Flow sensors measure the flow rate of liquid or gaseous media. They are used to monitor the volume or mass flow rate of a medium through a control system. Simple diagnostic and condition monitoring tasks can be performed by observing the flow rate; after all, a change in flow rate is often an indication that problems are likely to occur. Simple transmitters, called flow transmitters, send the physically measured variable as an electrical signal. The majority of flow sensors offer digital switching outputs or even digital and analog outputs.