A Buyer's Guide To Flow Meters

Flow Meter Technology Overview

Choosing the right flow meter technology is one of the most important decisions in process instrumentation. The wrong choice can result in poor accuracy, high maintenance costs, or even complete measurement failure. This guide will help you understand the major flow meter technologies and select the best option for your application.

Major Flow Meter Technologies

Magnetic Flow Meters (Magmeters)

Magnetic flow meters are ideal for conductive liquids and slurries. They work by applying a magnetic field to the flowing fluid and measuring the induced voltage.

*Best for:* Water, wastewater, slurries, acids, caustics, and other conductive liquids

*Not suitable for:* Hydrocarbons, gases, or non-conductive liquids

*Accuracy:* ±0.2% to ±0.5% of reading

*Key advantages:* No moving parts, no pressure drop, bidirectional measurement

Coriolis Flow Meters

Coriolis meters measure mass flow directly by detecting the Coriolis force on vibrating tubes. They are the most accurate flow meter technology available.

*Best for:* High-value fluids, custody transfer, density measurement

*Accuracy:* ±0.1% to ±0.2% of reading

*Key advantages:* Direct mass flow measurement, density measurement, handles two-phase flow

*Limitations:* High cost, limited to smaller pipe sizes economically

Vortex Flow Meters

Vortex meters measure the frequency of vortices shed by a bluff body inserted in the flow stream.

*Best for:* Steam, gases, and clean liquids

*Accuracy:* ±0.5% to ±1% of reading

*Key advantages:* No moving parts, handles high temperatures and pressures, multivariable versions available

*Limitations:* Not suitable for very low flow rates or viscous fluids

Ultrasonic Flow Meters

Ultrasonic meters use sound waves to measure flow velocity. Clamp-on versions require no pipe penetration.

*Best for:* Clean liquids, non-invasive measurement, large pipe sizes

*Accuracy:* ±0.5% to ±2% of reading (clamp-on); ±0.2% to ±0.5% (inline)

*Key advantages:* Clamp-on versions require no process shutdown, bidirectional

*Limitations:* Affected by entrained gas or solids

Differential Pressure Flow Meters

DP meters measure the pressure drop across a primary element (orifice plate, Venturi, etc.) to calculate flow.

*Best for:* Steam, gases, and liquids in larger pipe sizes

*Accuracy:* ±0.5% to ±2% of reading

*Key advantages:* Low cost, well-understood technology, wide range of primary elements

*Limitations:* Permanent pressure loss, requires upstream/downstream straight pipe

Thermal Mass Flow Meters

Thermal meters measure mass flow of gases by detecting the heat transfer from a heated element.

*Best for:* Gases, especially compressed air and natural gas

*Accuracy:* ±1% to ±2% of reading

*Key advantages:* Direct mass flow measurement, no moving parts, good for low flow rates

*Limitations:* Sensitive to gas composition changes

Selection Matrix

Application Considerations

Pipe Size

• Small pipes (< 1"): Coriolis or thermal mass
• Medium pipes (1"–8"): Most technologies applicable
• Large pipes (> 8"): Ultrasonic or DP meters most economical

Process Conditions

• High temperature (> 300°F): Vortex or DP meters
• High pressure (> 1000 PSI): Coriolis or DP meters
• Cryogenic: Coriolis or ultrasonic

Fluid Properties

• Viscous fluids: Coriolis or positive displacement
• Abrasive slurries: Magnetic with hard-liner electrodes
• Sanitary applications: Magnetic or Coriolis with sanitary connections

Conclusion

The right flow meter for your application depends on your fluid, process conditions, accuracy requirements, and budget. Instrivo's flow measurement specialists are available to help you navigate these choices and select the optimal solution.

Explore our complete flow meter catalog or contact us for a personalized recommendation.