Gas sensor calibration method and gas measurement method using the same

Abstract

A method for calibrating a gas sensor, the gas sensor being configured to measure the gas species (G x ) concentration (C x ), and the gas species has an absorption spectral band (Δ x ), and the gas sensor includes: a chamber configured to contain the gas, a light source (11), a measurement light detector (20) and a reference light detector (20). ref ), the gas sensor is as follows: the light source is configured to have a supply current passing through it to raise the light source to a certain temperature value; the measurement photodetector detects an absorption spectral band (Δ x ) including the measured spectral band (Δ mes ) the measured intensity (I mes (t)); the reference photodetector is designed to measure a reference spectral band (Δ ref ) the reference intensity (I ref (t)); the method includes determining a calibration function, preferably non-linear, that allows an intensity measured by the measurement photodetector in a measurement spectral band in the absence of a gas species to be estimated from a reference intensity measured in the reference spectral band.

Description

[Technical Field]

[0001] The technical field of the invention is optical methods for analyzing gases by using a light source of the black or grey body type and measuring the absorption of a light beam emitted by the light source. [Background technology]

[0002] It is common to resort to optical methods to analyze gases. Sensors can determine the composition of a gas based on the fact that the species that make up the gas have different spectral absorption characteristics. Therefore, by knowing the absorption spectral band of a gas species, its concentration can be determined by estimating the absorption of light passing through the gas using the Beer-Lambert law. This principle makes it possible to estimate the concentration of gas species present in a gas.

[0003] According to modern methods, the gas to be analyzed is spread between a light source and a photodetector (called a measurement photodetector), the latter intended to measure a light beam transmitted by the gas to be analyzed, which is partially absorbed by this gas. The light source is usually a source emitting in the infrared, and the method used is usually called NDIR detection, where NDIR stands for non-dispersive infrared. Such a principle is often used and is described in the literature, for example in U.S. Pat. No. 5,026,992 or WO 2007 / 064370.

[0004] A typical method generally involves measuring a light beam emitted by a light source, called a reference light beam, which is not absorbed or only negligibly absorbed by the gas being analyzed. Measuring the reference light beam allows for estimating the intensity of the light beam emitted by the source or the light beam that would be detected by the measurement light detector if not absorbed by the gas being analyzed. This technique is called "double beam." Comparing the light beam in the presence of gas with the light beam in the absence of gas can characterize the absorption of the gas. This includes, for example, determining the amount of gas species in the gas using a technique called NDIR absorption spectroscopy. The reference light beam is measured by a reference light detector, which may be a different resonance photodetector from the measurement light detector and is designed to be positioned facing the light source. The reference light detector is associated with a reference light filter. The reference light filter defines a reference spectral band in which the gas being analyzed does not exhibit significant absorption. Summary of the Invention [Problem to be solved by the invention]

[0005] The inventors have discovered that the use of a reference light beam to estimate the light beam that would be detected by the measurement light detector in the absence of absorption by the gas being analyzed can prove to be a significant source of uncertainty, and have proposed a method by which this disadvantage can be overcome in such a way as to improve the accuracy of the measurement. [Means for solving the problem]

[0006] A first subject of the present invention is a method for calibrating a gas sensor intended to determine the concentration of a gas species in a gas, the gas species being capable of absorbing light in an absorption spectral band, the gas sensor comprising: - a chamber configured to contain said gas; a light source, a measurement light detector, and a reference light detector, wherein the light source is configured to emit an incident light beam, the incident light beam traveling through the chamber toward the measurement light detector and the reference light detector; The gas sensor is as follows: - the light source is configured such that a supply current flows through it to raise the temperature of the light source to a temperature value; - said measurement light detector is designed to measure the intensity (called measurement intensity) of the light beam transmitted by the gas contained in said chamber and emitted by said light source in a measurement spectral band that includes said absorption spectral band; - said reference light detector is designed to measure a reference intensity of a reference light beam emitted by said light source in a reference spectral band; The method includes the following steps: (i) incorporating a calibration function, preferably non-linear, which allows the intensity measured in the measurement spectral band by the measurement photodetector in the absence of a gas species to be estimated from a reference intensity measured in the reference spectral band by the reference photodetector, and which calibration function is parameter dependent; (ii) filling said chamber with a gas containing zero concentration, or a concentration deemed to be zero, of said gas species; (iii) causing the measurement photodetector to measure a measurement intensity in the measurement spectral band and the reference photodetector to measure a reference intensity in the reference spectral band, and repeating step (iii) at different calibration instants while varying the source supply current between the different calibration instants; (iv) determining the parameters of said calibration function from the measurements obtained from (iii);

