Flow measurement is one of the most important tasks in process industries.
Whether it’s oil, gas, water, steam, or slurry, accurate flow data is needed for efficiency, safety, and cost control. Over the years, many types of flowmeters have been developed from simple orifice plates to advanced Coriolis and ultrasonic devices.
In this blog, I have prepared 100 objective questions with answers on flow measurement. These cover both basic principles and advanced concepts, making it a useful resource for students, engineers, and technicians who want to strengthen their knowledge or prepare for exams and interviews.
So, Let’s Start !
Flow Measurement Q & A - Part 1
1. The basic principle of flow measurement is based on:
a) Pascal’s Law
b) Boyle’s Law
c) Conservation of mass and energy
d) Hooke’s Law
Answer: c
2. An orifice plate flowmeter works on the principle of:
a) Hydrostatic pressure
b) Venturi effect
c) Bernoulli’s theorem
d) Piezoelectric effect
Answer: c
3. Which primary element is NOT used for differential pressure flow measurement?
a) Orifice plate
b) Venturi tube
c) Pitot tube
d) Bourdon tube
Answer: d
4. Which relation is correct for volumetric flow rate in differential pressure devices?
a) Q ∝ ΔP
b) Q ∝ √ΔP
c) Q ∝ ΔP²
d) Q independent of ΔP
Answer: b
5. Which type of orifice plate is used for measuring flow of dirty or viscous fluids?
a) Concentric orifice
b) Eccentric orifice
c) Segmental orifice
d) Quadrant edge orifice
Answer: b
6. A Venturi meter has lower permanent pressure loss than an orifice plate because:
a) It is smaller in size
b) It has smoother fluid contraction and expansion
c) It uses multiple tapping points
d) It operates at higher velocity
Answer: b
7. The discharge coefficient (Cd) of a flow element depends on:
a) Fluid density only
b) Reynolds number and geometry of the element
c) Pipe length
d) Temperature only
Answer: b
8. Pitot tubes measure:
a) Static pressure
b) Dynamic pressure
c) Velocity of fluid
d) All of the above
Answer: d
9. Electromagnetic flow meters measure:
a) Velocity of conductive liquids
b) Non-conductive liquids
c) Gas flow only
d) Steam flow
Answer: a
10. Which law is the basis of electromagnetic flowmeters?
a) Faraday’s Law of Electromagnetic Induction
b) Pascal’s Law
c) Hooke’s Law
d) Newton’s Second Law
Answer: a
11. Which of the following fluids cannot be measured by an electromagnetic flowmeter?
a) Acid
b) Slurry
c) Distilled water
d) Molten steel
Answer: c
12. Ultrasonic flow meters work on:
a) Frequency shift (Doppler effect) or transit-time difference
b) Strain measurement
c) Differential pressure
d) Vortex shedding
Answer: a
13. Which type of flowmeter is suitable for measuring slurry or wastewater with suspended solids?
a) Orifice plate
b) Electromagnetic flowmeter
c) Rotameter
d) Hot-wire anemometer
Answer: b
14. Vortex flowmeters measure flow using:
a) Differential pressure across an obstruction
b) Frequency of vortices shed behind a bluff body
c) Velocity-pressure conversion
d) Rotating impeller blades
Answer: b
15. A Coriolis mass flowmeter measures:
a) Velocity of fluid
b) Volume of fluid
c) Mass flow directly
d) Pressure difference
Answer: c
16. Turbine flowmeters are best suited for:
a) Dirty slurries
b) Cryogenic liquids and clean fluids
c) High-viscosity oils
d) Steam flow
Answer: b
17. Which of the following is a volumetric flowmeter?
a) Positive displacement meter
b) Electromagnetic meter
c) Venturi meter
d) Orifice meter
Answer: a
18. A rotameter is a type of:
a) Constant head meter
