Method of and Apparatus for Multiple Channel Flow Ratio Controller System

Abstract

A four channel gas delivery system comprising: an inlet channel; four outlet channels; four flow sensors; four control valves, each valve being arranged so as to control the flow from the inlet channel through a corresponding one of the outlet channels; a flow ratio control system configured so as to control the flow from the inlet channel through the corresponding outlet channels so that the following flow ratios are controlled: (a) a first ratio of flows between the outlet channels of a first pair; (b) a second ratio of flows between the outlet channels of a second pair; and (c) a third ratio of flows between the first pair of outlet channels relative to the second pair of outlet channels; wherein the third ratio is controlled by generating at least one bias signal respectively applied to at least one pair of valves, the bias signal being a function of a predetermined set point of the third ratio and measured values of the third ratio.

Dependencies are inferred from the claim text.