Method and Apparatus for Using a Gas Density Sensor to Measure and Control Gas Mixture Composition

An apparatus for controlling the blending of a gas mixture containing known components, comprising:

• a first control valve for controlling the flow of a first component;
• a second control valve for controlling the flow of a second component;
• a first gas density sensor configured and arranged to measure the density of a first mixture made by combining the first component and the second component;
• a third control valve for controlling the flow of a third component;
• a second gas density sensor configured and arranged to measure the density of a second mixture made by combining the first mixture with the third component;
• and
• a controller programmed to determined based on data from the first gas density sensor the relative compositions of the first component and the second component in the first mixture, and to determine based on the data from the second gas density sensor the relative compositions of the first mixture and the third component in the second mixture, and thus to determine the relative compositions of the first component, the second component, and the third component in the second mixture;
• and
• the controller being further programmed to control the first control valve, the second control valve, and the third control valve to obtain a desired relative composition of the first component, the second component, and the third component in the second mixture.

A method for measuring the composition of a gas mixture, comprising:

• measuring the density of a first mixture made by combining a first component and a second component;
• measuring the density of a second mixture made by combining the first mixture with a third component;
• and
• calculating based on the measured density of the first mixture the relative compositions of the first component and the second component in the first mixture, and calculating based on the measured density of the second mixture the relative compositions of the first mixture and the third component in the second mixture, and thus the relative compositions of the first component, the second component, and the third component in the second mixture.