Gas sensor for identifying gaseous components

Abstract

The invention relates to a gas sensor (1) comprising a chamber (2), said sensor further comprising:-a light source (10) configured to emit a light wave (11) propagating through said chamber and forming a first light cone (Omega 1) from said light source; -two measurement photodetectors located at two different distances from the light source; -a processing unit programmed to identify gaseous components present in the gas based on detection signals from the two measurement photodetectors.

Description

Technical Field

[0001] The technical field of this invention is an optical gas sensor, and more specifically a non-dispersive infrared sensor. Background Technology

[0002] The use of optical methods for gas analysis is quite common. Devices exist that determine the composition of a gas based on the fact that its components exhibit different spectral absorption characteristics. Therefore, given the absorption spectral bands of a gaseous component, its concentration can be determined by estimating the absorption of light passing through the gas using Beer-Lambert's law. This principle allows for the estimation of the concentration of gaseous components present in a medium.

[0003] The light source is typically an infrared emitter, and the method used is usually referred to by the term "NDIR detection," an acronym for Non-Dispersive Infrared. This principle has been frequently implemented and is described, for example, in numerous documents such as U.S. Patent 11,022,547 or U.S. Patent Application 20,220,214,267.

[0004] JP2022153291 (or US20220307976) describes a device comprising two photodetectors, each associated with a light source. The detection bandwidths of the photodetectors are different but close to each other. The photodetectors are arranged such that the corresponding optical path lengths between each light source and each photodetector are close (less than 5%), ideally equal.

[0005] In the most common method, the analyte gas extends between a light source and a photodetector (called a measurement photodetector), which is designed to measure light emitted by the source, transmitted through the analyte gas, and partially absorbed by the analyte gas. These methods typically involve measuring light emitted by the source that is not absorbed by the analyte gas; this light wave is called a reference light wave.

[0006] Comparing light waves in the presence of gas with those in the absence of gas allows for the characterization of gases. This involves, for example, using a technique known as "absorption NDIR" to determine the amount of gaseous components in the gas.

[0007] An alternative is described in US20120330568, which describes a gas sensor comprising one or more units, each unit including two photodetectors arranged at different distances across a chamber relative to a light source. A similar configuration is described in US8178832. A similar configuration is also described in JPH09-257704A, designed to limit the influence of contaminants on CO2 measurements.

[0008] Therefore, the equipment currently in use enables the quantification of gas concentration.

[0009] Each gaseous component absorbs light according to its own specific absorption spectral band. However, the absorption spectral bands of two different gaseous components may overlap at the same wavelength. This is the case, for example, with CH4 and C3H8, which absorb light at 3 µm and 3.37 µm, respectively. When measurements are taken near one of these wavelengths, it is impossible to determine whether the absorbing gaseous component is CH4 or C3H8 unless the gas composition is known beforehand. However, the absorbance of CH4 or C3H8 is different at each of these wavelengths, which can lead to errors in estimating the concentration of gaseous components. Furthermore, some gases may contain either CH4 or C3H8. Without further information, it may be difficult to accurately estimate the concentration of each gaseous component.

[0010] The inventors have designed a configuration that, in addition to quantification, can also identify the gaseous components present in a gas. Summary of the Invention

[0011] The first object of the present invention is to provide a method for identifying at least one gaseous component present in a gas, said gas extending inside a chamber, said gaseous component being selected from at least two candidate gaseous components, each candidate gaseous component absorbing light within an absorption spectral band, the sensor comprising:

[0012] - A light source that emits light, at least within the absorption spectral band;

[0013] - A first measuring photodetector is located at a first distance from the light source. The first measuring photodetector is configured to detect light waves emitted by the light source within a first detection spectral band, which is located within the respective absorption spectral bands of the two candidate gaseous components.

[0014] - A second measuring photodetector is located at a second distance from the light source, the second distance being different from the first distance. The second measuring photodetector is configured to detect light waves emitted by the light source within a second detection spectral band, the second detection spectral band being located within the absorption spectral band of at least one of the two candidate gaseous components.

[0015] The method includes:

[0016] a) Irradiate the gas using the light source;

[0017] b) Measure the intensity of light waves emitted by the light source and that have propagated through the cavity using the first and second measuring photodetectors;

[0018] c) A first detection signal is formed from the intensity measured by the first measuring photodetector, and a second detection signal is formed from the intensity measured by the second measuring photodetector;

[0019] d) Based on the first and second detection signals, identify the gaseous components present in the gas from the candidate gaseous components.