[0007] Step (i) may include incorporating a nonlinear parametric model of the calibration function, the parametric model being dependent on the parameters determined during step (iv).

[0008] Step (iv) may include: - iv-1) estimating a measurement intensity obtained from the measurement light detector using the calibration function from each reference intensity measured at each calibration time point; - iv-2) for each supply current value, comparing the measured intensity estimated during iv-1) with the measured intensity measured by said measuring photodetector; - iv-3) determining the parameters of the calibration function that minimizes the comparison obtained from iv-2);

[0009] During step (iii), the supply current may vary between two extreme values ​​corresponding to -15% and +15% respectively of the nominal supply current.

[0010] According to one embodiment, - step (iii) is carried out by subjecting said gas sensor to different values ​​of ambient temperature; Step (iv) is carried out incorporating the measurements obtained from (iii) for each ambient temperature value in order to obtain a calibration function associated with each temperature value.

[0011] According to one embodiment, - step (iii) is carried out by subjecting the gas sensor to different ambient temperature values; Step (iv) is carried out incorporating the measurements obtained from (iii) for all ambient temperature values ​​in order to obtain a calibration function common to all ambient temperature values.

[0012] According to one embodiment, one parameter of a calibration function forms an exponent applied to said reference intensities, said parameter being estimated during step (iv).

[0013] According to one embodiment, one parameter of the calibration function is a proportionality parameter that defines the proportionality relationship between the estimated intensity in the measured spectral band in the absence of a gas species and a reference intensity to which the index is applied, said proportionality parameter being estimated during step (iv).

[0014] According to one embodiment, the calibration function comprises a ratio of a numerator to a denominator such as: - the numerator includes a first multiplicative parameter applied to the reference intensity; - the denominator includes a second multiplication parameter applied to the reference intensity; - said first multiplication parameter and said second multiplication parameter are estimated during step (iv).

[0015] A second subject of the invention is a method for measuring the amount of gas species present in a gas, said gas species being capable of absorbing light in an absorption spectral band, said method comprising the following steps: a) disposing a gas between a light source and a measurement light detector, the light source being configured to emit an incident light beam, said incident light beam passing through the gas towards said measurement light detector, and a supply current passing through said light source so as to raise said light source to a temperature value; - b) illuminating the gas with said light source; - c) causing said measurement light detector to measure the intensity of the light beam transmitted by the gas in a measurement spectral band that includes the absorption spectral band (referred to as measurement intensity); - d) causing a reference photodetector to measure the intensity of a reference light beam emitted by the light source in a reference spectral band (called the reference intensity); Steps b) to d) are performed at measurement time points, said method comprising at each measurement time point: - e) incorporating a calibration function to estimate, from said reference intensity measured by said reference photodetector, the light beam intensity detected in the measurement spectral band by said measurement photodetector in the absence of a gas species; - f) estimating the amount of the gas species from the measured intensities measured during step c) of the intensities estimated during step e); The method is characterized in that the calibration function is established during a calibration phase, which is carried out by implementing steps (i) to (iv) of the method according to the first subject of the present invention.

[0016] The calibration function may be established in the following manner: - step (iii) is carried out by subjecting said gas sensor to different ambient temperature values; Step (iv) is carried out incorporating the measurements obtained from (iii) for each ambient temperature value in order to obtain a calibration function associated with each temperature value. step e) comprises: incorporating the ambient temperature around the gas sensor; Selecting the calibration function as a function of the ambient temperature.

