Types of flow sensors used in industries to measure fluid velocity and volumetric flowrates.

1. FLOW SENSORS

2. Introduction
• Flow is defined as the quantity of fluid (gas,
liquid, vapour or sublimate) that passes a
point per unit time
• It can be presented by a simple equation:
Flow (Q) = quantity/time
• It is the rate of change of a quantity. It is
either volumetric or mass flow rate.

3. Properties Affecting Fluid Flow
• Velocity of Fluid – the fluid speed in the direction of flow.
The fluid velocity depends on the head pressure that is forcing
the fluid through the pipe. The greater head pressure, the
faster fluid will flow.
• Pipe size – the larger the pipe, the greater the potential
flow rate
• Pipe friction – reduces the flow rate through the pipe. Flow
rate of the fluid is slower near walls of the pipe that at the
center.
• Fluid viscosity – its physical resistance to flow.

4. • The specific gravity of fluid – at any given operating
condition, the higher fluid’s specific gravity, the lower
its flow rate.
• Fluid condition – the condition of fluid (clear or
dirty) is one of the limitations in flow measurement,
some measuring devices blocked/plugged or eroded
if dirty fluids are used.
• Velocity Profiles – it has major effect on the accuracy
of most flow meters. It can be laminar, transitional or
turbulent flow.
Properties Affecting Fluid Flow

5. Importance of Fluid Measurement
• Measuring flow is one of the most important aspects
of process control
• The most diverse substances are transported and
distributed in piping system
• The fluid flowing through pipes have different
properties, so different flow measuring devices are
used
• The maintenance of definite rates of flow is
important for maximum efficiency and production

6. Types of Flow Meters
1. Differential pressure flow meters
2. Coriolis Flow meter
3. Vortex Flow meter
4. Ultrasonic Flow meter
5. Electromagnetic Flow meter
6. Thermal Flow meter

7. 1. Differential Pressure Flow Meters
- It works on the principle of partially
obstructing the flow in a pipe. This creates a
difference in the static pressure between the
upstream and downstream side of the device.
- The difference between static pressure
(referred to as differential pressure) is
measured and used to determine the
flowrate.

8.  
02
4
0
2
2
1
SVq
ppC
V ba





where:
 = ratio of meter diameter to pipe diameter ≈ 0.5 usually
S0 = cross sectional area of orifice
V = bulk velocity through the orifice/venturi or nozzle
C0 = discharge coefficient ≈ 0.61 for Re > 30,000

9. Some of the most common types of differential
flow meters are:
• orifice flow meter
• venturi flow meter
• nozzle flow meter
• pitot tube flow meter

10. Orifice Flow Meters
Orifice plates are the most common type
of Δp meter and are basically a machined
metal plate with a hole, as shown below.
The plate has a sharp upstream edge and
usually a bevelled edge downstream of
the flow.
Upstream face Downstream face

11. The components of a typical orifice
flow meter installation are:
• Orifice plate and holder
• Differential pressure transmitter
• Flow indicator or recorder

12. Advantages and Disadvantages
of Orifice Flow Meters
Advantages:
•Lower cost and easy to install
•Smaller physical size
•Flexibility to change throat to pipe diameter
ratio to measure a larger range of flow rates
Disadvantage:
•High pressure loss
•Large power consumption in the form of
irrecoverable pressure loss
•Susceptible to erosion or damage

13. Venturi Tubes
Venturi tube consists of a section
of pipe with a conical entrance, a
short straight throat, and a conical
outlet. The velocity increases and
the pressure drops at the throat.
The differential pressure is
measured between the inlet
(upstream of the conical entrance)
and the throat.

14.  

21
4
2
2
1
ppC
V v 



15. Advantages and Disadvantages
of Venturi Flow Meters
Advantages
• Moderately low pressure loss ( about 10% of ΔP )
• No moving parts
• Less susceptible to damage/wear
• Suitable for wet gas flow
Disadvantages
• Large physical size
• Greater cost to manufacture
• Greater susceptible to “tapping errors” in high Reynolds
number gas flows owing the high velocity fluid passing the
pressure tapping at the throat.

16. Flow Nozzles
Flow nozzles have a curved entry and a cylindrical throat, but
no divergent outlet section. Therefore, the discharge
coefficient is similar to Venturi tube, but the overall pressure
loss is similar to that of orifice plate.

17. Pitot Tubes
a.)it sense two pressures simultaneously, impact and static. The
impact unit consists of a tube with one end bent at right
angles toward the flow direction.
b.) These sensing tubes sense various velocity pressures across
the pipe, which are then averaged within the tube assembly
to give a representative flowrate of the whole cross section.
a.
b.

18. Features:
Easy to install
No pressure loss
Sensitive to up stream
disturbance
Not used for sticky and dirty
fluids

19. Coriolis Meter
Coriolis meters operate on the principle that, if a particle inside a rotating
body moves in a direction toward or away from the center of rotation, the
particle generates inertial forces that act on the body.

20. Coriolis meters create a rotating motion by
vibrating a tube or tubes carrying the flow, and
the inertial force (Coriolis force) that results is
proportional to the mass flow rate.

21. • During a no flow condition, there is no Coriolis effect and the
sine waves are in phase with each other.
• When fluid is moving through the sensor's tubes, Coriolis
forces are induced causing the flow tubes to twist in
opposition to each other. The time difference between the
sine waves is measured and is called Delta-T which is directly
proportional to the mass flow rate.

