JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III Year ELECTRONIC MEASUREMENTS AND INSTRUMENTATION Previous Question Paper (March - 2021 - R18)
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Main
A 50 V range voltmeter is connected across terminals A and B of the circuit shown in figure. Find the reading of the voltmeter under open circuit and loaded conditions. Find the accuracy and the loading error. If the voltmeter has a resistance of 1000 kΩ.
Answer
Assuming a voltage divider circuit with two resistors R1 and R2 connected in series across a source voltage V, the open circuit voltage V_oc across terminals A and B is V_oc = V * (R2 / (R1 + R2)). When the voltmeter with resistance R_m is connected, the loaded voltage V_L is determined by the parallel combination of R2 and R_m, resulting in V_L = V * (R_p / (R1 + R_p)) where R_p = (R2 * R_m) / (R2 + R_m).
The loading error is calculated as the difference between the true value and the measured value: Error = V_oc - V_L. The accuracy is expressed as a percentage: % Accuracy = (V_L / V_oc) * 100. Given R_m = 1000 kΩ, the high resistance minimizes the current drawn from the circuit, thereby reducing the loading effect compared to a lower resistance meter.
With help of a neat diagram, explain the block diagram of functional elements of the measurement system.
Answer
A measurement system consists of several functional elements that convert the physical quantity (measurand) into a readable output. The primary blocks are:
- Primary Sensing Element: Receives energy from the measurand and produces an output depending on the measurand.
- Variable Conversion Element: Converts the output of the sensor into a more suitable variable (e.g., mechanical displacement to electrical voltage) while preserving the information.
- Variable Manipulation Element: Manipulates the signal (e.g., amplification, filtering, or attenuation) to suit the next stage.
- Data Transmission Element: Transmits the signal from one location to another, such as through cables or telemetry.
- Data Presentation/Recording Element: Provides the final output in a human-readable format, such as a pointer on a scale, digital display, or a chart recorder.
These elements are connected in a sequence where the output of one stage acts as the input to the next, ensuring the signal is conditioned and displayed accurately.
Enumerate and explain the different types of dynamic characteristics of instruments.
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With help of a neat diagram explain the construction and working of the True RMS responding voltmeter.
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With relevant block diagram explain the working of a standard signal generator.
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With neat diagram explain the working of heterodyne wave analyzer.
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Briefly explain the working of the basic function generator with a neat diagram.
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Explain the working of the AF wave analyzer with help of a neat diagram.
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With neat diagram, enumerate the main components of CRT.
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Explain the working of a vertical amplifier with a relevant circuit diagram.
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With help of a neat diagram, explain the working of a sampling oscilloscope.
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Explain the working of dual-beam CRO with relevant diagram.
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A resistive strain gauge G = 2.2 is cemented on a rectangular steel bar with the elastic modulus E = 205 x 106 kN/m2 width 3.5 cm and thickness 0.55 cm. An axial force of 12kN is applied. Determine the change of the resistance of the strain gauge, ΔR, if the normal resistance of the gauge is R=100 Ω.
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Briefly discuss the working of LVDT with neat block diagram.
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In the Wheatstone bridge, the values of resistances of various arms are P= 1000 Ω, Q= 100 Ω, R= 2,005 Ω and S= 200 Ω. The battery bas an emf of 5 V and negligible internal resistance. The galvanometer bas a current sensitivity of 10 mm/μA and an internal resistance of 100 Ω. Calculate the deflection of the galvanometer and the sensitivity of the bridge in terms of deflection per unit change in resistance.
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With help of a neat diagram, explain the working of turbine type flow meter.
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