[0020] The method may include, after step d), estimating the proportion of the or each gaseous component identified in step d).

[0021] In an embodiment, the chamber includes:

[0022] - A first reference photodetector is located at a first distance from the light source. The first reference photodetector is configured to detect light waves within a first reference spectral band, which is considered not to be absorbed by each candidate gaseous component.

[0023] - A second reference photodetector is located at a second distance from the light source. The second reference photodetector is configured to detect light waves within a second reference spectral band, which is considered not to be absorbed by each candidate gaseous component.

[0024] The method can be as follows:

[0025] - The first detection signal includes the ratio between the light intensities detected by the first measuring photodetector and the first reference photodetector, respectively;

[0026] - The second detection signal includes the ratio between the light intensities detected by the second measuring photodetector and the second reference photodetector, respectively.

[0027] One possibility is that the first reference spectral band is the same as the second reference spectral band.

[0028] According to one possibility, the method includes:

[0029] - Prior to step d), multiple response functions are established, each capable of estimating the second detection signal from the first detection signal, and each response function is associated with a candidate gaseous component in the gas. The response functions are stored in the processing unit.

[0030] - During step d), the processing unit selects a response function that minimizes the difference between the following two:

[0031] • The second detection signal generated in step c);

[0032] • And the estimated value of the second detection signal obtained by applying the response function to the first detection signal generated in step c);

[0033] - Identify the gaseous component as the gaseous component associated with the selected response function.

[0034] According to one possibility, the method includes:

[0035] - Prior to step d), a plurality of response functions are established, each of which enables the estimation of the second detection signal from the first detection signal, and each response function is associated with the proportion of at least one candidate gaseous component in the gas, and the response functions are stored in the processing unit;

[0036] - During step d), the processing unit selects a response function that minimizes the difference between the following two:

[0037] • The second detection signal generated in step c);

[0038] • And the estimated value of the second detection signal obtained by applying the response function to the first detection signal generated in step c);

[0039] - The proportion of the gaseous component is determined as the proportion of the gaseous component associated with the selected response function.

[0040] According to one possibility, the method includes:

[0041] - Prior to step d), multiple response functions are established, each capable of estimating the second detection signal from the first detection signal, and each response function is associated with the proportion of at least two candidate gaseous components in the gas, and the response functions are stored in the processing unit;

[0042] - During step d), the processing unit selects a response function that minimizes the difference between the following two:

[0043] • The second detection signal generated in step c);

[0044] • And the estimated value of the second detection signal obtained by applying the response function to the first detection signal generated in step c);

[0045] - The ratio of the two substances is determined as the ratio of the gaseous component associated with the selected response function.

[0046] According to one possibility, the second absorption spectral band lies within the respective absorption spectral bands of the two candidate gaseous components.

[0047] One possibility is that the second reference spectral band coincides with the first reference spectral band.

[0048] A second object of the present invention is a gas sensor comprising a chamber configured to contain a gas that may comprise at least one gaseous component selected from at least two candidate gaseous components, each candidate gaseous component absorbing light within an absorption spectral band, the sensor further comprising:

[0049] - A light source, configured to emit light waves propagating within the cavity;

[0050] - A first measuring photodetector is located at a first distance from the light source. The first measuring photodetector is configured to detect light waves emitted by the light source within a first detection spectral band, which is located within the respective absorption spectral bands of the two candidate gaseous components.

[0051] - A second measuring photodetector is located at a second distance from the light source, the second distance being different from the first distance. The second measuring photodetector is configured to detect light waves emitted by the light source within a second detection spectral band, the second detection spectral band being located within the absorption spectral band of at least one of the two candidate gaseous components.

[0052] - The processing unit is programmed to implement steps c) and d) of the method according to the first objective of the invention based on the intensity measured by the first measuring photodetector and the second measuring photodetector, respectively.

[0053] The sensor may include:

[0054] - First reference photodetector (21) ref The first reference photodetector is located at the first distance from the light source and is configured to detect light waves within a first reference spectral band, which is considered not to be absorbed by each candidate gaseous component.

[0055] - and / or a second reference photodetector (22 ref Located at the second distance from the light source, the second reference photodetector is configured to detect light waves within a second reference spectral band, which is considered not to be absorbed by each candidate gaseous component.

