ME-402 Instrumentation and Control - 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
   aDescribe the role of standards and calibration in ensuring the accuracy and reliability of measurement systems. How are standards used to calibrate instruments, and why is calibration important? 7
   How to answer

   • Define standards (primary, secondary, working) and calibration
   • Explain calibration procedure using standards for traceability
   • Explain role in accuracy, reliability, error reduction
2. 7 Marks
   bAn electronic weighing scale is used to measure the weight of a substance. The scale has a stated accuracy of $\pm 0.02$ grams. During an experiment, the scale recorded a weight of $25.46$ grams for the substance. Calculate the absolute uncertainty in the measurement considering the scale's accuracy. Provide recommendations on how to mitigate and minimize uncertainties in weight measurements using this scale. 7
   How to answer

   • State absolute uncertainty = 7 stated accuracy = 7 0.02 g
   • Express result as 25.46 7 0.02 grams and relative uncertainty
   • List mitigation: calibration, averaging, environment control, proper handling
3. 7 Marks
   aDiscuss the static performance characteristics of measurement systems and how do they impact measurement accuracy? 7
   How to answer

   • Define static characteristics: accuracy, precision, sensitivity, linearity, hysteresis, repeatability, etc.
   • Explain each characteristic briefly
   • Explain impact on measurement accuracy and selection
4. 7 Marks
   bDiscuss the concept of dynamic response in instrument systems and how is it measured or quantified? 7
   How to answer

   • Define dynamic response and need for time-varying inputs
   • Explain parameters: time constant, response time, frequency response, damping
   • Explain measurement/quantification methods
5. 7 Marks
   aExplain displacement measurements using potentiometers. How do potentiometers convert mechanical displacement into electrical signals, and what are their limitations? 7
   How to answer

   • Explain potentiometer principle: resistance change with wiper position
   • Explain conversion of mechanical displacement to voltage signal
   • List limitations: wear, friction, limited resolution, noise
6. 7 Marks
   bDiscuss instrument static characteristics specifications. Explain how specifications are determined and how they inform instrument selection and evaluation. 7
   How to answer

   • List static characteristics specifications: range, span, accuracy, linearity, etc.
   • Explain how specifications are determined by calibration/testing
   • Explain use in instrument selection and evaluation
7. 7 Marks
   aDifferentiate between periodic input and harmonic signal in the context of dynamic analysis. How do these input signals affect the response of instrument systems, and what are their characteristics? 7
   How to answer

   • Define periodic input vs harmonic (sinusoidal) signal
   • Compare characteristics: frequency content, waveform, Fourier representation
   • Explain effect on instrument response: transient, steady-state, resonance
8. 7 Marks
   bDefine control systems and explain the difference between open-loop and closed-loop (feedback) control systems. Provide examples of each type of control system and discuss their advantages and limitations. 7
   How to answer

   • Define control system and open-loop vs closed-loop (feedback)
   • Give examples of each type
   • Compare advantages and limitations
9. 7 Marks
   aDiscuss the Fourier transform and its significance in analyzing signals in the frequency domain. How is the Fourier transform used to decompose signals into their constituent frequencies? 7
   How to answer

   • Define Fourier transform for time to frequency domain conversion
   • Explain decomposition into constituent frequencies/amplitude spectrum
   • Explain significance in signal analysis and filtering
10. 7 Marks
    bDiscuss the use of dead weight testers in pressure calibration. How do dead weight testers provide reference pressure values for calibration purposes? 7
    How to answer

    • Explain dead weight tester principle: known weight / piston area = pressure
    • Explain procedure for calibration of pressure gauges
    • Explain reference pressure generation and accuracy
11. 14 Marks
    Discuss the principles of linear and rotary variable differential transformers (LVDTs and RVDTs) in displacement measurements. How do LVDTs and RVDTs provide precise measurements of linear and angular displacements? 14
    How to answer

    • Explain LVDT construction and differential induction principle
    • Explain RVDT for angular displacement
    • Explain signal conditioning and precision advantages
12. 7 Marks
    aExplain the operation of stroboscopes in velocity measurements. How do stroboscopes use high-frequency light pulses to visualize and measure the motion of fast-moving objects? 7
    How to answer

    • Explain stroboscope principle of high-frequency flashing
    • Explain freezing motion / synchronization with rotating object
    • Explain measurement of speed from flash frequency
13. 7 Marks
    bIllustrate the construction of block diagrams for closed-loop control systems. What are the basic components of a block diagram, and how are they interconnected to represent the control system's structure and function? 7
    How to answer

    • List basic block diagram components: comparator, controller, plant, sensor, feedback
    • Draw neat labelled closed-loop block diagram
    • Explain interconnections and signal flow representing control function
14. 7 Marks
    aExplain the mathematical modelling of electrical systems. How are electrical circuits modelled using equations, and how do different components (e.g., resistors, capacitors, inductors) contribute to the overall system behaviour? 7
    How to answer

    • Explain need for mathematical modelling using differential equations
    • Write models for R, L, C using KVL/KCL and transfer function
    • Explain contribution to order, time constant and overall behaviour
15. 7 Marks
    bDescribe the operation of pressure measurement devices such as barometers and manometers. How do these devices utilize fluid columns to measure atmospheric or fluid pressure? 7
    How to answer

    • Explain barometer for atmospheric pressure and manometer for fluid pressure
    • Explain fluid column height proportional to pressure difference
    • Compare types: U-tube, well, inclined manometer