22. Coriolis Meter Advantages
• Measure mass flow rate directly
• Suitable for applications where temperature
and pressures fluctuate
• No obstructions in the fluid path
• Low cost of ownership
Coriolis Meter Limitations
• May not be suitable for viscous fluids as the
pressure drop increases with fluid viscosity

23. VORTEX FLOW METER
The vortex flow meter is used
for measuring the flow
velocity of gases and liquids in
pipelines flowing full.
MEASURING PRINCIPLE
Based on the development of a
Karman vortex shedding street
in the wake of a body built into
the pipeline.

24. VORTEX FLOW METER

25. VORTEX FLOW METER
Von Karman Vortex StreetVortex Sensor

26. Common Applications
• Custody transfer of natural gas metering
• Steam measurement
• Flow of liquid suspensions
• General water applications
• Liquid chemicals & pharmaceuticals
VORTEX FLOW METER

27. Advantages
• Vortex meters can be used for liquids, gases and steam
• Low wear (relative to turbine flow meters)
• Relatively low cost of installation and maintenance
• Low sensitivity to variations in process conditions
• Stable long term accuracy and repeatability
• Applicable to a wide range of process temperatures
• Available for a wide variety of pipe sizes
• Can also measure temperature, density or media levels are commonly
available
Disadvantages
• Low to medium pressure drop due to the obstruction in the flow path
• Not suitable for very low flow rates
VORTEX FLOW METER

28. A type of flow meter that measures the
velocity of a fluid with ultrasound to
calculate volume flow.
ULTRASONIC FLOW METER
MEASURING PRINCIPLE
The flow meter can measure the average velocity along the path of an
emitted beam of ultrasound, by averaging the difference in measured
transit time between the pulses of ultrasound propagating into and
against the direction of the flow (Transit Time Type) or by measuring the
frequency shift from the Doppler Effect (Doppler Shift Type).

29. ULTRASONIC FLOW METER
Transit Time
Ultrasonic Flow Meter
Doppler
Ultrasonic Flow Meter

30. ULTRASONIC FLOW METER

31. Advantages
• Obstruction less flow
• Unaffected by changes in temperature,
density or viscosity
• Bi-directional flow capability
• Low flow cutoff
• Corrosion-resistant
• Relative low power consumption
TRANSIT TIME
ULTRASONIC FLOW METER
Common Uses
Transit Time flow meters work with clean liquids like water,
oils and chemicals.
Disadvantages
• This type of meters are highly
dependent on the Reynolds number
(the velocity profile)
• It requires nonporous pipe material
(cast iron, cement and fiberglass
should be avoided)
• It requires periodic re-calibration
• Liquids with entrained gases cannot
be measured reliably.

32. Advantages
• The common clamps-on versions are easily
installed without process shutdown.
• It can be installed bi-directional.
• Flow measurement is not affected due to
change in the viscosity of the process.
• Generally suitable for measurements in large
water pipes
• The meter produces no flow obstruction
• Its cost is independent of line size.
DOPPLER
ULTRASONIC FLOW METER
Common Uses
• Heavily Aerated Liquids
• Raw Sewage
• Any Liquid with Over 100 ppm of Suspended Solids
Disadvantages
• The sensor may detect some sound
energy travelling in the causing
• interference reading errors.
• Its accuracy depends on the difference in
velocity between the particles, the
• fluid, the particle size, concentration, and
distribution.
• The instrument requires periodic re-
calibration.

33. Electromagnetic flow meters (Magnetic
flow or Mag meter) use Faraday’s Law of
Electromagnetic Induction to determine
the flow of liquid in a pipe.
Operating Principle
The operation of a magnetic flowmeter or mag meter is based upon
Faraday's Law, which states that the voltage induced across any
conductor as it moves at right angles through a magnetic field is
proportional to the velocity of that conductor.
ELECTROMAGNETIC FLOW METER

34. ELECTROMAGNETIC FLOW METER

35. ELECTROMAGNETIC FLOW METER

36. Common Applications
In order of usage:
• water/wastewater industry
• chemical
• food and beverage
• pulp and paper
• metals and mining
• pharmaceutical.
ELECTROMAGNETIC FLOW METER

37. Advantages
• Are bi-directional
• Have no flow obstruction
• Are available with DC or AC power
• It can measure multiphase; however, all
components should be moving at the
same speed
• It can install vertically or horizontally (the
line must be full, however)
• Can be used with fluids with conductivity
greater than 200 umhos/cm.
• Changes in conductivity value do not,
affect the instrument performance.
ELECTROMAGNETIC FLOW METER
Disadvantages
• It's above average cost
• It's large size
• Its need for a minimum electrical
conductivity of 5 to 20 μmhos / cm
• Its accuracy is affected by slurries containing
magnetic solids.
• The line must be full and have no air
bubbles (air and gas bubbles entrained in
the liquid will be metered as liquid, causing
a measurement error).
• In some applications, appropriate
mechanical protection for the electrodes
must be provided

38. Operates by monitoring the cooling
effect of a gas stream as it passes over a
heated transducer.
Operating Principle
The operation of thermal dispersion mass flow meters
is based King's Law that reveals how a heated wire
immersed in a fluid flow measures the mass velocity at
a point in the flow. It is based on the principle of
conductive and convective heat transfer.
THERMAL FLOW METER

39. THERMAL FLOW METER

40. Common Applications
Thermal flow meters are used almost
entirely for gas flow applications.
THERMAL FLOW METER

41. Advantages
• Thermal flow meters can measure the flow of some low-
pressure gases that are not dense enough for Coriolis
meters to measure.
Disadvantages
• Practical for gas flows only
• Subject to blockage by foreign particles or precipitated
deposits due to small openings in flow meter
• Power requirements excessive in larger pipe sizes
• Has to be taken out of process line for servicing
• Accurate field calibration is difficult
THERMAL FLOW METER

42. Thank You!