[0056] The invention will be better understood by reading the following description of the embodiments presented in conjunction with the accompanying drawings. Attached Figure Description

[0057] Figure 1An example configuration of a gas sensor according to the present invention is shown. In this example, the gas sensor includes two measuring photodetectors and two reference photodetectors.

[0058] Figure 2 The so-called relative absorbance of the two gaseous components as a function of concentration is shown.

[0059] Figure 3A and Figure 3B The diagram illustrates the variation of the second detection signal obtained by the second measuring photodetector and the second reference photodetector with the first detection signal obtained by the first measuring photodetector and the first reference photodetector.

[0060] exist Figure 3A Different concentrations of CH4 were considered.

[0061] exist Figure 3B Different concentrations of C3H8 were considered.

[0062] Figure 3C They are shown respectively Figure 3A and Figure 3B The curve represented in the figure.

[0063] Figure 3A , Figure 3B and Figure 3C The curve shown represents the sensor's response function.

[0064] Figure 4 The main steps of an embodiment of the method according to the present invention are illustrated schematically. Detailed Implementation

[0065] Figure 1 A gas sensor 1 according to the present invention is schematically shown. The gas sensor 1 includes a chamber 2 designed to contain a gas G to be analyzed. The gas to be analyzed includes at least one gaseous component G to be identified. x And preferably, its concentration C x The relative proportion in the gas needs to be determined.

[0066] Gaseous component G x In its unique one or more absorption spectral bands ∆λ x It absorbs light internally, especially infrared light.

[0067] The gas may contain one or more so-called candidate gaseous components. These are predetermined gaseous components that may be present in the gas. The candidate gaseous components absorb infrared light within at least one common absorption spectral band.

[0068] Sensor 1 also includes:

[0069] • Light source 10 is configured to emit light waves within the emission spectral band ∆λ within chamber 2. This emission spectral band can extend from near-ultraviolet to mid-infrared, for example from 200 nm to 20 µm, and is most commonly in the infrared region, with an emission spectral band ∆λ of, for example, from 1 µm to 20 µm.

[0070] • The first measurement photodetector 21 is configured in the first detection band ∆λ d,1 The internal detection light wave is called the transmitted light wave. This transmitted light wave is emitted by the light source 10 and has propagated through the chamber, gradually attenuating as it travels through the gas. The first measurement photodetector 21 can be associated with a bandpass filter 31, which defines a first detection spectral band ∆λ. d,1 The first photodetector 21 is located at a first distance d1 from the light source.

[0071] Optionally, a first reference photodetector 21 ref It is configured to detect a reference light wave. This is achieved by the first reference photodetector 21. ref The detected reference light wave is assumed to be unaffected by the gas G present in the chamber. In this example, the first reference photodetector 21 ref First reference spectral band ∆λ ref,1 An internally detected reference light wave is used, within which the attenuation of the light wave emitted by the source is considered negligible. First reference photodetector 21 ref It can be used with the first reference bandpass filter 31 ref Correspondingly, the first reference bandpass filter defines a first reference spectral band ∆λ. ref,1 For example, the first reference spectral band ∆λ ref,1 Centered at a wavelength of 3.91 µm. Using a first reference photodetector is optional but advantageous. Alternatively, the first reference photodetector 21 ref If it is not located inside the chamber 2 containing the gas, in this case, the first reference spectral band can be similar to the first detection spectral band.

[0072] The light source 10 can be pulsed, emitting light pulses typically lasting from 50 ms to 1 s. Specifically, it can be a filament-type infrared light source formed on a suspended thin film, through which an electric current passes. In this way, the suspended thin film is heated to a temperature of 400°C to 800°C, thereby emitting infrared light.

[0073] An important aspect of the present invention is that the gas sensor further includes:

[0074] The second measurement photodetector 22 is configured to operate in the second detection spectral band ∆λ d,2 The internal detection is called the transmitted light wave, and this second detection spectral band can be compared with the first detection spectral band ∆λ.d,2 Different or the same. The second measurement photodetector 22 can be associated with a second bandpass filter 32, which defines a second spectral detection band ∆λ. d,2 The second measuring photodetector 22 is located at a second distance d2 from the light source. The second distance d2 is different from the first distance d1. The relative difference between the first distance and the second distance is preferably greater than 10% or 20% in order to increase the difference between the light intensities detected by the first measuring photodetector 21 and the second measuring photodetector 22, respectively.

