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Flowmeters : Doppler Flowmeter

A flowmeter is an instrumentation device used to measure and record the flow rate of a gas or fluid. Ultrasonic flowmeters are primarily used in the measurement of natural gas and liquified natural gas (LNG) flows. An ultrasonic pulse is sent through the gas and the transmit time of the pulse is recorded both with and against the flow. The transit times can be used to calculate the average flow rate of the gas. In other fluids, the reflections of the ultrasonic pulse are recorded and the measured doppler shift is used to determine the fluid flow rate.