What is Magnetic Flow Meter?

Magnetic Flow Meter is a flow meter that measures the flow of conductive fluids. Abbreviated as EMF, also called Electromagnetic flowmeters. It is a kind of Volumetric flow meter. A magnetic flow meter measures the velocity of conductive liquids moving through a pipe or conduit. In the wastewater treatment industry, Magnetic Flow Meter is the best flow meter choice.

  • Measures liquids or liquid slurries that have a minimum conductivity of 5 µS/cm.
  • Sanitary type, PTFE anticorrosive materials are optional.
  • Clamps, flanges, insertion installation are optional.
  • Battery powered optional.
  • Low cost.
  • DN 6 to DN2000
  • High precision: 0.5%, 0.2% optional

Sino-Inst offers a variety of  Magnetic Flow Meters for flow measurement. If you have any questions, please contact our sales engineers.

Featured Magnetic Flow Meters

Magnetic Flow Meters Features

  • Measurement is not affected by the variation of flow density, viscosity, temperature, pressure and conductivity. High accuracy measurement is guaranteed according to the linear measurement principle.
  • No obstacle in the pipe, no pressure-loss and lower requirement for straight pipeline.
    DN 6 to DN2000 covers a wide range of pipe size. A variety of liners and electrodes are available to satisfy different flow characteristic.
  • Programmable low frequency square wave field excitation. Improving measurement stability and reducing power consumption.
  • Implementing 16 bits MCU, providing high integration and accuracy.
  • Full-digital processing, high noise resistance and reliable measurement. Flow measurement range up to 1500:1.
  • High definition LCD display with backlight.
  • RS485 or RS232 interface supports digital communication.Intelligent empty pipe detection and electrodes resistance measurement diagnosing empty pipe and electrodes contamination accurately.
  • SMD component and surface mount technology (SMT) are implemented to improve the reliability.

Magnetic flow meter working principle

Magnetic flow meters use the principle of Faraday’s Law of Electromagnetic Induction to measure the flow rate of liquid in a pipe. In the magnetic flowmeter pipe parts, a magnetic field is generated, and channeled into the liquid flowing through the pipe. 

Faraday’s Law states that the voltage generated is proportional to the movement of the flowing liquid. A conductor moving through a magnetic field produces an electric signal within the conductor. And the singal is proportional to the velocity of the water moving through the field. 

As fluid flows through the magnetic field, conductive particles in the fluid create changes. This variation is used to measure and calculate the velocity of water flow through the pipe. When the fluid moves faster, more voltage is generated. The electronic transmitter processes the voltage signal to determine liquid flow.

Magnetic flow meter principle – Faraday’s Formula

Faraday’s Formula
E is proportional to V x B x D where:

E = The voltage generated in a conductor
V = The velocity of the conductor
B = The magnetic field strength
D = The length of the conductor

What is the principle of magnetic flow meter?

To apply this principle to flow measurement with a magnetic flow meter. First is to state that the fluid being measured must be electrically conductive for the Faraday principle to apply.

As applied to the design of magnetic flow meters, Faraday’s Law indicates that:the signal voltage (E) is dependent on V, B, D.V is the average liquid velocity ;

B is the magnetic field strength ;

D is the length of the conductor ( which in this instance is the distance between the electrodes).

To learn more about Magnetic Flow Meters, this video by Emerson gives a good explanation.
Video source: https://www.youtube.com/watch?reload=9&v=lRSjYjg9WRo

Advantages of using Electromagnetic Flow Meters.

  • High precision and stability
  • Self-check
  • Two-way measurement
  • No pressure loss
  • No moving parts
  • May be for sanitary purposes
  • Large size available
  • Dirty liquid and mixed fructose are ok

Disadvantages of using Magnetic Flow Meters

  • Can not be used to measure gas, steam and liquids containing a lot of gas;
  • Cannot be used to measure liquid media with very low conductivity.
  • Cannot be used to measure high temperature media. At present, it is restricted by the lining material and electrical insulation material of the measuring tube of the electromagnetic flowmeter for general industry;
  • The electromagnetic flowmeter is easily affected by external electromagnetic interference.

Magnetic flow meter diagram

Dimensions of Converter, shown as Fig 3.

Magnetic flow meter diagram

Dimensions of Sensor, shown as Fig 4.

Magnetic flow meter diagram for sensor


1. Nominal Pressure 4.0 MPa for DN10-150; Nominal Pressure 1.6 MPa for DN10-1000; Nominal Pressure 1.0 MPa for DN10-1600; Nominal Pressure 0.6 MPa for DN10-2000. Other special pressure level can be designed on demand.

2. The length L increases 6 mm if ground flange is equipped; The length L increases 6 mm if inlet protection flange is equipped; The length L increases 6 mm if liner protection flange is equipped.

Magnetic flow meter accuracy

The accuracy of the electromagnetic flowmeter supplied by Sino-Inst is 0.5%, 0.2% optional.

How to understand the accuracy of electromagnetic flowmeter?

