GAS ANALYZER SYSTEM

• US 20090213380A1
• Filed: 04/30/2008
• Published: 08/27/2009
• Est. Priority Date: 02/21/2008
• Status: Active Grant

• Current Assignee: Thermo Fisher Scientific Incorporated
• Original Assignee: Thermo Fisher Scientific Incorporated
• Inventors: Marzoratti, Gaston E., Mouradian, Robert F., Nabar, Shrikrishna H., Appel, Dirk
• Granted Patent: US 7,835,005 B2
• Time in Patent Office: Days
• US Class Current: 356/437
• CPC Class Codes: G01N 2021/3133 with selection of wavelengths before the sample
• CPC Class Codes: G01N 2021/3174 Filter wheel
• CPC Class Codes: G01N 21/031 Multipass arrangements
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis
• CPC Class Codes: G01N 2201/1215 for interfering gases

Abstract

A gas analyzer system includes an optical source, an optical filter assembly, a controller, and an analyzer. The optical source generates an optical signal. The optical filter assembly includes different optical filters in which to filter the optical signal. During operation, the controller selects sequential application of each of the different optical filters in a path of the optical signal to modulate the optical signal using different frequency bands of optical energy. The modulated optical signal passes through an unknown sample. Based on absorption of the optical signal by the sample gas at different frequencies, the optical analyzer detects which types of multiple different gases are present in the sample.

Claims

1. A method comprising:

generating an optical signal;

at each of multiple frequency bands, measuring an intensity of the optical signal after passage of the optical signal through a sample gas potentially having multiple types of gases that absorb the optical signal in a same frequency band; and

detecting concentrations of the multiple types of gases in the sample gas based on absorption of the optical signal at the multiple frequency bands.

2. The method as in claim 1, wherein measuring the intensity of the optical signal at each of multiple frequency bands includes:

implementing a sequence of measuring absorbance of the sample gas at different frequency bands, the sequence including an absorbance measurement of the optical signal at a first frequency band followed by an absorbance measurement of the optical signal at a second frequency band followed by an absorbance measurement of the optical signal at a third frequency; and

initiating cyclical application of the sequence to repeatedly measure absorbance of the sample gas at the different frequency bands.

3. The method as in claim 2, wherein implementing the sequence includes:

initiating rotation of an optical filter wheel assembly to align filters of the optical filter assembly in a path of the optical signal to filter the optical signal at the different frequency bands, the rotation of the optical filter assembly including aligning a first filter of the optical filter assembly in the path of the optical signal to measure absorbance by the sample gas at the first frequency band followed by aligning a second filter of the optical filter assembly in the path of the optical signal to measure absorbance by the sample gas at the second frequency band followed by aligning a third filter of the optical filter assembly in the path of the optical signal to measure absorbance by the sample gas at the third frequency band.

4. The method as in claim 1, wherein detecting concentrations of the multiple types of gases in the sample gas includes:

utilizing absorbance measurements of the optical signal at a first frequency band and a second frequency band to calculate a concentration of a first gas present in the sample gas; and

utilizing absorbance measurements of the optical signal at the first frequency band and the second frequency band to calculate a concentration of a second gas present in the sample gas.

5. The method as in claim 1, wherein generating the optical signal includes:

producing the optical signal as a modulated optical signal via serial application of different optical frequency band filters in a path of the optical signal.

6. The method as in claim 1, wherein measuring an intensity of the optical signal at each of multiple frequency bands includes repeatedly measuring absorbance of the optical signal by the sample gas at the multiple frequency bands over multiple absorbance measurement collection cycles;

and

wherein detecting the concentrations of the multiple types of gases in the sample gas includes successively approximating the concentrations of the multiple types of gases based on collection of absorbance data over the multiple absorbance measurement collection cycles.

7. The method as in claim 1, wherein measuring an intensity of the optical signal at each of multiple frequency bands includes:

measuring absorbance of the optical signal by the sample gas at the multiple frequency bands in a first measurement cycle;

subsequent to the first measurement cycle, measuring absorbance of the optical signal by the sample gas at the multiple frequency bands in a second measurement cycle; and

wherein detecting concentrations of the multiple types of gases in the sample gas includes;

calculating the concentrations based at least in part on absorbance measurements obtained in the first cycle and absorbance measurements obtained in the second measurement cycle.

8. The method as in claim 7, wherein calculating the concentrations includes:

producing an absorbance measurement value by subtracting an absorbance measurement obtained in the first cycle from an absorbance measurement obtained in the second cycle; and

utilizing the produced absorbance measurement value to calculate a concentration of a first gas of the multiple types of gases in the sample gas.

9. The method as in claim 1 further comprising:

allocating a first frequency band of the multiple frequency bands to detect a concentration of a first gas type in the sample gas; and

allocating a second frequency band of the multiple frequency bands to detect a concentration of a second gas type in the sample gas.

10. The method as in claim 9, wherein measuring an intensity of the optical signal at each of multiple frequency bands includes:

measuring absorbance of the optical signal by the sample gas at the first frequency band and the second frequency band in a first measurement cycle;

subsequent to the first measurement cycle, measuring absorbance of the optical signal by the sample gas at the first frequency band and the second frequency band in a second measurement cycle; and

wherein detecting concentrations of the multiple types of gases in the sample gas includes;

calculating a concentration of the first gas type in the sample gas based at least in part on an absorbance measurement obtained in the second cycle for the first frequency band and an absorbance measurement in the first cycle for the second frequency band; and

calculating a concentration of the second gas type in the sample gas based at least in part on an absorbance measurement obtained in the second cycle for the second frequency band and an absorbance measurement in the first cycle for the first frequency band.

