Electrochemical gas measurement device with self-calibrating calibration and its method of use

Abstract

A self-calibrating measuring device (1) comprising a control device (3) configured to admit a fluidic medium (10) into a chamber (2), an electrochemical sensor (6) and a control element (7) configured to: - in an amperometric mode (A1), control the admission of the fluidic medium (10) into the chamber (2) and determine a first concentration measurement (C1) from a first electrical measurement (i1) of the electrochemical sensor (6) and a predetermined sensitivity coefficient (k), - in a coulometric mode, stop the admission of the fluidic medium (10) into the chamber (2),determine a second concentration measurement from a plurality of second electrical measurements of the electrochemical sensor during a predetermined time interval of total consumption of an electroactive gas (11) in the chamber (2) and modify the predetermined sensitivity coefficient (k) from the difference between the first and second concentration measurements (C1). Abstract figure: Figure 2,

Description

Title of the invention: Electrochemical gas measurement device with self-calibrating calibration and its method of use. Technical field

[0001] The present invention relates to the field of electrochemical gas measurement devices with autonomous calibration.

[0002] As is known, the concentration of an electroactive gas in an external fluidic medium, that is, a gas capable of being oxidized or reduced electrochemically, can be accurately determined by an electrochemical sensor, provided that the electrochemical sensor is properly calibrated. When electrically powered, the electrochemical sensor is configured to generate an electric current with an intensity that is a function of the amount of electroactive gas it consumes (the concentration of the electroactive gas in the external fluidic medium). The concentration of the electroactive gas is then determined from the supplied electrical intensity and two calibration constants: the baseline and the sensitivity coefficient.

[0003] In practice, for the same quantity of electroactive gas, a variation in the temperature and / or humidity level of the external fluidic medium alters the electrical current. To compensate for such a variation, it is necessary to recalibrate the electrochemical sensor, i.e., modify the baseline value and the sensitivity coefficient. Aging of the electrochemical sensor also tends to reduce its sensitivity and alter the electrical current supplied, thus necessitating its recalibration.

[0004] To recalibrate the electrochemical sensor, it is known to place it in several standard fluidic media corresponding to known gas mixtures with known concentrations. This requires uninstalling and then reinstalling the electrochemical sensor, which is costly in terms of time and resources. Furthermore, in the event of forgetfulness, delay, or unforeseen malfunction of the electrochemical sensor, an inaccurate concentration reading may be obtained.

[0005] French patent application FR3112206A1 discloses the calibration of an electrochemical sensor using a photoionization sensor. The photoionization sensor is configured to consume a gas mixture in a closed chamber and to generate a known quantity of ozone by photoionization of the dioxygen present in the closed chamber. Measuring the known quantity of ozone in the closed chamber using the electrochemical sensor allows for calibration. However, the use of a photoionization sensor makes the process expensive and complex.

[0006] Also known from US patent application 4384925A (in the embodiment shown in [Fig. 4]) is a device for detecting pollutants in the air comprising an electrochemical sensor configured to measure the concentration of pollutants in the open volume of a chamber by potentiometry. During a calibration phase, the chamber is closed to trap an air sample. A microprocessor calculates the amount of electrical charge (expressed in coulombs) generated by the pollutants in the sample before and after passing through a filter that retains the pollutants. The difference between these two measurements allows the electrochemical sensor to be calibrated, given the chamber volume, pressure, and air temperature. However, such a process is lengthy and expensive because it requires an air filtration circuit and several measurements.

[0007] The invention thus aims to eliminate at least some of these drawbacks. PRESENTATION OF THE INVENTION

[0008] The invention relates to a device for measuring at least one electroactive gas in an external fluidic medium, the measuring device being self-calibrating and comprising: • a room with a predetermined volume, • at least one control device configured to admit the external fluidic medium into the chamber, • at least one electrochemical sensor, positioned in the chamber, configured to be electrically powered and to provide an electrical measurement by consuming said at least one electroactive gas in the chamber, • at least one configured control device, in amperometric mode, for: • control the regulating device to allow the admission of the external fluidic medium into the chamber, • command the electrochemical sensor to perform an initial electrical measurement, and • determine a first concentration measurement of said at least one electroactive gas in the chamber, based on the first electrical measurement, a predetermined baseline, and a predetermined sensitivity coefficient, • said control unit being configured, in a coulometric mode, to: • control the regulation device to stop the admission of the external fluidic medium into the chamber, • command the electrochemical sensor to take a plurality of second electrical measurements during a predetermined time interval of total consumption of said at least one electroactive gas in the chamber, • determine a second concentration measurement of said at least one electroactive gas in the chamber, from the plurality of second electrical measurements, the predetermined time interval and the predetermined volume of the chamber, • measure an initial difference between the first concentration measurement and the second concentration measurement, and • modify the predetermined sensitivity coefficient if the first deviation is greater than a first predetermined maximum threshold.

