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In industrial, municipal, and laboratory applications, selecting the right flowmeter is critical to ensuring accurate and reliable fluid measurement. Among the most widely used non-intrusive technologies are ultrasonic and magnetic flowmeters. Each offers distinct advantages depending on the fluid properties, application conditions, and budget.
This article provides a clear comparison between ultrasonic and magnetic flowmeters, explaining how they work, where they excel, and how to choose the right type for your specific application.
Why Flowmeter Selection Matters
Impacts process efficiency and cost control
Ensures regulatory compliance (e.g. water utilities, pharma, food processing)
Critical for liquid batching, inventory control, and pumping systems
Misapplied flowmeters can lead to inaccurate dosing, poor quality control, or process failures
What is a Magnetic Flowmeter?
Also known as electromagnetic flowmeters or magmeters, these devices use Faraday’s Law of Electromagnetic Induction to measure flow. They are ideal for conductive liquids such as water, wastewater, slurries, acids, and chemicals.
Key Features:
No moving parts → minimal maintenance
Suitable for dirty, corrosive, or viscous fluids
High accuracy (±0.2% typical)
Not suitable for non-conductive fluids like oil or deionized water
Example Applications:
Water treatment plants
Mining and slurry transport
Chemical dosing systems
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What is an Ultrasonic Flowmeter?
Ultrasonic flowmeters measure flow rate by sending sound waves through the fluid and measuring the time shift. There are two main types:
Transit-Time: For clean liquids
Doppler: For fluids with particulates or bubbles
Key Features:
Non-intrusive (clamp-on or inline)
Ideal for clean or partially contaminated liquids
Measures both conductive and non-conductive fluids
Accuracy depends on pipe geometry and installation quality
Example Applications:
Building energy management (HVAC)
Water distribution
Food and beverage processing
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Side-by-Side Comparison
| Feature | Magnetic Flowmeter | Ultrasonic Flowmeter |
|---|---|---|
| Fluid Conductivity Needed | Yes | No |
| Suitable for Dirty Fluids | Yes | Limited (Doppler only) |
| Installation Type | In-line | Clamp-on or in-line |
| Maintenance Requirement | Low | Very Low |
| Pipe Material Limitation | No | Yes (pipe must transmit sound) |
| Power Supply | Required | Often battery or line powered |
Factors to Consider When Choosing
Fluid conductivity → Magnetic requires it, ultrasonic does not
Installation conditions → Ultrasonic clamp-on is ideal where pipe cutting isn’t feasible
Accuracy needs → Both offer high accuracy if correctly installed
Operating environment → Choose corrosion-proof housing if needed
Data interface requirements → Look for Modbus, HART, 4–20 mA, pulse output
Additional Flowmeter Technologies (Honorable Mentions)
| Type | Best For |
| Turbine | Low-viscosity fluids, batching |
| Coriolis | Mass flow, density measurement |
| Vortex | Steam or gas measurement |
| Thermal Mass | Air and gas flow |
Conclusion
Understanding the differences between magnetic and ultrasonic flowmeters allows for better instrumentation planning and optimized operations. For conductive and dirty fluids, magnetic meters are often preferred. For flexible, non-intrusive installations or non-conductive fluids, ultrasonic flowmeters offer a strong alternative.
Browse our full range of flow measurement instruments at Jansen calibration — trusted globally for precision industrial solutions.
