How to Properly Size Electromagnetic flow meters for Accurate Measurements

Saeed Lanjekar

10 Oct, 2025

6 Minutes

Essential Steps for Accurate Magnetic Flow Meter Sizing

Electromagnetic flow meters are widely used to measure the flow of conductive liquids in various industries. Proper sizing is crucial to ensure accurate measurements and efficient system performance.

This guide provides clear steps and considerations for selecting the right electromagnetic flow meter size.

Want to learn more about electromagnetic flow meters? Check our complete guide on what electromagnetic flowmeters are and how they work.

1. Understand the Basics of Electromagnetic flow meters

Electromagnetic flow meters operate on Faraday's Law of Induction. They generate a magnetic field across a pipe, and as conductive fluid flows through, it induces a voltage proportional to the flow velocity. This voltage is measured by electrodes and converted into a flow rate.

2. Determine Pipe Diameter

The size of the magnetic flow meter should match the inner diameter of the pipe. Accurate measurement depends on this alignment. For example, a DN100 (4") pipe typically requires a corresponding 100 mm magnetic flow meter.

3. Calculate Flow Velocity

Flow velocity is a key factor in sizing. Electromagnetic flow meters perform best when the fluid velocity is within the optimal range. For standard applications, a velocity between 1 and 5 m/s is ideal.

To calculate the required flow velocity, use the formula:

Flow Velocity (m/s) = Flow Rate (m³/h) / (π × (Pipe Diameter / 2)² × 3600)

4. Consider Fluid Properties

The nature of the fluid affects flow meter performance:

Conductivity: Electromagnetic flow meters require conductive fluids.
Viscosity: High-viscosity fluids may need higher velocities to maintain accurate measurements.
Solids Content: Fluids with suspended solids can cause abrasion; thus, higher velocities (3–5 m/s) are recommended to minimize deposition.

5. Account for Installation Conditions

Proper installation of a magnetic flowmeter is essential for accurate measurements:

Straight Pipe Length: Install the flow meter with at least 5 pipe diameters upstream and 2 pipe diameters downstream from bends, valves, or other disturbances.
Orientation: Ensure the meter is installed in the correct orientation as specified by the manufacturer.

6. Choose the Appropriate EM Flowmeter Type

Select the right EM flowmeter type based on application needs:

Integral Meters: Suitable for small to medium-sized pipes.
Split Meters: Ideal for larger pipes and industrial applications.
Insertion Meters: Used for large pipes where full-bore meters are impractical.

7. Evaluate Accuracy and Pressure Drop

Consider the trade-off between accuracy and pressure drop:

Accuracy: Smaller meters generally offer higher accuracy.
Pressure Drop: Smaller meters can increase pressure drop, affecting system efficiency.

8. Consult Manufacturer Guidelines

Always refer to the manufacturer's sizing charts and guidelines. For instance, Emerson provides detailed tables for selecting the appropriate meter size based on pipe diameter and flow rate.

9. Plan for Future Expansion

Anticipate future changes in flow conditions. Selecting a meter with a slightly higher capacity can accommodate future increases in flow rate without compromising performance.

10. Seek Professional Advice

If uncertain about sizing, consult with flow meter experts or manufacturers. They can provide insights and recommendations tailored to your specific application.

Contact Us

At Burak Metering, we specialize in manufacturing high-quality Electromagnetic flow meters in India suitable for various applications. Our products are designed for accuracy, durability, and ease of installation.