About Variable-Area Flowmeters
Variable-area flowmeters are often used with air and liquids that have minimal solids content. Because they mount directly in the line of flow, they create a restriction of flow, or pressure drop, which may make them unsuitable in certain applications.
There are several types of variable-area flowmeters, often called rotameters. The most common type has a moveable float that's housed in a vertical, tapered tube; the float moves up and down in the tube in proportion to the rate of flow. They are easy to install and have excellent repeatability, but must be mounted vertically (unless noted) because they use gravity for operation. Most flowmeters have a direct-reading scale that is calibrated and labeled to read in units such as gpm or scfm. scfm is cubic feet per minute @ standard conditions of atmospheric pressure (14.7 psia and 70° F).
Some flowmeters have a correlated scale that reads the distance the float is displaced (usually in millimeters). This reading must then be translated (correlated) into an actual flow rate via charts that are included. The charts take into account temperature and pressure variations and are therefore typically more accurate.
Mc Master Car has hundreds of flowmeters but there big and lota bucks here is a cheap one.
Flow Range, Fits Req'd Scale O'all
gpm Pipe OD Hole Size Ht. Ht. Each
5-40 1" 5/8"— 11/16" 2 5/8" 6" 4349K41 $59.42
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