# Common Interview Questions: Instrument and Control Engineers

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1. What are the process Variables?
2. Define all the process Variable and state their unit of measurement. ?
3. What are the primary elements used for flow measurement?
4. What are the different types of orifice plates and state their uses?
5. How do you identify an orifice in the pipe line?
6. Why is the orifice tab provided?
7.What is Bernoulli’s theorem and where it is applicable?
7. How do you identify the H. P. side or inlet of an orifice plate in line?
8. How do you calibrate a D. P. transmitter?
9. What is the seal liquid used for filling impulse lines on crude and viscous liquid ?
10. How do you carry out piping for a Different pressure flow transmitter on liquids, Gas and steam services Why ?
11. Draw and explain any flow control loop ?
12. An operator tells you that flow indication is more, How would you start checking?
13. How do you do a zero check on a D.P. transmitter ?
14. How would you do Glycol filling or fill seal liquids in seal pots 7 Draw and explain.
15. How do you calculate new factor from new range using old factor and old range?
16. How will you vent air in the D.P. cell? What if seal pots are used?
17. Why flow is measured in square root?
18. What is absolute pressure?
19. What is absolute zero pressure?
20. What is the maximum Vacuum?
21. What is Vacuum?
22. What are the primary elements for measuring pressure?
23. How will you calibrate an absolute pressure transmitter using vacuum manometer. Range 0-400mm abs?
24. You are given a mercury manometer range 0 -760 mm ? A vacuum gauge reads 60 mm vacuum. The test manometer reads 50 vacuum ? Which of the two in correct.
25. Why is an inclined manometer used ?
26. What is the principle of a pressure gauge ?
27. Draw and explain a pressure gauge ? What is the used of a Hair spring ?
28. Briefly explain the different methods of level measurement?
29. Explain how you will measure level with a different pressure transmitter.
30. How is D.P. transmitter applied to a close tank?
31. How is D.P. transmitter applied to an open tank?
32. How is D.P transmitter applied to a close tank & open tank with Dry leg?
33. What is purge level system?
34. Explain the working of a leveltrol.
35. How will you reverse an action of the leveltrol?
36. What is interface level? How do you calculate it?
37. How will you calibrate a leveltrol in the field?
38. How will you calibrate on interface level control. ?
39. How will you apply wt. lest calibration to a leveltrol.
40. What will happen if the displacer has fallen down while in line ?
41. What will happen if the displacer has a hole in it while in line?
42. What is the used of Suppression and elevation?
43. How will you commission D.P. transmitter in field in pressurized vessel.
44. How will you check zero of a level D.P. transmitter while is line?
45. Explain the working of an Enraf level gauge?
46. What are the different methods of temperature measurement? Explain
47. What is Pt 100 mean?
48. What is two wire and three wire R.T.D. system?
49. Draw a potentiometer temp. Measuring circuits and explain its?
50. What is the constant voltage unit?
51. Explain the working of a balancing motor.
52. What is burnout feature ? Explain
53. Why are Thermowells used ?
54. What type of sensing element would you use to measure very low temperature ?
55. What are skin temperature thermocouples ?
56. What is the specialty of thermocouples lead wires ?
57. What is the difference the a wheatstone bridge and a potentiometer ?
58. Explain the application of proportional integral and derivative action?
59. Where is on off control used?
60. What is reset-wind up?
61. Why is reset called integral and Rate derivative ?
62. Explain tuning of controllers.
63. Explain the working of an electronic P.I.D. controller.
64. What is an analogue integrator and an analogue differentiator ?
65. What is an anti reset wind up ?
66. What are De-saturators ?
67. Explain the working of Rotameter?
68. Explain the working of a magnetic meter.
69. Explain the working of a turbine meter.
70. Explain the working of a Pitot tube.
71. Where is the integral orifice used ?
72. What are types of taps used for orifices ?
73. What is Reynolds number ?
74. How would you choose differential range ?
75. What is positive Displacement meters ?
76. What is a control valves ?
77. What are the different types of control valves ?
78. What is the use of single seated valve ?
79. What is the use of double seated valve ?
80. What is Cv of a valve ?
81. What are the different types of actuators ?
82. What types of bonnets would you use of high temp. and very low temp. ?
83. How will you work on a control valve while it is line ?
84. What is the use of a valve positioner ?
85. When can a by pass be not used on a positioner ?
86. What is the use of butterfly valves ?
87. What is the use of three way valves ?
88. What are the different types of plugs ?
89. What is a cage valve ?
90. What is the use of link connected to the valve positioner ?
91. What is the use of booster relays ?
92. What is the use of Angle valves ?
93. What are the different valve characteristic ?
94. What is a solenoid valve ? Where it is used ?
95. How will you change the valve characteristics with positioner ?
110.How will you change the action of a control valve ?
96. How will you select the control valve characteristics ?
97. What is the effect of pipe reducers on valve capacity?
98. An operator tells you that a control valve in a stuck ? How will you start checking ?
99. Where is an Air to close and Air to open control valves used ?
100. Why does control valve operate at IS psi ?

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