JNTU
JNTU B.Tech III ELECTRICAL AND ELECTRONICS INSTRUMENTATION Previous Question Paper (February/March - 2022 - R16)
Answer any five questions. All questions carry equal marks.
Main
List the different types of errors that occur during measurement? Explain each one of them in detail.
Answer
Errors in measurement are defined as the difference between the measured value and the true value of a quantity. These errors are broadly classified into three main categories:
- Gross Errors: These are primarily caused by human mistakes in reading, recording, or calculating results. Examples include misreading an instrument scale, incorrect adjustment of an instrument, or improper application of a device. These can be minimized by taking multiple readings and ensuring careful observation.
- Systematic Errors: These errors occur due to shortcomings in the instrument or the measurement method. They are consistent and repeatable. They are further classified as:
- Instrumental Errors: Inherent defects in the instrument, such as friction in bearings, improper calibration, or loading effects.
- Environmental Errors: Caused by external conditions affecting the instrument, such as changes in temperature, pressure, humidity, or magnetic fields.
- Observational Errors: Errors such as parallax error during reading or incorrect alignment of the observer's line of sight.
- Random Errors: These are unpredictable errors that remain after gross and systematic errors have been eliminated. They arise from unknown, small fluctuations in experimental conditions like electronic noise, vibration, or slight variations in the measurand. Since they are random, they cannot be eliminated but can be minimized by applying statistical methods, such as calculating the arithmetic mean of a large number of readings or using standard deviation analysis.
State and explain Sampling theorem.
Answer
The Sampling Theorem, also known as the Nyquist-Shannon sampling theorem, states that a continuous-time signal can be perfectly reconstructed from its samples if the sampling frequency fs is greater than twice the maximum frequency component fm present in the signal.
Mathematically, this is expressed as:
The frequency 2fm is known as the Nyquist rate. If the sampling frequency is less than the Nyquist rate, the high-frequency components of the signal overlap with the lower-frequency components, a phenomenon known as aliasing, which leads to signal distortion that cannot be corrected during reconstruction.
Explain in detail about the Pulse width modulation.
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Explain with a diagram the operation of a triggered sweep generator.
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Describe with a block diagram the operation of a microprocessor based DVM.
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Describe with a diagram the operation of a vertical amplifier of a CRO.
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Explain the operating principle of a ramp type DVM with a neat block diagram.
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Explain with help of a block diagram the operation of a spectrum analyzer. State applications of a spectrum analyzer.
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Explain heterodyning. State the working principle of a heterodyne wave analyser with a neat diagram.
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Explain with a neat diagram the operation of a piezo-electric transducer.
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State the advantages of using differential output rather than a single output for measuring displacement.
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Write short notes on the following:
Measurement of strain
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Measurement of liquid level.
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