(SEM V) THEORY EXAMINATION 2024-25 SENSORS AND TRANSDUCERS

Subject Code: BEE052
Maximum Marks: 70
Time: 3 Hours
Paper ID: 310946

Question Paper Overview

SECTION A (2 × 7 = 14 Marks)

(Answer all questions briefly — fundamental definitions and concepts)

a. Define transducers and classify them.
b. Explain the working of an LVDT for displacement measurement.
c. Describe the role of Hall effect sensors in position measurement.
d. What are CCD and CMOS sensors?
e. What is a data acquisition system (DAS)?
f. What are the characteristics of smart sensors?
g. Why is signal amplification needed in signal conditioning?

SECTION B (Attempt any three × 7 = 21 Marks)

a. Explain the working principles of Potentiometer and LVDT for displacement measurement with neat diagrams.
b. Explain the principles of temperature measurement using Thermistors, Thermocouples, and RTD.
c. Explain the difference between machine vision and computer vision.
Discuss the components and applications of a typical machine vision system.
d. What are the main functions of signal conditioning equipment?
Explain the types of amplifiers used in instrumentation systems.
e. Describe the general structure and components of smart sensors.
Discuss their characteristics such as self-calibration, self-testing, and self-communication.

SECTION C (Attempt one part from each question × 7 = 35 Marks)

Q3

(a) A Strain Gauge with resistance 120Ω120\Omega120Ω and gauge factor 2 is connected in series with a ballast resistance of 120Ω120\Omega120Ω across a 12V supply.
Calculate the difference between output voltages (across the strain gauge) with no stress applied and with a stress of 140 MN/m², given that the modulus of elasticity = 200 GN/m².
OR
(b) Explain how force and pressure are measured using strain gauges, load cells, and piezoelectric sensors.

Q4

(a) Explain the principles of operation for flow sensors (Ultrasonic and Laser) and level sensors (Ultrasonic and Capacitive).
OR
(b) A thermocouple has a sensitivity of 0.05 mV/°C.

Reference junction = 0°C

Measured voltage = 4.5 mV

Find the measurement temperature.

If reference junction = 25°C (with same output 4.5 mV), find new temperature.

Q5

(a) Describe the role of CCD and CMOS sensors in imaging. Compare them in sensitivity, resolution, and power consumption.
OR
(b) Explain how a machine vision system assists a pick-and-place robot.
Describe the sensing, digitizing, image processing, and training steps.

Q6

(a) Describe the configuration and objectives of a Data Acquisition System (DAS).
Explain the roles of analog/digital I/O, counters, and timers.
OR
(b) Discuss the importance of data conversion in modern instrumentation systems.
Explain ADC and DAC working principles.

Q7

(a) Explain the applications of smart sensors in smart cities, industrial robots, and electric vehicles.
Discuss how they enhance efficiency and reliability.
OR
(b) Explain the working of smart sensors for body temperature and blood oxygen measurement.
Discuss their integration into wearable devices.

Key Topics for Revision

1. Transducers

Convert one form of energy to another.

Types:

Active (self-generating): e.g., thermocouple, piezoelectric.

Passive (require external power): e.g., LVDT, strain gauge.

2. LVDT (Linear Variable Differential Transformer)

Measures linear displacement.

Consists of a primary coil and two secondary coils.

Displacement changes the magnetic coupling, altering the differential output voltage.

3. Hall Effect Sensor

Based on voltage generated due to magnetic field acting on a conductor.

Used for position and speed measurement (e.g., motor control).

4. CCD vs CMOS Sensors

5. Data Acquisition System (DAS)

Converts physical signals → digital data.

Components: Sensors → Signal Conditioning → ADC → Microprocessor → Display/Storage.

6. Smart Sensors

Combine sensing, processing, and communication capabilities.

Characteristics:                              Self-calibration

Self-diagnosis                             Digital communication

Integration with IoT systems

7. Signal Conditioning

Amplifies, filters, and converts sensor signals for processing.

Amplifiers: Differential, Instrumentation, Isolation.

Needed to improve signal-to-noise ratio and accuracy.

8. Temperature Measurement

9. Strain Gauge

Gauge Factor (GF)=ΔR/Rϵ\text{Gauge Factor (GF)} = \frac{\Delta R / R}{\epsilon}Gauge Factor (GF)=ϵΔR/R​

For stress (σ = Eε),
ε = σ/E
Used in load cells, torque sensors, and pressure transducers.

10. Flow and Level Sensors

Ultrasonic Flow Sensor: Measures velocity via sound reflection.

Laser Flow Sensor: Uses Doppler shift for precision.

Capacitive Level Sensor: Detects dielectric changes.

Ultrasonic Level Sensor: Time-of-flight measurement.

11. ADC & DAC

ADC: Converts analog → digital (using sampling & quantization).

DAC: Converts digital → analog for actuators or displays.

Crucial for data logging and control systems.

12. Machine Vision

Uses cameras, sensors, and algorithms to interpret visual data.

Applications: Defect detection, robot guidance, quality control.

13. Smart Sensor Applications

14. Biomedical Smart Sensors

Temperature sensors: Thermistors or infrared-based.

SpO₂ sensors: Measure oxygen via light absorption at red/IR wavelengths.

Integrated in wearables (smartwatches, fitness bands).

Exam Tips

Prepare block diagrams for LVDT, DAS, and smart sensors.

Practice numerical problems on strain gauge and thermocouple.

Use comparative tables (e.g., CCD vs CMOS, Thermocouple vs RTD).

Write definitions + principles + diagrams for full marks.

Relate smart sensor applications to IoT and Industry 4.0.