What is a flow meter?

A flow meter is an instrument that indicates the flow rate to be measured and/or the total amount of fluid in a selected time interval. Simply put, it is a meter used to measure the flow of fluid in a pipe or open channel.

A flow meter also called a flow sensor, is a device or an instrument used to measure the linear, nonlinear, mass, or volumetric flow rate of a liquid or a gas.

What is a flow meter?

Here, let’s take a closer look at what is a flow meter.

You may like the wikipedia: Flow Measurement.

If you need to know the flow rate in you pipe, or river, that when you need a flow meter. So, flow meter is the instrument that can finish the flow measurement.

Flowmeters consist of a primary device, transducer, and transmitter. The transducer senses the fluid that passes through the primary device.

The transmitter produces a usable flow signal from the raw transducer signal. These components are often combined, so the actual flow meter may be one or more physical devices.

Different types of flow meters are available for different applications, and depending upon the requirement, a careful selection of flow meters is made.

For e.g., we prefer vortex flow meters flow steam flow measuremnet. And we like the ultrasonic flow meters for non-contact pipe flow measuremnt.

Turbine type flow meter cannot be used for measuring the flow in an unclear liquid (wastewater or corrosive liquids).

Flowmeters are devices that measure the rate of liquid, gas or vapor that passes through them.

Some flowmeters measure flow as the amount of fluid passing through the flowmeter during a time period (such as 100 liters per minute).

Other flowmeters measure the totalized amount of fluid that has passed through the flowmeter (such as 100 liters).

Flow measurement can be described by :
Q = A x v

Q is flow rate, A is the crosssectional area of the pipe, and v is the average fluid velocity in the pipe.

Putting this equation into action, the flow of a fluid traveling at an average velocity of a 1 meter per second, through a pipe with a 1 square meter cross-sectional area is 1 cubic meter per second.

Note that Q is a volume per unit time, so Q is commonly denoted as the “volumetric” flow rate.

Now consider the following equation:
W = rho x Q

Where W is flow rate (again – read on), and rho is the fluid density.

Putting this equation into action, the flow rate will be 1 kilogram per second, when 1 cubic meter per second of a fluid with a density of 1 kilogram per cubic meter is flowing.

(The same can be done for the commonly-used “pounds”. Without getting into details — a pound is assumed to be a mass unit.)

Note that W is a mass per unit time, so W is commonly denoted as the “mass” flow rate.

Now — which flow do you want to measure? Not sure? In some applications, measuring the volumetric flow is the thing to do.

Consider filling a tank.

Volumetric flow may be of interest to avoid overflowing a tank, where liquids of differing densities can be added.

(Then again, a level transmitter and high level switch/shutoff may obviate the need for a flowmeter.)

Consider controlling fluid flow into a process that can only accept a limited volume per unit time.

Volumetric flow measurement would seem applicable.

In other processes, mass flow is important.

Consider chemical reactions,where it is desirable to react substances A, B and C.

Of interest is the number of molecules present (its mass), not its volume.

Similarly, when buying and selling products (custody transfer) the mass is important, not its volume.

Understanding the relationship between Flow Rate and Pressure may help you calculate mass or volume flow.

You may like: Industrial flow meters

What are the types of flow meter? You may always hear words like: electromagnetic, vortex shedding, Coriolis, Ultrasonic, Venturi…. If you want to make better choice for your flow measurement, you may need to know more about the flow meter types. Flowmeters are used to measure the flow in a piping system. Let us see the types of flow meters by their different working principle.

Flow Metering Principles

From the measurement principle, the flowmeter can be divided into Volumetric flowmeters and Mass flwo meters.


  • Differential Head type
    • Orifice plates
    • Venturi meters
    • Annubar
  • Differential Area type (Rotameters)
  • Electromagnetic flowmeters
  • Ultrasonic flowmeters
  • Turbine flowmeters
  • Vortex flowmeters
  • Positive Displacement Meters


For different working principle, We offer different types of flow meters, like:

Extended reading: Gas Rotameter Tips

Where are flow meters used? Or, What does a flow meter measure?

At industrial sites, meters that measure fluid flow are referred to as flow meters or flow sensors.

It is one of the most important instruments in industrial measurement.

With the development of industry, the accuracy and range of flow measurement requirements are getting higher and higher.

In order to adapt to various purposes, various types of flowmeters have been successively launched,

widely used in oil and gas, petrochemical, water treatment, food and beverage.

Extended Reading: Rotameter vs Flow meter

Industries such as pharmaceuticals, energy, metallurgy, pulp and paper, and building materials.

