Transducer Interview Questions & Answers

  1. Question 1. What Is Instrument?

    Answer :

    It is a device for determining the value or magnitude of a quantity or variable.

  2. Question 2. List Three Sources Of Possible Errors In Instruments.?

    Answer :

    Gross Error, Systematic or Random errors.

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  4. Question 3. Define Instrumental Error?

    Answer :

    These are the errors inherent in measuring instrument because of their mechanical structure.

  5. Question 4. Define Limiting Error?

    Answer :

    Components are guaranteed to be with in a certain percentage of rated value. Thus the manufacturer has to specify the deviations from the nominal value of a particular quantity.

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  7. Question 5. Define Probable Error?

    Answer :

    It is defined as r = ± 0.6745s where s is standard deviation.
    Probable error has been used in experimental work to some extent in past, but standard deviation is more convenient in statistical work.

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  9. Question 6. Define Environmental Error?

    Answer :

    These are due to conditions in the measuring device, including conditions in the area surrounding the instrument, such as the effects of changes in temperature,humidity.

  10. Question 7. Define Units.?

    Answer :

    It is necessary to define a physical quantity both in kind and magnitude in order to use this information for further proceedings. The standard measure of each kind of physical quantity is named as the unit.

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  12. Question 8. Define Standards?

    Answer :

    The physical embodiment of a unit of measurement is a standard. For example, the fundamental unit of mass in the international system is the kilogram and defined as the mass of a cubic decimeter of water at its temperature of maximum density of 4°c.

  13. Question 9. Mention The Purpose Of The Measurement.?

    Answer :

    • To understand an event or an operation.
    • To monitor an event or an operation.
    • To control an event or an operation.
    • To collect data for future analysis
    • To validate an engineer design.
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  15. Question 10. What Are The Methods Of Measurement?

    Answer :

    • Direct comparison method
    • Indirect comparison method
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  17. Question 11. Define Odds?

    Answer :

    The specification of limiting error is in itself uncertain because the manufacture himself is not sure about the accuracy because of the presence of random errors.

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  19. Question 12. Define Transducer And Give An Example.?

    Answer :

    Transducer is a device which convert one form of energy into electrical energy. A thermocouple converts heat energy into electrical voltage.

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  21. Question 13. What Is Primary Transducer?

    Answer :

    Bourdon tube acting as a primary transducer, senses the pressure and convert the pressure into displacement. No output is given to the input of the bourdon tube. So it is called primary transducer. Mechanical device can act as a primary transducer.

  22. Question 14. What Is Secondary Transducer?

    Answer :

    The output of the Bourdon tube is given to the input of the LVDT. There are two stages of transduction, firstly the pressure is converted into a displacement by the Bourdon tube then the displacement is converted into analog voltage by LVDT. Here LVDT is called secondary transducer. Electrical device can act as a secondary transducer.

  23. Question 15. What Is Passive Transducer?

    Answer :

    In the absence of external power, transducer cannot work and it is called a passive transducer. Example capacitive , inductive, resistance transducers.

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  25. Question 16. What Is Active Transducer?

    Answer :

    In the absence of external power, transducer can work and it is called active transducer. Example velocity, temperature, light can be transdued with the help of active transducer.

  26. Question 17. What Is Analog Transducer?

    Answer :

    These transducers convert the input quantity into an analog output which is a continuous function of time. Thus a strain gauge, an LVDT, a thermocouple or a thermistors may be called analog transducer, as they give an output which is a continuous function of time.

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  28. Question 18. Give The Classification Of Units.?

    Answer :

    1.Absolute units
    2.Fundamental and derived units
    3.Electromagnetic units
    4.Electrostatic units

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  30. Question 19. Define Primary Fundamental And Auxiliary Fundamental Units.?

    Answer :

    Fundamental units in mechanics are measures of length,mass and time and those are fundamental to most other physical quantities and hence they are called Primary fundamental units Measures of certain physical quantities in thermal ,electrical and illumination fields are also represented by fundamental units and are used only where those disciplines are involved and hence called auxiliary fundamental units.

  31. Question 20. Define Static Calibration.?

    Answer :

    It refers to a process in which all the inputs(desired,modifying,interfering) except one are kept at some constant values.

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  33. Question 21. Define Traceability.?

    Answer :

    The ability to trace the accuracy of the standard back to its ultimate source in fundamental standards of National Institute of Science and Technology is termed “Traceability”.