b) Variable area flowmeter
c) Positive displacement meter
d) Differential pressure meter
Answer: b
19. Which factor affects the accuracy of a rotameter?
a) Viscosity of fluid
b) Density of fluid
c) Flow profile
d) All of the above
Answer: d
20. In a hot-wire anemometer, flow is measured based on:
a) Heat loss from a heated wire due to fluid velocity
b) Pressure drop across wire
c) Voltage fluctuation in circuit
d) Magnetic field variation
Answer: a
Flow Measurement Q & A - Part 2
21. The accuracy of an orifice plate flowmeter decreases mainly due to:
a) High velocity
b) Wear and tear at the orifice edge
c) Pipe roughness
d) Flow disturbances upstream
Answer: b
22. Which factor is most important for the Reynolds number in flow measurement?
a) Viscosity, density, velocity, and pipe diameter
b) Pressure only
c) Temperature only
d) Gravity only
Answer: a
23. Flow nozzles are preferred over orifice plates for:
a) Slurry service
b) Clean, high-velocity fluids
c) Low-pressure applications
d) Gasoline measurement
Answer: b
24. A Venturi tube is most accurate when:
a) Installed vertically only
b) Flow is fully developed with no disturbances
c) Installed close to bends
d) Used in laminar flow only
Answer: b
25. Which primary element is suitable for compressible fluids like gas and steam?
a) Orifice plate
b) Venturi tube
c) Vortex flowmeter
d) All of the above
Answer: d
26. The pressure recovery in a flowmeter is highest for:
a) Orifice plate
b) Flow nozzle
c) Venturi tube
d) Pitot tube
Answer: c
27. A rotameter should be installed:
a) Horizontally with scale
b) Vertically with upward flow
c) Vertically with downward flow
d) At any angle
Answer: b
28. Which fluid property does an electromagnetic flowmeter not depend on?
a) Conductivity (above minimum threshold)
b) Density
c) Viscosity
d) Pressure
Answer: b
29. Which type of ultrasonic flowmeter requires particles or bubbles in the fluid?
a) Transit-time ultrasonic meter
b) Doppler ultrasonic meter
c) Coriolis mass flowmeter
d) Vortex meter
Answer: b
30. Which type of flowmeter measures mass flow directly without compensation?
a) Coriolis
b) Electromagnetic
c) Orifice
d) Venturi
Answer: a
31. Vortex shedding frequency is proportional to:
a) Velocity of fluid
b) Density of fluid
c) Pressure of fluid
d) Viscosity of fluid
Answer: a
32. Which flowmeter is based on Kármán vortex street phenomenon?
a) Turbine meter
b) Vortex meter
c) Hot-wire anemometer
d) Positive displacement meter
Answer: b
33. Positive displacement flowmeters are suitable for:
a) Gas flow only
b) Steam flow
c) Clean liquids with low flow rates
d) Both gases and liquids at high velocity
Answer: c
34. Which unit is most commonly used for volumetric flow rate?
a) Pascal
b) Litre per second (L/s)
c) Joule per second
d) Newton per meter
Answer: b
35. Which flowmeter is most suitable for custody transfer of natural gas?
a) Orifice plate
b) Ultrasonic flowmeter
c) Vortex flowmeter
d) Turbine flowmeter
Answer: b
36. Which type of flowmeter is best for high-viscosity liquids like oils?
a) Orifice
b) Positive displacement
c) Rotameter
d) Pitot tube
Answer: b
37. Flow measurement in open channels is commonly done using:
a) Orifice meter
b) Venturi flume / weirs
c) Turbine meter
d) Electromagnetic meter
Answer: b
38. A weir flow measurement depends primarily on:
a) Height of liquid above crest (head)
b) Length of weir plate
c) Liquid density
d) Pipe diameter
Answer: a
39. The discharge through a rectangular weir is proportional to:
a) Head (H)
