Current position > News detail
『Ultrasonic vs Magnetic Flow Meter: Selecting External Acoustic vs Inline Induction』Related information(v cone flow meter|rotary gas meter|gallon meter|gear meter|metal tube rotameter|glass tube rotameter|nutating disk meter|transit time ultrasonic flow meter|wedge flow meter|pd meters|hydraulic flow meter|ultrasonic water flow meter|water flow meter|air flow meter|magnetic water flow meter|oxygen flow meter|gas flow meter|argon flow meter|air velocity meter|gasoline flow meter|fuel flow meter|ultrasonic water meter|digital water meter|nitrogen flow meter|solid flow meter|Oxygen tank flow meter|digital water flow meter|diesel fuel flow meter|steam flow meter|02 flow meter|compressed air flow meter|oil flow meter|liquid flow meter)
Ultrasonic vs Magnetic Flow Meter: Selecting External Acoustic vs Inline Induction
Quick Answer
Select a magnetic flow meter when the liquid is conductive and you need inline accuracy from 0.2 to 0.5 percent. Select a clamp-on ultrasonic flow meter when the fluid is non-conductive, when the pipe cannot be shut down, or when the pipe size exceeds DN300. Silver Instruments supplies both meter families with 4-20 mA HART output and ATEX Zone 1 options.
This ultrasonic vs magnetic flow meter selection guide starts with one practical filter. Check the electrical conductivity of the fluid. That single value removes half of the wrong meter choices before you review pressure, temperature, or cost.
Fluid Conductivity Decides the First Cut
In practice, a magnetic flow meter needs a minimum liquid conductivity. Many industrial models require at least 5 µS/cm. Some magmeters need 20 µS/cm for stable readings on water with very low solids. Seawater, wastewater, acids, caustic soda, and most food products have enough conductivity. A seawater line in Oman can show about 50,000 µS/cm. That is an easy magnetic flow meter application.
Do not select a magnetic meter for diesel, jet fuel, edible oil, demineralized water, or solvent. These fluids often sit below 1 µS/cm. In those cases, the signal becomes weak and unstable. An external acoustic meter reads the fluid velocity without any electrical contact. That is why we often quote clamp-on ultrasonic flow meters for a paint manufacturer in Vietnam on a solvent transfer line.
So the first rule is simple. Conductive and full pipe means a magnetic flow meter is a strong candidate. Non-conductive or unknown conductivity means ultrasonic is often the safer route.
Installation Access and Shutdown
An inline induction magnetic meter needs a pipe cut, flanges or wafer mounting, and process shutdown. This is normal for new skids, plant turnarounds, and water utility projects. An Indonesian water utility on DN600 raw water billing lines installed Silver Instruments EMF series inline meters with PTFE liners because they wanted full pipe flow and stable billing data.
A clamp-on ultrasonic flow meter mounts on the outside of the pipe. No cutting and no wetted parts. A clamp-on unit can be mounted in one shift without taking the line down. This is useful on chilled water loops, fire water lines, and old process pipes where welding or flange work is not allowed. Most engineers skip the intrusive step when the line is live and there is no scheduled shutdown window.
But there is a trade. The clamp-on sensor needs a clean pipe surface and a straight run upstream and downstream. A magnetic meter also needs a straight run, but it is less sensitive to pipe wall conditions. Heavy rust, thick scale, or loose paint can block the ultrasonic signal.
Inline Induction Magnetic Flow Meter in Practice
Silver Instruments EMF series covers DN15 to DN800 with 316L electrodes and PTFE or rubber liners. Outputs include 4-20 mA HART, Modbus RTU, and pulse. Typical accuracy is 0.5 percent of reading, with 0.2 percent available on calibrated units. Use these meters for raw water, drinking water, wastewater, brine, and many food products.
On dirty water, the electrode can collect coating. Choose a meter with a self-cleaning electrode or schedule a quick electrode wipe during shutdown. For abrasive slurry, consider an EMF series with a ceramic liner and Hastelloy electrodes. This avoids liner damage on fast moving solids.
