Circuit of R-2R ladder with R and 2R resistors and switches
    • Current division and binary weighted summation principle
    • Output voltage expression $V_o = -V_{ref} \times (digital\ input)/2^n$
11. 7 Marks
    aWhat is the importance of measuring probes of CRO, their types, explain 10:1 probe with diagram?
    How to answer

    • Need for probes: loading, isolation, attenuation
    • Types: direct, attenuator, high voltage, current, active
    • 10:1 probe: 9M series resistor, compensation, circuit and frequency response
12. 7 Marks
    bDerive the equation for unknown capacitance using Schering bridge. List its applications.
    How to answer

    • Schering bridge circuit with arms $Z_1, Z_2, Z_3, Z_4$ and balance condition $Z_1 Z_4 = Z_2 Z_3$
    • Derivation for unknown $C_x$ and dissipation factor $D$
    • Applications: cable insulation, capacitor testing, high voltage measurements
13. 7 Marks
    aList the types of errors in measurement and discuss about the importance of calibration.
    How to answer

    • Types of errors: gross, systematic, random; instrumental, environmental, observational
    • Methods to reduce errors
    • Importance of calibration: traceability, accuracy assurance
14. 7 Marks
    bExplain the working principle of integrating type ADC, along with diagram.
    How to answer

    • Types: single slope, dual slope integrating ADC
    • Block diagram: integrator, comparator, counter, control logic
    • Working: integration of input then reference, time proportional to voltage
15. 5 Marks
    aFind out resolution of a 5 bit ADC, having voltage range of 10V. Also find out the range for MSB and % of error in conversion.
    How to answer

    • Resolution formula $Resolution = V_{range}/2^n$
    • Calculation: $10V/32 = 0.3125V$
    • MSB range and % error / quantization error calculation
16. 5 Marks
    bExplain the working principle of piezoelectric transducer.
    How to answer

    • Piezoelectric effect: direct and inverse effect
    • Materials: quartz, PZT, barium titanate
    • Construction and charge/voltage generation with applied force
17. 4 Marks
    cWhat are graticules in CROs?
    How to answer

    • Definition of graticule as calibrated grid on CRO screen
    • Internal vs external graticules
    • Use for voltage, time and frequency measurement