Patent ID: 8738187

Claim:
A mass flow control system comprising: a plurality of mass flow controllers configured for use with a plurality of flow paths, each between a gas inlet and an outlet, one mass flow controller for each of the flow paths, respectively, each mass flow controller including a mass flow sensor operative to sense the mass flow along the respective flow path and a control valve, responsive to a control signal, for controlling the mass flow through the corresponding outlet, wherein the mass flow sensor includes (i) a bypass channel with a laminar flow element, and (ii) a dead volume between the laminar flow element and the control valve; a pressure sensor for each of the flow paths, wherein each pressure sensor is coupled to and configured to measure pressure in the dead volume of the respective mass flow controller and is operative to measure fluctuations in pressure of gas along the respective flow path; and at least one process controller operative to generate each control signal as a function of the sensed mass flow and measured fluctuations in pressure of gas so as to provide a constant flow of gas at each of the outlets irrespective of fluctuations in pressure of gas at the respective gas inlet.