Method for analysing a gas using an optical sensor

A method for measuring an amount of a gas species present in a gas, the gas absorbing light in an absorption spectral band, the method comprising:

• a) placing the gas between a light source and a measurement photodetector, the light source being configured to emit an incident light wave, the incident light wave propagating through the gas to the measurement photodetector, the light source being passed through by an electrical supply current, so as to bring the light source to a temperature value;
• b) illuminating the gas with the light source;
• c) measuring, with the measurement photodetector, a measurement intensity of a light wave transmitted by the gas, in a measurement spectral band comprising the absorption spectral band;
• d) measuring, with a reference photodetector, a reference intensity of a reference light wave, the reference light wave being emitted by the light source in a reference spectral band;
• wherein b), c) and d) are implemented at a plurality of measurement times;
• the method further comprising, at each measurement time:
• e) on the basis of the reference intensity measured by the reference photodetector, taking into account a correction function representative of a variation in an intensity of the incident light wave in the measurement spectral band relatively to an intensity of the incident light wave in the reference spectral band;
• f) estimating an amount of the gas species, on the basis of the measurement intensity measured in c), of the reference intensity measured in d), and of the correction function taken into account in e);
• wherein the correction function is established beforehand in a calibrating phase, by comparing, at various temperature levels, or at various supply-current levels, the light intensities emitted, by a test light source, in the measurement spectral band and in the reference spectral band, respectively, the test light source being considered to be representative of the light source employed in b), at each measurement time.