THEORY EXAMINATION (SEM–IV) 2016-17 ELECTRICAL INSTRUMENTATION AND PROCESS CONTROL

Subject: Electrical Instrumentation and Process Control (NEE403)

Exam Type: Theory
Semester: IV (4th Semester)
Session: 2016–17
Duration: 3 Hours
Maximum Marks: 100

Section A – Short Answer Questions (10 × 2 = 20 Marks)

This section checks your understanding of basic instrumentation concepts, transducers, and telemetry systems.

Topics Covered:

Primary vs. Secondary Transducers: Differences and examples.

Capacitive Transducer: Use in measuring displacement, pressure, or acceleration.

RTD (Resistance Temperature Detector): Why platinum is used instead of gold.

Hall Effect Transducer: Working principle and applications.

Resistive Transducers: Classification based on application.

Piezoelectric Effect: Principle and its use in pressure sensors.

Telemetry: Need for data transmission systems in instrumentation.

LCD (Liquid Crystal Display): Working principle.

Digital Oscilloscope vs. Analog Oscilloscope: Advantages of digital technology.

Section B – Descriptive / Numerical Questions (5 × 10 = 50 Marks)

This section focuses on measurement systems, sensors, controllers, and data acquisition.

Key Questions:

Low Pressure Measurement:               Using a diaphragm gauge with diagram and explanation.

Strain Gauge Problem:                        Given data:

Beam length = 0.1 m                             Cross-sectional area = 4 cm²

Young’s modulus (E) = 207 GN/m²        Gauge resistance = 240 Ω

Gauge factor = 2.2                                 Resistance change = 0.013 Ω

Find: Change in beam length and force applied.

Telemetry Systems:

Explain radio frequency telemetry and compare PAM (Pulse Amplitude Modulation) vs PCM (Pulse Code Modulation).

Magnetic Tape Recorder:    Basic components, working, and direct recording techniques.

SMART Sensor:     Advantages and construction compared to traditional sensors.

Proportional Controller Problem:

Temperature control between 50°C–130°C.

Set point = 73.5°C, Controller output = 50%.

Find proportional offset for proportional gains of 0.1 and 10.

Digital vs. Analog Data Acquisition Systems:

Advantages and block diagram of modern Digital Data Acquisition Systems (DAS).

Short Notes:

(i) Optoelectronic Sensors – principle and uses.

(ii) Self-Regulation in Processes – concept with examples.

Section C – Analytical / Long Questions (2 × 15 = 30 Marks)

This section tests deeper understanding and analytical ability through design-oriented and theoretical problems.

Questions:

LVDT (Linear Variable Differential Transformer):

Working principle with neat diagram.                              Characteristics curve and applications.

Given: Secondary voltage = 5V, Range = ±25 mm.         Find output voltage when the core is –18.75 mm from the center.

Plot output voltage vs core position from +18.75 mm to –10 mm.

PID Controller:

Describe Proportional, Integral, and Derivative control actions.

Explain system behavior when derivative action is added.

List tunable parameters of a PID controller.

Spectrum Analyzer:

Definition, working principle, and importance in signal analysis.

Comparison between analog and digital tape recording.

Discuss various digital recording techniques with waveform diagrams.

Major Topics Covered

Transducers and sensors (LVDT, strain gauge, capacitive, piezoelectric, RTD)

Data transmission and telemetry              Smart sensors and modern instrumentation

Signal acquisition (DAS systems)              Control systems and PID tuning

Spectrum analysis and recording techniques

Purpose of the Paper

This exam evaluates understanding of measurement principles, sensor technology, and process control systems used in automation and industrial instrumentation.
It emphasizes both practical calculations (e.g., strain gauge, LVDT, PID offset) and theoretical understanding of smart sensors, telemetry, and control devices.