### EI2251 - Industrial Instrumentation - I - 2 Marks with Answers

INDUSTRIAL INSTRUMENTATION - I
QUESTION BANK
UNIT-I   Measurement Of Force, Torque And Velocity
PART-A
1.      Define Force.
It is a quantity that produces a change in the size or shape or the motion of a body.
Force is given as,
F = MA  Where, F =Force, M=Mass (kg), A=Acceleration (m/sec2)
It is defined as a transducer that converts an input mechanical force into an electrical output signal. It is commonly known as Load transducers or load sensor.
3.      What are the types of Load cell? (May 2013)
4.      What is the principle of Strain Gauge measurement?
This type of load cell converts the load acting in them into electrical signal. The strain gauges are bonded onto the beam that deforms when weight is applied. This change in the dimension of the strain gauge causes its resistance to change. This change in resistance becomes a measure of the applied force.
5.      Define magneto-elastic effect?
This effect is based on the change in permeability of ferromagnetic material under     applied stress.
6.      Define Torque.
It is defined as the rotational force at a distance and it is given by
T = FR
Where T=Torque in Nm;    F= force in N;     R = Perpendicular distance in m;
7.      What are the classifications of tachometer?
Mechanical Tachometer & Electrical Tachometer
8.      Define the principle of  Capacitive Tachometer.
Capacitive Tachometer uses the principle of charging a capacitor and discharging through a meter alternatively. The average discharge current would be proportional to the speed.
9.      What is pressductor?
Magneto-elastic type load cell is called pressductor .The degree of change has a direct relationship with applied stress or force.
10.  Define Stroboscope. (May 2013)
The stroboscope is a simple, portable manually operated device which may be used for measurement of periodic or rotary motions.
11.  Give few Applications of Drag-cup tachometer?
Drag-cup tachometer is used in
Automobiles which measure the angular speed of the wheel, in Aircraft Engines,
in measuring locomotive speed.
12.  What is meant by Strobotron?
The Stroboscope consists of a source of flashing light whose frequency can be varied & controlled .This Source is called strobotron.
13.  Define speed.
Speed is a variable refers to the revolutions per minute of some piece of rotating equipment.
14.  What is revolution counter?
Revolution counter is a device for counting or recording the number of revolutions made by a rotating shaft of motor or engine.
15.  What are the instruments used for the measurement of torque?
The instruments used for the measurement of torque are
Mechanical Torsion meter, Electrical  Torsion meter, Optical Torsion meter, Strain
Gauge Torsion meter
16. What is prony brake?
The prony brake is a device which is most popular for determining the torque exerted by engines or motors .It consists of a hollow drum attached to the motor shaft and an arm attached to a band with friction which passes around the drum
The free end of the arm is attached with the hanging scale.
17. What are the fundamental forces of nature?
Gravitational Force, Electromagnetic force, Strong interaction force that holds
atomic nucleus together, Weak Interaction force.
18. What are the types of electromagnetic tachometer?
The types of electromagnetic tachometer are
AC Tachometer, DC Tachometer.
19. What are the types of electric tachometer?
Eddy current or Drag type, Electric generator type, Contact less type, Frequency
type, Ignition type, Stroboscopic type
20. What are the types of mechanical tachometer?
Revolution counter with time period, Centrifugal force tachometer, Resonance
tachometer.
21. What are the limitations of AC tachometer?
1. The difficulty with this system is that at low speed the frequency of   output voltage is low and hence it is very difficult to smooth out the ripples in the output voltage wave shape.
2. High speeds also present a problem. At high speeds the frequency increases and therefore, the impedance of coils of tachometer increases.
22. In a stroboscopic tachometer if four stationary marks are used, then what
will be the speed of the tachometer?
Speed n= f/4, Here f= frequency in hertz.
23. What are the factors affecting the accuracy of force measurement?
·         Force must either be reasonably constant in value.
·         Force must act perpendicular to the platform of scale.
·         The measurement may require correction for local variation in gravitational constant.
·         The delicate parts of force measuring devices must be properly maintained.
24. What are the applications of load cell? (Dec 2012)
Measurement of torque, force, pressure etc…
25. What is the principle of DC tachogerator? (Dec 2012)
DC tachogenerator converts mechanical energy into electrical energy when a conductor moves in a magnetic field.
