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22420 2019 Summer model answer paper[Msbte study resources]
Electrical engineering (EET301)
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(Autonomous) (ISO/IEC-27001-2005 Certified)
SUMMER– 2019 Examinations Subject Code: 22420 Model Answer Page 1 of 23
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- The answers should be examined by key words and not as word-to-word as given in the model answer scheme.
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Q Attempt any FIVE of the following 10 Marks a) Define active and passive transducers. Ans: 1. Active Transducer: - ------------------------------------------------------------------- (1 Mark)
- These transducers do not need any external source of power for their operation. Therefore, they are also called as self-generating type transducers.
- The active transducer are self-generating devices which operate under the energy conversion principle.
- Passive Transducer: - ------------------------------------------------------------------- (1 Mark)
- These transducers need external source of power for their operation. So they are not self-generating type transducers.
b) List any four units of pressure. Ans: (Any four units expected: 1/2 marks each)
- The following are units of Pressure
Pascals (Pa or N/m2)—N stands for newton which is SI unit of pressure
Psi - Pounds per square inch (PSI)
Bar – 105 Pascals
mm Hg-millimeters of Mercury 1mm of Hg = 1 Torr
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SUMMER– 2019 Examinations Subject Code: 22420 Model Answer Page 2 of 23
- Torr – 133 Pa
- cm H2O – 1 cmH2O = 98 Pa
c) Define laminar and turbulent flow. Ans: Laminar flow: - ----------------------------------------------------------------------------- (1 Mark)
- Laminar flow occurs when the fluid flows in infinitesimal parallel layers with no disruption between them. For laminar flow Reynolds number Re < 2300 OR
- The flow in which fluid flows smoothly such that fluid layers are parallel to each other OR
- No streamlines intersect each other, such type of flow is known as laminar flow. OR
- When all the molecules of flow are parallel to each other, it is called Laminar flow.
Turbulent flow: - --------------------------------------------------------------------------- (1 Mark) 1. Turbulent flow occurs when the fluid does not flow in parallel layers, the lateral
mixing is very high, and there is a disruption between the layers. Re > 4000
OR 2. When all the molecules of flow are scattered without fixed position it is called Turbulent flow. OR 3. The flow in which fluid flows in zig-zag manner and fluctuate irregularly in such a way that its velocity changes irregularly, such type of flow is known as turbulent flow.
d) List any two non-contact type level measurement methods. Ans: (Any Two types expected: 1 mark each)
- The following are non-contact type level measurement methods
Ultrasonic type level measurement
Nuclear radiation type level measurement
Radar type level measurement
Capacitive level transducer.
Load cell type level transducer.
(Autonomous) (ISO/IEC-27001-2005 Certified)
SUMMER– 2019 Examinations Subject Code: 22420 Model Answer Page 4 of 23
It changes resistance value as its temperature changes following a positive slope (resistance increases when temperature is increasing).
Q. 2 Attempt any THREE of the following 12 Marks a) State the selection criteria for transducers (any eight points). Ans: (Any Eight points expected: 1/2 marks each)
- Operating range
- Operating principle
- Sensitivity
- Accuracy
- Frequency response and resonant frequency
- Errors
- Environmental compatibility
- Usage and ruggedness.
- Electrical aspect.
- Stability and Reliability
- Loading effect
- Static characteristics
- Noise immunity b) Draw constructional details of C-types Bourdon tube and explain its working
Ans:
Constructional details of C-types Bourdon tube : (Figure: 2 Mark & Explanation :2 Mark)
or equivalent figure Explanation:-
- The Bourdon tubes are made out of an elliptically sectioned flat tube bent in such a way as to produce the above mentioned shapes.
- One end of the tube is sealed or closed and physically held.
- Other end of tube is held fixed at one end (the end connected to the pressure source)
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SUMMER– 2019 Examinations Subject Code: 22420 Model Answer Page 5 of 23
- Whose pressure is to be measured enters the tube, the tube tends to straighten out on account of the pressure.
- This causes the movement of the free end which is measured.
- A pointer is mounted on the shaft. The needle moves over a circular scale that indicates the pressure. The position of the needle is determined by a balance between the Bourdon tube developed torque acting on the shaft and the torque due to the shaft mounted spring that opposes its movement.