[0009] Advantageously, the self-calibrating measuring device according to the invention comprises an electrochemical sensor adapted for simple, rapid, and inexpensive self-calibration by combining two different measurement modes: an amperometric mode and a coulometric mode. The amperometric mode allows for the simple and practical measurement of an electroactive gas, namely a gas that can be oxidized or reduced electrochemically, based on the electrical current supplied by the redox reaction at its electrodes and two calibration constants: the baseline and the sensitivity coefficient. The coulometric mode, on the other hand, allows for the measurement of the electroactive gas based on the amount of charge produced by its total consumption in a small, closed volume. The coulometric mode makes it possible to determine a concentration that is independent of temperature, humidity level, or sensor aging.Comparing the two amperometric and coulometric modes thus allows for a useful readjustment of the sensitivity coefficient.

[0010] According to one aspect of the invention, the control element is also configured, in coulometric mode, to: • to command the electrochemical sensor to take a third electrical measurement at the end of the predetermined time interval for the total consumption of said at least one electroactive gas in the chamber, • measure a second deviation between the third electrical measurement and the predetermined baseline, and • modify the predetermined baseline if the second deviation is greater than a second predetermined maximum threshold.

[0011] The self-calibrating measuring device advantageously allows, by combining the two modes of amperometric and coulometric measurement, the recalibration of the electrochemical sensor's baseline. This consists, once all the electroactive gas has been consumed in the closed volume by the coulometric measurement, of performing an amperometric measurement in a simple and practical manner. The third measurement The electrical measurement is advantageously implemented following the second electrical measurement, each allowing for the readjustment of a calibration constant. The second electrical measurement thus makes it possible to generate a sample with a known zero electroactive gas concentration for performing the third electrical measurement.

[0012] According to one aspect of the invention, the control element is configured, in coulometric mode, to: • determine a measurement curve from the plurality of second electrical measurements, • determine the quantity of electric charge by integrating the measurement curve over the predetermined time interval, and • determine the second concentration measurement of said at least one electroactive gas in the chamber from the amount of electrical charge and the predetermined volume of the chamber.

[0013] Such a coulometric measurement is advantageously independent of the temperature and humidity level of the external fluidic medium, unlike the amperometric measurement.

[0014] According to one aspect of the invention, the predetermined volume of the chamber is less than 10 mL, preferably less than 5 mL, and more preferably less than 2.5 mL. The chamber thus allows a very small volume of the external fluidic medium to be contained. This enables the electrochemical sensor to rapidly consume all of the electroactive gas present. The second electrical measurement advantageously includes a reasonable acquisition time, on the order of a few minutes, in particular two to three minutes.

[0015] According to one aspect of the invention, the predetermined volume of the chamber is greater than 0.5 mL, preferably greater than 1 mL. Such a volume is sufficient to allow for reliable and accurate coulometric measurement.

[0016] According to one aspect of the invention, the control device is in the form of a pump or a fan. A pump or a fan, when running, ensures the intake of the external fluidic medium into the chamber, as well as its discharge to the outside.

[0017] According to one aspect of the invention, the measuring device comprises at least one supply conduit for the chamber with the external fluidic medium, preferably having a diameter of less than 5 mm, and preferably at least five times shorter than a length of the conduit. Advantageously, such a conduit with a small diameter and a low diameter-to-length ratio ensures circulation of the external fluidic medium only if it is forcibly driven, for example by a pump or fan. In the absence of forced circulation, the chamber can be considered a closed volume. This eliminates the need for valves.

[0018] According to one aspect of the invention, the measuring device comprises at least one auxiliary sensor of said at least one electroactive gas in the chamber having a predetermined auxiliary baseline, the control element also being configured, in coulometric mode, to: • to command the auxiliary sensor to take a fourth electrical measurement at the end of the predetermined time interval for the total consumption of said at least one electroactive gas in the chamber, • measure a third deviation between the fourth electrical measurement and the predetermined auxiliary baseline, and • modify the predetermined auxiliary baseline if the third deviation is greater than a predetermined third maximum threshold.

[0019] Advantageously, it is thus possible to recalibrate a sensor other than the electrochemical sensor. The second electrical measurement advantageously allows the generation of a sample with a known zero electroactive gas concentration, in which the fourth electrical measurement is carried out.

[0020] According to one aspect of the invention, the auxiliary sensor is in the form of a metal oxide semiconductor sensor or a photoionization sensor. Such sensors include a baseline that must be recalibrated when there is a change in temperature, humidity level, or sensor aging.

