Mitigation of gas memory effects in gas analysis

Apparatus for measuring a time variable concentration of an analyte in a sample gas, the apparatus comprising:

• a sample chamber capable of admitting said sample gas for analysis;
• a sensor operatively connected to said sample chamber and capable of measuring a concentration of said analyte in said sample gas;
• a gas flow controller capable of altering a partial pressure of said analyte in said sample chamber;
• wherein said gas flow controller is configured to maintain said partial pressure substantially constant, provided said measured concentration is within a predetermined control range;
• wherein said gas flow controller maintains said partial pressure substantially constant by:
• i) altering a total pressure in said sample chamber;
• and
• ii) mixing a known fraction of inert gas with said sample gas in said sample chamber, wherein said inert gas is known to not include said analyte.

A method of measuring a time variable concentration of an analyte in a sample gas, the method comprising:

• admitting said sample gas to a sample chamber for analysis;
• measuring a concentration of said analyte in said sample gas with a sensor operatively connected to said sample chamber;
• controlling a partial pressure of said analyte in said sample chamber with a gas flow controller to maintain said partial pressure substantially constant, provided said measured concentration is within a predetermined control range;
• wherein said measuring a concentration of said analyte in said sample gas comprises:
• measuring a chamber concentration of said analyte in gas in said sample chamber;
• and
• determining said concentration of said analyte in said sample gas from said measured chamber concentration;
• wherein said controlling said partial pressure of said analyte in said sample chamber comprises mixing a known fraction of inert gas with said sample gas such that a sample gas fraction in said chamber is R<1.

A method of measuring a time variable concentration of an analyte in a sample gas, the method comprising:

• admitting said sample gas to a sample chamber for analysis, wherein said sample gas in said sample chamber has one or more gas flow parameters;
• measuring concentrations of said analyte in said sample chamber with a sensor at two or more distinct values of said gas flow parameters;
• providing a mathematical memory effect model which can provide an estimate for true analyte concentration from said two or more concentration measurements;
• providing said estimate of said true analyte concentration as an output.