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Flow meter - Flow measurement for liquids, water, gas and steam

Flow meter and fluids flow measurementFlow meter and fluids flow measurement

Suitable flow measuring devices for your liquid, water, gas and steam flow measurement.
Our flow sensors reduce your production costs and improve your energy efficiency.


Discover our range of flow measurement and instrumentation

How to measure the mass or volume flow of liquid, water, gas or steam

How to measure the mass or volume flow of liquid, water, gas or steam? 
Everything you need to know about flow measurement.

Our experts explain the definition, operation and principle, and introduce you to the different types of flow transmitters, their installation and maintenance.

Industrial flow meters measure the flow of fluids in pipes and are used in most industrial processes. There are several types of flow meters.
In order to choose the most suitable flow meter technology for a particular application, it is important to consider the process conditions, the desired range and accuracy, the cleanliness requirements of the fluid and whether it will be used to measure liquids or gases.

What is flow meter and what is the definition of flow analysers?

A distinction is made between a volumetric flow meter and a mass flow meter. A volumetric flow meter is a versatile instrument that measures the amount of fluid (volume) that passes through a given point in a certain time. The flow is measured in a pipe with these flow measuring instruments which measure the volume and flow rate of the fluid. (Flow meter water, a gas flow measurement, and a steam flow meter).

Some flow measurement devices measure the mass flow rate, i.e. the mass of fluid flowing through a pipe over a given period of time. Conversion between volume flow rate and mass flow rate is possible when the density of the fluid is known and other characteristics such as pressure and temperature are also known.

Note: flow sensors and flow indicators should not be confused. The flow meter measures the value of the flow, the flow indicator advises whether the fluid is moving in a circuit.

Flow meter measurement - How to measure flow rate and what is the flow meter unit?

Flow meter measurement - How to measure flow rate and what is the flow meter unitVolumetric flow for measuring the flow of liquids and gases, usually represented by the symbol Q, is normally expressed in m3/h or l/s.
Mass flow is expressed in grams per second (g/s) or kilograms per hour (kg/h).
A common mistake made when installing flow meters is to confuse total meters with flow units.
Total flow sensors measure the flow that has passed through the meter since it was first turned on.  

How to choose a flow meter? 

How to choose a flow meterModern flowmeters are manufactured using many different technologies, which exploit a variety of physical phenomena. Their search and selection requires the verification of a number of parameters.                                 

  •  Nature of the fluid and types of flow meters     

Liquid flow meter and water flow sensor, gas flow meter (e.g. air) or steam flow meter are not the same, so you need to consider what will be flowing through the pipe. The choice depends of the flow meter application and types of fluid.   

  • Flow meter technology :  Volumetric flow meter or mass flow meter       

How to choose a flow meter environmentFlow transmitter is capable of measuring volumetric flows, but in some cases, you may wish to measure mass flows as well.

  • Fluid flow measurement - Fluid operating conditions

What is the maximum pressure of the fluid flow to be measured?
What is the minimum and maximum temperature of the medium to be measured?
The ability of a flow rate meter to measure temperature depends on the type of flow sensor.
Some flow measurement devices are only suitable for measuring a single temperature, while others can measure a wide range of temperatures.
What are the minimum and maximum flow rates you will be measuring ?

  • Size of the pipe
  • Pressure losses

For a low flow rate, the pressure drop involved in installing a flow transmitter is a major cost factor.
Minimising pressure loss means minimising frictional losses in the pipework.
How to choose a flow meter accuracyOne of the main objectives in designing a flow sensor is to minimise frictional pressure drop as much as possible.
The pressure drop across a flow transmitter should be minimal and constant under different operating conditions.

