Method for recalibrating an electronic nose

A method for recalibrating an electronic nose suitable for characterizing target compounds present in a gas sample introduced into a measurement chamber, the measurement chamber comprising at least one sensitive site having receptors with which the target compounds are able to interact via adsorption/desorption, the electronic nose comprising a processing unit in which is pre-stored a first correction function expressing a variation in a parameter representative of a measurement signal associated with a reference gas as a function of a relative humidity, the method comprising:

• successively injecting, into the measurement chamber, reference gases not containing target compounds, the reference gases injected one after the other and having various predetermined non-zero values of relative humidity, wherein successively injecting the reference gases comprises a plurality of injection cycles, each cycle being formed from an injection of a first reference gas having a first relative humidity and of an injection of various second reference gases having various second relative humidities, so as to obtain a plurality of relative-humidity differences between each second relative humidity and the first relative humidity, the relative-humidity differences being different from one another;
• determining, in the course of each injection, a measurement signal representative of the interactions of the receptors with the reference gas present, at various measurement times, in response to an excitation signal transmitted to the sensitive site, then determining, for each reference gas, a baseline representative of the determined measurement signal, the baseline being associated with the relative humidity of the reference gas present;
• and
• determining a second correction function expressing a variation in a parameter representative of the measurement signal associated with the reference gas as a function of relative humidity, on the basis of the determined baselines and of the predetermined values of relative humidity, the second correction function then being stored in the processing unit instead of the first correction function.

A method of using an electronic nose for characterizing target compounds, wherein:

• the electronic nose comprises:
• a measuring device comprising:
• a measurement chamber suitable for receiving a gas sample containing compounds of interest to be characterized, and comprising at least one sensitive site having receptors with which the target compounds are able to interact via adsorption/desorption;
• a measuring unit suitable for determining a measurement signal representative of the interactions of the receptors with at least the gas present, at various measurement times, in response to an excitation signal transmitted to the sensitive site;
• a humidity sensor suitable for measuring relative-humidity values of the gas present in the measurement chamber;
• a fluidic supplying device comprising:
• a source of a reference gas, the source of the reference gas being connected to the measurement chamber;
• a source of target compounds, the source of the target compounds being connected to the measurement chamber, the gas sample being formed from a gas and from the target compounds;
• a fluidic recalibrating device comprising at least one source of at least one reference gas, the at least one source of the at least one reference gas being suitable for supplying the measurement chamber with reference gases having various relative-humidity values;
• and
• a processing unit suitable for:
• determining a corrective parameter on the basis of:
• at least one measured relative-humidity value;
• and
• a predetermined correction function associated with the sensitive site and expressing a variation in a parameter representative of the measurement signal associated with a reference gas as a function of the at least one measured relative-humidity value;
• determining a useful signal via correction of the measurement signal associated with the gas sample on the basis of at least the determined corrective parameter;
• characterizing the target compounds on the basis of the determined useful signal;
• and
• determining a second correction function, on the basis of the various relative-humidity values of the reference gas present in the measurement chamber, and of the corresponding measurement signals,
• the method comprising a plurality of phases of characterizing the target compounds, including a first characterizing phase performed before recalibrating the electronic nose, and a second characterizing phase performed after the recalibration, each characterizing phase comprising:
• injecting into the measurement chamber:
• during a first phase, the reference gas not containing the target compounds, and
• during a second phase, the gas sample comprising the target compounds;
• determining, in the course of the injecting, the measurement signal representative of the interactions of the receptors with at least the gas present, at various measurement times, in response to the excitation signal transmitted to the sensitive site;
• measuring the relative-humidity values in the first phase and the second phase in the measurement chamber, respectively, the relative-humidity values being different from one another;
• determining the corrective parameter associated with the sensitive site, on the basis of at least the measured relative-humidity value from the second phase and of the predetermined correction function expressing the variation in the parameter representative of the measurement signal associated with the reference gas as the function of the at least one measured relative-humidity value;
• determining the useful signal via correction of the measurement signal associated with the gas sample, on the basis of at least the determined corrective parameter;
• and
• characterizing the target compounds on the basis of the determined useful signal,
• the first characterizing phase using a pre-stored first correction function,
• the recalibration determining the second correction function, and
• the second characterizing phase using the determined second correction function.