EX-604-A Electronic Instrumentation - Jun 2025 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
   aExplain in detail the working of a dual-beam CRO and contrast it with a dual-trace CRO.
   How to answer

   • Definition and construction of dual-beam CRO with two electron guns/beams
   • Working of dual-trace CRO with single gun and electronic switching (alternate/chopped)
   • Comparison points: construction, cost, frequency range, interaction
   • Diagram of CRT and block diagram for both types
2. 7 Marks
   bExplain the construction and working of time base circuits. How does sweep synchronization affect the accuracy of waveform display?
   How to answer

   • Block diagram and construction of time base / sweep generator
   • Working: sawtooth generation, blanking, triggering
   • Role of sweep synchronization for stable display
   • Effect of poor sync on jitter, drift and measurement accuracy
3. 7 Marks
   aDiscuss the role and significance of post-deflection acceleration in CRT-based CROs. How does it affect the beam velocity and spot size?
   How to answer

   • Concept of post-deflection acceleration (PDA) in CRT
   • Need for high brightness without loss of deflection sensitivity
   • Effect on beam velocity increase after deflection
   • Effect on spot size, brightness and deflection defocusing
4. 7 Marks
   bExplain the working of Wein's bridge oscillator and how it can be used for frequency determination.
   How to answer

   • Bridge circuit with Wien network and amplifier
   • Barkhausen condition and balance for oscillation
   • Frequency formula $f = 1/(2\pi RC)$
   • Use as frequency determination by null/balance method
5. 7 Marks
   aA Maxwell bridge is used to measure an inductive impedance the bridge constants at balance are $C_1 = 0.01 \mu F$, $R_1 = 470 K\Omega$, $R_2 = 5.1 K\Omega$ and $R_3 = 100 K\Omega$. Find the series equivalent of the unknown impedance.
   How to answer

   • Maxwell bridge balance equations for $R_x$ and $L_x$
   • Substitute $C_1, R_1, R_2, R_3$ values
   • Calculate series resistance and inductance
   • State series equivalent impedance $Z = R_x + j\omega L_x$
6. 7 Marks
   bCompare and contrast the operation of Schering Bridge and De Sauty's Bridge in terms of frequency response and dielectric loss measurement.
   How to answer

   • Principle of Schering bridge for capacitance and loss
   • Principle of De Sauty's bridge for capacitance comparison
   • Comparison of frequency dependence and accuracy
   • Comparison for dielectric loss / dissipation factor measurement
7. 7 Marks
   aWrite short notes on :

   1. i)Thermocouple
   2. ii)Hall effect transducers
   How to answer

   • Thermocouple: Seebeck effect, construction, output emf
   • Hall effect transducer: principle, Hall voltage, applications
   • Characteristics, advantages and limitations
   • Typical instrumentation uses
8. 7 Marks
   bDifferentiate between photo-voltaic, photo-conductive and photo-diode transducers. Which one is more suitable for low-intensity light detection and why?
   How to answer

   • Operating modes: photovoltaic vs photoconductive vs photodiode
   • Biasing, linearity, speed and sensitivity differences
   • Suitability for low-intensity light with justification
   • Applications and example characteristics
9. 7 Marks
   aExplain the concept of digital multiplexing in transducer interfacing. How does it improve system efficiency in industrial automation?
   How to answer

   • Concept of digital multiplexing and transducer interfacing
   • Time-division / channel scanning principle
   • How sharing ADC, bus reduces hardware and cost
   • Benefits for industrial automation efficiency and speed
10. 7 Marks
    bDiscuss :

    1. i)Electrophoretic image display vs Liquid vapor display
    2. ii)Analog recorders vs Digital XY recorders
    How to answer

    • Electrophoretic vs liquid vapor display: principle and features
    • Analog recorders vs digital XY recorders: working
    • Comparison of speed, accuracy, storage and applications
    • Suitable use cases for each type
11. 7 Marks
    aCompare fixed-frequency and sweep frequency signal generators.
    How to answer

    • Block diagram of fixed-frequency signal generator
    • Block diagram of sweep-frequency generator
    • Comparison of frequency control, applications and complexity
    • Advantages for testing filters, amplifiers
12. 7 Marks
    bExplain the operation of a heterodyne wave analyzer. How does it differ from a frequency selective wave analyzer in sensitivity and selectivity?
    How to answer

    • Block diagram of heterodyne wave analyzer
    • Principle of mixing with variable local oscillator
    • Comparison with frequency selective analyzer in sensitivity
    • Comparison in selectivity, bandwidth and applications
13. 7 Marks
    aExplain the operation of dual slope integrating type digital voltmeter. Compare it with successive approximation type in terms of accuracy and speed.
    How to answer

    • Dual-slope integrating DVM: integration and de-integration phases
    • Relation $V_{in} = V_{ref} \cdot T_2/T_1$ and noise rejection
    • Successive approximation operation principle
    • Comparison of accuracy, speed, cost and noise immunity
14. 7 Marks
    bWhat is the role of RS232C and IEEE-488 (GPIB) interfaces in instrumentation systems? Compare them with modern USB and Ethernet-based control systems.
    How to answer

    • Role of RS232C serial and IEEE-488 GPIB parallel interfaces
    • Features: distance, speed, addressing, handshake
    • Comparison with USB and Ethernet on speed and networking
    • Modern instrumentation control advantages
15. 14 Marks
    Write short notes on (any two)

    1. a)Multi-input sampling oscilloscope
    2. b)LVDT
    3. c)Digital tachometer
    4. d)Wobbly scope
    How to answer

    • Principle and block diagram of selected two topics
    • Construction and working with key specifications
    • Advantages, limitations and applications
    • Neat labeled diagram for each