Method And Apparatus For Determining Marker Gas Concentration Using An Internal Calibrating Gas
First Claim
1. A spectrometer system for measuring the concentration of a marker gas in a gas mixture, the system comprising:
- a spectrometer gas sample cell;
a spectrometer light source adapted to pass a light beam through the gas sample cell;
a spectrometer detector adapted to produce a signal sampling characteristic of the gas mixture in response to light passing through the gas mixture; and
a spectrometer computer adapted to acquire the signal sampling from the spectrometer detector over a signal acquisition interval and generate a gas mixture spectrum;
wherein the spectrometer computer is further adapted to analyze the gas mixture spectrum to determine a marker gas absorption intensity and a calibration gas absorption intensity as a function of time over a plurality of signal acquisition intervals to identify a signal acquisition interval where a known concentration calibration gas absorption intensity corresponds to an independently known calibration gas concentration and a simultaneous marker gas absorption; and
to calculate a ratio of the simultaneous marker gas absorption intensity to the known concentration calibration gas absorption intensity and multiplying the ratio by a proportionality constant to determine concentration of the marker gas.
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Abstract
A method and an apparatus for measuring the concentration of a specific gas component of a gas mixture including another gas whose concentration is independently known using light absorption spectroscopy are provided. A method and an apparatus for assessing human airway inflammation by measuring the concentration of exhaled NO and CO2 present in orally exhaled breath using light absorption spectroscopy are also provided. NO concentration is determined at the time during breath sampling corresponding to a known exhaled CO2 concentration. Methods and apparatus are further provided for measuring NO concentration in orally exhaled human breath that analyze breath emanating from the lower airways and lungs, while excluding breath from the nasal cavity. They include steps and apparatus for discarding initially exhaled breath, flowing breath through an analysis chamber using a vacuum pump and flowing breath through an analysis chamber using a vacuum pump at an initial flow rate and later at a flow rate higher than the initial flow rate.
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Citations
31 Claims
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1. A spectrometer system for measuring the concentration of a marker gas in a gas mixture, the system comprising:
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a spectrometer gas sample cell;
a spectrometer light source adapted to pass a light beam through the gas sample cell;
a spectrometer detector adapted to produce a signal sampling characteristic of the gas mixture in response to light passing through the gas mixture; and
a spectrometer computer adapted to acquire the signal sampling from the spectrometer detector over a signal acquisition interval and generate a gas mixture spectrum;
wherein the spectrometer computer is further adapted to analyze the gas mixture spectrum to determine a marker gas absorption intensity and a calibration gas absorption intensity as a function of time over a plurality of signal acquisition intervals to identify a signal acquisition interval where a known concentration calibration gas absorption intensity corresponds to an independently known calibration gas concentration and a simultaneous marker gas absorption; and
to calculate a ratio of the simultaneous marker gas absorption intensity to the known concentration calibration gas absorption intensity and multiplying the ratio by a proportionality constant to determine concentration of the marker gas. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method for comparing a concentration of a marker gas to a concentration of a calibration gas, wherein the calibration gas and marker gas are intrinsic in a gas sample and wherein the calibration gas has an independently known concentration, the method comprising:
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placing the gas mixture sample in a spectrometer gas sample cell over a sampling interval;
illuminating the gas mixture sample within the spectrometer gas sample cell over the sampling interval to generate a signal sampling characteristic of the gas mixture sample;
generating a plurality of gas mixture spectra;
analyzing the gas mixture spectra to measure a marker gas intensity and a calibration gas intensity for each of the plurality of spectra as a function of time over the sampling interval to identify a single spectrum wherein a known concentration calibration gas intensity corresponds to an independently known calibration gas concentration and a simultaneous marker gas intensity; and
calculating a ratio of the simultaneous marker gas intensity to the known concentration calibration gas intensity and multiplying the ratio by a proportionality constant to determine concentration of the marker gas. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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Specification