About this previous year paper
Course: B.Tech (Mechanical Engineering)
Subject Code: EME403
Subject Title: Measurement and Metrology
Exam Type: Theory
Duration: 3 Hours
Maximum Marks: 100
SECTION – A (10 × 2 = 20 Marks)
Short, direct questions to test conceptual clarity
| No. | Question | Explanation |
|---|---|---|
| (a) | What is Static Response? | The behavior of a measuring system when subjected to a constant (steady-state) input — defines accuracy and sensitivity. |
| (b) | Define Interchangeability. | Ability to replace one component with another of same specification without modification. |
| (c) | Precautions with Slip Gauges. | Clean surfaces, use wringing technique, avoid temperature variation, and handle with care to prevent corrosion. |
| (d) | Progressive Error in Screw Gauge. | Cumulative error caused by pitch or lead imperfections in the screw thread. |
| (e) | Define Limit and Tolerance. | Limit → maximum/minimum permissible size; Tolerance → difference between them. |
| (f) | Temperature Measuring Instruments. | Thermocouple, Pyrometer, Thermistor, Resistance thermometer. |
| (g) | Force vs Torque. | Force = linear push/pull (N); Torque = rotational effect of force (N·m). |
| (h) | What is Comparator? | Device for comparing unknown dimension with a known standard. |
| (i) | Define Straightness. | Deviation of a line from an ideal straight line. |
| (j) | Errors Using Sine Bar. | Arise from sine bar deformation, incorrect roller spacing, or angle over 15° causing calculation error. |
SECTION – B (5 × 10 = 50 Marks)
Conceptual and descriptive questions focusing on measurement principles
(a) Generalized Measuring System
Components:
Primary Sensing Element – detects input (e.g., pressure diaphragm).
Transducer Element – converts signal to electrical form.
Signal Conditioning – amplifies or filters.
Output Device – indicates, records, or controls.
(b) Types of Errors in Measurement
Systematic Errors: calibration, environmental, observational.
Random Errors: unpredictable, due to small uncontrollable factors.
Gross Errors: human mistakes in observation or computation.
(c) Sigma Comparator
Construction: Plunger, mechanical linkage, amplifying lever, and dial indicator.
Working: Converts small linear displacement into amplified pointer movement.
Use: For high-precision comparison of parts within micron range.
(d) AC Laser Interferometer
Principle: Interference of light waves — measures distance, flatness, and straightness.
Working: Laser beam split into two paths; phase difference between reflected beams indicates displacement or misalignment.
Advantage: Extremely high accuracy (up to nanometer level).
(e) Roundness Measurement
V-Block Method: Workpiece rotated in a V-groove; deviations indicate roundness error.
Three-Point Probe: Measures eccentricity and form error more accurately.
Limitation of V-Block: Not suitable for non-circular deviations and large eccentricities.
(f) Pitch Measurement (Threads)
Pitch Measuring Machine: Uses microscope, micrometer heads, and optical systems to measure lead, pitch, and angle of threads.
Applicable for: Internal and external threads.
(g) LVDT (Linear Variable Differential Transformer)
Construction: Primary coil and two secondary coils with movable soft iron core.
Principle: Differential voltage induced in secondary coils corresponds to displacement.
Advantages: High accuracy, frictionless operation, infinite resolution.
(h) Taylor’s Principle of Gauge Design
“A GO gauge should check maximum material condition; a NO-GO gauge should check minimum material condition.”
Types:
Ring Gauge: For external diameter checks.
Plug Gauge: For internal hole measurements.
SECTION – C (2 × 15 = 30 Marks)
Application-based and analytical questions
Q3. (i) Thermocouples
Principle: Seebeck effect — EMF generated between two dissimilar metals when temperature difference exists.
Types: Iron–Constantan, Copper–Constantan, Chromel–Alumel.
Applications: Temperature measurement in furnaces, engines, etc.
(ii) Strain Gauge Torque Meter
Measures torque through strain produced in shaft surface.
Wheatstone bridge detects resistance change in strain gauges → calibrated for torque.
Q4. Pressure Measurement
(i) Piezo-Electric Pressure Transducer
Quartz crystal generates charge proportional to applied pressure.
Advantage: High frequency response, suitable for dynamic pressures.
(ii) Variable Capacitance Transducer
Pressure changes plate spacing or dielectric → capacitance change.
Used for: Low pressure, high-sensitivity measurement.
Q5. Linear & Angular Measurement
(i) Vernier Caliper
Used for internal, external, and depth measurements.
Principle: Difference between main and vernier scale readings gives precision (0.02 mm typical).
(ii) Limitation of Sine Bar
Not suitable for angles >15° due to cosine error, limited roller accuracy, and setup instability.
Summary
This Measurement and Metrology (EME403) paper thoroughly tests:
Principles of precision measurement
Instrument operation (comparators, transducers, interferometers)
Error analysis and tolerance design
Linear, angular, and surface measurement
Modern metrological tools (laser, strain gauge, LVDT)