ME-402 Instrumentation & Control - Jun 2026 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
   aWhat is an instrument system? Give its classification and describe the functional elements of a measurement system with a block diagram.
   How to answer

   • Definition of instrument system as assembly for measurement
   • Classification: mechanical, electrical, electronic, etc. / active-passive, null-deflection
   • Functional elements: primary sensor, transducer, signal conditioner, display/record
   • Block diagram flow from measurand to output
   • Example of each element
2. 7 Marks
   bWhat is calibration? Discuss the standards used in measurement and the need for traceability.
   How to answer

   • Definition of calibration by comparison with standard
   • Hierarchy of standards: primary, secondary, working, international
   • Concept of traceability chain to national standards
   • Need for traceability: accuracy, consistency, quality assurance
   • Calibration procedure briefly
3. 7 Marks
   aDefine the static performance characteristics: accuracy, precision, sensitivity, linearity, hysteresis and resolution.
   How to answer

   • Define accuracy as closeness to true value
   • Precision, sensitivity, linearity definitions
   • Hysteresis and resolution definitions
   • Distinguish static vs dynamic characteristics
   • Examples/units for each
4. 7 Marks
   bDistinguish between systematic and random errors. A pressure gauge of range $0-500$ kPa has an accuracy of $\pm 1\%$ of full scale. Determine the maximum possible error and the percentage error when it reads $100$ kPa.
   How to answer

   • Distinguish systematic errors: causes, correctable, bias
   • Distinguish random errors: causes, statistical treatment
   • Maximum error = 1% of 500 kPa = 5 kPa
   • Percentage error at 100 kPa = 5/100 x 100 = 5%
   • Comment on full-scale accuracy effect at low readings
5. 7 Marks
   aDiscuss measurement uncertainty and its analysis. What are sequential and random tests?
   How to answer

   • Definition of measurement uncertainty and sources
   • Steps of uncertainty analysis: propagation, confidence
   • Sequential tests: varying one variable at a time
   • Random tests: randomized order to average effects
   • Need for replication
6. 7 Marks
   bDescribe data acquisition and data reduction. How are data outliers detected?
   How to answer

   • Purpose of data acquisition system components
   • Data reduction: averaging, filtering, curve fitting
   • Definition of outlier and its causes
   • Methods: Chauvenet, 3-sigma, Grubbs test, plots
   • Action on detected outliers
7. 7 Marks
   aDiscuss the dynamic characteristics of instruments. Formulate the system equation of a first order instrument and obtain its response to a step input.
   How to answer

   • Define dynamic characteristics: speed of response, lag, fidelity
   • First-order differential equation: tau dx/dt + x = k f(t)
   • Step input solution using initial condition
   • Time constant and steady-state response
   • Plot of response vs time
8. 7 Marks
   bA first order thermometer of time constant $5$ s is suddenly placed in a fluid at $100^{\circ}C$ from an initial temperature of $20^{\circ}C$. Determine the temperature indicated after $10$ s.
   How to answer

   • First-order step response formula T = T_fluid + (T0 - T_fluid) e^{-t/tau}
   • Given tau=5 s, t=10 s, T0=20 C, T_fluid=100 C
   • Compute exponent e^{-2} ~ 0.1353
   • Indicated temperature ~ 89.2 C
   • Interpretation of lag
9. 7 Marks
   aDiscuss the response of a second order instrument to a harmonic input and the effect of damping ratio on it.
   How to answer

   • Second-order equation with natural frequency and damping ratio
   • Transfer function / frequency response to harmonic input
   • Magnification factor and phase vs frequency ratio
   • Effect of damping ratio zeta <1, =1, >1
   • Resonance and isolation regions
10. 7 Marks
    bWhat is compensation in instruments? Discuss the response of an instrument to a transient input and to a random signal input.
    How to answer

    • Definition of compensation: correcting dynamic errors
    • Types: series, feedback compensation
    • Transient input response: impulse/step characteristics
    • Random signal input: statistical description, PSD
    • Mean, RMS response of instrument
11. 7 Marks
    aDescribe thermometry based on thermal expansion: liquid in glass and bimetallic thermometers.
    How to answer

    • Principle of thermal expansion thermometry
    • Liquid-in-glass: construction, fluid, scale, working
    • Bimetallic: two metals, coil/strip deflection
    • Ranges, advantages, limitations
    • Applications
12. 7 Marks
    bCompare a thermocouple, a resistance thermometer and a thermistor.
    How to answer

    • Working principle of each: Seebeck, RTD resistance, semiconductor
    • Comparison on range, sensitivity, linearity, cost
    • Advantages/limitations table
    • Response time and accuracy
    • Typical applications
13. 7 Marks
    aDescribe the working of an orifice meter and a venturi meter with neat sketches. Compare them.
    How to answer

    • Orifice meter: construction, orifice plate, pressure taps, formula
    • Venturi meter: convergent-divergent, pressure recovery
    • Neat sketches of both with flow and manometer
    • Comparison: loss, cost, accuracy, Cd
    • Applications
14. 7 Marks
    bA venturi meter of inlet diameter $200$ mm and throat diameter $100$ mm carries water. If the pressure difference is $30$ kPa and $C_d = 0.98$, calculate the discharge. Also describe the rotameter.
    How to answer

    • Venturi discharge formula Q = Cd*A1*A2/sqrt(A1^2-A2^2)*sqrt(2*dp/rho)
    • Given D1=200 mm, D2=100 mm, dp=30 kPa, Cd=0.98, water rho=1000
    • Compute areas and velocity approach factor
    • Discharge value in m3/s / L/s
    • Rotameter: variable area, float, tube, working
15. 7 Marks
    aDescribe the working of a strain gauge and define gauge factor.
    How to answer

    • Principle: resistance change with strain
    • Construction: bonded wire/foil, Wheatstone bridge
    • Derivation of gauge factor G = (dR/R)/(dl/l)
    • Gauge factor ~2 for metals, high for semiconductors
    • Temperature compensation
16. 7 Marks
    bDescribe the LVDT for displacement measurement and the load cell for force measurement.
    How to answer

    • LVDT: primary, two secondaries, movable core, differential output
    • Characteristics: linear range, phase, sensitivity
    • Load cell: elastic member + strain gauges for force
    • Bridge circuit and calibration for weight/force
    • Applications of both