  34. Question 22. What Are Random Errors Or Residual Errors.?

    Answer :

    The happenings or disturbances about which we are unaware and lumped together are called random errors or residual errors.Since these errors remain even after the systematic errors are taken care of,they are called residual errors.

  35. Question 23. Give One Property Of Piezo-electric Crystal.?

    Answer :

    When a force is applied to piezo-electric crystals ,they produce an output voltage.

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  37. Question 24. Define An Inverse Transducer.give An Example.?

    Answer :

    A device which converts an electrical quantity into an non-electrical quantity.A piezo-electric crystal acts as a inverse transducer because whwn a voltage is applied across its surfaces ,it changes its dimensions causing a mechanical displacement.

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  39. Question 25. List The Factors Responsible In Selection Of A Transducer.?

    Answer :

    1.Operating principle
    3.Operating range.

  40. Question 26. Define Static Characteristics.?

    Answer :

    static characteristics of a measurement system are, in general, those that must be considered when the system or instrument is used to measure a condition not varying with time.

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  42. Question 27. What Is Dynamic Characteristics?

    Answer :

    Many measurements are concerned with rapidly varying quantities and , therefore, for such cases we must examine the dynamic relations which exist between the output and the input . This is normally done with the help of differential equations . Performance criteria based upon dynamic relations constitute the Dynamic Characteristics.

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  44. Question 28. Mention Different Types Dynamic Characteristics?

    Answer :

    1. Zero- order transducers
    2.  First – order transducers
    3. Second-order transducers
    4.  Higher-order transducers
  45. Question 29. What Are The Test Inputs Of The Transducer?

    Answer :

    1. Impulse input
    2.  Step input
    3.  Ramp input
    4.  Parabolic input 
    5.  Sinusoidal input
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  47. Question 30. Define- Zero Order Transducer.?

    Answer :

    The input- output relationship of a zero- order transducer is given by

    Y(t) = K r(t)

    Where r(t) is the input, Y(t) is the output and K is the static – sensitivity of the transducer.

    Example for zero- order transducer is a potentiometer.

  48. Question 31. What Is Frequency Response Of Zot.?

    Answer :

    Frequency response is thus defined as the steady – state output of a transducer When it is excited with sinusoidal input . the frequency response is represented with the help of two plots namely amplitude radio verses frequency and phase angle shift versus frequency.

  49. Question 32. What Is Damping Ratio?

    Answer :

    The damping ratioV is an important parameter which decides the nature of oscillation in the transducer output . when V =0 , the second – order system is said to be un damped and the system behaves like an oscillator . when V =1 , the second – order system is said to be critical damped and when V >1 , the second – order system is said to be over damped.

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  51. Question 33. Compare Accuracy And Precision.?

    Answer :

    Accuracy is the closeness to true value whereas precision is the closeness amongst the readings .

    precision is the degree of closeness with which a given value may be repeatedly measured.

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  53. Question 34. What Is Threshold?

    Answer :

    When the input to a transducer is increased from zero, there is a minimum value below which no output can be detected .This minimum value of the input is defined as the threshold of the transducer.

  54. Question 35. What Is Range And Span?

    Answer :

    The range of the transducer is specified as from the lower value of input to higher value of input.

    The span of the transducer is specified as the difference between the higher and lower limits of recommended input values.

  55. Question 36. What Is Rise Time ?

    Answer :

    It is defined as time required for the system to rise from 0 to 100 percent of its final value.

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  57. Question 37. What Is Potentiometer?

    Answer :

    Basically a resistance potentiometer, or simply a POT, (a resistive potentiometer used for the purposes of voltage division is called a POT) consists of a resistive element provided with a sliding contact. The POT is a passive transducer.

  58. Question 38. What Are The Advantages And Disadvantages Of Potentiometer?

    Answer :

    Advantages : 

    • Inexpensive
    • Useful for measurement of large amplitudes
    • Efficiency is very high
    • Frequency response of wire wound potentiometers is limited

    Disadvantages :

    Require a large force to move

  59. Question 39. What Are The Different Types Of Strain Gauge?

    Answer :

    1. Unbonded metal strain gauges
    2. Bonded metal wire strain gauges
    3. Bonded metal foil strain gauges
    4. Vacuum deposited thin metal film strain gauges
    5. Sputter deposited thin metal strain gauges
    6. Bonded semiconductor strain gauges
    7. Diffused metal strain gauges.
  60. Question 40. What Are The Factors To Be Considered For Bonded Strain Gauge?

    Answer :

    • Filament construction
    • Material of the filament wire
    • Base carrier material or backing material
    • Cement used to bond the filament to the carrier
    • Lead wire connections.
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  62. Question 41. What Is Inductance Transducer?