b) H²
c) H^3/2
d) √H
Answer: c
40. Which flowmeter has no moving parts and negligible pressure drop?
a) Electromagnetic flowmeter
b) Turbine flowmeter
c) Positive displacement meter
d) Orifice plate
Answer: a
Flow Measurement Q & A - Part 3
41. Which flowmeter is based on the principle of angular momentum?
a) Turbine meter
b) Gyroscopic flowmeter
c) Coriolis meter
d) Positive displacement meter
Answer: c
42. A Pitot-static tube measures:
a) Static pressure only
b) Dynamic pressure only
c) Both static and total pressure
d) Velocity head only
Answer: c
43. Which of the following is a direct method of mass flow measurement?
a) Orifice plate
b) Coriolis flowmeter
c) Venturi meter
d) Vortex flowmeter
Answer: b
44. Which of these flowmeters is sensitive to fluid density changes?
a) Electromagnetic flowmeter
b) Coriolis flowmeter
c) Ultrasonic flowmeter
d) Orifice meter
Answer: d
45. The Strouhal number is important in which flowmeter?
a) Rotameter
b) Vortex shedding meter
c) Pitot tube
d) Venturi
Answer: b
46. The working principle of thermal mass flowmeters is based on:
a) Pressure drop
b) Cooling effect of fluid on heated sensor
c) Vortex frequency
d) Doppler shift
Answer: b
47. Turbine flowmeter accuracy reduces mainly due to:
a) Blade wear and dirt accumulation
b) Pressure fluctuations
c) Temperature variation
d) Pipe roughness
Answer: a
48. The K-factor of a turbine meter is defined as:
a) Pressure loss coefficient
b) Pulses generated per unit volume of fluid
c) Density correction factor
d) Ratio of input/output power
Answer: b
49. Which type of flowmeter provides bidirectional flow measurement?
a) Orifice plate
b) Venturi tube
c) Coriolis mass flowmeter
d) Rotameter
Answer: c
50. The discharge coefficient of a Venturi tube is usually close to:
a) 0.5
b) 0.61
c) 0.75
d) 0.98
Answer: d
51. Ultrasonic transit-time flowmeters require:
a) Clean fluids with little or no solids
b) Gas bubbles for operation
c) Only high-pressure operation
d) Magnetic field
Answer: a
52. In a differential pressure flowmeter, square-root extraction is required because:
a) Flow rate ∝ (ΔP)²
b) Flow rate ∝ ΔP
c) Flow rate ∝ √ΔP
d) Flow rate independent of ΔP
Answer: c
53. Which flowmeter has the best accuracy for custody transfer in oil & gas?
a) Orifice plate
b) Coriolis mass flowmeter
c) Venturi tube
d) Pitot tube
Answer: b
54. An inclined manometer is used for:
a) High-pressure gas flow
b) Low differential pressure measurement
c) Steam flow
d) Dirty slurry
Answer: b
55. The minimum conductivity required for an electromagnetic flowmeter to work is typically:
a) 0.01 µS/cm
b) 1 µS/cm
c) 5 µS/cm
d) 20 µS/cm
Answer: b
56. The main disadvantage of an electromagnetic flowmeter is:
a) Cannot measure conductive fluids
b) Cannot measure non-conductive fluids
c) High pressure drop
d) Low accuracy
Answer: b
57. Ultrasonic Doppler meters are most suitable for:
a) Clean water
b) Slurry and fluids with suspended solids
c) Distilled water
d) Steam flow
Answer: b
58. Which flowmeter is most commonly used in HVAC water systems?
a) Rotameter
b) Orifice plate
c) Electromagnetic flowmeter
d) Positive displacement meter
Answer: c
59. In positive displacement flowmeters, flow is measured by:
a) Number of cycles of moving chambers
b) Pressure drop across the device
c) Velocity profile
d) Sound frequency shift
Answer: a
60. Which factor most affects vortex flowmeter performance?
a) Fluid conductivity
b) Fluid compressibility
c) Viscosity and Reynolds number
d) Pipe wall thickness
Answer: c
Flow Measurement Q & A - Part 4
61. Which factor is used to correct volumetric flow to mass flow?
a) Temperature
b) Pressure
c) Density
d) All of the above
Answer: d
62. Which type of flowmeter works on the principle of fluid oscillation?
a) Coriolis meter
b) Oscillatory vortex meter
c) Thermal mass meter
d) Rotameter
Answer: b
63. The accuracy of turbine flowmeters is typically:
a) ±5%
b) ±2%
c) ±1% or better
d) ±0.1%
Answer: c
64. The head loss in a Venturi meter is usually:
a) 20–30% of differential pressure
b) 10% of differential pressure
c) 1–5% of differential pressure
d) Equal to ΔP
Answer: c
65. Which flowmeter is most affected by fluid viscosity changes?
a) Electromagnetic meter
b) Turbine flowmeter
c) Coriolis flowmeter
d) Ultrasonic transit-time meter
Answer: b
66. Which is the best flowmeter for measuring cryogenic liquids?
a) Turbine meter
b) Orifice plate
c) Coriolis meter
d) Rotameter
Answer: a
67. The discharge through a V-notch weir is proportional to:
a) H
b) H²
c) H^3/2
d) H^5/2
Answer: d
68. An ultrasonic flowmeter using clamp-on transducers is:
a) Non-intrusive
b) Intrusive
c) High pressure drop
d) Positive displacement
Answer: a
69. Which flowmeter requires conductivity above a threshold to operate?
a) Turbine
b) Electromagnetic
c) Ultrasonic Doppler
d) Vortex
Answer: b
70. Which type of flowmeter is commonly used for steam measurement?
a) Vortex flowmeter
b) Rotameter
c) Positive displacement meter
d) Electromagnetic meter
Answer: a
71. Which factor has negligible effect on electromagnetic flowmeters?
a) Fluid conductivity (above minimum)
