Magnetic Flow Meters: Basic Principles

Magnetic Flow Meter
Magnetic flow meters are used in many industrial applications. The device is preferred due to being cost-effective, providing accurate volumetric measurement, and an obstruction-less pathway for slurries and aggressive chemicals.

The operation of magnetic flow meters is different than other measurement devices. The post will highlight the basic principles of the device and also shed light on pros, cons, and industrial application.

Basic Principle of Magnetic Flow Meters 

Magnetic flow meters are also known as electromagnetic flow meters or mag meters. The principle of magnetic flow meter is based on Faraday’s Law of Electromagnetic induction. The law states that a voltage produced across a conductor as it moves through the magnetic field at right angles is directly proportional to the velocity of that conductor.

The device creates a magnetic field to channel the flow of fluid through a pipe. As the fluid passes through the magnetic field, a voltage signal is created. The faster the fluid flows through the pipe, the higher the voltage produced by the device.

The voltage is picked up by electrode sensors that are located inside the tube. The signals are then conveyed to an electronic transmitter that processes the signal to determine the velocity of the fluid flow.

Benefits of Magnetic Flow Meters

Magnetic Flow MeterMagnetic flow meters can be installed in shorter meter runs since they don’t require much upstream and downstream runs. The volumetric flow meters have little or no moving parts and require less maintenance making them a cost-effective option for many industrial applications.

Another benefit of the industrial application of magnetic flow meters is that they have a low-pressure drop. Only a slight pressure drop results depending on the length of the tube.  This results in more accurate measurement of the liquid flow velocity.

Magnetic flow devices are based on the principle of a linear relationship between the measuring signal and flow rate. In contrast, most other pressure devices work on the principle of a square law relationship. This results in a higher rangeability and accuracy of the magnetic meters.

An important thing that you should keep in mind is that the magnetic flow meters are susceptible to air bubbles. The device cannot differentiate between the process fluid and entrained air. So, the air bubbles will result in an incorrect reading. Air bubbles will cause the meter to give a high reading.

Another thing to remember is that the pipe should be filled completely with water. An incorrect reading will result if the pipe is not full. A solution for this is to install the sensor about 45 to 130 degree angle.

Application of Magnetic Flow Meters

Magnetic flow meters can measure velocities of all conductive liquids including water, slurries, and acids. More specifically, the device can measure velocities of liquids with electrical conductivity greater than 5μS/cm.

Since the flow meter is obstruction-less, the device is generally applied to measure the velocity of dirty, sanitary, abrasive, and corrosive liquids.

However, the device cannot be used for measuring velocities of liquids with low electrical conductivity such as boiler feed water, deionized water, and hydrocarbons. In addition, the device can also not measure the velocity of gasses.

Types of Magnetic Flow Meter 

You can find three common types of a magnetic flow meter in the market. The devices are suitable for different industrial application.

Insertion Magnetic Flow Meter

The insertion magnetic flow meter is best for measuring liquid flow in large pipes. The device is simple to install and deliver accurate measurement across a range of pipe sizes.

Inline Magnetic Flow Meter

Inline magnetic flow meter is ideal for situations where high accuracy is necessary. The device is generally used for measuring the liquid flow of slurries, wastewater, food, and pulp.

Unlike insertion magnetic flow meters, inline flow meters don’t require a straight pipe. Moreover, they are best in assessing liquid with higher flow rates.

Low-flow Magnetic Meters 

Low-flow magnetic meters are great for assessing liquid with low flow rates. They are designed in a way to prevent fouling. Similar to insertion magnetic flow meters, the low-flow meters do not require straight pipe. In addition, the device can be used in situations where little space is available between the elbow and the meter.

Magnetic flow meters are reliable in measuring velocities of conductive fluid. The devices have a wide range of industrial application, particularly in commodity transfer. They provide accurate reading and undergo less wear and tear. They are a reliable and cost-effective option for measuring the fluid flow of all conductive fluids.

The device can be used to accurately measure the fluid flow of untreated sewage water, processed water, and aggressive chemicals in water treatment, mining operations, and pulp and paper industries.