    Answer :

    Transducers based on the variation of inductance are another group of importance devices used in many application. In these transducers self inductance or the mutual of a couple of coils is changed when the quantity to be measured is varied.

  63. Question 42. Mention Three Principles Of Inductance Transducer.?

    Answer :

    • Change of self inductance
    • Change of mutual inductance
    • Production of eddy currents.
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  65. Question 43. What Is Lvdt?

    Answer :

    The Linear Variable Differential Transformer (LVDT) is the most common mutual inductance element. This can be considered to be a versatile transducer element for most of the electromechanical measuring systems with regards to resolution, hysteresis, dynamic response, temperature characteristics, linearity and life.

  66. Question 44. What Is Null Voltage?

    Answer :

    Ideally the output voltage at the null position should be equal to zero. However, in actual practice there exists a small voltage at the null position.

  67. Question 45. Explain The Principle Of Induction Potentiometer?

    Answer :

    The primary is excited with alternating current. This induces a voltage in to the secondary. The amplitude of this output voltage varies with the mutual inductance between the two coils and this varies with the angle of rotation.

  68. Question 46. Explain The Principle Of Variable Reluctance Accelerometer?

    Answer :

    Another common version of the variable reluctance principle. This is an accelerometer for measurement of accelerometer for measurement of acceleration in the range ± 4g. Since the force required to accelerate a mass is proportional to the acceleration.

  69. Question 47. What Is The Principle Of Capacitive Transducer?

    Answer :

    Many industrial variables like displacement, pressure, level, moisture, thickness etc can be transduced into an electrical variation using capacitance variation as the primary sensing principle.

  70. Question 48. What Are The Advantages Of Capacitive Transducers?

    Answer :

    • They require only small force to operate.
    • Have a good frequency response.
    • Extremely sensitive.
    • High input impedance
  71. Question 49. What Are The Uses Of Capacitive Transducer?

    Answer :

    it Can be used for measurement of linear and angular displacement. Can be used for measurement of force and pressure.  It can be used as pressure transducer.  Measurement of humidity in gases.  Commonly used for measurement of level, density, weight.

  72. Question 50. What Is Digital Transducer?

    Answer :

    These transducer convert input quantity into an electrical output which is in the form of pulses.

  73. Question 51. What Is Piezoelectric Transducer?

    Answer :

    They convert pressure or force into electrical charge. These transducers are based upon the natural phenomenon of certain non-metal and di-electric components.

  74. Question 52. What Are The Suitable Materials For Piezo Electric Transducer?

    Answer :

    Primary quartz, Rochelle salt, ammonium dihydrogen phosphate (ADP), and ceramics with barium titanate, dipotassium tartrate, potassium dihydrogen phosphate and lithium sulfate.

  75. Question 53. What Are The Suitable Materials For Magnetostrictive Transducer?

    Answer :

    Iron , nickel, 68 permalloy, ferroxcube ect.

  76. Question 54. What Is Magnetostrictive Transducer?

    Answer :

    The permeability can increase or decrease depending upon the material, type of stress , and the magnetic flux density in the sample.

  77. Question 55. What Is Fibre Optic Transducer?

    Answer :

    Fibre optic cable consists of outer core and inner cladding.Data is transmitted in the form of light.It is used for measuring displacement,torsion.

  78. Question 56. Compare Digital Transducer With Analog.?

    Answer :

    Digital transducer give digital outputs. Analog transducers outputs are continuous functions of time. If these analog transducers are to be interfaced with digital devices, then one has to use analog to digital converters.

  79. Question 57. What Is Piezoelectric Effect?

    Answer :

    A piezoelectric material is one in which an electric potential appears across certain surfaces of a crystal if the dimensions of the crystal are changed by the application of the mechanical force.

  80. Question 58. What Id Digitiser?

    Answer :

    Digital encoding transducer or digitiser, enable a linear or rotary displacement to be directly converted into digital form without intermediate form of analog to digital (A/D) conversion.

  81. Question 59. What Is Zero Error Of The Transducer?

    Answer :

    In this case output deviates from the correct value by a constant factor over the entire range of transducer.

  82. Question 60. What Are The Disadvantages Of Capacitive Transducers?

    Answer :

    1. The metallic parts of the capacitive transducers must be insulated from each other.
    2. Non-linear behaviour.
    3. This leads loading effects.
    4. The cable may be source of loading resulting loss of sensitivity.