Are there portable devices that can mesure flow inside pipes from the outside ?

Question

I'd like to check the flow in several points of a big pipe system, so I'd need a portable and flexible device I could carry along. Are there any ways to achieve this ?

Answer 1

Here is one example:
http://www.omega.com/ppt/pptsc.asp?ref=FD-400&Nav=gree02

Omega has other similar types, and if they do, then so do other manufacturers.

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