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Variable area flowmeters

Variable area flow meters with variable area work by varying the cross-sectional area of the device in response to flow, creating a measurable effect that indicates the flow measurement. Flow through the orifice moves an internal float up through the area chamber. The external body of this chamber is scaled in flow units for each application. As flow increases, the fluid generates more force and moves the float further up the internal chamber body.

The most common type is a variable area flow meter in a vertical measuring tube that balances the downward weight of a float with the upward force of the flowing fluid. Using a spring instead of a float allows this type of flow meter to be installed in horizontal pipes because the operation of the float is not dependent on gravity when the spring is used. These flowmeters are called variable area metal tubes and can be read locally because their measuring tubes have markings that relate the position of the float (which can be seen) to the flow rate of the fluid. Flow meters with remote signals are usually made of metal tubing and include a flow transmitter that detects the height of the float to determine fluid flow.Variable surface flow meters offer a versatile approach to measuring the flow rate of fluids in a variety of applications. In addition to the type discussed earlier with a float in a vertical measuring tube, there are several other configurations that make variable surface flow meters effective.