[0021] The invention also relates to a method of using the measuring device as described above, the method of use comprising at least one calibration phase in which the control element implements the amperometric mode and the coulometric mode. Such a method is advantageously simple, quick, and inexpensive to implement. It does not require any other sensor or filtering element to calibrate the electrochemical sensor.

[0022] According to a preferred aspect, the calibration phase is implemented periodically. This allows for regular recalibration of the electrochemical sensor and prevents any inaccurate concentration measurements, which can be difficult to detect.

[0023] According to one aspect of the invention, the method of use comprises at least one measurement phase in which the control element implements only the amperometric mode. The amperometric mode is advantageously simple and quick to implement, which allows for efficient measurement. Moreover, due to the integrated calibration, such a measurement is also accurate and reliable, since the calibration constants are regularly readjusted. PRESENTATION OF THE FIGURES

[0024] The invention will be better understood upon reading the following description, given by way of example, and referring to the following figures, given by way of non-illegible examples. figuratives, in which identical references are given to similar objects.

[0025] Fig. 1 is a schematic representation of a self-calibrating measuring device according to one embodiment of the invention.

[0026] Fig. 2 is a schematic representation of an amperometric mode of the measuring device of Fig. 1.

[0027] Fig. 3 is a schematic representation of a coulometric mode of the measuring device of Fig. 1.

[0028] Fig. 4 is a schematic representation of a curve obtained from a plurality of second electrical measurements of an electrochemical sensor of the measuring device during the coulometric mode of Fig. 3.

[0029] Fig. 5 is a schematic representation of a method of using the self-calibrating measuring device according to an embodiment of the invention.

[0030] Fig. 6 is a schematic representation of a self-calibrating measuring device and in particular of the coulometric mode, according to another embodiment of the invention.

[0031] Fig. 7 is a schematic representation of a self-calibrating measuring device according to another embodiment of the invention in amperometric mode.

[0032] The [Fig.8] is a schematic representation of the self-calibrating measuring device of the [Fig.7] in coulometric mode.

[0033] It should be noted that the figures set out the invention in detail to implement the invention, said figures being of course able to serve to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0034] With reference to [Fig. 1], the invention relates to a measuring device 1 for one (or more) electroactive gas(s) 11 in an external fluidic medium 10, which is self-calibrating and comprises: • a chamber 2 having a predetermined volume V, • a regulating device 3 configured to admit the external fluidic medium 10 into chamber 2, • an electrochemical sensor 6 configured to be electrically powered and to provide an electrical measurement by consumption of the electroactive gas 11 in chamber 2, and • a control body 7.

[0035] According to the invention, the control element 7 is configured, in an amperometric mode A1 illustrated in [Fig. 2], to: • control the regulating device 3 to allow the admission of the external fluidic medium 10 into chamber 2, • command the electrochemical sensor 6 to perform a first electrical measurement, and • determine a first measurement of the concentration Cl of the electroactive gas 11 in chamber 2, from the first electrical measurement il, a predetermined baseline j and a predetermined sensitivity coefficient k,

[0036] According to the invention, the control element 7 is configured, in a coulometric mode A2 illustrated in [Fig. 3], to: • control the regulating device 3 to stop the admission of the external fluidic medium 10 into chamber 2, • command the electrochemical sensor 6 to take several second electrical measurements i2 during a predetermined time interval At of total consumption of the electroactive gas 11 in chamber 2, • determine a second concentration measurement C2 of the electroactive gas 11 in chamber 2, from the second electrical measurements i2, the predetermined time interval At and the predetermined volume V of chamber 2, • measure an initial difference between the first Cl concentration measurement and the second C2 concentration measurement, and • modify the predetermined sensitivity coefficient k if the first deviation is greater than a first predetermined maximum threshold a.

[0037] According to a preferred aspect illustrated in [Fig. 3], the control element 7 is also configured, in coulometric mode A2, to: • to command the electrochemical sensor 6 to take a third electrical measurement i3 at the end of the predetermined time interval At of total consumption of the electroactive gas 11 in chamber 2, • measure a second deviation between the third electrical measurement and the predetermined baseline, and • modify the predetermined baseline j if the second deviation is greater than a second predetermined maximum threshold X.

[0038] In the example of [Fig. 1], chamber 2 has inert walls that do not interact with the electroactive gas(s) 11, for example ozone (O3), nitrogen dioxide (NO2), nitric oxide (NO), carbon monoxide (CO), sulfur dioxide (SO2), ethanol (C2H5OH), formaldehyde (HCOH), chlorine (Cl2), bromine (Br2), fluorine (F2), hydrogen peroxide (H2O2), methane (CH4), ethylene (C2H4), acetylene (C2H2), ammonia (NH3), hydrogen sulfide (H2S), and oxygen (O2). This prevents distortion of the measurements, particularly in the co- In coulometric mode A2, chamber 2 has a small volume V, between 0.5 mL and 10 mL. Preferably, the volume V of chamber 2 is less than 5 mL, preferably less than 2.5 mL. This allows the electrochemical sensor 6 to rapidly consume the electroactive gas 11, resulting in an acceptable predetermined time interval At on the order of a few minutes, namely between 2 and 3 minutes. Preferably, the volume V is also greater than 1 mL to increase the reliability and accuracy of measurements in coulometric mode A2.

