How does a vortex meter work?
The basic concept is that there is a flow obstruction, or shedder, that causes the flow to separate and then shed swirls or vortexes of flow. The rate at which the swirls are shed is directly proportional to the amount of flow passing the shedder. However, one should note that at very low densities flowing slowly there is very little energy in each vortex swirl. At some point in the flow range the energy is too low for the sensor to detect and the meter goes to zero. For liquids, the lower limit of the operating range is determined by the Reynolds number of the flow. The Reynolds number (Re) is viscosity dependant and as the viscosity goes up, the Re goes down. Vortex meters are linear in output to an Re of 20,000. Below that, the vortex shedding process starts becoming less regular until is becomes so irregular that it is unreliable. For optimum performance in a vortex meter, the viscosity of the liquid should be water-like. As the flow strikes the shedder located in the middle of the