[0017] A third subject of the invention is a gas sensor intended to determine the concentration of a gas species in a gas, said gas species being capable of absorbing light in an absorption spectral band, said sensor comprising: - a chamber configured to contain said gas; a light source, a measurement light detector, and a reference light detector, wherein the light source is configured to emit an incident light beam, the incident light beam traveling through the chamber toward the measurement light detector and the reference light detector; The gas sensor is as follows: - a supply current is passed through said light source in order to raise said light source to a certain temperature value; - said measurement light detector is designed to measure the intensity of the light beam transmitted by the gas contained in said chamber and emitted by the light source in a measurement spectral band, which includes an absorption spectral band (called measurement intensity); - said reference light detector is designed to measure a reference intensity of a reference light beam emitted by a light source in a reference spectral band; said sensor comprises a processing unit programmed to store a calibration function, preferably non-linear, established according to the first subject of the present invention and to apply said calibration function to the reference intensity measured by said measurement light detector.

[0018] According to one embodiment, the gas sensor includes a temperature sensor configured to measure the ambient temperature at the time of measurement, and the processing unit is programmed to select a calibration function as a function of the ambient temperature from among a plurality of calibration functions each associated with a different ambient temperature.

[0019] The present invention will be better understood from a reading of the description of the embodiments set forth in the remainder of the specification in connection with the figures listed below. [Brief explanation of the drawings]

[0020] [Figure 1A] FIG. 1A shows an example of a gas sensor that can be used to practice the present invention. [Figure 1B] FIG. 1B shows a schematic diagram of the emission spectrum of a blackbody type light source. [Figure 2A] 2A and 2B show the error in measuring CO2 and CH4 concentrations, respectively, as a function of the error in estimating the light beam reaching the measurement photodetector. [Figure 2B] 2A and 2B show the error in measuring CO2 and CH4 concentrations, respectively, as a function of the error in estimating the light beam reaching the measurement photodetector. [Figure 3]FIG. 3 shows the main steps in a method for calibrating and using a gas sensor. [Figure 4A] 4A shows measurements made during calibration of the intensity of a light beam reaching a measurement photodetector in a measurement spectral band at different calibration time points. FIG. 4A also shows an estimate of the measured intensity in the measurement spectral band at each calibration time point as a function of the intensity measured in the reference spectral band by a reference photodetector. [Figure 4B] FIG. 4B shows the mean square error between the estimated and measured values ​​of the intensity of the light beam reaching the measurement sensor for different gas sensors and incorporating different calibration functions. [Figure 5A] Figure 5A shows measurements of the intensity of a light beam reaching an image sensor in a measurement spectral band at different calibration times taken during calibration. Figure 5A also shows an estimate of the intensity measured in the measurement spectral band at each calibration time as a function of the intensity measured in the reference spectral band. [Figure 5B] FIG. 5B shows the mean square error between the estimated and measured values ​​of the intensity of the light beam reaching the measurement sensor for different gas sensors and incorporating different calibration functions. [Figure 6A] 6A and 6B show examples of tests on sensors with and without the present invention. [Figure 6B] 6A and 6B show examples of tests on sensors with and without the implementation of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Overview of Certain Embodiments FIG. 1A shows an example of a sensor 1 for a gas G. The gas G is measured in a quantity c x (t), for example, the gas species G for which the concentration is to be determined x This gas species has an absorption spectral band Δ x absorbs a measurable proportion of light at

[0022] The gas sensor 1 comprises a chamber 10 defining an interior space, within which are present: The light source 11 emits a light beam 12, called the incident light beam, capable of illuminating the gas G prevailing in the interior space. The incident light beam 12 has an illumination spectral band Δ 12 Extend over. The light detector 20 is called the measurement light detector and is configured to detect the light beam 14 transmitted by the gas G (the latter) under the effect of illumination of the latter by the incident light beam 12. The light beam 14 is denoted by the term measurement light beam. It is the measurement light detector 20 that detects the gas species G x Absorption spectrum band Δ x The measured spectral band Δ is defined as a function of mes It is detected by. - Reference Photodetector 20 ref is the reference spectral band Δ ref A light beam 12 called the reference light beam in ref The reference spectral band Δ ref is the spectral band in which the absorption of the light beam 12 by the gas G can be considered negligible.

