The RNL Series meter is an insertion-style flow meter designed to offer high accuracy measurements over an extremely large flow range. The meters have no moving parts and are virtually maintenance-free. The RNL Series is suitable for most low-viscosity liquids. All meters in this series are loop-powered devices with 4-20 mA output and may also be configured for 3-wire frequency pulse output.

An everyday example of a vortex shedding phenomenon is a flag waving in the breeze: the flag waves due to the vortices shed by air moving across the flagpole. Within the flow meter, as flowing liquid moves across the tiny strut or “bluff bar”, vortices are also shed but on a smaller scale. The meter transmits an ultrasonic beam through the vortex pattern downstream of the strut. As vortices are shed, the carrier wave of the ultrasonic signal is modified. This change in the carrier wave is measurable and moves in proportion to the number of vortices shed.
Digital processing enables the vortices to be counted, and this value is converted into a velocity. Software converts velocity into a volumetric flow rate, in units of measure selected by the operator. Racine Vortex flow meters utilize the smallest strut in the industry, which allows for high sensitivity; superior performance at low flow rates and low pressure drop.