PART-B
1. Explain the method of force measurement using Strain gauge load cell.
2. Describe the principle and construction of 1) Piezo electric load cell 2) Drag cup DC tachogenerator (Dec 2012)
3. With neat diagram explain, the construction and working of 1) Capacitive torque transducer 2) Stroboscope (Dec 2012)
4. Explain the magneto-elastic load cell with neat Diagram. (May 2013)
5. Explain the DC and AC tachogenerator with relevant diagram and mention its merits and demerits. (May 2013)
6. Explain how the torque is measured by strain gauge torsion meter?
8. Describe Drag-cup type tachometer
9. Explain Strobotron.
10. Describe regular twist.
Unit-II Measurement of Acceleration, vibration, density and viscosity
PART –A
1. Define acceleration?
The ratio in which the velocity changes with respect to time, measured in m/s2,   A=dv/dt,
1. What is seismic Instrument?
A system which consists of a mass- spring and damper combination housed in a chamber is called seismic instrument.
1. What are the needs of accelerometer?
For the measurement of shock and vibration
For gross measurement of acceleration and vibration in vehicles  like aircraft and submarines
1. What are the methods of vibration measurement?
Methods based on sensor, mechanical measurement, electrical measurement, optical measurement
1. What are the types of accelerometer?
LVDT Accelerometer, Seismic accelerometer, Piezo-electric accelerometer, Strain gauge accelerometer, Variable reluctance accelerometer
1. Give different modes of Seismic instruments?
(i)                 Displacement mode: with large Mass and soft Spring
(ii)               Acceleration mode: with soft mass and stiff spring
1. Define Vibration?
A force which oscillates about some specific reference point, generally continuous and time varying with some degree of repetitive nature is called vibration, expressed in terms of Cycles /sec, strokes/minute, m/s,..
1. Give the classification of Calibration of vibrational pick-up?
Constant Acceleration method, Tilting support method, Centrifuge method
Sinusoidal motion method and Transient motion method
1. What are the choices of vibrational pick up?
mechanical impendence pick-up, sensitivity, frequency range, phase characteristics
1. Define Density?
Density of a material is the ratio of weight of the material to the unit volume. Density of liquids and gas depends on temperature and pressure. Expressed in kg/m3.
1. Give some units of density?
Kg/m3, Kg/liter, g/cm3, ounce/inch3, pounds/inch3, pounds /gallon, pounds/bushel,  slug/feel3
1. What is API scale?
American petroleum institute introduced the method of  expressing the specific gravity called as API degree in 1921
Degree API=(141.5/SG at 60F)-131.5
1. What is baume Scale?
The Baume scale is actually two scale, one liquids heavier than water and other liquids lighter that water, ◦Be
1. What are the applications of bridge type gas densitometer? (May 2013)
To determine the mass and volume of products, To evaluate the quality of product, To determine calorific value of fluids
1. Define viscosity
The resistance which arises from the lack of slipperiness of the of liquid other things being proportional to the velocity of liquid. This lack of slipperiness is called viscosity.
1. What is Newtonian fluid?
When shear stress is applied the fluid undergoes continuous deformation and if the force-flow relation is linear, it obeys the Newton’s law of viscosity and hence called Newtonian fluids.
1. What is non-Newtonian fluid?
If the force flow relation is of fluid non linear, it does not obey the Newton’s law of viscosity and the fluid is called Non-Newtonian fluid.
1. Define Kinematic viscosity.
Kinematic viscosity is the ratio of absolute viscosity (μ)to density (ρ) of the fluids.(ν)
1. What is specific viscosity?
It is the ratio of absolute viscosity of the fluid to absolute viscosity of the standard fliud at constant temperature.
1. What is relative viscosity?
It is the ratio of absolute viscosity of fluid at given temperature to absolute temperature of standard fluid at 20 degrees
1. Define Viscosity Index.
It is an empirical number that indicates the effect of change of temperature on viscosity of a fluid., the larger viscosity index indicates lower sensitivity to temperature.
1. Define Consistency.
When continuous deformation occurs, the fluid tries to oppose with a frictional resistance called as consistency.
