Ultrasonic flow meters use acoustic signals to determine flow velocity and derive volume flow. Obtaining mass flow requires the appropriate gas/fluid-property relationship or additional compensated measurements; ultrasonic velocity measurement alone is not automatically a direct mass-flow measurement.
Common measurement principles
- Transit time: compare acoustic travel times with and against the flow. Their difference is related to velocity, from which volume flow is calculated using the flow-path geometry.
- Beam deflection: some designs evaluate how a moving fluid changes an acoustic beam; the implementation and performance are design-dependent.
- Doppler: measure frequency shifts from moving acoustic scatterers. The medium must contain suitable particles or bubbles for the chosen design.
Some instruments use external clamp-on sensors and do not introduce a restriction into the pipe. Open-channel applications can combine a suitable velocity measurement with a level/area measurement, but that is a different arrangement from a closed-pipe meter.
Ultrasonic methods can be useful where direct contact is difficult, provided the materials, acoustic path, medium and approvals fit the application. They are not universally unsuitable for high-temperature service, nor universally suitable for corrosive, radioactive or flammable media: use the selected model's limits and relevant application requirements.
Transit-time designs commonly need an adequate acoustic path in relatively clean media; Doppler designs need suitable scatterers. Temperature, gas composition, deposits and pipe conditions can all influence the usable method and measurement quality.
Flowmethod designs, develops, manufactures and supports gas mass flow controllers, meters and custom gas-control and mixing systems. Configurations are matched to the customer's process and operating requirements.
For selection, installation or technical enquiries, contact Flowmethod: Mr. Dou, +86 180 3818 3381; doufeijin@hotmail.com. See Contact for the full contact list.