Gas analyzer method and apparatus
First Claim
1. A method for determining the relative amounts of first and second gases in an unknown mixture of gases, comprising, directing radiant energy serially through a first reference volume of said first gas, a second reference volume of said second gas, and a sample volume of the unknown gas mixture, said radiant energy having a wavelength spectrum including characteristic absorption wavelengths of said first and second gases, modulating the absorption of the radiant energy by the first and second reference volumes and the sample volume at first, second, and third frequencies, respectively, detecting the amount of radiant energy passing serially through the first and second reference volumes and the sample volume, developing first and second corresponding sideband signals resulting from heterodyning of the energy modulated at the first and third frequencies and at the second and third frequencies, respectively, and obtaining a ratio of said first and second sideband signals.
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Abstract
A method and apparatus are described for determining relative amounts of first and second gases in an unknown mixture of gases. Radiant energy is directed serially through reference volumes of the first and second gases and a volume of the unknown gas. The absorption of the radiant energy by the respective gas volumes is varied at different frequencies. The amount of radiant energy passing through the respective gas volumes is detected and a signal is developed representative of the ratio of the amounts of the first and second gases.
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Citations
18 Claims
- 1. A method for determining the relative amounts of first and second gases in an unknown mixture of gases, comprising, directing radiant energy serially through a first reference volume of said first gas, a second reference volume of said second gas, and a sample volume of the unknown gas mixture, said radiant energy having a wavelength spectrum including characteristic absorption wavelengths of said first and second gases, modulating the absorption of the radiant energy by the first and second reference volumes and the sample volume at first, second, and third frequencies, respectively, detecting the amount of radiant energy passing serially through the first and second reference volumes and the sample volume, developing first and second corresponding sideband signals resulting from heterodyning of the energy modulated at the first and third frequencies and at the second and third frequencies, respectively, and obtaining a ratio of said first and second sideband signals.
- 5. A method for determining the relative amounts of first and second gases in an unknown gas mixture, comprising, directing radiant energy serially through a first reference volume of said first gas, a second reference volume of said second gas, a sample volume of the unknown gas mixture, and a third reference volume containing a predetermined ratio of said first and second gases, said radiant energy having a wavelength spectrum including characteristic absorption wavelengths of said first and second gases, modulating the absorption of the radiant energy by the first and second reference volumes, the sample volume, and the third reference volume, detecting the amount of radiant energy passing serially through the first, second, and third reference volumes and the sample volume, and developing signals representative thereof, and processing such signals to derive an output signal representative of the ratio of the ratio of the amounts of the first and second gases in the sample volume to the ratio of the amounts of the first and second gases in the third reference volume.
- 8. Apparatus for determining the relative amounts of first and second gases in an unknown gas mixture, comprising, means for containing a first reference volume of the first gas, a second reference volume of the second gas, and a sample volume of the unknown gas mixture, means for directing radiant energy having a wavelength spectrum including characteristic absorption wavelengths of the first and second gases through the first and second reference volumes and the sample volume, means for modulating the absorption of the radiant energy by the first and second reference volumes and the sample volume at first, second and third frequencies, respectively, means for detecting the amount of radiant energy passing serially through the first and second reference volumes and the sample volume, demodulator means for developing first and second corresponding sideband signals in the detected radiant energy arising from the first and third frequencies and arising from the second and third frequencies, respectively, and means for obtaining a ratio of said first and second sideband signals.
- 12. Apparatus for determining the relative amounts of first and second gases in an unknown gas mixture, comprising, a first reference cell for containing a volume of the first reference gas, a second reference cell for containing a volume of the second reference gas, a sample cell for containing the unknown gas mixture, a third reference cell for containing a volume of a mixture of the first and second gases in a predetermined ratio, a source for directing radiant energy serially through said reference cells and said sample cell, means for modulating the density of gases contained in said reference and sample cells, a detector for detecting the amount of radiant energy passing through said reference and sample cells, and signal processing means coupled to said detector for developing an output signal representative of the ratio of the amounts of the first and second gases in said sample cell to the ratio of the amounts of the first and second gases in said third reference cell.
Specification