Flow Measurement · Glossary

What is an Ultrasonic Flow Meter?

transit time and DopplerFlow Measurement

An ultrasonic flow meter measures velocity from the difference in travel time of sound pulses sent with and against the flow.

Ultrasonic Flow Meter Explained

Transit time meters send pulses diagonally across the pipe in both directions. The pulse with the flow arrives sooner; the time difference gives the average velocity along the path. Clamp on versions fit outside the pipe.

Doppler meters instead use reflections from bubbles or particles and suit dirty liquids. Multi path meters average several paths and are used for custody transfer of gas.

Ultrasonic Flow Meter Formula

v = L ÷ (2 cos θ) × (t_up − t_down) ÷ (t_up × t_down)

L	acoustic path length
θ	path angle to the pipe axis
t_up, t_down	transit times against and with the flow

Calculators for Ultrasonic Flow Meter

CalculatorUltrasonic Transit Time Flow CalculatorFree online calculator with formula and worked example.CalculatorPipe Flow Velocity CalculatorFree online calculator with formula and worked example.

Frequently Asked Questions

What is an Ultrasonic Flow Meter?

An ultrasonic flow meter measures velocity from the difference in travel time of sound pulses sent with and against the flow.

Transit time or Doppler?

Transit time for clean liquids and gases; Doppler only when there are enough particles or bubbles to reflect the sound.

Why does a clamp on meter need pipe data?

It must know wall thickness, material and lining to calculate the sound path and flow area.

Learn more on the blog

Types of flow meters

A practical guide on instrumentationblog.in with more detail on ultrasonic flow meter and how it is applied on real plants.

Read Full Article

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