ME-402 Instrumentation and Control - Jun 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
   aExplore the classifications of instrument systems based on their function and application. Provide examples of instrument systems in different domains.
   How to answer

   • Definition of instrument system classification by function - indicating, recording, controlling
   • Classification by application - mechanical, electrical, electronic domains
   • Examples in different domains with use-cases
   • Summary table of types vs functions
2. 7 Marks
   bA pressure transducer has a resolution of 0.01 bar. If the pressure reading fluctuates between 3.45 bar and 3.52 bar due to noise and signal instability, determine the overall uncertainty in the pressure measurement, considering factors such as signal-to-noise ratio and sampling rate.
   How to answer

   • Given resolution 0.01 bar and fluctuation range 3.45-3.52 bar
   • Estimate uncertainty components: resolution, noise spread, SNR, sampling
   • Combine uncertainties to overall uncertainty
   • Interpretation for pressure measurement reliability
3. 7 Marks
   aDefine the dynamic characteristics of instruments. How do dynamic characteristics differ from static characteristics, and why are they important in understanding instrument behavior?
   How to answer

   • Define dynamic characteristics: speed of response, lag, fidelity, dynamic error
   • Contrast with static characteristics with examples
   • Importance for transient behavior and control stability
   • Examples of first and second order instrument response
4. 7 Marks
   bA servo motor is subjected to a step input signal with a magnitude of 10 V. The motor's transfer function is $H(s) = \frac{50}{s(s+10)}$. Determine the time constant and settling time of the motor's response to the step input.
   How to answer

   • Rewrite $H(s)$ in standard first-order form to identify pole/time constant
   • Compute time constant $\tau = 0.1$ s from $s+10$
   • Apply step input of 10 V and find response expression
   • Estimate settling time ~ $4\tau$ for 2% criterion
5. 7 Marks
   aDescribe measurement errors and uncertainties in instrument systems. Explain the factors influencing measurement errors and how uncertainties are quantified and managed.
   How to answer

   • Define systematic, random errors and uncertainty
   • Factors: calibration, environment, loading, human, noise
   • Quantification: standard deviation, confidence intervals, error propagation
   • Management: calibration, compensation, averaging, traceability
6. 7 Marks
   bCompare analysis, sequential, and random tests used in assessing instrument system performance.
   How to answer

   • Purpose of analysis, sequential and random tests
   • Procedure and data collection for each test type
   • Comparison on cost, time, statistical validity
   • Selection criteria for performance assessment
7. 7 Marks
   aExplain the process of formulating system equations for dynamic systems. Describe the key variables and parameters involved and their relationships.
   How to answer

   • Steps: define system, identify elements, free-body diagrams, apply laws
   • Key variables: displacement, velocity, force; parameters: mass, damping, stiffness
   • Form of differential equations and transfer functions
   • Example of mechanical/electrical analogy
8. 7 Marks
   bExplain the concept of non-harmonic signals in dynamic analysis. What are the sources of non-harmonic signals, and how do they impact instrument response?
   How to answer

   • Define non-harmonic / non-sinusoidal signals
   • Sources: transients, noise, nonlinearities, switching
   • Impact: distortion, resonance, measurement error
   • Analysis approach: Fourier, superposition
9. 7 Marks
   aDescribe the response of instrument systems to random signal input. What are random signals, and how do instruments analyse and interpret these signals?
   How to answer

   • Define random signals: statistical nature, PSD, mean/variance
   • Instrument response: filtering, averaging, correlation
   • Analysis tools: probability distribution, autocorrelation
   • Interpretation for measurement accuracy
10. 7 Marks
    bExplore the mathematical modelling of mechanical systems. How are mechanical systems represented mathematically, and what types of equations are used to describe their behaviour?
    How to answer

    • Lumped mass-spring-damper representation
    • Newton's laws to second-order ODEs
    • Types of equations: time-domain ODE, transfer function, state-space
    • Example derivation and physical interpretation
11. 14 Marks
    Explore different types of pressure gauges and transducers. What are the working principles of mechanical, electronic, and piezoelectric pressure sensors?
    How to answer

    • Types: Bourdon, diaphragm, bellows, strain-gauge, capacitive, piezoelectric
    • Working principle of mechanical gauges
    • Working principle of electronic transducers
    • Working principle of piezoelectric sensors with applications
12. 7 Marks
    aDiscuss the role of electrical circuits in strain gauge measurements. How are strain gauges connected in Wheatstone bridge configurations, and how is the output signal processed to determine strain?
    How to answer

    • Role of bridge circuit for small resistance change detection
    • Quarter, half, full bridge connections of strain gauges
    • Bridge output voltage relation to strain and gauge factor
    • Signal conditioning: amplification, filtering, calibration
13. 7 Marks
    bDescribe the working principle of bimetallic thermometers. How do bimetallic strips utilize differential thermal expansion to measure temperature?
    How to answer

    • Construction of bonded bimetallic strip
    • Differential thermal expansion bending principle
    • Conversion of deflection to temperature indication
    • Applications and limitations
14. 7 Marks
    aDescribe velocity measurements using electromagnetic techniques. How are electromagnetic sensors used to measure linear and rotational velocities?
    How to answer

    • Principle of electromagnetic induction / Faraday's law
    • Linear velocity: magnetic flowmeter, LVDT-type pickups
    • Rotational velocity: tachogenerator, magnetic encoder
    • Advantages for non-contact measurement
15. 7 Marks
    bExplore the concept of electric resistance thermometry. How do changes in electrical resistance of conductive materials correlate with temperature variations?
    How to answer

    • Resistance-temperature relationship and TCR
    • Materials: platinum, copper, nickel; RTD construction
    • Bridge measurement and linearization
    • Correlation of resistance change to temperature