What does rotameter mean in practice?
The float indicates the flow in a vertical, graduated pipe and is read at the height specified by the manufacturer.
When does it matter?
Viscosity, density, mounting position and dirt affect the indication, therefore the air scale is not intended to measure water.
Which solutions are related to it?
The range is selected so that the typical flow is in the middle of the scale, and the pipe and float are periodically cleaned.