1. Define Dynamic viscosity.
It is the ratio of Shear stress to velocity gradient.   μ= τ/(dv/dy)
1. Define Co-efficient of viscosity?
The force required per unit area to maintain unit difference of velocity between two parallel plates. F=ηA v/d ;η =Co-efficient of viscosity
1. Give some commonly used Specific gravity in industries?API Degree, Baume Degree(Be), Balling Degree(Ba),brix degree(Br), Skis, Richter, Tralles, Quevenne, Twadell
2. What are the disadvantages of LVDT? (May 2013)
Sensitive to temperature , Measurement not perfectly linear, Not feasible for long range measurement.
PART-B
1. Explain in detail about LVDT and Strain gauge Accelerometer. Give its merit and demerits.
2. Explain in detail about piezo electric and variable reluctance accelerometer. (May 2013)
3. Say the types of vibration measurement. Explain seismic instrument? (Dec 2012)
4. How relative motion is measured using seismic instruments.
5. What is vibration pick-up? How it is calibrated?
6. Give some commonly used specific density units in industries.
7. Explain float type and bridge type density meter? (May 2013)
8. Explain pressure head type and ultrasonic type density meter.
9.      How Saybolt viscometer is used for measuring density.
10.  Explain about rotameter type viscometer.
11.  Explain ultrasonic densitometer? (Dec 2012)
UNIT-III Pressure Measurement
PART-A
1. Define Absolute pressure
The force exerted by the fluid per unit area of the wall of the container is called the absolute pressure.
2. Define Gauge pressure
It is the difference between the absolute and the local atmospheric pressure.
Pg = Pa - Ps
3. Define vacuum pressure
Vacuum pressure is the amount by which atmospheric pressure exceeds the absolute pressure.
Pv =Ps - Pa
4. Give some units of pressure
Pascal ,psi, kg/cm2 , bar etc.
5. What are the types of manometers?
U - tube manometer‚ Well type manometer‚ Inclined type manometer ‚Ring balance manometer‚ Micro manometer
6. State the principle of U- tube manometer
The U-tube manometer is the simplest measuring instrument used for gauge pressure measurement by balancing the pressure against the weight of a column of liquid.
7. What are the types of elastic pressure gauges?
Bourdon tubes ‚ Bellows‚ Diaphragms
8. Explain the principle of Bourdon tube pressure gauge
Bourdon tube is a device that senses pressure and converts the pressure into displacement. Since the bourdon tube displacement is a function of the applied pressure it may be amplified and indicated by a pointer.
Simple construction‚ Moderate price‚ useful for measurement of low, medium, high pressures‚ Used to measure absolute, gauge, differential pressures
Not suited for dynamic measurements‚ Errors will occur
10. State the principle of Diaphragms
The pressure to be measured is applied to the diaphragm, causing it to deflect. That deflection is being proportional to the applied pressure.
11. What are the types of diaphragms?
Flat type and Corrugated type
12. State the principle of LVDT and STRAIN GAUGE
LVDT:
The differential output voltage of the secondary winding of the LVDT is proportional to the vibrational displacement experienced by the mass caused due to acceleration; the differential output voltage becomes a measure of acceleration.
Strain Gauge:
When the strain gauge is stretched or compressed, its resistance changes on the account of the fact that both length and diameter of the strain gauge changes. This change in resistance will be proportional to the torque in the shaft.
13. State the principle of capacitive pressure transducer
The output of a parallel plate capacitor depends on the gap between its movable and fixed plates. Due to pressure, if the gap between the plates is altered, its capacitance also changes. This change in capacitance becomes a measure of pressure.
Simple construction‚ useful for measurement of low, medium, high pressures and Used to measure absolute, gauge, differential pressures
Errors will occur
15. State the principle of Piezoresistive pressure sensor
When a wire is subjected to pressure from all sides its electrical resistance changes. This change in resistance occurs due to the distortion produced in the crystal when subjected to external pressure.
16. What are the applications of Piezoresistive pressure sensor?
1. Household appliances   - washing machine, vacuum cleaner
2. Automotive appliances - oil level, gas level
3. Biomedical appliances - blood pressure measurement
17. State the principle of Mc leod gauge
Compression of a sample of the low pressure gas to a level which is sufficiently high so that it can be read with the use of a simple manometer.
18. What are the advantages and limitations of Mc leod gauge
Independent of gas composition and linear relationship exists
It should obey boyle‘s law and It cannot give a continuous output.
