rotometer

in atmospheric chemistry
https://doi.org/10.1351/goldbook.R05418
A device, based on @S06028@, for measuring rate of fluid flow. It is a tapered vertical tube having a circular cross-section in which a float moves in a vertical path to a height dependent upon the rate of fluid flow upward through the tube.
Source:
PAC, 1990, 62, 2167. (Glossary of atmospheric chemistry terms (Recommendations 1990)) on page 2211 [Terms] [Paper]