Patent ID: 7669594

Claim:
An apparatus for controlling the flow of a gas mixture of variable proportions, the apparatus comprising a conduit for the flow of gas; a delivery means for delivery to the conduit of a gas mixture having gaseous components in controlled variable proportions; a regulator for regulating the flow of gas through the conduit; a driver for operating the regulator; a setpoint signal generator for generating a setpoint signal according to a desired setpoint; a volumetric flow meter situated downstream of the valve for determining a volumetric flow rate of gas independently of the composition of the flow of gas; a feedback signal generator associated with the volumetric flow meter, said feedback signal corresponding to the flow rate measured by the volumetric flow meter; and an adjustment signal generator for generating an adjustment signal for controlling the driver by which the regulator is operated to open or close by an amount corresponding to the adjustment signal to achieve a desired flow rate corresponding to the desired setpoint, which adjustment signal generator comprises a comparator for comparing the setpoint signal and the feedback signal.