EX-303 Electrical Measurement and Measuring Instruments - Dec 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 static and dynamic characteristics of measuring instruments in detail. Discuss accuracy, precision, sensitivity, resolution, repeatability, drift, and response time with suitable examples.
   How to answer

   • Define static vs dynamic characteristics
   • Explain accuracy, precision, sensitivity, resolution, repeatability, drift
   • Explain dynamic terms: response time, speed, lag, fidelity
   • Give suitable examples for each
2. 7 Marks
   bExplain the concept of errors in measurement. Classify errors and describe the sources of errors and methods used for their reduction.
   How to answer

   • Define error: true vs measured value
   • Classify: gross, systematic, random errors
   • Describe sources: instrumental, environmental, observational
   • Discuss reduction: calibration, correction, statistical methods
3. 7 Marks
   aDiscuss the classification of instruments. Explain deflection type and null type instruments, giving suitable examples and applications.
   How to answer

   • Classify instruments: absolute/secondary, analog/digital, indicating/recording/integrating
   • Explain deflection type principle with example
   • Explain null type principle with example
   • List applications of each type
4. 7 Marks
   bDescribe the construction and working principle of D'Arsonval galvanometer. Explain how it is used as a basic measuring instrument.
   How to answer

   • Describe construction: magnet, coil, suspension, pointer
   • Explain working: Lorentz force and deflecting torque
   • Derive deflecting torque and control
   • Explain use as basic voltmeter, ammeter, ohmmeter
5. 7 Marks
   aExplain the methods of converting a galvanometer into an ammeter and voltmeter. Derive the necessary expressions.
   How to answer

   • Explain shunt for ammeter conversion with circuit
   • Derive shunt resistance expression $R_{sh}=R_g/(m-1)$
   • Explain series multiplier for voltmeter conversion
   • Derive multiplier expression $R_s=R_g(n-1)$
6. 7 Marks
   bExplain PMMC, MI, and Electrodynamometer type instruments. Compare their construction, working principles, advantages, and disadvantages.
   How to answer

   • Explain PMMC construction and DC working
   • Explain MI attraction/repulsion types and AC working
   • Explain electrodynamometer construction and power measurement
   • Compare advantages, disadvantages and applications
7. 7 Marks
   aExplain the construction and working of digital multimeters and wattmeters. Discuss their applications and limitations.
   How to answer

   • Describe block diagram and construction of digital multimeter
   • Explain working for V, I, R measurement
   • Explain digital wattmeter principle
   • Discuss applications and limitations
8. 7 Marks
   bExplain the construction, principle, and applications of instrument transformers. Describe current transformers (CT) and potential transformers (PT) in detail.
   How to answer

   • Define instrument transformers and need
   • Explain CT construction, ratio and operation
   • Explain PT construction, ratio and operation
   • List applications in metering and protection
9. 7 Marks
   aExplain the necessity of instrument transformers in high voltage and high current measurements. Discuss their advantages and limitations.
   How to answer

   • Explain isolation and range extension need
   • Discuss safety and cost advantages
   • Discuss ratio, phase and burden errors
   • List limitations and precautions
10. 7 Marks
    bExplain the measurement of power in three-phase circuits using two-wattmeter and three-wattmeter methods. Discuss advantages and limitations.
    How to answer

    • Draw connections for two-wattmeter method
    • Derive $P=W_1+W_2$ and power factor expression
    • Explain three-wattmeter method for 4-wire system
    • Compare advantages, limitations and balanced vs unbalanced load
11. 7 Marks
    aExplain the measurement of power factor using single-phase and three-phase electrodynamometer type and moving iron type instruments.
    How to answer

    • Explain electrodynamometer power factor meter construction
    • Explain MI power factor meter construction
    • Describe single-phase and three-phase connections
    • Explain deflection proportional to phase angle
12. 7 Marks
    bExplain Wheatstone bridge and Kelvin's double bridge with circuit diagrams. Discuss their applications in resistance measurement.
    How to answer

    • Draw Wheatstone bridge and balance condition
    • Draw Kelvin double bridge to eliminate lead resistance
    • Derive $R_x$ expressions for both
    • Discuss medium vs low resistance applications
13. 7 Marks
    aExplain inductance and capacitance measurement using bridge methods. Discuss sources of errors and precautions.
    How to answer

    • Explain AC bridges for L: Maxwell, Hay, Anderson
    • Explain AC bridges for C: Schering, De Sauty
    • Discuss balance equations and phasor conditions
    • List error sources and precautions
14. 7 Marks
    bExplain magnetic measurements. Describe B-H curve determination, hysteresis loop, and measurement of power loss in sheet metal using Lloyd-Fisher square.
    How to answer

    • Define magnetic measurements and B-H curve
    • Explain hysteresis loop determination
    • Describe Lloyd-Fisher square for iron loss
    • Explain separation of hysteresis and eddy current loss
15. 7 Marks
    aExplain the working of electronic energy meters. Compare them with electromechanical energy meters.
    How to answer

    • Explain block diagram of electronic energy meter
    • Describe sensing, ADC, multiplication and display
    • Compare construction and accuracy with electromechanical
    • List advantages like tamper detection and limitations
16. 7 Marks
    bExplain the selection criteria for measuring instruments. Discuss reliability, cost, loading effect, and environmental factors affecting measurements.
    How to answer

    • List selection criteria: range, accuracy, sensitivity
    • Discuss reliability, cost and loading effect
    • Explain environmental factors: temperature, humidity, EMI
    • Give example of proper instrument selection