[0075] Optionally, a second reference photodetector 22 ref It is configured to detect the reference light wave. This is achieved by the second reference photodetector 22. ref The detected reference light wave is considered not to be attenuated by the gas G present in the chamber. Second reference photodetector 22 ref Second reference spectral band ∆λ ref,2 The internal detection reference light wave, within this second reference spectral band, has a negligible attenuation of the light wave emitted by the source, and this second reference spectral band can be compared with the first reference spectral band ∆λ. ref,1 Same. Second reference photodetector 22 ref It can be used with the second reference bandpass filter 32 ref Correspondingly, the second reference bandpass filter defines the second reference spectral band ∆λ. ref,2 .

[0076] Each measuring photodetector 21, 22 and each reference photodetector 21 ref ,twenty two ref It can be a thermopile, a pyroelectric detector, or a photodiode. Each photodetector is configured to generate a detection signal, the amplitude of which corresponds to the intensity of the detected light wave.

[0077] According to one possibility, the device includes a single reference photodetector, such as a first reference photodetector 21. ref Given the reference intensity measured by the first reference photodetector and the distance between the first measuring photodetector 21 and the second measuring photodetector 22, the reference intensity at the level of the second measuring photodetector 22 can be determined by calculation. Conversely, the device may consist only of the second reference photodetector 22. ref Given the reference intensity measured by the second measuring photodetector 22 and the distance between the first measuring photodetector 21 and the second measuring photodetector 22, the reference intensity at the first measuring photodetector 21 can be determined by calculation.

[0078] Now consider gaseous component G selected from candidate gaseous components. xAccording to Beer-Lambert's law, the intensity I of the light wave detected by each photodetector depends on the gaseous component G under discussion. x Concentration C x :

[0079]

[0080] in:

[0081] - µ(C x The attenuation coefficient (C) depends on the concentration C being calculated. x ;

[0082] - l is the thickness of the gas through which the light wave passes in the chamber;

[0083] - I0 corresponds to the intensity of the wave that is detected or will be detected by a photodetector in the absence of absorbing gas in the chamber.

[0084] The comparison between l and I0, expressed as a ratio I / I0, corresponds to the gaseous component G under consideration. x The resulting attenuation att. µ(C) can thus be determined during each pulse from light source 10. x This allows the estimator C x Because C x and µ(C x The relationship between them is known.

[0085] The intensity I0 can be predetermined, for example, during calibration, or measured when there is no gas in chamber 2. When the sensor includes a reference photodetector, the reference intensity I0 is measured by the reference photodetector. ref This allows for the measurement of changes in I0.

[0086] The sensor includes a processing unit 40, which receives data from measuring photodetectors 21 and 22 and any reference photodetector 21, respectively. ref ,twenty two ref The measured signals. The processing unit 40 uses these signals to perform calculations, thereby enabling:

[0087] - Identify at least one gaseous component present in the gas, the substance being selected from a predetermined list of candidate gaseous components;

[0088] - Preferably, the concentration of the gaseous component or each identified gaseous component is estimated.

[0089] The processing unit 40 includes, for example, one or more microprocessors, each of which then performs a specific operation.

[0090] Each detection spectral band is located within the absorption spectral band of at least one candidate gaseous component. Preferably, at least one detection spectral band, or even each detection spectral band, is located within the absorption spectral band of several candidate gaseous components, and more preferably, within the absorption spectral band of each candidate gaseous component.

[0091] This invention is based on the fact that by comparing the intensity of the signal detected by each measuring photodetector after the light source is activated, at least one gaseous component present in the gas can be identified from the candidate gaseous components.

[0092] The detection of CH4 or C3H8 was simulated using a sensor as described in patent application US20220214267A1.

[0093] The arrangement of the first measuring photodetector and the first reference photodetector at a first distance d1 = 1.71 cm from the light source was simulated. The arrangement of the second measuring photodetector and the second reference photodetector at a second distance d2 = 4.04 cm from the light source was also simulated.

[0094] Each measurement photodetector includes a filter that defines a detection spectral band centered at 3.37 µm. For modeling purposes, only the intensity detected at a wavelength of 3.37 µm is considered. As noted in the prior art, the 3.37 µm wavelength lies within the absorption spectral bands of CH4 and C3H8. Alternatively, the first filter 31 is centered at 3 µm and the second filter 32 is centered at 3.37 µm, or vice versa. Alternatively, each filter is centered at a wavelength of 3 µm.

