A flow controller, which is commonly referred to as a "mass flow controller" is a device that measures and controls the flow of liquids and gases. It is predominantly designed to control a specific type of gas or liquid at a particular range of flow rate. They automatically control the flow rate because they are calibrated in such a way, that enables them to have an auto set flow rate which is sent via an electric signal. This is achieved without being affected by external conditions, nor changed in the pressure.RS Components offer a selection of highly accurate controllers from leading brands including SMC, Omron. Burkert and Cynergy3. Mass flow controllers are used in a wide range of industrial applications when the accurate flow control rate is required.