[0023] Reference spectral band Δ ref is the measured spectral band Δ mes is different.

[0024] The light beam 11 is arranged in an illumination spectral band Δ 12 configured to emit an incident light beam 12 across an illumination spectral band Δ 12 The latter can extend between the near ultraviolet and mid-infrared, for example, between 200 nm and 10 μm, typically between 1 μm and 10 μm. x Absorption spectrum band Δ x is the illumination spectral band Δ 12The light source 11 may in particular be a pulsed beam, the incident light beam 12 being typically a pulse of duration between 100 ms and 1 s. The light source 11 may in particular be a suspended filament type light source heated to a temperature between 400°C and 800°C. Its emission spectrum is defined by an illumination spectral band Δ 12 corresponds to the emission spectrum of a black body.

[0025] The measurement photodetector 20 preferably detects the absorption spectral band Δ x A measurement spectral band Δ that encompasses all or part of mes is associated with an optical filter 18 that defines

[0026] In the example considered, the measuring light detector 20 is a thermopile, capable of transmitting a signal that depends on the intensity of the detected light beam, or alternatively, the measuring light detector may be a photodiode or any other type of light detector.

[0027] Reference Photodetector 20 ref is placed next to the measurement light detector 20 and is of the same type. ref The reference optical filter 18 is associated with an optical filter called ref is the reference spectral band Δ corresponding to the range of wavelengths that are not absorbed by the gas species considered ref Define the reference passband Δ ref is, for example, the wavelength λ ref Centered around 3.91 μm.

[0028] The intensity I of the light beam 14 at the measurement time t, detected by the measurement light detector 20 and referred to as the measurement intensity, mes (t) is the concentration at the time of measurement, c x Depends on (t):

number

[0029] JPEG0007730908000002.jpg20170

[0030] Equation (1) assumes control of the intensity I0(t) of the incident light beam 12 at the measurement time t.

[0031] FIG. 1B shows the emission spectrum of a blackbody type light source 11, which follows Planck's law:

number

[0032] The emission spectrum S of the light source 11 corresponds to the variation of the luminance L(λ, T) as a function of λ when the light source reaches a temperature T. Typically, the temperature T is comprised between 400°C and 800°C.

[0033] FIG. 1B shows the illumination spectral band Δ 12 The reference wavelength λ is spread between 1 μm and 10 μm. ref and measurement wavelength λ mes is also shown by a dashed line.

[0034] This type of light source is particularly advantageous because the illumination spectrum S can be modulated simply by modulating the temperature T of the light source. Thus, for each temperature T, there is an associated illumination spectrum S.

[0035] It is known that the emissivity of blackbody or greybody type light sources can change over time. The time variation of the radiation of the light source 11 is measured by the reference photodetector 20. ref The reference photodetector 20 is considered by ref is a reference light beam 12 that indicates the incident light beam 12 emitted by the light source 11 ref The reference light beam 12 is designed to detect ref is detected by the reference photodetector 20 without interacting with or significantly interacting with the gas G. ref to reach.

[0036] TIFF0007730908000004.tif34166

[0037] TIFF0007730908000005.tif34166

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[0038] Using equation (1), c x (t) is obtained.

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[0039] TIFF0007730908000008.tif28166

[0040] TIFF0007730908000009.tif16166-λ ref = 3.91 μm, and λ mes,x = 4.26 μm, which corresponds to the absorption wavelength of CO2: see Figure 2A; - λ ref = 3.91 μm, and λ mes,x= 3.25 μm, which corresponds to the absorption wavelength of CH4: see Figure 2B.