  • The external environment
  • Installation conditions of flow measuring devices

In general, the installation conditions of future flow rate sensors should also be considered.
When a pipe network has bends, valves, diameter changes and other irregularities, disturbances in the fluid flow of the medium occur and some measurement technologies are sensitive to these disturbances.
In order to avoid measurement errors due to these disturbances, it is necessary to place enough straight pipe in front of the flow transmitter so that the fluid flow is not disturbed.
This straight length of pipe in front of flow measuring instruments is expressed in terms of the pipe diameter (DN).
Other factors to consider are the accuracy and repeatability of the flow rate meter, but also the analogue or pulse output signal and the communication protocol.

  • Accuracy must be stable, i.e. the variation in measurement error when the operating environment changes is within a fixed range.
  • The flow sensor must have high repeatability, i.e. the difference between two consecutive measurements must be within a fixed range. This ensures that the meter can measure the same flow rate under different pressure conditions and with varying input rates.
  • The output signal is available as 4-20mA, 0-10V, 4-20mA/0-10V, pulse, digital HART, MODBUS.

How does a flow meter work and what is its principle?

Have you ever wondered how a flow sensor works? Let's discuss the different popular flow rate
measurement technologies for measuring the flow of liquids, gas and steam.

What are the different industrial flow meters technologies?

Magnetic flow meter

Magnetic flow meterMag flow meter consists of a transmitter and a sensor that measure flow.
When a fluid passes through a pipe, the sensor of the electromagnetic flow meter placed outside measures an induced voltage generated by the liquid.
The transmitter measures the voltage produced by the sensor, transforming it into a flow rate value. Mag flow meters measures the flow rate using a pair of electrodes and a collection of coils.
The coils of the magnetic flow meter are driven by the transmitter as a result of applied currents.
Once energized, a magnetic field is formed between the two coils.
When the pipe is filled and the fluid begins to flow, the force of the magnetic field separates the negatively and positively charged particles from the fluid.

Faraday's Law, described mathematically as E = k*B*D*V, is a flow principle of electromagnetic flow rate sensors.
The induced voltage (E) is directly proportional to the velocity (V) of the fluid flowing in the magnetic field (B).
The electrode circuit transmits the induced voltage to the transmitter, which transforms the velocity into a quantitative measurement.
The volume of the fluid is estimated from this known velocity and the surface area of the pipe.

Why choose an magnetic flow meter ?Magnetic flow meter principle measurement
  • Economical for liquids such as water, waste water, aggressive chemicals and sludge
  • Low maintenance of the flow rate meter (not sensitive to particles, no moving parts, no clogging)
  • Wide variety of flow meter application (lining materials, electrode options, pipe diameters)
  • Bi-directional flow metering
  • High measurement dynamics (measurement of very small and very large volume flows)

Ultrasonic flow meters

Ultrasonic flowmetersTransit time difference method

This method is based on the fact that the transmission rate of an ultrasonic signal depends on the flow velocity.An ultrasonic wave moving with the flow moves faster than a wave moving against the flow.
Two transducers are installed opposite each other on the outer wall of the pipe. The sensors each emit an ultrasonic pulse and detect the difference in transit time of the pulse to calculate the flow rate.

Why choose an ultrasonic flow meter?

Non-intrusive clamp-on ultrasonic flowmeters offer many advantages:

  • High measurement dynamics
  • No process interruption during installation of the flow sensor
  • No direct contact with the fluid
  • Low installation costs
  • Low maintenance

Differential pressure flow meters and primary elements

Differential pressure flow meters and primary elements

Differential pressure (DP) technology uses a variation of Bernoulli's principle to measure the volumetric flow rate of fluid in a pipe.
In our application of Bernoulli's principle, it is stated that the velocity of the flow increases and the pressure decreases as the flow passes through a restriction in the pipe following fluid dynamics.
This allows us to determine the differential pressure across the restriction. The square root of this differential pressure is proportional to the flow rate.
A differential pressure (DP) flowmeter consists of two elements, a primary element that causes a pressure drop and a secondary element (a pressure sensor) to measure the differential pressure.
There are different types of primary element : orifice plate flow meters, venturi flow meter, pitot tubes, monoblock orifice and annular chambers, nozzles, wedge, integrated orifice plate, micro venturi, V-cone® flow meter.