  1. Measurement of gas mass flow in industrial pipelines
  2. Smoke flow rate measurement from the chimney
  3. Calciner flue gas flow measurement
  4. Air flow measurement during gas process
  5. Compressed air flow measurement
  6. Gas flow measurement during semiconductor chip manufacturing process
  7. Gas flow measurement in sewage treatment
  8. Gas flow measurement in heating ventilation and air conditioning systems
  9. Flux recovery system gas flow measurement
  10. Measurement of combustion gas flow in a combustion boiler
  11. Gas flow measurement of natural gas, flare gas, hydrogen, etc.
  12. Measurement of carbon dioxide gas flow during beer production
  13. Measurement of gas mass flow in the production process of cement, cigarette and glass factory
  14. Open channel

Extended reading: Ultrasonic Insertion Flow Meter for Lined/Large Pipes

Mass flow rate vs Volumetric flow rate is what we must use in flow measurement and control. In this post, we compare the concept of volume flow and mass flow and the conversion between the two.

Mass Flow Rate vs Volumetric Flow Rate

Commonly used flow meters, such as orifice plates. Turbine flowmeter. Vortex flowmeter. Electromagnetic Flowmeter. Rotameter. The flow measurement value of the ultrasonic flowmeter and oval gear flowmeter is the volume flow of fluid. Coriolis mass flow meters and thermal gas mass flow meters measure mass flow.

Read more Mass Flow Rate vs Volumetric Flow Rate

When measuring flow, the temperature of the medium and the pressure of the pipe have a great influence on the measurement.

Different flow meters have for you the pressure and temperature tolerance range. More than the rated pressure and temperature range, it will affect the measurement accuracy of the flowmeter. Or even damage the flowmeter.

Therefore, when choosing a flowmeter, be sure to clarify the measurement of temperature and pressure.

Guess you like: What is Reynolds number?

How to select the right flow meter for your application?

There are no “universal” flow meters which are suitable for all applications.

Selecting the proper technology for your application requires, writing a flow specification which covers the use of the meter.

There are usually trade-offs with each meter type, so knowing the critical specifications will be important.

There are some question that need to be answered before choosing a Flow Sensor.

  1. What is the fluid being measured?
  2. Do you require rate measurement and/or totalization?
  3. If the liquid is not water, what viscosity is the liquid?
  4. Do you require a local display on the flow meter or do you need an electronic signal output?
  5. What is the minimum and maximum flowrate?
  6. What is the minimum and maximum process pressure?
  7. What is the minimum and maximum process temperature?
  8. Is the fluid chemically compatible with the flowmeter-wetted parts?
  9. If this is a process application, what is the size of the pipe?

Read more General-purpose Flow Totalizer for Data collection and calculation

Which flowmeter do you need? Choose your flowmeters below

Magnetic Flow Meters

Magnetic flow meter is also called electromagnetic flow meter, mag flow meter or magmeter. Suitable for the measurement of conductive liquids.

Turbine Flow Meters

Turbine flow meters are velocity flow meters, also called impeller flow meters. Used to measure the instantaneous flow and cumulative flow of liquids and gases.

Vortex Flow Meters

Vortex flow meter, also called Vortex shedding flow meter. Vortex Flow Meter is suitable for flow measurement of steam and various liquids and gases.

Precession Vortex Gas Flowmeter

Precession vortex flowmeter is a new type of gas flowmeter. It can be used for the measurement of natural gas, propane, air, nitrogen and other gases.

Ultrasonic Flow Meters

The ultrasonic flow meter measures the liquid flow rate quickly and effectively. There are two types of ultrasonic flowmeter technology: Doppler frequency shift and transit time.

Ultrasonic Gas Flow Meters

Ultrasonic Gas Flow Meter uses the principle of measuring the transit time of ultrasonic waves in the pipeline. Ultrasonic Gas Flow Meter is an ideal choice for various gas measurements.

Differential Pressure Flow Meters

Differential Pressure Flow Meter is also called DP flow meter. Differential pressure flow meters use the principle of differential pressure to measure the flow of liquid, gas and steam.

Volumetric Flow Meters

Volumetric Flow Meter, as a mechanical flow meter, is also called Positive displacement flowmeter. It can measure the volume flow of high viscosity and corrosive fluids.

All flow meters can work with the AMS TREX, HERE !

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Mechanical Flow Meters

Selection Guide What is a mechanical flow meter? Mechanical flow meters are a type of flow…

Sino-Inst offer over 20 flow meters, with Best Price.

A wide variety of flow meters options are available to you, such as free samples, paid samples.

About 13% of these are magnetic flow meter, 14% are Insertion Magnetic Flow Meter, 25% are Venturi flow meter,

13% are Handheld ultrasonic flow meter, and others are Liquid Turbine Flow Meters.

Sino-Inst is wastewater flow meter suppliers, located in China.

Wastewater flow meter products are most popular in North America, Mid East, and Eastern Europe.

The United States, and India, which export 99%, 1%, and 1% of ultrasonic level transmitter respectively.

You can ensure product safety by selecting from a certified supplier, with ISO9001, ISO14001 certification.

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