- Bourdon tubes normally measure gauge pressure.
- The materials used for Bourdon tubes are brass, phosphor bronze, beryllium copper, and steel
c) What is piezo electric effect? Name two piezo electric materials. Ans: Piezoelectric Effect: ------------------------------------------------------------------------ (2 Marks) When pressure or force is applied on piezoelectric crystals such as quartz crystal then an electric charge is generated across that crystal. OR Piezoelectric Effect is the ability of certain materials to generate an electric charge in response to applied mechanical stress. Piezoelectric Materials: - (Any Two Material expected: 1 marks each)
Barium Titanate.
Rochelle salts.
Quartz crystal.
Topaz
Tourmaline
lead titanate
lead zirconate titanate
lithium sulphate
(Autonomous) (ISO/IEC-27001-2005 Certified)
SUMMER– 2019 Examinations Subject Code: 22420 Model Answer Page 7 of 23
- At steady state condition record the gauge reading and weight
- increasing weights until the full range or maximum pressure is applied to
the gauge and then decreasing weights until the gauge reads zero pressure. 8. Calculate the error at each gauge reading and ensure that it is within the acceptable accuracy limits.
Q Attempt any THREE of the following 12 Marks
a) Compare orifice plate with venturi tube with reference to: (i) Working principle (ii)Construction (iii) Cost (iv) Pressure loss Ans: (Each Point: 1 Mark)
S Points Venturi Flow Meter Orifice Plate Meter 1 Working principle Works on venturi effect. The Venturi effect is the reduction in fluid pressure that results when a fluid flows through a constricted section of pipe.
When fluid passes through orifice, there is large drop in pressure that is indicative of flow rate
2 Construction It has The venturi meter has a converging conical inlet, a cylindrical throat and a diverging recovery cone works on venturi effect:
An orifice meter is essentially a cylindrical tube that contains a plate with a thin hole in the middle of it. 3 cost Expensive, carefully fabricated, purchase from proper manufacture
Cheap & easy to install. Homemade orifice plate possible 4 Pressure loss Low High b) Draw and explain block diagram of instrumentation system. Ans: block diagram of instrumentation system : (Figure: 2 Mark & Explanation :2 Mark)
OR
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SUMMER– 2019 Examinations Subject Code: 22420 Model Answer Page 8 of 23
or equivalent figure
- Primary Sensing Element:-
- It is also known as "First Sensing Elements“ The Element (Part) of an
instrument which makes first contact with the measure and is called the primary sensing element.
- For example, In Ammeter (which is used to measure current), the coil carrying the current to be measured is the primary sensing element
- Variable conversion Element:-
- The output of the Primary sensing element may not be suitable for the actual measurement system.
- A variable conversion element merely converts the output signal of the
primary sensing element into a more suitable variable or condition useful to the function of the instruments
- Also keep in mind, that the original information about the measurand must be retained during the process of such conversion
- Variable Manipulation Element:-
- The level of the output from the Variable conversion element may not be enough for the next stage
- It manipulates the signal represented by some physical variable, to perform
the intended task of an instrument.
(Autonomous) (ISO/IEC-27001-2005 Certified)
SUMMER– 2019 Examinations Subject Code: 22420 Model Answer Page 10 of 23
Application :- ---------------------------------------------------------------- (1 Mark) - Measuring gauge, absolute, atmospheric and differential pressures. - vacuum measurement - leak testing and tank liquid level - pressures at critical points in gas-train systems
ii) Bellows. ---------------------------------------------------------------- (1 Mark)
or
or equivalent figure
Application :- ---------------------------------------------------------------- (1 Mark) - Measuring gauge , absolute, atmospheric and differential pressures. - Vacuum measurement. - low pressure gauges are suitable for chemical, petrochemical, plant construction, pneumatic systems and cleanrooms.
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SUMMER– 2019 Examinations Subject Code: 22420 Model Answer Page 11 of 23
Q Attempt any THREE of the following 12 Marks
a)
Explain the principle of operation of Doppler type ultrasonic flow meter with a neat labeled sketch. Ans: (Figure: 2 Mark & Explanation :2 Mark) Sketch of Doppler type ultrasonic flow meter
or
or equivalent figure
The Doppler Effect Ultrasonic Flow meter use reflected ultrasonic sound to measure the fluid velocity.
