The Hontzsch vortex effect flowmeter is one of the rare instruments that can measure gases with suspended particles. This metering instrument offers a turndown ratio of 1:160, which is remarkably high.
The Hontzsch vortex effect flow meter works on the principle of whirlwinds- the Karman effect. The stream of gas enters the restricted passage, and then splits into small whirlpools or vortexes to avoid the obstruction. These whirlpools are variable pressure zones and the rate of generation of these vortexes is directly proportional to the speed of the fluid.
Theory of operation:
This method of flow measurement involves placing a bluff body (called a shedder bar) in the path of the fluid. As the fluid passes this bar, disturbances in the flow called vortices are created. The vortices trail behind the cylinder, alternatively from each side of the bluff body. The frequency at which these vortices alternate sides is essentially proportional to the flow rate of the fluid. Inside, atop, or downstream of the shedder bar is a sensor for measuring the frequency of the vortex shedding. This sensor is often a piezoelectric crystal, which produces a small, but measurable, voltage pulse every time a vortex is created.