External Acoustic Ultrasonic Flow Meter in Practice
Silver Instruments UFS series clamp-on ultrasonic flow meters fit DN25 to DN1200. They work on clean liquids with low viscosity. They also work on some oils and solvents that a magnetic meter cannot read. Typical accuracy is 1.0 to 2.0 percent of reading for a standard clamp-on installation. That is enough for process balance, pump verification, and temporary flow surveys.
Use a clamp-on unit when the pipe is large, the fluid is non-conductiv
_600x400.jpg)
Accuracy, Maintenance, and Cost
Magnetic flow meters win on accuracy. They are the first choice for custody transfer in water networks and for dosing systems where kg/h or L/min control matters. The ultrasonic clamp-on meter is not usually a billing device. It is a process tool and a fast diagnostic tool.
Maintenance is different. An inline magnetic meter has liner and electrode wear over time. A clamp-on ultrasonic meter has no wetted parts, but the coupling gel between the sensor and pipe degrades. Reapply the gel every 12 to 24 months. Clean the pipe surface before every reinstallation. We have seen this on customer sites many times. A rusty pipe can reduce signal strength to zero.
Cost also changes with pipe size. Below DN100, a small magnetic flow meter is often lower cost than a clamp-on ultrasonic meter. Above DN300, the clamp-on meter usually wins on installed cost because there is no pipe cutting, no flanges, and no crane time.
Signal Output and Hazardous Area
Both meter families support 4-20 mA HART, Modbus RTU, and pulse. For oil and gas installations, specify ATEX Zone 1 or Zone 2 certification. Silver Instruments can supply EMF series and UFS series with remote transmitters for high temperature or hazardous area mounting. Temperature ratings are often 120 °C for standard magmeters and 150 °C for standard clamp-on transducers.
Recommended Selection Path
Start with conductivity. If the fluid has more than 5 µS/cm and the pipe can be isolated, select a Silver Instruments EMF series magnetic flow meter. This gives the best accuracy and long term stability for water, wastewater, chemicals, and food liquids. For non-conductive fluids, live lines, or pipe sizes above DN300, select a Silver Instruments UFS series clamp-on ultrasonic flow meter. It gives fast installation and good process data without a shutdown.
Tell us your pressure (bar), temperature (°C), pipe size (DN), and flow range. We will recommend one model and send a quote. Call Silver Instruments at +86-135-1213-1526. WhatsApp 86-135-12131526. WeChat +86 13512131526. Website flow-meter.com.au.
FAQ
Which flow meter works for non-conductive fluids?
Use a clamp-on ultrasonic flow meter. Diesel, oil, demineralized water, and solvents often fall below 1 µS/cm and do not work with a standard magnetic meter. The ultrasonic sensor reads velocity through the pipe wall.
What is the minimum conductivity for a magnetic flow meter?
Many industrial magnetic flow meters need at least 5 µS/cm. Some low conductivity models work down to 0.05 µS/cm, but the process conditions must be stable and the pipe must be full. Confirm the exact fluid value before ordering.
Can a clamp-on ultrasonic meter be used on old pipes?
Yes, but the pipe surface must be clean. Remove loose rust, thick paint, and scale at the sensor locations. If the pipe wall is heavily corroded inside, the signal may not pass. In that case, use an inline magnetic flow meter after a pipe section replacement.
Which meter is better for DN500 pipes?
For installed cost and no shutdown, a clamp-on ultrasonic flow meter is often the better choice above DN300. For billing accuracy and a permanent water network installation, an inline magnetic flow meter is worth the piping work.
Do both meters support ATEX Zone 1 and HART output?
Yes. Silver Instruments EMF series and UFS series can be supplied with 4-20 mA HART, Modbus RTU, and pulse. For oil and gas, ask for ATEX Zone 1 or Zone 2 certification at the time of quotation.
Contact Silver Automation Instruments for a fast selection. Send your fluid type, conductivity, pressure, temperature, pipe size, and flow range. We respond within one business day.