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Omega is a very broad line distributor, and rarely all that cheap.
Over a pretty wide range of Reynolds numbers - IIRR from about 3000 to
100,000 - vortex shedding flow meters are just as good, and mechanically simpler. I don't know how cheap or popular they are - I worked on one in 1973, and was mightily impressed, but I've not kept in touch with the field since. Google produced this - the second out of 14,600 hits.
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