[0095] Figure 2 The quantized signal S is shown. c The evolution of the signal, expressed as a percentage, comprises a combination of light intensities measured by each photodetector.

[0096]

[0097] exist Figure 2 In the diagram, the CH4 curve and the C3H8 curve correspond to the cases where only CH4 and only C3H8 are present in the gas, respectively. The x-axis corresponds to the concentration (in ppm), and the y-axis corresponds to the quantization signal S defined according to expression (2). c .

[0098] It was observed that for the same quantized signal S c (As defined in (2)), the concentrations of the two candidate gaseous components are different. For example, the quantization signal S equals 1%. cThe concentrations corresponding to CH4 and C3H8 are approximately 10,000 ppm and 600 ppm, respectively. When no prior assumptions about the gaseous components that may be present in the gas are available, the same quantization signal S... c This could be due to the drastically different concentrations of the two gaseous components. When a sensor is used to trigger an alarm when a threshold concentration is exceeded, for example, with a CH4 concentration of 6000 ppm, an alarm might be triggered even if the gas does not contain CH4 and the C3H8 concentration is only a few hundred ppm higher. This corresponds to a false alarm.

[0099] To avoid this situation, two measuring photodetectors were used, which were arranged such that the light waves arriving at them followed different optical path lengths.

[0100] This invention utilizes:

[0101] - The difference in optical path length between the light source and each measuring photodetector;

[0102] - Difference in absorbance between candidate gaseous components: In this example, at 3.37µm, the absorbance of C3H8 is greater than that of CH4.

[0103] In this example, the candidate gaseous components are CH4 and C3H8. The following signals are generated from the intensities detected by each photodetector:

[0104] - A first detection signal S1, measured by the first measuring photodetector 21, represents the absorbance of the gas. The first detection signal S1 is formed from the light intensity I1 detected by the first measuring photodetector 21. Preferably, the first detection signal is formed by the light intensity I1 and the light intensity detected by the first reference photodetector 21. ref Detected light intensity I ref,1 The ratio between them is formed.

[0105] Therefore, based on one possibility, In this example,

[0106] - A second detection signal S2, measured by the second measuring photodetector 22, represents the absorbance of the gas. The second detection signal S2 is formed from the light intensity I2 detected by the second measuring photodetector 22. Preferably, the second detection signal is formed by the light intensity I2 and the absorbance measured by the second reference photodetector 22. ref Detected light intensity I ref,2 The ratio between them is formed.

[0107] Therefore, based on one possibility, In this example,

[0108] An important aspect of the present invention is to identify at least one gaseous component present in a gas based on a first detection signal and a second detection signal.

[0109] Figure 3A The first detection signal (x-axis—%) and the second detection signal (y-axis—%) for different concentrations of methane (CH4) are shown. This corresponds to the sensor's response function f for CH4. CH4 .

[0110] Figure 3B The first detection signal (x-axis—%) and the second detection signal (y-axis—%) for different concentrations of propane (C3H8) are shown. This corresponds to the sensor's response function f for C3H8. C3H8 .

[0111] Figure 3A and Figure 3B This was obtained by modeling using several discrete concentrations, corresponding to the points shown on each of these graphs. Then, a second-order polynomial was used to interpolate the points on each curve. Figure 3A and Figure 3B The equation for each polynomial and the correlation coefficient R² are shown.

[0112] Figure 3C The combination is shown Figure 3A and Figure 3B These two response functions are described. The response functions are also shown. The response function corresponds to the ratio of x% CH4 and y% C3H8. x and y are real numbers strictly between 0 and 1. The response function is stored in the processing unit.

[0113] An important aspect of this invention is the identification of at least one gaseous component present in the analyzed gas based on a first detection signal and a second detection signal. In this example, if If so, the identified gaseous component is CH4. The gaseous component identified is C3H8.

[0114] Therefore, processing unit 40 is programmed as follows:

[0115] - Calculate the first detection signal S1 and the second detection signal S2 based on the intensities I1 and I2 measured by the first photodetector and the second photodetector, respectively;

[0116] - At least one gaseous component is identified based on the first detection signal S1 and the second detection signal S2. In this example, response functions associated with different gaseous components have been predetermined. The identified gaseous component corresponds to the gaseous component associated with the response function that produces the minimum difference between the following two:

[0117] The measured signal S2;

[0118] and the estimated value of the measured signal S2 obtained by applying the response function to the first detection signal S1. : .

