Subject: Electronic Measurements and Instrumentation (NEC403)
Exam Type: Theory
Semester: IV (4th Semester)
Session: 2016–17
Time: 3 Hours
Maximum Marks: 100
Section A – Short Answer Questions (10 × 2 = 20 Marks)
This section checks fundamental theoretical concepts and basic definitions in measurement and instrumentation.
Topics Covered:
Random Error & Gross Error: Definition, cause, and how they affect measurement accuracy.
Accuracy vs. Precision: Difference between closeness to true value and repeatability.
Dissipation & Quality Factor (Q): Relationship between energy loss and circuit sharpness.
Rise Time & Fall Time: Signal response times in transient analysis.
Instrument Calibration: Concept and need for maintaining measurement reliability.
True Value: Theoretical exact value of a measured quantity.
Johnson Noise & Shot Noise: Fundamental electronic noise sources and characteristics.
Multimeter: Construction, working, and types (analog/digital).
Binder & Twisters: Tools used in wire harnessing and cable management.
Transducers & Inverse Transducers: Difference in function and signal conversion direction.
Section B – Descriptive / Analytical Questions (5 × 10 = 50 Marks)
This section emphasizes instrument construction, working principles, and analytical descriptions
Key Questions Include:
Electronic Voltmeter (Source Follower Type): Explain operation and circuit.
Describe range extension. Use of zero adjustment and calibration resistors.
Piezoelectric Transducers: Construction, principle, and modes of operation.
Application in pressure, acceleration, and vibration measurement.
Kelvin Double Bridge: Principle and circuit diagram.
Use in low-resistance measurement for high accuracy.
PMMC Instrument (Permanent Magnet Moving Coil): Construction and operation.
Mathematical proof showing linear scale behavior.
X–Y Recorder: Construction and working with block diagram.
Used for plotting one variable against another in analog systems.
Plotter: Working procedure and usage in automated graphical recording.
Ammeter to Voltmeter Conversion: Circuit modification and theory for range conversion.
Delay Line in CRO:
Explanation of why delay lines are used in the vertical section of CROs to synchronize sweep and signal trace.
Section C – Long Analytical / Application-Based Questions (2 × 15 = 30 Marks)
This section evaluates advanced concepts and instrument applications
Questions Include:
Measurement Using CRO:
(a) Frequency measurement procedure using time base and waveform period.
(b) Explanation of Pulse Distortion and Attenuator Probe with diagrams.
Measuring Instruments and Systems:
(a) Q-Meter: Working, use for measuring inductance, capacitance, and Q-factor.
(b) DC Ammeter and Voltmeter: Working principles and calibration process.
(c) Digital Frequency Meter System: Block diagram and working of counting-based frequency measurement.
Short Notes on Practical Devices:
(a) Digital Storage Oscilloscope (DSO): Operation, features, and applications in waveform analysis.
(b) Capacitance & Inductance Bridges: Measurement methods and balancing conditions.
(c) Dual Trace Oscilloscope: Construction, working, and uses for comparing two signals.
Major Topics Covered
Measurement fundamentals and errors Analog and digital measurement instruments
Oscilloscope systems (CRO, DSO, Dual Trace) Electrical bridges and calibration techniques
Transducers and sensors Frequency and waveform measurement techniques
Noise analysis and accuracy parameters
Purpose of the Paper
This paper tests both theoretical understanding and practical knowledge of electronic measuring instruments.
Students are expected to:
Understand instrument working principles and measurement standards.
Apply theory to real-world test setups like CROs, bridges, and transducers.
Demonstrate skill in error minimization and calibration procedures.
