Flow Measurement

Will SAW–Technology Become the Perfect Wave for Flow Measurement?

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The Rayleigh angle at which the sound waves are released into the fluid differs for every propagation velocity. In connection with the cycles and the received signal characteristics, and depending on whether the signals have flowed through the medium once or more than once, this generates an “acoustic fingerprint”.

This unique signature can be used to calculate the flow rate, density and temperature. The fanning out of the surface waves into the medium and the multiple reception of the signals make the measurement independent of the flow profile and resistant to fault.

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From Flow Measurement to Multi–Parameter Sensors

There are even more possibilities, however, with the delay time measurement method. “If you use other measuring instruments,” continued Erbe, “something has to flow. We take a different approach. If the fluid is not moving in the pipe, we can measure it. Then the delay delta is just zero.”

The technology has potential for further growth due to the fact that this method also identifies the temperature and density of the medium, almost as a “by-product” as it were. Given that mass flow rate can be easily calculated from these data, there is nothing standing in the way of its development into a multiple parameter solution. But that is not all. “We are also thinking in terms of viscosity and concentration measurement,” confirmed Erbe, “and that really is high-end!”

Just What Customers Demand

Until then Flowave has to persuade the users of its benefits, starting with hygienic processes or water of low conductivity (e.g. ultra-pure water). Other options, which so far could only be measured with Coriolis instruments, shall follow at a later date. “We asked ourselves what was uppermost priority for our customers,” explained Erbe, “in view of the fact that they need to spend an exorbitant amount of money on something which they do not even need at this junction.”

He conceded that the Coriolis measuring technique does have its justification, but in many cases the accuracy of a mag meter would be entirely sufficient. If it would work, that is — which cannot easily be guaranteed with media of poor conductivity or non-flowing liquids. “There have been no viable alternatives yet because they cannot supply the necessary capacity for cleanliness, hygiene or accuracy.”