[0119] More generally, several response functions can be established corresponding to different components, such as response functions associated with components x% CH4 and y% C3H8. Figure 3C middle:

[0120] - Function f CH4 This corresponds to x% CH4 and y% C3H8, where x=100 and y=0;

[0121] - Function f C3H8 This corresponds to x% CH4 and y% C3H8, where x=0 and y=100;

[0122] - Function The dashed lines represent x% CH4 and y% C3H8.

[0123] The response function can be established numerically and / or based on measurements using a calibration gas with one or more known components.

[0124] Therefore, this invention can identify gaseous components present in a gas from a plurality of candidate gaseous components. It can also estimate the relative proportions of different candidate gaseous components. This is achieved by means of predetermined response functions, each of which is associated with a candidate gaseous component or a mixture of candidate gaseous components. The identification of each gaseous component present in the gas and its proportion is achieved by selecting a value such that the measured S2 is compared with the estimated value. It is performed by minimizing the difference between the response functions.

[0125] Once the gaseous component is identified, its concentration in the gas can be determined based on the value of the selected response function, taking into account that each value of the response function corresponds to a concentration. The concentration in the gas can also be determined based on the first detection signal and / or the second detection signal, for example by implementing a quantization signal as described in (2).

[0126] Figure 4 The main steps of the present invention are illustrated schematically.

[0127] Step 90: Sensor Calibration: This involves defining the sensor's response function by considering different concentrations of various predetermined candidate gaseous components. Each response function allows estimation of the second detection signal based on the measurement of the first detection signal S1. Each response function is associated with a specific proportion of each candidate gaseous component.

[0128] Step 100: Introduce gas into chamber 2 and irradiate the gas with a light source.

[0129] Step 110: Detect the light intensity using the first and second measuring photodetectors and the reference photodetector.

[0130] Step 120: Generate detection signals that represent the light attenuation caused by the gas between the light source and each measuring photodetector.

[0131] Step 130: Using a calibration function, identify at least one gaseous component present in the gas from the list of candidate gaseous components, and determine the proportion of each identified gaseous component. This specifically involves determining a response function that minimizes the difference between the second detection signal and an estimate of the second detection signal based on a response function applied to the first detection signal.

[0132] Step 140: Optionally, the concentration of each gaseous component identified in step 130 is quantified. This quantification may be performed based on the value of a response function or based on at least one detection signal.

[0133] In the described example, the first distance d1 is less than the second distance d2. The invention also applies to configurations where the second distance d2 is less than the first distance d1. However, it is preferred that the difference between the two distances is greater than 10%, or even 20%.

[0134] In one possible configuration, three photodetectors can be used, located at three different distances from the light source. This allows for the detection of a gaseous component from three candidate gaseous components, or the estimation of the concentrations of the three different gaseous components, based on the principles described above.

[0135] This invention can be applied to gas detection in environmental monitoring or industrial gas control applications, especially in the food industry, petroleum industry or gas distribution.

Claims

1. A method for identifying at least one gaseous component present in a gas, said gas extending inside a chamber (2), said gaseous component being selected from at least two candidate gaseous components, each candidate gaseous component absorbing light within an absorption spectral band, the sensor comprising: - A light source that emits light, at least within the absorption spectral band; - A first measuring photodetector (21) is located at a first distance (d1) from the light source. The first measuring photodetector is configured to detect light waves emitted by the light source within a first detection spectral band, which is located within the respective absorption spectral bands of the two candidate gaseous components. - A second measuring photodetector (22) is located at a second distance (d2) from the light source, the second distance being different from the first distance. The second measuring photodetector is configured to detect light waves emitted by the light source within a second detection spectral band, the second detection spectral band being located within the absorption spectral band of at least one of the two candidate gaseous components. The method includes: a) Irradiate the gas using the light source (10); b) Measure the intensity of light waves emitted by the light source and that have propagated through the cavity (2) using the first measuring photodetector (21) and the second measuring photodetector (22); c) A first detection signal is formed from the intensity measured by the first measuring photodetector (S1), and a second detection signal is formed from the intensity measured by the second measuring photodetector (S2). d) Based on the first detection signal and the second detection signal, identify the gaseous components present in the gas from the candidate gaseous components; The method is characterized in that the first distance is at least 10% larger than the second distance, such that the corresponding optical path difference between the light source and each measuring photodetector is at least 10%.

