EC-302 Electronic Measurements and 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 the following terms in detail.

   1. i)Accuracy
   2. ii)Precision
   3. iii)Resolution
   How to answer

   • Define accuracy as closeness to true value with error concept
   • Define precision as repeatability / closeness among repeated readings
   • Define resolution as smallest increment detectable / display least count
   • Differentiate the three with example
2. 7 Marks
   bExplain the working of chopper type DC voltmeter in detail.
   How to answer

   • Need for DC voltmeter with high sensitivity and chopper modulation concept
   • Block diagram: input, chopper, AC amplifier, demodulator, meter
   • Working during chopper ON/OFF converting DC to AC and back
   • Advantages and applications
3. 7 Marks
   aWrite the applications of CRO and explain the concept of dual trace CRO.
   How to answer

   • List applications: voltage, current, frequency, phase, waveform observation
   • Concept of dual trace for simultaneous display of two signals
   • Alternate and chopped modes with electronic switch
   • Block diagram of dual trace CRO
4. 7 Marks
   bExplain the working of digital storage oscilloscope with suitable diagram.
   How to answer

   • Need for storage of fast transient waveforms
   • Block diagram: ADC, memory, DAC, CRT control
   • Write, store and readout modes of operation
   • Advantages over analog storage
5. 7 Marks
   aDraw the circuit diagram of Schering bridge and explain its operation.
   How to answer

   • Circuit with four arms: ratio arms, standard capacitor, unknown capacitor with loss
   • Balance condition derivation for Cx and Rx
   • Phasor / operation at AC null detector
   • Use for capacitance and dielectric loss measurement
6. 7 Marks
   bDiscuss about the impedance measurement by Q-meter.
   How to answer

   • Principle of Q-meter: Q = Vc/V and resonance
   • Circuit and procedure tuning to resonance
   • Measurement of impedance / inductance / capacitance from Q
   • Applications and limitations
7. 7 Marks
   aWhat is Thermocouple? Explain working principle of piezo-electric transducer.
   How to answer

   • Define thermocouple and Seebeck effect
   • Construction with two dissimilar metals and reference junction
   • Piezo-electric effect: charge on mechanical stress
   • Construction, working and applications of piezo-electric transducer
8. 7 Marks
   bWhat is transducer? Classify the transducers.
   How to answer

   • Define transducer as energy conversion device
   • Classification basis: active/passive, primary/secondary
   • Classification by principle: resistive, inductive, capacitive, piezoelectric etc.
   • Examples for each class
9. 7 Marks
   aDiscuss about the working of LED in detail.
   How to answer

   • Construction of LED: PN junction with direct bandgap material
   • Electroluminescence and recombination mechanism
   • Circuit operation and characteristics
   • Applications in displays and indicators
10. 7 Marks
    bDescribe the operation of sweep frequency generator with diagram.
    How to answer

    • Purpose of sweep frequency generator for frequency response testing
    • Block diagram with sweep oscillator and marker
    • Operation of frequency sweeping with time base
    • Applications
11. 7 Marks
    aDraw and explain the operation of successive approximation ADC.
    How to answer

    • Block diagram: sample-hold, comparator, SAR, DAC
    • Step-by-step successive comparison from MSB to LSB
    • Timing / conversion example
    • Advantages and applications
12. 7 Marks
    bDraw and explain the working of 3 bit R-2R ladder DAC.
    How to answer

    • Circuit of 3-bit R-2R ladder with R and 2R network and op-amp
    • Working as binary-weighted current division
    • Output voltage formula Vo = -Vref * digital value / 8
    • Advantages over weighted resistor DAC
13. 7 Marks
    aExplain in case of DVM: What is the significance of $\frac{1}{2}$ digit?

    1. i)$3\frac{1}{2}$ digits
    2. ii)$5\frac{1}{2}$ digits
    How to answer

    • Meaning of 3-1/2 digits: 1999 max count and 1V range example
    • Meaning of 5-1/2 digits: 199999 max count and higher resolution
    • Significance of 1/2 digit: leading digit 0 or 1 for overrange
    • Effect on range and resolution of DVM
14. 7 Marks
    bExplain the resolution and sensitivity of DVM in detail.
    How to answer

    • Define resolution as smallest voltage change displayed
    • Relation of resolution to number of digits and range
    • Define sensitivity as smallest measurable / slope response
    • Factors affecting DVM sensitivity
15. 7 Marks
    aWrite short note on Hay's bridge.
    How to answer

    • Bridge configuration for high-Q inductance measurement
    • Balance equations and Q factor expression
    • Operating procedure and advantages
    • Applications and limitations
16. 7 Marks
    bWrite short note on LCD.
    How to answer

    • Construction and liquid crystal principle with polarization
    • Types: TN, STN, TFT and seven-segment operation
    • Drive requirements: AC excitation and low power
    • Advantages, limitations and applications