For more information on magnetic flow meters, contact Thompson Equipment Company (TECO) by calling 800-528-8997 or by visiting

Comprehensive Guide for ABB VA Master FAM540 Metal Cone Variable Area Flowmeter

The VA Master FAM540 flowmeter can be utilized for measuring the flow of liquids, steam and gases, especially when aggressive or opaque fluids are to be metered. It is ideal for the chemical, pharmaceutical and food and beverage industries.

This PDF document is a comprehensive collection of data sheets, commissioning instructions, operating instructions, and a spare parts list for the FAM540.

Document Includes

  • Data Sheets (DS_FAM540_EN_D_1)
  • Commissioning Instructions (CI_FAM540_EN_B_1)
  • Operating Instructions (OI_FAM540_EN_D_1)
  • Spare Parts List (SPL_FAM540_EN_C)

Operating Principle Behind the Badger Meter RCT1000 Coriolis Flowmeter

This video explains the operating principle behind the Badger Meter Coriolis flowmeter.

The RCT1000 Coriolis flowmeter gives you the ability to measure mass, volume, density and temperature - providing control options to synchronize precision processes. More than simply a flow meter, the RCT1000 by Badger Meter is capable of controlling process flow by sending commands to other instrumentation, such as valves and pumps.

Thompson Equipment (TECO)

April 11, 2019 is Global Reman Day - Pass the Word

What is Reman?

Global Reman DayRemanufacturing is a comprehensive and rigorous industrial process by which a previously sold, leased, used, worn, or non-functional product or part is returned to “like-new” or “better-than-new” condition, from both a quality and performance perspective, through a controlled, reproducible, and sustainable process.

Global Reman Day is a day to advance the remanufacturing industry through remanufactured-hosted events and workforce development initiatives. Remanufacturing is good for the environment and the economy. Thompson Equipment (TECO) has been a pioneer in the remanufacturing of process instrumentation and flow meters for decades now, and continues to innovate in these areas.

The positive environmental impact remanufacturing instrumentation has on the on the environment has always been crystal clear to TECO.  Ending up in a dumpster is a terrible waste of reusable component parts. With a little effort, experience, and knowledge, a wide variety of used process instrumentation can be brought back to life, arguably better than new. Another benefit is the remanufactured item generally comes with a considerable cost savings over new.

Promotional, educational, and technical events are being held on April 11 all over the world! To find out more about Reman Day, and remanufacturing in general, visit

Magnetic Flowmeters Used in Industry

Magnetic Flow Meter
Magnetic flow meter.
Magnetic flow meters are effective for monitoring the flow rate of fluids that present difficult handling problems, such as corrosive acids, sewage, rock and acid slurries, sand and water slurries, paper pulp stock, rosin size, detergents, bleaches, dyes, emulsions, tomato pulp, milk, soda, and beer. Magnetic flow meters mainly are applicable to liquids that have a conductivity of 0.1 microsiemens per centimeter or greater. They are not applicable to petroleum products or gases.

Measurement Principal

The basis of the magnetic flow meter is Faraday's Law of Electromagnetic Induction. In summary, a voltage induced in a conductor (i.e., the fluid flowing in the conduit) moving in a magnetic field is proportional to the velocity of the conductor. This relationship can be expressed mathematically as follows:
internal view magmeter
Internal view of flow tube.


E = induced voltage
C = constant
B = magnetic flux density
D = diameter of conduit
v = velocity of fluid

In principle, the fluid flowing through the pipe passes through the magnetic field. This action generates a voltage that is linearly proportional to the average velocity in the plane of the electrodes. If the velocity profile changes due to swirl or helical flow patterns, the total measured velocity is unaffected as long as the velocity profile across the pipe is symmetrical. Non-symmetrical flow profiles may cause flow rate measurement errors of several percent.

In operation, the magnetic coils create a magnetic field that passes through the flow tube and into the process fluid. When the conductive fluid flows through the flow meter, a voltage is induced between the electrodes, which are in contact with the process fluid and isolated electrically from the pipe walls by a nonconductive liner to prevent a short circuit in the electrode signal voltage. Grounding is required for magnetic flow meters to shield the relatively low voltage signal that is measured at the electrodes from the relatively high common-mode potentials that may be present in the fluid. If the pipe is conductive and comes in contact with the flow meter, the flow meter should be grounded to the pipe both upstream and downstream of the flow meter. If the pipe is constructed of a nonconductive material, such as plastic, or a conductive material that is insulated from the process fluid, such as plastic-lined steel pipe, grounding rings should be installed in contact with the liquid.

