A rotameter is a device that measures the volumetric flow rate of fluid in a closed tube.
It belogns to a class of meters called variable are flow meters which measure flow rate by allowing the cross-sectional area the fluid travels through to vary, causing a measurable effect.
Rotameter is the most widely used variable area flow meter. Its principle of operation can be further discused and explained by our techncial expersts in sales department and suitability to your applciations.
Most gases like O2, N2, etc can be measure by Rota meters.