19. State the principle of thermal conductivity gauges
When a conductivity wire gets heated electric current flows through it. The rate at which heat is dissipated from this wire depends on the conductivity of the surrounding media.
20. What are the types of thermal conductivity gauge?
Pirani gauge‚ Thermocouple type conductivity gauge and Ionization gauge
21. State the principle of hot cathode type ionization gauge
The hot filament of the hot cathode gauge emits electrons into the vacuum, where they collide with gas molecules to create ions. These positively charged ions are accelerated towards a collector where they create a current in a ion gauge detector circuit. The amount of current is proportional to the gas density.
22. Write some application of pressure measurements
Steam boiler‚ tanks and container and manufacturing and chemical industries
23. Define ionization
It is a process of knocking off an electron from an atom and thus producing a free electron and positively charged ion.
24. What is bellows elements?
When pressure is applied to the bellow element the bellow element will deflect and a displacement will be produced. That displacement will be proportional to the applied pressure.
25. What are the shapes of bourdon tube available?
C -type‚ spiral type and  helical type
26. What is the advantage of using well type manometers? (June 2012)
Even for a small displacement of liquid level in a well, there will be a very large change of height of liquid column in other limb. This results in increase in sensitivity.
27. Mention the application of dead weight tester. (Dec 2012)
Friction force between piston and cylinderUncertainty of value of effective are A and Uncertainty of value of gravitational constant
28. What are the merits of elastic type pressure gauge? (May 2011)
Elastic type pressure gauges are used for the measurement of very high pressure upto about 700 MN/m2 Good accuracy and Maximum safety
29. What are the demerits of dead weight tester (June 2013)
The area upon the weight force acts is neither the area of piston nor the area of the cylinder and Kinetic friction is applied rather than static friction
30. What is calibration? (May 2011)
An experimental procedure to find and correct errors in measuring instruments
PART – B
1. Explain Bourdon tube and its types
2. Explain about bellows with neat diagram
3. Explain about diaphragm with diagram
4. Explain Piezoresistive pressure sensor and capacitive pressure transducer (May 2011)
5. Explain hot and cold cathode type ionization gauge
6. Describe the pressure measurement using (i) LVDT with diagram, (ii) Capacitive transducer (Dec 2011)
7. Explain the pressure measurement for the following categories (i) McLeod gauge (ii) Thermal conductivity gauge (Dec 2011)
8. Discuss the principle and the construction of LVDT with neat diagram. Explain the merits and demerits (Dec 2012)
9. With a neat sketch derive and explain any two types of Manometers. (June 2012)
10. How are the following transducers used to measure low pressure? (i) Thermocouple vacuum gauge (ii) Pirani gauge (iii) Ionization gauge (Dec 2010)
11. Explain the concept of vacuum measurement with one example (May 2011)
UNIT-IV Temperature Measurement
PART-A
1. Define temperature
Temperature of a substance is a measure of hotness or coldness of that substance. It is the thermal state of a body which determines whether it will give heat or receive heat from other bodies.
1. What are the types of filled in system thermometers
Gas filled thermometer‚ Liquid filled thermometer‚ Mercury filled thermometer and Vapour pressure thermometer
1. What are the sources of error in filled in systems
Ambient temperature error‚ Head or elevation error‚ Immersion error‚ Barometric error and Radiation error
1. State the principle of bimetallic thermometers
·         All metals expand or contract with change in temperature
·          The temperature coefficient of expansion is not same for all metals and therefore their rates of expansion or contraction are different.
1. State the application of bimetallic thermometers
Used in control system‚ Used in air conditioning‚ Used in refineries, oil burners, tyre vulcanisers.
Simple, inexpensive‚ Withstand about 50% over ranges in temperature and accuracy +1%
Not recommended above 400 0 c and errors will occur
7. State the principle of RTD (Dec 2012, May 2011)
When RTD is subjected to temperature changes its resistance will change. This change in resistance becomes a measure of temperature.
