EX-604-A Electronic Instrumentation - Dec 2024 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
   aDraw a sketch to illustrate electrostatic deflection. Define deflection factor and deflection sensitivity for a CRT.
   How to answer

   • Sketch of CRT with electron gun, deflecting plates, screen showing electrostatic deflection
   • Definition of deflection factor as voltage required per unit deflection
   • Definition of deflection sensitivity as deflection per unit voltage
   • Relation that sensitivity is reciprocal of deflection factor
2. 7 Marks
   bSketch the construction of a dual-beam oscilloscope. Briefly explain.
   How to answer

   • Block/construction sketch of dual-beam oscilloscope with two electron guns or beam splitter
   • Identification of CRT, vertical/horizontal systems for two channels
   • Brief working for simultaneous display of two signals
3. 7 Marks
   aWhat is the loss factor of a capacitor? How can it be measured? Describe a bridge circuit that can measure this factor. How is it related to the Q-factor?
   How to answer

   • Definition of loss factor / dissipation factor tan delta for capacitor
   • Bridge circuit for measurement e.g. Schering bridge, balance conditions
   • Measurement procedure and phasor explanation
   • Relation to Q-factor as reciprocal Q = tan delta
4. 7 Marks
   bA supply of $12V$ is impressed across a Wien bridge. The $3^{rd}$ arm and the $4^{th}$ arm resistances are $10\text{ k}\Omega$ and $4.7\text{ k}\Omega$ respectively. If the ratio arm resistances are $8.8\text{ k}\Omega$ each, what are the capacitances if the bridge is balanced at a frequency of $13\text{ kHz}$?
   How to answer

   • Wien bridge balance conditions for frequency and resistance ratio
   • Formula $f = 1/(2\pi RC)$ applied at 13 kHz
   • Use of arm ratio 10 kΩ / 4.7 kΩ and 8.8 kΩ ratio arms
   • Calculation of capacitance values for balance
5. 7 Marks
   aWhy is Anderson loop proposed for impedance measurement? What is the basic circuit topology?
   How to answer

   • Limitation of conventional AC bridges requiring iterative balancing
   • Advantage of Anderson loop with non-iterative / rapid measurement
   • Basic loop topology with current source and voltage ratio measurement
6. 7 Marks
   bName a few AC bridges used in practice and specify which bridge is used for measurement of what type of impedance?
   How to answer

   • List of practical AC bridges: Maxwell, Hay, Schering, Wien, Anderson, De Sauty
   • Quantity measured by each: inductance, capacitance, frequency
   • Matching of bridge to low-Q / high-Q / lossy components
7. 7 Marks
   aWhat change does occur in a strain gauge for measurement of strain and how does it occur?
   How to answer

   • Principle of strain causing dimensional change in gauge
   • Change in resistance due to length, area and resistivity effects
   • Mechanism of bonded gauge following specimen strain
8. 7 Marks
   bWhat is a gauge factor? Does it depend on the electrical property of the material only or any other property? Explain.
   How to answer

   • Definition of gauge factor as $(dR/R)/\epsilon$
   • Dependence on Poisson ratio, piezoresistive and geometric effects
   • Not only electrical property but mechanical properties also
9. 7 Marks
   aExplain with necessary circuit diagram how an instrumentation type amplifier can be adapted to a bridge circuit for measurement of strain.
   How to answer

   • Bridge circuit with strain gauge as one arm and instrumentation amplifier
   • Circuit diagram with three-op-amp instrumentation amplifier
   • How differential bridge output is amplified for strain indication
10. 7 Marks
    bDiscuss the constructional features of an LVDT.
    How to answer

    • Construction: primary, two secondaries, movable core
    • Winding arrangement and magnetic coupling
    • Differential output principle with core displacement
11. 7 Marks
    aHow is Hall voltage generated in a Hall device? What do you mean by geometrical correction factor in such a device?
    How to answer

    • Hall effect with current and magnetic field producing transverse voltage
    • Formula for Hall voltage $V_H$ and role of Hall coefficient
    • Meaning of geometrical correction factor for finite geometry
12. 7 Marks
    bHow is seebeck effect utilized for the measurement of temperature? Describe what type of materials are required for producing such sensors?
    How to answer

    • Seebeck effect with two dissimilar metals and temperature gradient
    • Thermocouple circuit and emf-temperature relation
    • Required materials: thermoelectric pairs, Seebeck coefficients
13. 7 Marks
    aDraw the block diagram of a function generator. How is its frequency controlled by an external voltage input?
    How to answer

    • Block diagram: VCO/integrator, comparator, shaper for sine/square/triangle
    • Role of external voltage controlling VCO frequency
    • Frequency control mechanism and sweep input
14. 7 Marks
    bHow is data logger different from Data Acquisition System (DAS)?
    How to answer

    • Definition of data logger vs DAS functions
    • Differences in real-time processing, channels, speed and interfacing
    • Applications distinguishing standalone logging vs computer-based acquisition
15. 14 Marks
    Write short notes on any two of the following.

    1. a)GPIB electric interface
    2. b)Digital pH meter
    3. c)Heterodyne wave analyzer
    4. d)Sweep generator
    5. e)Wobbly scope
    How to answer

    • Brief principle, block diagram and use of any two chosen instruments
    • Key specifications and measurement application
    • Advantages/limitations in electronic instrumentation