By measuring the frequency shift between the Ultrasonic frequency source, The receiver, and The fluid carrier, the relative motion are measured.
The resulting frequency shift is named the Doppler Effect.
The fluid for which pipe flow rate is being measured must have material like particles or air bubbles that will reflect ultrasonic waves
A signal of known ultrasonic frequency (0 to 10MHz) is transmitted through
fluid , which has uniform velocity (v)
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SUMMER– 2019 Examinations Subject Code: 22420 Model Answer Page 13 of 23
Construction & working:- - Fig. shows a capacitance type liquid level indicator. It consist of an insulated
capacitance probe (which is a metal electrode) firmly fixed near and parallel to the metal wall of the tank.
If the liquid in the tank is non-conductive, the capacitance probe and the tank wall form the plates of a parallel plate capacitor and liquid in between them acts as the dielectric.
If the liquid is conductive the capacitance probe and liquid form the plates of the capacitor and the insulation of the probe acts as the dielectric.
A capacitance measuring device is connected with the probe and the tank wall,
which is calibrated in terms of the level of the liquid in the tank.
When the level of liquid in the tank rises, the capacitance increases.
When liquid level of the tank decreases, the capacitance also decreases.
Change in the capacitance is measured and is displayed on the indicator calibrated in terms of liquid level
c) Compare RTD and thermistor on the basis of: (i) temperature coefficient (ii) linearity(iii) temperature (iv) range and cost
Ans: (Each Point: 1 Mark)
Sr. Points RTD Thermistor
1 temperature coefficient
Positive temperature coefficient of resistance.
PTC and NTC both types are available 2 linearity It has linear temperature versus resistance curve.
It has nonlinear temperature versus resistance curve.
3 temperature Used in medium to high Temperature range: -100 C to 650 C.
Used in low to medium Temperature range: -50 C to 300 C
4 range and cost Temperature range: - 100 C to 650 C. Cost is high
Temperature range: -50 C to 300 C They are cheaper as compared to RTD
(Autonomous) (ISO/IEC-27001-2005 Certified)
SUMMER– 2019 Examinations Subject Code: 22420 Model Answer Page 14 of 23
d) State any two advantages and disadvantages of electromagnetic flow meter. Ans: Advantages of Magnetic Flowmeter: - - -------------------------------------------------- (2 Marks)
- It can handle slurries and greasy materials.
- It can handle corrosive fluids.
- It has very low pressure drop.
- It is totally obstruction less.
- It is available in large pipe sizes and capacity as well as in sever construction materials.
- It is capable of handling low and very high-volume flow
- It can be used as bidirectional meter.
Disadvantage of Magnetic Flowmeter: - --------------------------------------------- (2 Marks)
- It is relatively expensive.
- It works only with fluids which are adequate electrical conductors.
- It is relatively heavy, especially in larger sizes.
- It must be full at all times.
- It must be explosion proof when installed in hazardous electrical areas
e)
Suggest a suitable level transducer for following application: (i) Level control of liquid, powders and fine grained solids within mining (ii) Chemical processing and food industries (iii) Tank level monitoring in chemical, water treatment (iv) Oil level in transformer. Ans: (Each Point: 1 Mark)
i. Level control of liquid, powders and fine grained solids within mining:- Capacitive Transducer, Radar level (microwave) Transducer, laser beam type
ii processing and food industries:- Capacitive Transducer, Radar level meter
iii. Tank level monitoring in chemical, water treatment:- Ultrasonic level transducer, load cell type
iv. Oil level in transformer: - sight Glass , optical sensor (LDR), Float type level transducer
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SUMMER– 2019 Examinations Subject Code: 22420 Model Answer Page 16 of 23
Residual voltage: - ---------------------------------------------------------------- (1 Marks) The output voltage is ideally zero, when core is at center or null position. harmonics in excitation voltage and capacitance coupling between primary and secondary coils usually results in small but non zero null voltage called residual voltage Residual voltage Diagram: ------------------------------------------------------------- (1 Marks)
or equivalent figure
b) Why Rotameter is called variable area flowmeter? Explain the working of rotameterwith neat diagram. State its one advantage and one disadvantage. Ans: (Rotameter: - 1 Mark, Figure: 1 Mark & Explanation :1 Mark, One Advantage: - 1 mark and One Disadvantage: -1 mark)
Rotameter :- An variable-area flowmeter is one where the fluid must pass through a restriction whose area increases with flow rate. The height of the float is directly proportional to the flowrate Neat diagram of rotameter
(Autonomous) (ISO/IEC-27001-2005 Certified)
SUMMER– 2019 Examinations Subject Code: 22420 Model Answer Page 17 of 23
or equivalent figure
Working of Rotameter: -
- It consists of a vertical tube with conical cone or shape.