8. State the application of RTD
Measurement of temperature‚ Temperature control processes‚ Temperature compensation and Vacuum measurement
9. Write the advantage and limitation of resistance thermometers
Highly sensitive ‚small, thin and responds quickly
Fragile and limited to few hundred degree temperature range
10. What are the shapes of thermistors?
11. What are the materials used in thermistors?
Materials are manganese, nickel, cobalt, copper, iron and uranium
12. What are the three electrical methods of temperature measurements?
Thermistors‚ RTD and Thermocouple
13. What is the relationship between Celsius and Fahrenheit?
0 C / 100 = ( 0 F – 32) / 180
14. What are the types of bimetallic thermometers?
Helical and Spiral
15. Explain about Ambient temperature effect
The change of ambient temperature causes volume changes in the capillary tube and bourdon tube thereby causing error in measurement.
If the thermometer bulb is placed at a different height compared to bourdon tube elevation error occurs.
The effect due to the change in atmospheric pressure is called as barometric effect.
If the bulb is not properly immersed or fully immersed and the head is not properly insulated, heat from the bulb is lost due to conduction. This causes the immersion error.
Radiation errors occur due to temperature difference between the bulb and other solid bodies around.
Simple construction‚ requires low maintenance‚ no need for electrical power and low cost
Need a large bulb for accuracy and sensitivity is much lower
21. What is the relation between Kelvin and centigrade?
0 K =    0 C +273.15
22. What is the relation between Rankine and Fahrenheit?
0 R = 0  F + 459.69
23. Define boiling point, freezing point and triple point
Boiling point:
Boiling point is the temperature at which the substance changes from physical state and becomes a gas.
Freezing point:
Freezing point is the temperature at which the substance changes from physical state and becomes a solid.
Triple point:
At a particular temperature and pressure at which three different phases of one substance can exist in equilibrium is known as triple point.
24. What are the methods of temperature measurements?
Expansion thermometers‚ filled system thermometers‚ electrical temperature instruments and pyrometers.
25. Mention the sources of error in filled in system thermometer (Dec 2011)
Errors are, ambient temperature effect head or Elevation effectbarometric effect immersion effect and radiation effect:
26. What are the difference between RTD and Thermistors (Dec 2011)
RTD:
When RTD is subjected to temperature change its resistance changes and it can be measured using bridge circuit. This change in resistance becomes a measure of temperature.
Thermistors:
When thermistors are subjected to temperature change its resistance changes and it can be measured using bridge circuit. This change in resistance becomes a measure of temperature.
27. Mention the merits of thermistors (Dec 2012)
Compact and inexpensive and good stability
28. Mention the application of thermistors. (May 2011)
Measurement of power at High frequencymeasurement of thermal conductivitymeasurement of flow, level and pressure of liquids and vacuum measurement
29. What are the advantages of RTD (June 2013)
Simple construction‚ requires low maintenance‚ no need for electrical power and low cost
30. What is RTD? (Dec 2010)
RTD means resistance thermometer detector. It is also called as electrical resistance thermometer. It is a semiconductor device which has positive temperature coefficient of resistance
PART – B
1. Explain filled system thermometers with its types (June 2012)
2. What are the possible sources of errors in filled system thermometers and how it is compensated? (Dec 2011)
3. Explain in detail about RTD and its characteristics
4.  Explain in detail about thermistors and its characteristics
5. How temperature scale has been standardized? What are the fixed points and how they are used in temperature standards?
6. Explain bimetallic thermometer and its types (Dec 2010, Dec 2011, and Dec 2012)
7. Discuss the electrical methods of measuring temperature
8. Describe the construction and working of 3 wires and 4 wires RTDs. (Dec 2010, May 2011, Dec 2012, and June 2012)
9. Explain the different types of expansion thermometers
10.  Discuss the various types of vacuum pressure measurement

PART-A
1. Define Seebeck effect? (Nov 2012)
When pair of dissimilar metals are joined together, emf is induced at the junction of the metals, this effect is called Seebeck effect.
2. Define Peltier effect.
When a pair of dissimilar metals is joined together, emf is induced at the junction of the metals. If the metal is connected to an external circuit some amount of current is drawn, due to which the induced emf will be slightly altered.
3. What is Thomson effect?
When a pair of dissimilar metals is joined together, emf is induced at the junction of the metals. If temperature gradient exists along either / both of the metal, the junction emf may undergo an additional slight alteration called as Thomson effect.
