Abstract: One embodiment of the invention comprises a mass flow controller comprising a digital controller, a valve, and a sensor. The digital controller is adapted to implement a control loop having a proportional signal modifier in series with an integral signal modifier. The integral signal modifier is adapted to receive a combination signal and output an integrated signal. The valve is adapted to receive the integrated signal and adjust a valve opening in accordance with the integrated signal. The sensor is adapted to output a measured flow rate signal indicative of an actual fluid flow rate in the mass flow controller. The measured flow rate signal is received by the proportional signal modifier and used in conjunction with a setpoint signal to determine the error signal.