JNTU
JNTU B.Tech IV ELECTRONIC MEASURING INSTRUMENTS Previous Question Paper (September - 2022 - R16)
Answer any Five Questions. All Questions Carry Equal Marks.
Main
What is the type of response in electromechanical recorders? Derive the necessary equations.
Answer
Electromechanical recorders typically exhibit a second-order system response, characterized by a combination of inertia, damping, and restoring forces. The movement of the recording pen is governed by the differential equation of a mechanical system:
Where:
- J is the moment of inertia of the moving system.
- D is the damping coefficient.
- K is the spring constant (restoring force).
- θ is the angular displacement of the pen.
- T(t) is the input torque proportional to the measured signal.
Dividing by J, the equation becomes:
Defining the undamped natural frequency ωn = √(K/J) and the damping ratio ζ = D / (2√(KJ)), the equation is expressed in standard form:
The response is generally underdamped (ζ < 1) to ensure fast tracking of the signal, though critical damping (ζ = 1) is preferred to avoid overshoot in high-precision recording.
A 153± 25% resistance is connected to a power supply source operating at 313V dc. What range of current would flow if the resistor varied over the range of ±13% of its expected value? What is the range of error in the current?
Answer
Given: Nominal Resistance R = 153 Ω, Supply Voltage V = 313 V. The variation range is ±13% of the nominal value.
1. Calculate the resistance range:
2. Calculate the current range (I = V/R):
3. Calculate the nominal current (I_nom):
4. Calculate the range of error:
The absolute error range is from (I_min - I_nom) to (I_max - I_nom):
The current flows in the range of 1.810 A to 2.351 A, with an error range of -0.236 A to +0.305 A.
Explain the working of Sine wave generator that works in the frequency range of 20Hz-20KHz.
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With a neat block diagram, explain the working of generators that are used in transient response testing of amplifiers.
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With a neat diagram, explain how DC as well as AC current and voltage can be measured.
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The Lissajous pattern on a CRO is stationary and has five horizontal and three vertical tangencies. The frequency of the horizontal input is 1000Hz. Determine the frequency of vertical input.
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With a neat diagram, explain about the recorders that are well suited for low frequency AC inputs obtained from quantities varying slowly at frequencies upto 100c/s, or in special cases upto 1000c/s.
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Explain how high frequency signals can be recorded as well as the data can be replayed almost indefinite number of times.
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With a neat diagram, explain about Piezoelectric transducer and also derive the expression for coupling coefficient.
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Explain how displacement can be measured using a neat diagram.
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What is the significance of repeatability and reproducibility?
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With a neat block diagram, explain the operation of generator which can generate any arbitrary wave.
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A series type ohmmeter is designed to operate with a 6V battery. The meter movement has an internal resistance of 2KΩ and requires a current of 120 μA for full scale deflection. The value of R1 is 49K.
i) Assuming the battery voltage has fallen to 5.9V, calculate the value of R2 required to “0” the meter.
ii) Under the condition mentioned in (i), an unknown resistance is connected to the meter, causing a 60% deflection. Calculate the value of the unknown resistance.
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A 500μA meter movement with an internal resistance of 800Ω is to be used in 0-200mA current meter. Find the value of the required shunt.
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Name and explain various static characteristics of measuring systems.
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Write a short note on AF signal generator.
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