INSTRUMENTATION & CONTROL (ME-402) - Important Questions

Explain what calibration is, the role of measurement standards and traceability, and why calibration is needed and how it is performed.

Explain the functional elements of a generalized measurement / instrument system with block diagram

Explain / discuss the static performance characteristics of measurement systems with diagrams and their impact on accuracy

Explain the meaning of uncertainties in measurement, including factors influencing them and how they are quantified and managed.

Explain the data acquisition and data reduction system, including how data outliers are detected.

Define the static performance characteristics: accuracy, precision, sensitivity, linearity, hysteresis and resolution

Distinguish between systematic and random errors and determine maximum error and percentage error for a $0$-$500$ kPa gauge with $\pm 1\%$ full-scale accuracy reading $100$ kPa.

Discuss measurement uncertainty and its analysis, including sequential and random tests.

Explain the classification / types of instrument systems based on function and application, with examples and diagrams.

For a pressure gauge of range $1000\text{ kN/m}^2$ with accuracy $\pm 1\%$ of full scale deflection, find possible readings for a true pressure of $100\text{ kN/m}^2$ and compare with error specified as $\pm 1\%$ of true value.

Explain error in measurement and discuss the various types and sources of errors in measurements and measuring instruments.

Calculate absolute uncertainty for a $25.46$ g weighing-scale reading with $\pm 0.02$ g accuracy and recommend how to mitigate uncertainties.

Discuss dynamic characteristics of instruments, formulate the system equation of a first-order instrument and obtain its step input response.

Numerical on first-order thermometer step response to find indicated temperature after given time.

Discuss the response of a second order instrument to harmonic input and effect of damping ratio

What is compensation in instruments? Discuss the response of an instrument to a transient input and to a random signal input.

Explain briefly harmonic signal and non-harmonic signal

Describe first-order and second-order measurement systems with suitable examples.

Discuss the concept of dynamic response in instrument systems and how is it measured or quantified? 7

Differentiate between periodic input and harmonic signal and their effect on instrument response

Explain the Fourier transform and its significance in analyzing signals in the frequency domain and decomposing signals into constituent frequencies.

Define dynamic characteristics of instruments, how they differ from static characteristics, and why they are important.

Numerical on step response of servo motor from transfer function to find time constant and settling time.

Explain the process of formulating system equations for dynamic systems, including key variables, parameters and their relationships.

Explain with sketch the construction and working of a dead-weight pressure gauge/tester, how it provides reference pressure for calibration, and its advantages and limitations.

Explain the role of thermal expansion in thermometry, including liquid-in-glass and bimetallic thermometers.

Compare a thermocouple, a resistance thermometer and a thermistor.

Describe the working of an orifice meter and a venturi meter with neat sketches. Compare them.

Numerical calculation of discharge through a venturimeter given diameters, pressure difference and $C_d$, and description of a rotameter.

Explain the principle, construction and working of resistance temperature detectors (electric resistance thermometry) and their applications

Discuss the construction, working principle and applications of (i) thermistor and (ii) bi-metallic strip.

Describe the operation of barometers and manometers and how fluid columns are used to measure atmospheric or fluid pressure.

What does a venturimeter measure? Explain its construction and working principle.

Define orifice meter (including its uses) and discuss its working principle with neat diagram.

What is a U-tube manometer? Discuss its construction, working and applications.

Explain types of pressure gauges and transducers and working principles of mechanical, electronic and piezoelectric pressure sensors

Explain the working principle of an electrical resistance strain gauge and define gauge factor

Describe the LVDT for displacement measurement and the load cell for force measurement.

Given gauge resistance, bar area, Young's modulus and load producing a measured resistance change, determine the gauge factor

List the procedure to mount a paper-backed strain gauge on the surface under study

Explain the method of usage of resistance strain gauge for bending compressive and tensile strains.

Explain potentiometers and how they measure displacement by converting mechanical displacement into electrical signals, including limitations.

Explain the operation of a stroboscope and how high-frequency light pulses are used to visualize and measure the velocity of fast-moving objects.

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

Discuss 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?

Describe velocity measurements using electromagnetic techniques. How are electromagnetic sensors used to measure linear and rotational velocities?

Given gauge resistance, gauge factor and applied tensile stress, calculate the change in resistance of a bonded strain gauge

Explain the working principle of a strain gauge load cell with a neat sketch.

Define control system and explain/differentiate open-loop vs closed-loop (feedback) control systems with block diagrams, examples, advantages and limitations.

Suggest and explain a suitable automatic closed-loop control system with block diagram for maintaining constant water level in a boiler.

Illustrate 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

Explain 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

Explore the mathematical modelling of mechanical systems. How are mechanical systems represented mathematically, and what types of equations are used to describe their behaviour?

Explain closed-loop (feedback) control system, including its concept, working and advantages.

Write short notes on servomechanism, temperature control system and position control system.