Magnetic flow meters can be used in pipes that range in diameter from 0.25 to 240 cm (0.1 to 96 in.). Magnetic flow meters are available for flow rates in the range of 0.008 liters per minute (L/min) (0.002 gallons per minute [gal/min]) to 570,000 L/min (150,000 gal/min). Since magnetic flow meters do not place an obstruction in the pipe, the devices do not cause a loss in fluid pressure. Also, straight pipe requirements do not apply to this flow monitor device. Magnetic flow meters are insensitive to density and viscosity and can measure flow in both directions. In addition, because they cause no obstructions, magnetic flow meters often are used to measure the flow rate of slurries.


If all components of a magnetic flow metering system are calibrated as a unit, system accuracies of ±0.5 percent of flow rate are possible. However, normal accuracy specifications are ±1.0 percent of flow rate. Higher accuracy systems match the primary flow meter with a transmitter in the factory.

For more information on magnetic flow meters, contact TECO by calling 800-528-8997 or visit their web site at

Hydraulic Fracturing Terms and Definitions

Hydraulic Fracturing Terms and DefinitionsHydraulic fracturing is the process of using fluid, sand, chemicals, and gels to create or exploit small fractures in a sub-surface rock layer formations in order to stimulate production from oil and gas wells. This fracturing creates paths and reservoirs which increase the rate at which fluids can be taken from the wells. In some cases, this process can increase production by many hundreds of percent.

Below are common terms and definitions* used in the hydraulic fracturing process:
  • Additive Pumps – used to inject liquid additives; different types based on the additive type and additive rate.
  • Annulus – Area between two concentric casing strings or tubular strings.
  • Bottom Hole Treating Pressure (psi) – pressure being applied to the formation including net pressure.
  • Centrifugal Pumps – used on the low pressure equipment to mix and move fluid.
  • Clean Volume (gal or bbl) – volume of fluid pumped without proppant.
  • Dirty Volume (gal or bbl) – volume of fluid pumped with proppant.
  • Flowmeter – used to measure and transmit fluid flow rates; different types depending on application.
  • Frac Gradient (psi/ft) – pressure at which fluid will cause the formation rock to part.
  • High Pressure Pumps – Positive displacement pumps used for pumping downhole.
  • Hydraulic Horsepower (hhp) – horsepower being applied to the formation while pumping .
  • Hydrostatic Pressure (psi) – pressure the fluid column exerts on the formation.
  • Instantaneous Shut-in Pressure (psi) – a pressure used to calibrate the frac gradient.
  • Kick-outs – mechanical or electrical devices that activate at a preset pressure to disengage high pressure pumps.
  • Liquid Additive (gal/Mgal) – any liquid chemical added to the fluid system for a specific purpose
  • Max Pressure (psi) – the maximum WHTP that will be allowed.
  • Net Pressure (psi) – excess pressure over frac pressure required to extend the fracture .
  • Perf Friction Pressure (psi) – pressure drop across the perforations.
  • Pipe Friction Pressure (psi) – friction pressure of the fluid being pumped down the wellbore.
  • Pop-off – a mechanical device activates at a preset pressure to prevent damage to surface and downhole tubular.
  • Pressure Transducer – device used to measure and transmit pressure data.
  • Proppant – small diameter material used to keep the fracture open.
  • Proppant Concentration (lb/gal) – the amount of proppant added to one gal of fluid.
  • Shut-in Pressure (psi) – a pressure used to calibrate the frac gradient.
  • Solid Additive (lb/Mgal) – a solid chemical added to the fluid system for a specific purpose.
  • Treatment Rate (bpm) – the downhole rate that fluid is entering the formation pumping.
  • Wellhead Treating Pressure (psi) – the surface pressure at the wellhead during.
Thompson Equipment (TECO) manufactures highly engineered flowmeters designed for optimum performance in fracing applications. Contact TECO to discuss any severe flow measurement application.


* from workshop titled "Fracture Design and Stimulation – Monitoring" (DC01:570405.2)

The Role of the High and Low Pressure Ports on a Differential Pressure Transmitter

It's easy to misunderstand the role of the high and low pressure port on differential pressure transmitters. This video clearly explains their real meaning and role.