[0041] TIFF0007730908000010.tif45166

[0042] Considering (2), I ref (t) and I0(t) can be expressed as follows for each time point t:

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[0043] TIFF0007730908000012.tif16166

[0044] TIFF0007730908000013.tif22166

[0045] 3 shows the main steps in the implementation of the present invention. In a calibration phase 90, a calibration function is defined. The calibration phase includes steps 91 to 93. The calibration function obtained from the calibration phase is then used during the gas sensor use phase: steps 100 to 160.

[0046] TIFF0007730908000014.tif16166

[0047] In this step, an analytical model of the calibration function is defined. The analytical model is defined by one or more parameters θ. The quantity θ corresponds to a parameter of the model or to all parameters of the model.

[0048] TIFF0007730908000015.tif4145

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[0049] Z is a positive real coefficient. According to this model, θ=Z.

[0050] TIFF0007730908000017.tif25165

[0051] This model is as follows:

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[0052] This model is obtained by simplifying equations (6) and (7).

number

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[0053] Similarly:

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[0054] Combining (10) and (11) we get:

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[0055] According to the model in equation (9), θ = (Z, α), α may be determined in advance or during the calibration process.

[0056] A third analytical model might be:

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[0057] A third analytical model is obtained by considering the following quantities:

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[0058] From (10), (15) and (16),

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[0059] From (17), T(k) can be expressed as:

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[0060] From (11), (14) and (16)

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[0061] Using (18), we get:

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[0062] TIFF0007730908000029.tif10165

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[0063] Combining (21) and (22) we get:

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[0064] wavelength λ ref To account for the width of the spectral bands for λ and λ, respectively, equation (23) can be generalized as follows:

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[0065] When considering the model obtained from equation (23), we follow the model of equation (13) or (24), θ = (Z,γ,ξ,σ) or θ = (Z,ξ,σ), where Z,γ,ξ,σ are positive real numbers.

[0066] The fourth model is as follows:

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[0067] According to this model, θ = (Z, β). · Step 91 :Calibration measurement

[0068] During this step, the gas sensor detects the gas species G x Therefore, during each measurement, the gas is exposed to a gas that does not contain or contains a negligible amount of I mes (k) = I0(k). ref (k) and I mes The (k) measurements are performed at different calibration times k.

[0069] Between different calibration points, the supply current supplied to the light source 11 is changed, and therefore the voltage across the terminals of the light source 11 is changed. This allows the light source to be raised to different temperature levels. For one and the same value of current, I mes (k) and I ref (k) different measurements are taken.

[0070] Typically, a light source is associated with a nominal current value, whether defined in terms of current intensity or voltage. Preferably, during calibration, the supply current is varied between two extreme values, each comprised between -15% and +15% of the nominal value. · Step 92 : Estimation of parameter θ

[0071] TIFF0007730908000034.tif23166

[0072] TIFF0007730908000035.tif9115

[0073] TIFF0007730908000036.tif462

[0074] Figure 4A shows the calibration measurement results of the sensor from 21 different light source supply current values. The supply current value was varied between two extreme values ​​corresponding to -15% and +15% of the light source's nominal current value, respectively. The sensor was as described in EP 3593119. 4000 measurements were made at one measurement per second, and the measured gas species was CO2. At each calibration time point k, I mes (k) and I ref Measurements of (k) were performed. From all measurements, the parameters θ of the calibration function were estimated considering the parametric models described in equations (8), (9), (23), and (25), respectively. Figure 4A shows the following as a function of time (horizontal axis, in seconds): TIFF0007730908000037.tif17141

[0075] TIFF0007730908000038.tif11165

[0076] The calibration described in connection with Figure 4A was performed on 14 different sensors. Figure 4B shows the mean squared error (MSE on the vertical axis) for each sensor (horizontal axis), where MSE is obtained using the following formula:

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[0077] Curves a and b in Figure 4B correspond to the parametric models established in equations (9) and (23), respectively. Curve c) corresponds to the previously established linear model (equation (8)) with Z = 1.11977. Models a) and b) prove to be particularly relevant.