- It is constant pressure drop variable flow meter in which float is free to move within it the fluid flows through the tube from bottom to the top
- When no fluid is flowing the float reset at the bottom of the tube
- The float is made of such a diameter that it completely blocks the inlet section
- When a flow starts in a pipeline and the fluid reaches the float, the buoyancy effect of fluid makes the float lighter
- The float has a density greater than that of flowing material so that the buoyancy effect alone is not sufficient to lift the float
- The float remains close until the pressure of flowing material (fluid flow or Drag ) + buoyancy effect of fluid exceeds the downward pressure due to the weight of the float 𝑖. 𝑒 𝑊 = 𝑆 + 𝐴
where
W= Weight of float
S= Fluid flow or Drag
A= Buoyancy effect
- The float then rises and floats within the flowing medium (Pipe) in proportional to the flow rate
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SUMMER– 2019 Examinations Subject Code: 22420 Model Answer Page 19 of 23
ii) Meter shows less value of flow measured:------------------------------------- (2 Marks)
S. POSSIBLE CAUSES CORRECTIVE ACTION OR REMEDIES 1 ➢ Les measurement if the Flow has more than 10% solids/bubbles
➢ Flow material required less than 10% solid/bubbles 2 ➢ If the pulsations are large, the instantaneous flow may temporarily exceed the rated flow range of the flow meter. In this situation, the flow displayed on the flow meter is smaller than the actual flow
➢ One possible way to reduce pulsations is by using a damper such as an accumulator
iii) Meter shows high value of flow measured------------------------------------- (2 Marks)
POSSIBLE CAUSES CORRECTIVE ACTION OR REMEDIES ➢ Doppler meters will tend to track bubbles over solids ➢ Air bubbles will rise faster than the slurry
➢ Check minimum % of solids (5%)
➢ Check minimum particle size ( >100 um)
➢ Perform calibration and check if Accuracy
is +/- 5% unless calibrated on the pipe
Q Attempt any TWO of the following 12 Marks
a) What is pyrometry? Explain working of optical pyrometer with neat diagram. Stateits one application. Ans: (Pyrometry: - 1 Mark, Figure: 2 Marks & Explanation :2 Marks, One Application: - 1 Mark) Pyrometry: -
- When physical contact with the medium to be measured is not possible due to very high temperature, Pyrometers are used. Operation of pyrometer is based on thermal radiation. Radiation pyrometry measures the radiant heat emitted by hot body.
- Diagram of optical pyrometer
(Autonomous) (ISO/IEC-27001-2005 Certified)
SUMMER– 2019 Examinations Subject Code: 22420 Model Answer Page 20 of 23
or equivalent figure
Working of Optical Pyrometer :- - The optical pyrometer is a non-contact type temperature measuring device. - It works on the principle of matching the brightness of an object to the brightness of the filament which is placed inside the pyrometer. - It consists the lens which focuses the radiated energy from the heated object and targets it on the electric filament lamp. - The intensity of the filament depends on the current passes through it. - Hence the adjustable current is passed through the lamp. - There are three condition of optical pyrometer 1. Case 1:-Equal brightness - The magnitude of the current is adjusted until the brightness of the filament is similar to the brightness of the object. - When the brightness of the filament and the brightness of the object are same, then the outline of the filament is completely disappeared.
- Case 2:- Filament looks bright
- The filament looks bright when their temperature is more than the temperature of the source.
22420 2019 Summer model answer paper[Msbte study resources]
Course: Electrical engineering (EET301)
University: Rashtrasant Tukadoji Maharaj Nagpur University
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