Why choose a DIFFERENTIAL PRESSURE flow meter ?
  • Simple device with no moving parts
  • Economical
  • Installation in any position
  • Wide range of applications and processes (gases, liquids, steam)

How to install a flow sensor ?

How to install a flow sensorWhen installing flow measuring instruments, remember to install the meter in a straight section of pipe to eliminate disturbances from bends, valves and other obstructions.

How do I set up a flow meter?

If you want to set up a flow rate meter, you have to do the commissioning.


Installing the instruments and connecting the pipes is called commissioning.
This is a complex job that requires a team of skilled people with a lot of experience.
This can be done by trained instrumentation technicians or by the manufacturer's technical services.

Flow meter training

The user training stage is very important in order to configure the flow sensor according to expectations.
This training ensures that you have the knowledge to read the flow meter screen, use the configuration menu and the parameters.
You will be able to ask all your questions.

How should a flow meter be maintained?

How should a flow meter be maintained

The importance of effective and regular maintenance of flow rate sensors is that in normal operation, flow analysers are exposed to a wide variety of contaminants.
These can be in the form of suspended solids carried by the medium being measured (such as dirt in water) or liquid/solid deposits formed on the outer surface of the flow transmitter (such as scale or corrosive materials).
To minimise the risk of fouling and to ensure accurate measurement over long periods of time, it is necessary to clean it regularly.
Ideally, a flow meter should be cleaned once a year, or more frequently if it is exposed to particularly harsh conditions.

Cleaning in-line flow rate meter not only extends their life, but also ensures optimum performance at all times.
Regular cleaning prevents dirt and other blockages from building up in your meters, eliminating false readings and ensuring that you get an accurate reading every time you use them.

Non-intrusive flow meters have the advantage of not being in direct contact with the fluid and do not require maintenance.

Calibration is important because it ensures accurate readings.
If a flow rate meter is not properly calibrated, it will not provide reliable data that can be used for maintenance and plant improvement.
It is also important to calibrate meters before they are put into service, as poor calibration can lead to a decrease in accuracy over time.
Calibration ensures that fluid flow measurement is taken at a consistent point that provides accurate results every time.

The best way to ensure the continued accuracy of your equipment is to use ongoing verification, maintenance and calibration services.
A well-maintained flow meter will operate more efficiently than one that is not, resulting in lower operating costs for your business.

How do you test a flow meter and calibrate a flow meter?

How do you test a flow meter and calibrate a flow meterA flow sensor needs to be regularly calibrated to ensure that it continues to provide accurate readings.
Calibration is the process of checking that the flow rate meter is working properly and providing accurate readings.
Calibration should be carried out in accordance with the manufacturer's specifications, usually on an annual basis.
Calibrating the flow transmitter involves comparing its output with a known input.
This can be done using an external reference by comparing the output with another device, such as a secondary flow meter.
Calibration is usually carried out by the manufacturer or supplier of the flow measurement equipment.
However, if the warranty period has expired or the manufacturer or supplier does not provide a calibration service, you can send your flow meter to a specialist company for calibration.

Flow meter applications - What are the areas of application of flow meters?

Flow meter applications water and wastewaterThe different classes of flow meters are used for flow measurement and control in a variety of applications, including the paper industry, mining and metallurgy, water and wastewater, food processing, chemical and petrochemical, oil and gas.
Flow meter applications paper industryThey are suitable for a wide range of applications, from clean or dirty liquids, through highly corrosive or abrasive gases, to saturated and superheated steam.
The appropriate flow meter technology should be chosen according to the application and the constraints of the industrial environment. 

Fuji Electric France is at your disposal to HELP YOU FIND THE RIGHT SOLUTION FOR YOUR APPLICATION

Fuji Electric France is at your disposal to help you find the right solution for your application