The absolute value of the difference between the measured value and the true value is compared with the true value, and the number in front of the obtained percentage is the accuracy. If the number is less than 0.5 and greater than 0.2, the general accuracy is called 0.5 level.

For example: the measured value is 100.5 or 99.5, the true value is 100, and the obtained percentage is 0.5%, which means that the accuracy is 0.5. But if the number in front of the percentage is less than or equal to 0.2, it is called 0.2 level accuracy.

Such as:

  • Rosemount magnetic flow meter’s Accuracy: Up to 0.15% of volumetric flow rate accuracy over 13:1 flow turndowns, 0.25% over 40:1 flow turndown
  • Yokogawa magnetic flow meter Accuracy: ±0.35% of flow rate

Read more about: Why Is Turndown Ratio Important?

Magnetic Flowmeter Applications

Electromagnetic flowmeters have been used for more than 50 years and have been widely used worldwide. The fields involve water/sewage, chemical, pharmaceutical, paper, food and other industries.

Large-caliber meters are mostly used in water supply and drainage projects.

Small and medium calibers are often used in places where solid and liquid are both equal and difficult to detect fluids or high requirements.

Small calibers and tiny calibers are often used in places with hygiene requirements such as the pharmaceutical industry, food industry, and biological engineering.

  • Water / Wastewater Industry
  • Food and Beverage
  • Metals
  • Brewing, Distilling, and Wine makening
  • HVAC
  • Chemical
  • Pulp and Paper
  • Pharmaceutical
  • Mining, Mineral Processing

Extended Reading: Metal Tube Flow Meter Applications

Magnetic flow meter troubleshooting

Every measurement process is unique. Any instrument may have problems during use.

In the process of using the electromagnetic flowmeter, if there is a measurement problem. Please check whether the following problems occur first, and try the corresponding solutions.

If the problem is not listed below, please contact Sino-Inst staff in time. We will provide you with suggestions for problem solving.

No displaya) Check the connection of power supply;
b) Check fuse;
c) Check the voltage of power supply;
d) Check if the LCD contrast can be adjusted. Adjust it if possible;
e) Return to base, if a) to d) are OK.
Coil Alarma) Check if terminal EXT+ and EXT- are open;
b) Check if coil resistance is less than 150Q;
c) Replace converter if a) and b) are OK.
Empty Pipe Alarm and Electrodes Alarma) Check if the sensor pipe is filled with fluid;
b) Check the connection of signal wiring;
c) Connect the terminal SIG1, SIG2 and SIG GND. If the alarm display disappears, it is confirmed the converter is normal. The alarm may be caused by the bubble in the fluid;
d) For electrodes alarm, measure the resistance between two electrodes with a multimeter. The read should be between 3 to 50k. Otherwise, the electrodes are contaminated or covered.
High AlarmIncrease the flow range.
Low AlarmReduce the flow range.
Inaccurate Measurementa ) Check if the sensor pipe is filled with the fluid to be measured .
b) Check the wiring;
c ) Check if the sensor factor and flow zero are the same as those on the calibration sheet .

Extended Reading: Guide: Magnetic Flowmeter Installation

Magnetic flow meter price

Magnetic Flow Meter has different calibers, different materials, different media, different linings, different meter heads, and different functions, so the price is different!

The Magnetic Flow Meter price list is attached below for reference only!

The final quotation is subject to the parameters!

Diameter/DNLining rubber (USD)Lined with PTFE (USD)ElectrodePower Material
DN15485 647 316L (Standard configuration)24V/220VCarbon steel
DN20493 647 316L (Standard configuration)24V/220VCarbon steel
DN25500 647 316L (Standard configuration)24V/220VCarbon steel
DN32537 654 316L (Standard configuration)24V/220VCarbon steel
DN40566 654 316L (Standard configuration)24V/220VCarbon steel
DN50588 662 316L (Standard configuration)24V/220VCarbon steel
DN65618 676 316L (Standard configuration)24V/220VCarbon steel
DN80676 691 316L (Standard configuration)24V/220VCarbon steel
DN100706 750 316L (Standard configuration)24V/220VCarbon steel
DN150728 794 316L (Standard configuration)24V/220VCarbon steel
DN200757 838 316L (Standard configuration)24V/220VCarbon steel
DN250809 985 316L (Standard configuration)24V/220VCarbon steel
DN300926 1118 316L (Standard configuration)24V/220VCarbon steel
DN350985 1368 316L (Standard configuration)24V/220VCarbon steel
DN4001081 1441 316L (Standard configuration)24V/220VCarbon steel
DN5001184 1765 316L (Standard configuration)24V/220VCarbon steel
DN6001368 1904 316L (Standard configuration)24V/220VCarbon steel
DN7001640 3574 316L (Standard configuration)24V/220VCarbon steel
DN8002556 3868 316L (Standard configuration)24V/220VCarbon steel
DN9003088 4574 316L (Standard configuration)24V/220VCarbon steel
DN10004044 5926 316L (Standard configuration)24V/220VCarbon steel
Note: Electromagnetic flowmeters are different in price due to different calibers, different materials, different media, and different functions!

