(SEM V) THEORY EXAMINATION 2023-24 SENSORS AND TRANSDUCERS

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SECTION A — Short Answers (2 × 10 = 20)

(a) Difference between a Sensor and a Transducer

Parameter	Sensor	Transducer
Definition	Detects physical change (like temperature, pressure, light).	Converts one form of energy to another (non-electrical → electrical).
Output	Non-electrical (may be mechanical, thermal, etc.)	Electrical signal proportional to the physical quantity.
Example	Thermistor, LDR	Thermocouple, LVDT

(b) Advantages of Electrical Transducers

Electrical signals are easy to amplify, process, and transmit over long distances.

They offer high sensitivity and quick response. Compact and lightweight design.

Compatible with digital data acquisition systems.

(c) Properties of a Thermocouple

Seebeck Effect: Generates voltage proportional to temperature difference between junctions.

Wide Temperature Range: -200°C to +1800°C depending on material type.

Rugged, inexpensive, and suitable for dynamic temperature measurements.

(d) RTD — Full Form & Difference from Thermistor RTD: Resistance Temperature Detector.

Difference:
| RTD | Thermistor |
|------|-------------|
| Made of metals (usually platinum). | Made of semiconductor materials. |
| Has linear resistance–temperature relation. | Highly nonlinear but more sensitive. |
| Expensive, slower response. | Cheaper, faster response. |

(e) What are Imaging Sensors?

Devices that convert light into electrical signals to form digital images.
Types: CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor) sensors used in cameras, robotics, and surveillance.

(f) Why Image Processing is Needed? To enhance image quality (contrast, noise removal).

To extract useful information (object detection, measurement).

For automation, pattern recognition, and quality inspection.

(g) Need for Signal Conditioning Converts weak sensor outputs into usable form.

Performs amplification, filtering, linearization, and A/D conversion.

Ensures accurate, noise-free data for controllers or microprocessors.

(h) Applications of DAC (Digital-to-Analog Converter)

Converts digital signals from computers/microcontrollers into analog form.

Used in motor speed control, waveform generation, audio systems, and process control.

(i) Self-Calibration in Smart Sensors

Smart sensors use microprocessors to auto-correct for drift, temperature variation, or aging effects.

Ensures long-term accuracy.

Reduces manual recalibration needs.

(j) Need of Industrial Robots

Perform repetitive, hazardous, or precision-based tasks.

Increase productivity, safety, and consistency in manufacturing.

Used in assembly, welding, painting, and inspection.

SECTION B — Descriptive Questions (Any 3 × 10 = 30)

(a) Classification of Transducers

Based on Energy Conversion: Active (self-generating) / Passive (requires external power).

Based on Function: Primary / Secondary.

Based on Output Signal: Analog / Digital.

Based on Principle: Resistive, Inductive, Capacitive, Piezoelectric, etc.

(b) Proximity & Vibration Sensors

Proximity Sensor: Detects object presence using electromagnetic or optical fields.

Accelerometer (Vibration Sensor): Converts acceleration (vibration) into electrical output using piezoelectric effect.

(c) Imaging Sensors — CCD vs CMOS

Parameter	CCD	CMOS
Power Consumption	High	Low
Image Quality	High, less noise	Moderate, more noise
Speed	Slow	Fast
Cost	Expensive	Economical
Use	Cameras, Astronomy	Smartphones, Robotics

(d) Data Acquisition System (DAS)

Includes sensor → signal conditioner → ADC → computer.
Example: Temperature monitoring using RTD sensor, amplifier, ADC, and display system.

(e) Structure of Smart Sensors

Contains:

Sensing element Signal conditioning circuit Microprocessor for processing

Communication interface (wired/wireless)

SECTION C — Long Answers (Any 1 from each Q)

3(a) Optical Encoder

Converts rotary or linear motion into digital pulses.

Consists of light source, rotating disc with slots, and photodetector.
Used for speed and position measurement in robotics, CNC machines.

4(a) Thermistor vs RTD

Already covered — Thermistor is semiconductor-based, highly sensitive but nonlinear; RTD is metal-based, precise but slower and costlier.

4(b) Thermal Imaging

Uses infrared radiation to create images showing temperature variations.
Applications: Electrical fault detection Medical diagnostics

Night vision and surveillance Industrial safety monitoring

5(a) Machine Vision vs Computer Vision

Aspect	Machine Vision	Computer Vision
Purpose	Industrial automation	General image understanding
Environment	Controlled (factory)	Real-world (dynamic)
Hardware	Cameras, sensors, lighting	Software-heavy (AI, deep learning)
Example	Quality control	Face recognition

6(a) Functions of Signal Conditioning

Amplification Filtering Isolation Linearization

Analog-to-Digital conversion

6(b) Counters vs Timers

Feature	Timer	Counter
Function	Measures time intervals	Counts pulses or events
Input	Internal clock	External pulses
Example	Stopwatch	Event counter

7(a) Smart Sensors in Smart Cities

Used for air quality monitoring, traffic control, waste management, street lighting, and smart parking.
Enable data-driven IoT-based urban management.