A variable area meter is a flow meter that measures volumetric flow of liquids and gases. VA Meters typically consist of a Tapered tube (Glass or Metal) and a float which could also be described as a shaped weight. There are numerous float shapes in use, but spheres and ellipsoids are the most common.
The float is pushed up by the drag force of the flow and pulled down by gravity. As the flow increases, the float rises in the tapered tube until reaching a point where the upward force exerted by the flow and downward force of gravity are in balance. As the float settles to a stable position, a reading can be taken typically by using the top of the float as a point of reference against an internally mounted flow scale.
Advantages & Disadvantages
With the exception of those meters equipped with transmitters, alarms, etc., standard VA meters require no power. They are simple to use and because the flow tube span increases proportionally as the float moves up, the scale is considered to be approximately linear. Other than those VA Meters that are equipped with a spring loaded float, gravity dictates that VA meters be used in a vertical position with the flow going up. Like a turbine meter, VA meters are set up for specific conditions. Any change in specific gravity, viscosity, process temperature, etc., can affect the overall accuracy of the meter.
Typical applications for a VA Meter include:
- Chemical Injection
- Boiler Control
- Purge Applications
- Tank Blanketing
and any simple flow measurement application measuring gasses and/or clean, low viscosity liquids.
Our catalog of products includes, low-flow, glass-tube flow meters, armored metal tube flow meters, high-flow, glass-tube flow meters, and plastic tube flow meters. We are proud to represent Brooks Instrument and Hedland flow meters, both of which are available for immediate purchase on ShopCross!