A flow control system comprises a flow sensor, a valve controller, a signal processor, a control processor and an interface. The flow sensor generates a sensor signal characterizing a flow rate. The valve controller controls the flow rate as a function of a control output. The signal processor converts the sensor signal into a flow signal characterizing the flow rate as a function of time, and the control processor generates the control output as a function of a setpoint and the flow signals. The interface receives an input representative of the setpoint, transmits a flow output representative of the flow signals, and transmits a diagnostic output directly indicative of an operational condition of the flow control system.