Factors affecting the price of Magnetic Flow Meters

  1. The larger the diameter of the flowmeter, the higher the price. For example, DN250 electromagnetic flowmeter is more expensive than DN25 electromagnetic flowmeter. On the contrary, the smaller the diameter, the lower the price.
  2. The flowmeter is divided into: integrated type and split type. Split type electromagnetic flowmeter is more expensive than integrated type electromagnetic flowmeter. The high reason is that the expensive money for the split type is shielded wire money.
  3. The flowmeter is divided into: ordinary type, anti-corrosion type, anti-corrosion type. The price of electromagnetic flowmeter is higher than that of ordinary electromagnetic flowmeter. The reason for the higher price is that the lining is distinguished. The anti-corrosion type is tetrafluoroethylene lining, mainly for measuring acid Alkaline medium. The common type is rubber lining, mainly for measuring sewage and ordinary water medium.

  1. According to the standard of output signal connection and excitation (or power supply) connection, there are four-wire system and two-wire system;
  2. According to the assembly method of converter and sensor, there are split type and integrated type;
  3. According to the connection method of the flow sensor and the pipeline, there are flange type, clamping type, sanitary type, and insert type;
  4. According to whether the electrode of the flow sensor is in contact with the measured liquid, there are contact type and non-contact type;
  5. According to the structure of the flow sensor, there are short tube type and plug-in type (plug-in electromagnetic flowmeter);
  6. Classified by purpose, there are general type, explosion-proof type, sanitary type, anti-intrusion type and diving type (open channel flowmeter) for open channel flow measurement.

You may like: Digital Flow Meters Guide| Liquid and Gas

Magnetic flowmeters are used in water treatment plants to measure treated and untreated sewage, process water, water, and chemicals.

Where can you use a magnetic flow meter

Water and wastewater applications include the custody and transfer of liquids in the main pipe between water/wastewater areas.

Applications in the mining and mineral processing industries include process water and process slurry streams and heavy media streams.

In order of usage, water/wastewater industry, chemical, food and beverage, oil and gas (although not for oil and gas fluids but in support of the processes), power, pulp and paper, metals and mining, and pharmaceutical.

When choosing a suitable electromagnetic flowmeter, Sino-Inst recommends that you consider the following parameters in turn:

  1. Pipe diameter;
  2. Installation structure;
  3. Electrode material;
  4. Lining material;
  5. Power supply requirements;
  6. Signal output requirements;
  7. Pipeline pressure;
  8. Medium temperature

Extended reading: What Is Difference Between Rotameter And Flow Meter?

Installation requirements

Magnetic flow meter installation guidelines
  1. The measured medium must be a conductive liquid. The pipe should be filled. There must be no air bubbles.
  2. During installation, the flow direction of the measured medium is consistent with the flow direction indicated by the flow meter;
  3. The straight pipe section of 5DN in front and 3DN in back must be guaranteed (DN is the diameter.). If there are mainstreams such as valves, elbows, and reducing heads in the front section, it is recommended that “before 10DN and after 5DN”
  4. The flowmeter should be avoided as much as possible: negative pressure in the measuring tube. Try to avoid large vibrations. Corrosive gas and other places with harsh installation environment around;
  5. The flowmeter should avoid ferromagnetic objects and equipment with strong electromagnetic fields (such as large motors, large transformers, etc.). So as not to affect the working magnetic field and current signal of the sensor;
  6. For the convenience of maintenance, it is recommended to install a bypass pipe at the flowmeter installation location.
  7. When the flowmeter is installed at high altitude or underground, sufficient space for installation, debugging and maintenance should be reserved. In addition, make corresponding measures according to different protection levels;
  8. Should fully understand the corrosiveness of the measured medium and the characteristics of the flowmeter, and strictly prevent the flowmeter from being corroded;
  9. When welding or flame cutting near the sensor, take isolation measures to prevent the lining from heating. And it must be confirmed that the instrument sensor signal line is not connected to prevent damage to the sensor.
Magnetic flow meter installation guidelines 1
Magnetic flow meter installation guidelines 2

Extended Reading: Insertion Flowmeter Types

  1. Mass flow meters and electromagnetic flow meters are different types of flow meters. The mass flow meter measures the mass of the fluid. The electromagnetic flowmeter is a volume flowmeter, which measures the volume of fluid.
  2. The mass flow meter can measure non-conductive media. And more special media such as high temperature, low temperature and high viscosity. Electromagnetic flowmeters can only measure conductive media, mostly wastewater.
  3. The accuracy of the mass flow meter is higher.
  4. The cost of mass flow meters is several times that of electromagnetic flow meters.

Extended reading: metal tube flow meter

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Sino-Inst offer over 50 Magnetic Flow Meters, with Best Price.

A wide variety of Magnetic 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 ultrasonic flow meter, and others are Liquid Turbine Flow Meters.

Sino-Inst is Magnetic Flow Meters suppliers, located in China. Magnetic Flow Meters products are most popular in North America, Mid East, and Eastern Europe. The United States, and India, which export 99%, 1%, and 1% of Magnetic Flow Meters respectively.