b) Fluid density
c) Pipe diameter
d) Magnetic field strength
Answer: b
72. Coriolis flowmeters also provide measurement of:
a) Temperature and density
b) Pressure and viscosity
c) Conductivity
d) Level
Answer: a
73. Which flowmeter is most suitable for natural gas custody transfer?
a) Vortex
b) Ultrasonic
c) Rotameter
d) Venturi
Answer: b
74. The minimum straight pipe length requirement before an orifice plate is usually:
a) 2D
b) 5D
c) 10D or more
d) No requirement
Answer: c
75. Which type of flowmeter provides highest turndown ratio?
a) Orifice plate
b) Coriolis
c) Rotameter
d) Vortex
Answer: b
76. Ultrasonic transit-time flowmeters cannot work properly when:
a) Fluid is very clean
b) Fluid contains bubbles or solids
c) Fluid is conductive
d) Pipe is horizontal
Answer: b
77. Which flowmeter can measure bi-directional flow without recalibration?
a) Orifice plate
b) Coriolis
c) Turbine
d) Pitot tube
Answer: b
78. The pressure drop across an orifice meter is:
a) Fully recoverable
b) Partially recoverable
c) Negligible
d) Zero
Answer: b
79. The measuring principle of a thermal mass flowmeter is based on:
a) Heating fluid directly
b) Measuring cooling effect on a heated sensor
c) Pressure drop
d) Vortex shedding
Answer: b
80. Which flowmeter has the least maintenance in slurry service?
a) Orifice plate
b) Turbine
c) Electromagnetic
d) Rotameter
Answer: c
Flow Measurement Q & A - Part 5
81. Which flowmeter is most suitable for custody transfer of crude oil?
a) Coriolis
b) Vortex
c) Electromagnetic
d) Rotameter
Answer: a
82. A rotameter reading depends on:
a) Density and viscosity of the fluid
b) Pressure drop only
c) Pipe roughness
d) Flow direction only
Answer: a
83. Which flowmeter requires a power supply for operation?
a) Venturi tube
b) Orifice plate
c) Electromagnetic flowmeter
d) Rotameter
Answer: c
84. Which flowmeter type is most accurate for batching applications?
a) Turbine meter
b) Orifice meter
c) Pitot tube
d) V-notch weir
Answer: a
85. The principle of a swirl flowmeter is based on:
a) Rotating impeller
b) Creating a swirling motion of fluid and measuring frequency
c) Thermal heating
d) Coriolis effect
Answer: b
86. Which flowmeter is commonly used for measuring fuel gas in boilers?
a) Orifice plate
b) Ultrasonic flowmeter
c) Vortex flowmeter
d) Rotameter
Answer: c
87. In an orifice flowmeter, the vena contracta is the point of:
a) Maximum static pressure
b) Minimum velocity
c) Minimum cross-sectional area and maximum velocity
d) Zero flow
Answer: c
88. Which flowmeter can measure both liquid and gas flow without recalibration?
a) Coriolis
b) Electromagnetic
c) Turbine
d) Rotameter
Answer: a
89. Which device is used for open channel flow measurement?
a) Orifice plate
b) V-notch weir
c) Rotameter
d) Vortex meter
Answer: b
90. The permanent pressure loss is highest in which flowmeter?
a) Venturi tube
b) Flow nozzle
c) Orifice plate
d) Electromagnetic meter
Answer: c
91. Which flowmeter is most affected by installation orientation?
a) Rotameter
b) Coriolis
c) Electromagnetic
d) Vortex
Answer: a
92. Which flowmeter can measure non-Newtonian fluids accurately?
a) Orifice
b) Coriolis
c) Vortex
d) Pitot
Answer: b
93. The output of a vortex flowmeter is generally:
a) Voltage proportional to flow
b) Frequency signal proportional to velocity
c) 4–20 mA signal only
d) Thermal signal
Answer: b
94. Which parameter must be known to convert volumetric flow to mass flow?
a) Pressure
b) Density
c) Temperature
d) All of the above
Answer: d
95. The calibration of a positive displacement meter is usually expressed in:
a) Pulses per second
b) Volume per revolution
c) Pressure drop
d) Resistance
Answer: b
96. Which type of flowmeter works on the principle of displacement of fluid by fixed volume chambers?
a) Turbine
b) Rotameter
c) Positive displacement meter
d) Vortex
Answer: c
97. Which flowmeter is often called a variable head meter?
a) Orifice meter
b) Rotameter
c) Venturi tube
d) V-notch weir
Answer: a
98. Which flowmeter is preferred for ultrapure water measurement?
a) Electromagnetic flowmeter
b) Turbine meter
c) Ultrasonic transit-time flowmeter
d) Rotameter
Answer: c
99. Which flowmeter measures flow without contact with the fluid?
a) Clamp-on ultrasonic flowmeter
b) Orifice plate
c) Vortex
d) Pitot tube
Answer: a
100. The main advantage of a Coriolis flowmeter is:
a) No moving parts and direct mass flow measurement
b) Lowest cost
c) Simplest installation
d) Works without power supply
Answer: a
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