[0078] A new calibration was performed by reducing the variation of the light source supply current. The supply current value was varied between two extreme values ​​corresponding to 5% and +5% of the nominal light source current value, respectively. In this interval, seven different light source supply current values ​​were considered.

[0079] 1050 measurements were taken at one measurement per second. At each calibration point k, I mes (k) and I ref Measurements of (k) were carried out. From all the measurements, the parameters θ of the calibration function were estimated by considering the parametric models described in equations (8), (9), (23) and (25), respectively. Figure 5A shows the following as a function of time (horizontal axis - units: seconds): TIFF0007730908000040.tif17141

[0080] TIFF0007730908000041.tif11164

[0081] Calibration as described in connection with Figure 5A was performed on 14 different sensors. Figure 5B shows for each sensor (horizontal axis) the mean squared error (MSE on the vertical axis), which is the MSE obtained according to equation (31). In Figure 5B, curves a, b, and c correspond to the parametric models established according to equations (8), (9), and (23), respectively. Curve d corresponds to the previously established linear model (equation (8)) with Z = 1.11977. Models b) and c) are found to be particularly relevant.

[0082] The use of a gas sensor using the calibration function described above will now be described with reference to FIG. Step 100: Illumination of gas at measurement time t; Step 110: Reference Photodetector 20 ref Reference spectral band Δ ref Reference intensity I ref Measurement of (t). Step 120: Measure spectral band Δ by measuring photodetector 20 mes Measurement of the intensity I(t) of radiation 14 transmitted by the gas at TIFF0007730908000042.tif16166

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[0083] TIFF0007730908000044.tif46166

[0084] TIFF0007730908000045.tif22166

[0085] TIFF0007730908000046.tif10165

Claims

1. A method for calibrating a gas sensor, the gas sensor detecting a gas species (G ｘ ) concentration (c ｘ ), and the gas species has an absorption spectral band (Δ ｘ ) and the gas sensor includes: a chamber (10) adapted to contain said gas; - a light source (11), a measurement light detector (20) and a reference light detector (20 ｒｅｆ ), wherein the light source (11) is configured to emit an incident light beam (12), which passes through the chamber and is incident on the measurement light detector (20) and the reference light detector (20). ｒｅｆ ) proceed towards; The gas sensor is as follows: - said light source is configured to have a supply current passing through it so as to raise said light source to a certain temperature value; - the measuring photodetector detects the absorption spectral band (Δ ｘ ) including the measured spectral band (Δ ｍｅｓ ) the intensity (I) of the light beam (14) emitted by the light source and transmitted through the gas contained in the chamber. ｍｅｓ (t)) (called the measurement intensity); - the reference photodetector detects a reference spectral band (Δ ｒｅｆ ) the reference intensity (I) of the reference light beam emitted by the light source (11) ｒｅｆ (t)) is designed to measure; The method comprises the following steps: (i) incorporating a calibration function (f) that is non-linear, where said calibration function is a function of a reference intensity (I ｒｅｆ ) from the intensity (I) measured in the measurement spectral band by the measurement photodetector in the absence of gas species. ０ ), said calibration function depending on the parameter (θ); (ii) filling said chamber with a gas containing zero concentration, or a concentration considered to be zero, of said gas species; (iii) measuring the intensity (I) in the measurement spectral band at the measurement photodetector (20); ｍｅｓ (k)) and measure the reference photodetector (20 ｒｅｆ ) and the reference intensity (I ｒｅｆ (k)) and repeating step (iii) at different calibration time points (k) while varying the source supply current between the different calibration time points; (iv) From the measurements of (iii), determine the parameters (θ) of said calibration function.

2. 10. The method of claim 1, wherein step (iv) comprises: - iv-3) Determine the parameter (θ) of the calibration function that minimizes the comparison obtained from iv-2).

