Electromagnetic flow meters, or magnetic meters, are a reliable and accurate solution for measuring the flow of conductive liquids within pressurized pipelines in numerous industrial and civil sectors. In this article, we explore the operating principle of these devices, their main advantages, and typical applications. Finally, we present some models from our range of ISOMAG electromagnetic flow meters.
How do electromagnetic flow meters work?
The operating principle of electromagnetic flow meters is based on Faraday’s Law, or the law of electromagnetic induction, which states that a conductive fluid passing through a magnetic field generates a voltage proportional to its velocity.
The mathematical formula is: E = k * B * D * V. The induced voltage (E) is directly proportional to the velocity (V) of the flow passing through the magnetic field (B) and to dimensional factors such as k (wetted area) and D (internal diameter).
The electromagnetic flow meter is equipped with a pair of electrodes placed on opposite sides of the meter, which detect this voltage. A converter processes the signal to calculate the velocity and thus the volumetric flow rate of the fluid.
To ensure the proper functioning of the electromagnetic flow meter, it is essential that the pipe is completely filled and that the liquid is electrically conductive.
What are the advantages of electromagnetic flow meters?
Below are the key strengths of electromagnetic flow meters:
- They offer high accuracy even under critical operating conditions.
- Unlike other measurement technologies, they have no moving parts, which simplifies maintenance and ensures a longer operational life.
- They are suitable for use with abrasive fluids (containing solid particles) and have no limitations on fluid viscosity.
- There is no pressure loss for full-bore meters, as the fluid passage is unobstructed.
- Insertion versions can be used in pipelines with a wide range of nominal diameters.
However, they also have some limitations that should be considered when selecting them for a specific application:
- They only work with conductive fluids and are therefore unsuitable for measuring non-conductive water or oils.
- Full-bore models, although advantageous in the long term due to low maintenance, have a higher initial installation cost compared to other flow measurement instruments (insertion or clamp-on types).
What are the typical applications?
Thanks to their versatility, electromagnetic flow meters are used in many industrial sectors: potable and wastewater treatment, chemical industry, food and beverage industry, energy sector, and fiscal transactions for MID or OIML-certified versions. In industries such as mining, these meters are often the only effective solution for measuring mineral slurries containing suspended solids or sand-water mixtures.
What are the main causes of measurement errors?
Measurement errors in electromagnetic flow meters can arise from several factors, often related to installation or fluid characteristics. One of the most common causes is the presence of air bubbles in the fluid, which can interrupt contact between the fluid and the electrodes, leading to unstable or incorrect readings.
Deposits or scaling on the electrodes can also affect signal detection. Another cause of inaccurate measurements is low fluid conductivity: electromagnetic meters require a minimum conductivity level (usually >5 µS/cm) to function properly. Errors can also occur due to improper installations, such as positioning the meter in a pipe section that is not fully filled or too close to bends that create turbulence and distort the flow velocity profile.
Finally, electrical interference from nearby motors or high-voltage cables can disturb the generated electrical signal, compromising measurement accuracy and to minimize these errors, it is crucial to follow the manufacturer’s guidelines for installation and selection of the most suitable meter for the specific application.
How to choose electromagnetic flow meters?
After understanding the operation, advantages, and applications of electromagnetic flow meters, it is essential to know how to choose the most suitable model for your needs. Selection depends on several factors, including the type of fluid to be measured, operating conditions, and specific application requirements.
To identify the right meter, it is crucial to assess the pipeline diameter, fluid temperature, and pressure, as well as the material of the internal lining and electrodes, which must be compatible with the measured substance to avoid corrosion or contamination. Additionally, the required accuracy and extra features, such as digital communication or integration with control systems or product certifications, can influence the choice.
Consulting an expert supplier like ISOIL Industria allows not only the identification of the most suitable device but also access to qualified technical support for optimal installation and use of the instrument.
Have you explored the ISOMAG range of meters?
ISOIL Industria is a global leader in the production of flow meters. If you are looking for an advanced solution for flow measurement, ISOMAG electromagnetic flow meters provided by the company are designed to meet your most complex operational requirements. Among the available models is the ISOMAG MS2500 flanged sensor, a universal solution suitable for all applications and flow ranges, available in a wide range of diameters from DN 25 to DN 3000.
The sensor body can be made of Carbon Steel or Stainless Steel AISI304/316. It can be used with fluids at temperatures rang ing from -20 to +180°C. Accuracy and repeatability data depend on the chosen converter.
Another flagship model is the MS 3810 insertion sensor, designed for mounting on pressurized lines with diameters from 80 to 8000 mm. It is ideal for temporary measurement campaigns, pipeline monitoring, and leak detection.
The sensor is available in a wide range of lengths for installation in pipelines of different diameters. It can be used with fluids at temperatures from 0 to 100°C and pressures up to 25 bar, with installation possible without interrupting flow. In the potable water market, HVAC systems, and cooling plants, the MS1000 “wafer” sensor is widely used.
Easy to install due to its flange-free design, it is inserted between various types of counter flanges (UNI, DIN, ANSI, JIS, etc.). It is available in diameters from DN 25 to DN 400 and can be used with fluids at temperatures from -20 to +110°C.
All ISOMAG flow meters are calibrated on ISO17025-certified calibration benches and the original accuracy is guaranteed for the entire lifespan of the meter when operated in accordance with its technical specifications.
Do not hesitate to contact our specialists for more information about these and other instruments.