Method of gas composition determination, adjustment, and usage

A method of determining a gas composition in a process chamber, comprising:

• coupling a device to a process chamber, wherein a first cavity of the device is thermally coupled to a second cavity of the device and the first cavity and second cavity are at a first temperature, wherein the first cavity comprises a first outlet and a first inlet and the second cavity comprises a second outlet and a second inlet;
• introducing a first gas into the first cavity via the first inlet;
• introducing a gas mixture comprising the first gas and a second gas into the second cavity via the second inlet;
• determining a first difference between a frequency of a first harmonic and a frequency of the second harmonic of the first gas;
• determining a second difference between a frequency of a first harmonic and a frequency of the second harmonic of the gas mixture;
• and
• based on a ratio of the first difference to the second difference, determining a concentration of the second gas in the second cavity.

A system comprising:

• a gas monitoring module comprising an outside wall and an interior wall, wherein the interior wall forms a first cavity having a first inlet and a first outlet and a second cavity of the gas monitoring module comprising a second inlet and a second outlet, wherein the first cavity and the second cavity are thermally coupled;
• a first thermocouple associated with the first cavity;
• and
• a second thermocouple associated with the second cavity.