4. What is Thermocouple?
A temperature measuring device formed by connecting two dissimilar metals and is based on the principle of Seebeck effect, Peltier effect and Thomson effect.
5. Say the effects that thermocouple is based on?
Seebeck effect, Peltier effect, Thomson effect
6. What are the various types of Thermocouple junctions?
Reference junction (or) cold junction (or) standard junction and hot junction (or) measuring junction (or) desired temperature junction.
7. What is Thermopile? (May 2013)
A series of identical thermocouple connected together in a casing is called thermocouple. Used for measuring average temperature.
8. Define law of homogeneous circuit?
An emf will not be induced in a circuit with a system consisting of homogeneous metal.
9. Define law of intermediate metals? (May 2013, May 2011)
The net emf in the circuit remains unaltered if a third metal is introduced, provided the junctions formed by the third metal is at same temperature.
10. Define law of intermediate temperature. (May 2013)
The emf generated at the junction temperature T1& T3 is equal to the algebraic sum of emf generated at the junction in T1-T2 and T2-T3, where T2 lies between T1 & T2.
11. Give few types of Thermocouple with composition and temperature range?
J-type  :  Iron and Constantan  : -200 to 1000
K type : Chromel- Alumel        : -2000 to 1200
T type  : Copper- Constantan    : -200 to 350
12. What are the compensating techniques used in Thermocouple? (May 2013)
Reference junction compensation (ice bath compensation).
Isothermal block compensation.
13. What is Isothermal block.
A strip or a block where uniform temperature is maintained is called Isothermal block.
14. Give some merits and demerits of Thermocouple.
Merits:     Wide temperature range, Inexpensive, Good reproducibility
Demerits: Nonlinear response, Need compensating Circuits.
15. What are the sources of error in Thermocouple?
Ø  Junction formed by Faulty soldering technique.
Ø  Thermocouple may be used outside their applicable range.
Ø  Faulty reference junction compensation may be employed.
Ø  Installation faults.
Ø  Usage of wrong type of thermocouple.
16. What are radiation methods of temperature measurement?
17. Define Pyrometer.
Technique for measuring temperature without contact. It depends on the relation between temperature of heat body and electromagnetic radiation emitted by the black body.
18. Give the classification of Pyrometer?
Radiation pyrometer, Optical pyrometer, Selective / partial pyrometer, Two color pyrometer
19. What are the uses of Radiation Pyrometer?
Used for very high temperature measurement 700c -3500c without the actual     contact with the radiating body, Very high response.
20. What is Black body?
A body which absorbs all radiation without transmitting and radiation any is called Black body. A black body radiates energy at all spectral wavelength at a maximum rate corresponding to its temperature.
21. What is Grey body?
An object having emittance less than unity and constant at all wavelength is
Called Grey body
22. Give some application of Pyrometer?
Used for very high temperature measurement 700c -3500c
23. What are factors that affect the response of Thermocouple?
Size or thickness of the thermocouple wires, Sheath material, protection tube and thermo well, Position /location of the thermocouple with respect to process
24. What is principle used in Optical Pyrometer.
Within the visible region a given wavelength has a fixed color and the energy of radiation is interpreted as intensity or brightness. Hence the brightness of the light of given color emitted by hot source, indicates the value of temperature.
25. Why protective sheath is used in Thermocouple.
Protecting the thermocouple metals from contamination and rusting. Preventing against oxidizing, sulphating and in molten baths. To with stand thermal and mechanical shocks.
26. Demerits of Optical Pyrometer ( May 2011)
1. It is based on an observer judging 2 colors to be the same.
2. It requires direct line of sight to the object (or furnace) which the              temperature is to be measured
PART-B
1. Explain the Thermocouple junctions and different types of Reference junction used.
2. Explain the fabrication of Industrial Thermocouple and protective sheath.
3. Explain the Thermocouple laws.
4. Explain Cold junction compensation in Thermocouple.(May 2011)
5. What is Thermocouple? How Thermocouple is used for measuring temperature?
6. Explain Fiber optic temperature measurement.(May 2011)
8. Explain Optical radiation pyrometer.(May 2011, May 2013)
9. Explain Total radiation pyrometer.(May 2013)
10. Explain Two-color radiation pyrometer.(May 2011, May 2013)
11. Explain Signal conditioning circuit for thermocouple.(Nov 2011)

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