11. The method as in claim 1, wherein measuring the intensity of the optical signal at each of multiple frequency bands includes:

measuring an intensity of the optical signal in a first frequency band, the first frequency band including optical energy at a wavelength around 2.5 micrometers;

measuring an intensity of the optical signal in a second frequency band, the second frequency band including optical energy at a wavelength around 4.6 micrometers;

measuring an intensity of the optical signal in a third frequency band, the third frequency band including optical energy at a wavelength around 4.8 micrometers;

measuring an intensity of the optical signal in a fourth frequency band, the fourth frequency band including optical energy at a wavelength around 5.2 micrometers;

measuring an intensity of the optical signal in a fifth frequency band, the fifth frequency band including optical energy at a wavelength around 6.2 micrometers; and

measuring an intensity of the optical signal in a sixth frequency band, the sixth frequency band including optical energy at a wavelength around 3.2 micrometers.

12. The method as in claim 1, wherein measuring the intensity of the optical signal at each of multiple frequency bands includes:

measuring an intensity of the optical signal in a first frequency band to detect a concentration of water in the sample gas, the first frequency band including optical energy at a wavelength around 2.5 micrometers;

measuring an intensity of the optical signal in a second frequency band to detect a concentration of carbon monoxide in the sample gas, the second frequency band including optical energy at a wavelength around 4.6 micrometers;

measuring an intensity of the optical signal in a third frequency band to detect a concentration of carbon dioxide in the sample gas, the third frequency band including optical energy at a wavelength around 4.8 micrometers;

measuring an intensity of the optical signal in a fourth frequency band to detect a concentration of nitric oxide in the sample gas, the fourth frequency band including optical energy at a wavelength around 5.2 micrometers;

measuring an intensity of the optical signal in a fifth frequency band to detect a concentration of nitrogen oxide in the sample gas, the fifth frequency band including optical energy at a wavelength around 6.2 micrometers; and

measuring an intensity of the optical signal in a sixth frequency band to detect a concentration of methane in the sample gas, the sixth frequency band including optical energy at a wavelength around 3.2 micrometers.

18. The system as in claim 1, wherein the analyzer is configured to:

repeatedly measure absorbance of the optical signal by the sample gas at the multiple frequency bands over multiple absorbance measurement collection cycles; and

successively approximate the concentrations of the multiple types of gases based on collection of absorbance data over the multiple absorbance measurement collection cycles.

13. A system comprising:

an optical source to generate an optical signal;

a detector to measure an intensity of the optical signal after passing of the optical signal through a sample gas; and

an analyzer to detect which of multiple gases are present in the sample gas based on measuring absorbance of the optical signal by the sample gas at different optical frequency bands, at least two gases of the multiple gases absorbing the optical signal in a same frequency band.

14. The system as in claim 13, wherein the analyzer is configured to:

implement a sequence of measuring absorbance of the sample gas at different frequency bands, the sequence including an absorbance measurement of the optical signal at a first frequency band followed by an absorbance measurement of the optical signal at a second frequency band followed by an absorbance measurement of the optical signal at a third frequency; and

initiate cyclical application of the sequence to repeatedly measure absorbance of the sample gas at the different frequency bands.

15. The system as in claim 14 further comprising:

an optical filter wheel assembly including multiple filters; and

wherein the analyzer is configured to initiate rotation of the optical filter wheel assembly to align the filters of the optical filter assembly in a path of the optical signal to filter the optical signal at the different frequency bands.

16. The system as in claim 13, wherein the analyzer is configured to:

utilize absorbance measurements of the optical signal at a first frequency band and a second frequency band to calculate a concentration of a first gas present in the sample gas; and

utilize absorbance measurements of the optical signal at the first frequency band and the second frequency band to calculate a concentration of a second gas present in the sample gas.

17. The system as in claim 13 further comprising:

a controller configured to produce the optical signal as a modulated optical signal via serial application of different optical frequency band filters in a path of the optical signal.

19. The system as in claim 13, wherein the analyzer is configured to:

measure absorbance of the optical signal by the sample gas at the multiple frequency bands in a first measurement cycle;

subsequent to the first measurement cycle, measure absorbance of the optical signal by the sample gas at the multiple frequency bands in a second measurement cycle; and

calculate the concentrations based at least in part on absorbance measurements obtained in the first cycle and absorbance measurements obtained in the second measurement cycle.

20. The system as in claim 19, wherein the analyzer is configured to:

produce an absorbance measurement value by subtracting an absorbance measurement obtained in the first cycle from an absorbance measurement obtained in the second cycle; and

utilize the produced absorbance measurement value to calculate a concentration of a first gas of the multiple types of gases in the sample gas.

21. The system as in claim 20, wherein the analyzer is configured to:

measure absorbance of the optical signal by the sample gas at the first frequency band and the second frequency band in a first measurement cycle;

subsequent to the first measurement cycle, measure absorbance of the optical signal by the sample gas at the first frequency band and the second frequency band in a second measurement cycle;

calculate a concentration of the first gas type in the sample gas based at least in part on an absorbance measurement obtained in the second cycle for the first frequency band and an absorbance measurement in the first cycle for the second frequency band; and

calculate a concentration of the second gas type in the sample gas based at least in part on an absorbance measurement obtained in the second cycle for the second frequency band and an absorbance measurement in the first cycle for the first frequency band.

22. A computer program product including a computer-readable media having instructions stored thereon for processing data information, such that the instructions, when carried out by one or more processing devices, enables the one or more processing device to perform operations of:

generating an optical signal;

at each of multiple frequency bands, measuring an intensity of the optical signal after passing of the optical signal through a sample gas potentially having multiple types of gases that absorb the optical signal in a same frequency band; and

detecting concentrations of the multiple types of gases in the sample gas based on absorption of the optical signal at the multiple frequency bands.