3. 3. A method according to claim 1 or 2, wherein during step (iii) the supply current varies between two extreme values ​​corresponding respectively to -15% and +15% of the nominal supply current.

4. step (iii) is to measure the temperature of the gas sensor at an ambient temperature (T ａ ) different values ​​of Step (iv) determines the calibration function (f Ｔａ (iii) for each temperature value to obtain a temperature The method according to any one of claims 1 to 3.

5. - step (iii) is carried out by subjecting said gas sensor to different ambient temperature values; step (iv) is carried out incorporating the measurements obtained from (iii) for all said temperature values ​​in order to obtain a calibration function common to all said ambient temperature values; The method according to any one of claims 1 to 3.

6. One parameter of the calibration function is the reference intensity (I ｒｅｆ 6. The method according to claim 1, wherein said parameter is estimated during step (iv).

7.

8. The method of any one of claims 1 to 7, wherein the calibration function comprises a ratio of a numerator to a denominator such that: - the numerator comprises a first multiplication parameter applied to the reference intensity; the denominator includes a second multiplication parameter applied to the reference intensity; said first multiplication parameter and said second multiplication parameter are estimated during step (iv).

9. The gas species present in the gas (G ｘ ) amount (c ｘ ), wherein the gas species has an absorption spectral band (Δ ｘ ) a method for absorbing light in a liquid crystal display, the method comprising the steps of: a) placing a gas between a light source (11) and a measuring light detector (20), said light source (11) being configured to emit an incident light beam (12) that travels through said gas towards said measuring light detector (20), and passing a supply current through said light source in order to raise said light source to a certain temperature value; b) illuminating the gas (G) with said light source (11); -c) the measurement photodetector (20) detects the absorption spectral band (Δ ｘ ) including the measured spectral band (Δ ｍｅｓ ) the intensity (I ｍｅｓ (t)) (referred to as the measurement intensity); - d) Reference photodetector (20 ｒｅｆ ) and the reference spectral band (Δ ｒｅｆ a reference light beam (12) which is a reference light beam emitted by the light source (11) at ｒｅｆ ) intensity I ｒｅｆ (t) (referred to as the reference intensity); Steps b) to d) are performed at a measurement time (t); The method includes, at each measurement time point: f) determining the gas species (G) from the intensity estimated during step e) and the measured intensity measured during step c); ｘ ) amount (c ｘ (t)) is estimated; The calibration function is established during a calibration phase, which is carried out by implementing steps (i) to (iv) of the method according to any one of claims 1 to 8.

10. 10. The method of claim 9, wherein the calibration function is established in the following manner: - step (iii) is carried out by subjecting said gas sensor to different ambient temperature values; - step (iv) is carried out incorporating the measurements obtained from (iii) for each ambient temperature value in order to obtain a calibration function associated with each temperature value;

11. A gas sensor intended to determine the concentration of a gas species in a gas, said gas species exhibiting an absorption spectral band (Δ ｘ ) and the sensor comprises: a chamber (10) adapted to contain said gas; - a light source (11), a measurement light detector (20) and a reference light detector (20 ｒｅｆ ), wherein the light source (11) is configured to emit an incident light beam (12), which passes through the chamber and is incident on the measurement light detector (20) and the reference light detector (20). ｒｅｆ ) proceed towards; The gas sensor is as follows: - a supply current is passed through said light source in order to raise said light source to a certain temperature value; - the measuring photodetector detects the absorption spectral band (Δ ｘ ) designed to measure the intensity (called measurement intensity) of a light beam (14) emitted by said light source (11) and transmitted through the gas contained in said chamber, in a measurement spectral band including: - the reference photodetector detects a reference spectral band (Δ ｒｅｆ ) of the reference light beam emitted by the light source (11) at ｒｅｆ (t)) is designed to measure; - the sensor comprises a processing unit (30) programmed to store an established non-linear calibration function according to any one of claims 1 to 8 and to apply said calibration function to the reference intensity measured by the measurement light detector.

12.

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