variable Area Flow meter (Rotameter) calibration
The variable area flow meter or Rotameter is the simple, low cost, direct reading indicator for measuring flow of liquids or gases It is used on clean, low viscosity fluids, such as light hydrocarbons.
In a Rotameter, a moving body called the float represents a restriction in the line. Since the float moves freely within the tube, the pressure drop across the float remains constant as the flow rate changes.
The tube is designed so that the area of the annulus is proportional to the height of the float in the tube. The scale can be very nearly linear over the range.
Conventional Rotameters permit flow measurement as low 0.1 cm3/ min of water or an equivalent gas flow.
For measuring very small flows, down to 0.05 cm3 / min, variable area meters are available with glass tube having non-circular cross-sections. Metal tube Rotameters are used for measuring low flows of liquids or gases of high temperatures and pressure.
These instruments can be used to determine liquid flows as low as 10cm3 / min. at 500? F and pressure above 300 psi.