Low flow flowmeters
Variable area flowmeters are basically vertical internally tapered tubes mounted with the large end at the top. A float or rotor with an outer diameter slightly less than the minimum diameter of the tube is placed inside the tube. The clearance space between the float and the tube forms an annular passage or orifice. As the tube is tapered, the area of this orifice is larger when the float is near the top than it is when the float is near the bottom. By connecting the tube into a fluid flow line so flow direction is from bottom to top, the float will move upward and be supported at a point where the orifice is just large enough to pass the fluid flowing through the system.
These flowmeters are equipped with a needle valve which allows an accurate regulation of the desired flow. Accuracy ±3% f.s.
One or two adjustable switches (optical detector, inductive sensor or reed switch) upon request.