Binary gas purity analyzer
Systems and methods for detecting a composition of a binary gas mixture are provided. Such methods and systems include, with a species-dependent mass flow meter, sensing a mass flow rate of a binary gas mixture comprising gases of differing gas correction factors and, with a species-independent pressure sensor, sensing a total pressure of the binary gas mixture. An output representative of a relative concentration of one gas of the binary gas mixture is provided. The relative concentration is determined as a function of the sensed mass flow rate and the sensed total pressure.
1. A method of analyzing a composition of a binary gas mixture, comprising:
with a species-dependent mass flow meter, sensing a mass flow rate of a binary gas mixture comprising gases of differing gas correction factors;
with a species-independent pressure sensor, sensing a total pressure of the binary gas mixture; and
providing an output representative of a relative concentration of one gas of the binary gas mixture, the relative concentration determined as a function of the sensed mass flow rate and the sensed total pressure, wherein the function is in accordance with the following:
P T =f P ( Q a ,Q b ,T )
Q MFM =f Q ( Q a ,Q b ,T )
wherein Q a is a mass flow of a first gas of the binary gas mixture, Q b is a mass flow of a second gas of the binary gas mixture, T is a temperature of the gas mixture, Q MFM is the sensed mass flow rate, and P T is the sensed total pressure;
wherein f P and f Q are defined as follows:
P T =f P ( Q a ,Q b ,T )=( k 1· Q a +k 2· Q b ) T
Q MFM =f Q ( Q a ,Q b ,T )= k 3· Q a +k 4· Q b +k 5· T
where k1-k5 are constants.
2. The method of claim 1 , further comprising determining the constants k1-k5.
3. The method of claim 1 , further comprising maintaining a substantially constant volumetric flow of the binary gas mixture through a chamber.
4. The method of claim 3 , wherein the chamber is evacuated by a constant volume pump.
5. The method of claim 4 , wherein the function is in accordance with the following:
Q a =( Q MFM −GCF b ·P T ·S )/( GCF a −GCF b )
Q b =P T ·S−Q a
where Q a is a mass flow of a first gas of the binary gas mixture, Q b is a mass flow of a second gas of the binary gas mixture, GCF a is a gas correction factor of the first gas, GCF b is a gas correction factor of the second gas, Q MFM is the sensed mass flow rate, P T is the sensed total pressure, and S is a pumping speed of the constant volume pump.
6. The method of claim 5 , further comprising determining the pumping speed S.
7. The method of claim 1 , further comprising determining a gas correction factor of each of the gases of the binary gas mixture.
8. The method of claim 1 , wherein the output is a percentage volumetric flow of the one gas of the binary gas mixture with respect to a total volumetric flow of the binary gas mixture.
9. The method of claim 1 , wherein the output is an alarm indicating the relative concentration of one gas of the binary gas mixture is above or beneath a threshold value.
10. The method of claim 1 , wherein the species-dependent mass flow meter is a thermal mass flow meter.
11. A system for analyzing a composition of a binary gas mixture, comprising:
a species-dependent mass flow meter configured to sense a mass flow rate of a binary gas mixture comprising gases of differing gas correction factors;
a species-independent pressure sensor configured to sense a total pressure of the binary gas mixture;
a controller configured to provide an output representative of a relative concentration of at least one gas of the binary gas mixture, the relative concentration determined as a function of the sensed total pressure and the sensed mass flow rate; and
a chamber and an output pump, the output pump configured to evacuate the binary gas mixture from the chamber
wherein the function is in accordance with the following:
Q a =( Q MFM −GCF b ·P T ·S )/( GCF a −GCF b )
Q b =P T ·S−Q a
where Q a is a mass flow of a first gas of the binary gas mixture, Q b is a mass flow of a second gas of the binary gas mixture, GCF a is a gas correction factor of the first gas, GCF b is a gas correction factor of the second gas, Q MFM is the sensed mass flow rate, P T is the sensed total pressure, and S is a pumping speed of the output pump.
12. The system of claim 11 , further comprising a temperature sensor and wherein the function is in accordance with the following:
P T =f P ( Q a ,Q b ,T )
Q MFM =f Q ( Q a ,Q b ,T )
where Q a is a mass flow of a first gas of the binary gas mixture, Q b is a mass flow of a second gas of the binary gas mixture, T is a temperature of the gas mixture as sensed by the temperature sensor, Q MFM is the sensed mass flow rate, and P T is the sensed total pressure.
13. The system of claim 12 , wherein f P and f Q are defined as follows:
P T =f P ( Q a ,Q b ,T )=( k 1· Q a +k 2· Q b ) T
Q MFM =f Q ( Q a ,Q b ,T )= k 3· Q a +k 4· Q b =k 6· T
where k1-k5 are constants.
14. The system of claim 11 , wherein the output pump is configured to maintain a constant volumetric flow of the binary gas mixture through the chamber.
15. The system of claim 11 , wherein the mass flow meter is a mass flow controller, the mass flow controller configured to supply the binary gas mixture to a volume.
16. The system of claim 15 , wherein the binary gas mixture is supplied to the volume at a rate that maintains a constant pressure of gases within the volume.
17. The system of claim 11 , wherein the output is a percentage volumetric flow of the one gas of the binary gas mixture with respect to a total volumetric flow of the binary gas mixture.
18. The system of claim 11 , wherein the output is an alarm indicating the relative concentration of one gas of the binary gas mixture is above or beneath a threshold value.
19. The system of claim 11 , wherein the species-dependent mass flow meter is a thermal mass flow meter.