2. The method of claim 1, further comprising, after step d), estimating the proportion of the gaseous components or each gaseous component identified in step d).

3. The method according to claim 1 or claim 2, further comprising, after step d), estimating the amount of the gaseous component or each gaseous component identified in step d).

4. The method according to any one of the preceding claims, wherein, The chamber includes: - First reference photodetector (21) ref The first reference photodetector is located at a first distance from the light source and is configured to detect the light wave within a first reference spectral band, which is considered not to be absorbed by each candidate gaseous component. - Second reference photodetector (22) ref The second reference photodetector is located at a second distance from the light source and is configured to detect the light wave within a second reference spectral band, which is considered not to be absorbed by each candidate gaseous component. And among them: - The first detection signal includes the ratio between the light intensities detected by the first measuring photodetector and the first reference photodetector, respectively. ; - The second detection signal includes the ratio between the light intensities detected by the second measuring photodetector and the second reference photodetector, respectively. .

5. The method according to claim 4, wherein, The first reference spectral band is the same as the second reference spectral band.

6. The method according to any one of the preceding claims, comprising: - Before step d), establish multiple response functions. Each response function enables the estimation of the second detection signal from the first detection signal, and each response function is associated with a candidate gaseous component in the gas, and the response functions are stored in the processing unit (40); - During step d), the processing unit selects a response function that minimizes the difference between the following two: • The second detection signal (S2) generated in step c); • and the estimated value of the second detection signal obtained by applying the response function to the first detection signal (S1) generated in step c). ); - Identify the gaseous component as the gaseous component associated with the selected response function.

7. The method according to any one of claims 1 to 5, comprising: - Before step d), establish multiple response functions. Each response function enables the estimation of the second detection signal from the first detection signal, and each response function is associated with the proportion of at least one candidate gaseous component in the gas, and the response functions are stored in the processing unit; - During step d), the processing unit selects a response function that minimizes the difference between the following two: • The second detection signal (S2) generated in step c); • and the estimated value of the second detection signal obtained by applying the response function to the first detection signal (S1) generated in step c). ); - The proportion of the gaseous component is determined as the proportion of the gaseous component associated with the selected response function.

8. The method of claim 7, comprising: - Before step d), establish multiple response functions. Each response function enables the estimation of the second detection signal from the first detection signal, and each response function is associated with the ratio of at least two candidate gaseous components in the gas, and the response functions are stored in the processing unit; - During step d), the processing unit selects a response function that minimizes the difference between the following two: • The second detection signal generated in step c); • And the estimated value of the second detection signal obtained by applying the response function to the first detection signal generated in step c); - The ratio of the two gaseous components is determined as the ratio of the gaseous components associated with the selected response function.

9. The method according to any one of the preceding claims, wherein, The second absorption spectral band is located within the respective absorption spectral bands of the two candidate gaseous components.

10. A gas sensor (1) comprising a chamber (2) configured to contain a gas (G) that may include at least one gaseous component selected from at least two candidate gaseous components, each candidate gaseous component absorbing light within an absorption spectral band, the sensor further comprising: - A light source (10) is configured to emit light waves propagating within the cavity; - A first measuring photodetector (21) is located at a first distance (d) from the light source. The first measuring photodetector is configured to detect light waves emitted by the light source within a first detection spectral band, which is located within the respective absorption spectral bands of the two candidate gaseous components. - A second measuring photodetector (22) is located at a second distance (d2) from the light source, the second distance being different from the first distance. The second measuring photodetector is configured to detect light waves emitted by the light source within a second detection spectral band, the second detection spectral band being located within the absorption spectral band of at least one of the two candidate gaseous components. - The processing unit (40) is programmed to perform steps c) and d) of the method according to any one of the preceding claims based on the intensity measured by the first measuring photodetector and the second measuring photodetector, respectively. - The sensor makes the first distance at least 10% greater than the second distance, such that the corresponding optical path difference between the light source and each measuring photodetector is at least 10%.

11. The sensor according to claim 10, comprising: - First reference photodetector (21) ref The first reference photodetector is located at the first distance from the light source and is configured to detect the light wave within a first reference spectral band, which is considered not to be absorbed by each candidate gaseous component. - and / or a second reference photodetector (22 ref Located at the second distance from the light source, the second reference photodetector is configured to detect the light wave within a second reference spectral band, which is considered not to be absorbed by each candidate gaseous component.

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