[0039] With reference to [Fig. 1], the measuring device 1 in this example comprises an inlet conduit 4 for the external fluidic medium 10 into the chamber 2 and a discharge conduit 5 for the external fluidic medium 10 to the outside. The conduits 4 and 5, together with the control device 3, ensure the supply of the external fluidic medium 10 to the chamber 2.

[0040] As illustrated in [Fig. 1], the regulating device 3 is connected to the control element 7 and is configured: • upon receipt of a command from the control unit 7, such as a first signal SI (amperometric mode Al), to authorize the admission of the external fluidic medium 10 into chamber 2, and its discharge to the outside. Chamber 2 thus delimits an open volume in amperometric mode AL • upon receiving a command from the control unit 7, such as a second signal S2 (coulometric mode A2), to stop the admission of the external fluidic medium 10 into chamber 2 and its discharge to the outside. Chamber 2 thus delimits a closed volume in coulometric mode A2.

[0041] Preferably, the control device 3 is in the form of a pump or a fan, configured to be activated upon receipt of the first signal S1 and deactivated upon receipt of the second signal S2. Preferably, the inlet duct 4 has a diameter of less than 5 mm. Preferably, the inlet duct 4 has a length at least five times its diameter, preferably at least eight times. The same is preferably true for the discharge duct 5. This allows the circulation of the external fluid 10 to be regulated without the use of valves. When the pump or fan is deactivated, the small diameter of the ducts 4 and 5 significantly limits exchanges with the outside, so that the chamber 2 defines a closed volume. The small diameter-to-length ratio also contributes to this effect.

[0042] It is understood that the measuring device 1 could include a different number of conduits 4, 5, dedicated solely to inlet or outlet or both, and of any diameter. Furthermore, the measuring device 1 could include, in addition or instead of the pump / fan, one or more valves to help regulate the circulation of the external fluidic medium 10 in chamber 2.

[0043] In the example of Figures 7 and 8, the control device 3 is in the form of a four-way solenoid valve combined with a pump. The four-way solenoid valve is movably mounted between a first position in the amperometric mode A1 and a second position in the coulometric mode A2. In the amperometric mode A1 ([Fig. 7]), the solenoid valve defines an open circuit in which the external fluidic medium 10 is admitted from the outside into the inlet conduit 4 and discharged to the outside through the outlet conduit 5. In the coulometric mode A2 ([Fig. 8]), the solenoid valve defines a closed circuit by fluidically connecting the outlet conduit 5 to the inlet conduit 4.

[0044] With reference to [Fig. 1], the electrochemical sensor 6 is configured to be electrically powered, to consume the electroactive gas 11 present in chamber 2, and to provide an electrical measurement based on the quantity of electroactive gas 11 consumed. The electrical measurement is conventionally expressed as an electrical current. The electrochemical sensor 6 conventionally comprises two, three, or four measuring electrodes configured to react chemically with the electroactive gas 11 by a redox reaction. An electrochemical sensor is known to those skilled in the art and will not be described further.

[0045] Still referring to [Fig. 1], the control element 7, for example a microprocessor, is connected to the electrochemical sensor 6. The control element 7 is in this example represented as an element external to the electrochemical sensor 6, but it could just as easily be integrated into the electrochemical sensor 6. The control element 7 is also connected to a data storage element 8, such as a database, represented externally in [Fig. 1] but which could just as easily be internal to the control element 7.

[0046] As illustrated in Figures 2 and 3, the control unit 7 is configured to command electrical measurements il, i2, i3 to the electrochemical sensor 6 in order to determine the concentration of the electroactive gas 11 and / or recalibrate the electrochemical sensor 6. The control unit 7 includes an amperometric mode Al dedicated to current measurement and a coulometric mode A2 dedicated in synergy with the amperometric mode Al to calibration.

[0047] With reference to [Fig. 5], the method of using the measuring device 1 comprises: • a calibration phase Pcal, in which the control element 7 implements the amperometric mode A1 and the coulometric mode A2, preferably in that order, and • preferably, a measurement phase for SMEs, in which the control body 7 only implements the amperometric mode Al.

[0048] Preferably, the calibration phase Pcal is implemented periodically, following a measurement phase Pmes and before another measurement phase Pmes. The calibration phase Pcal verifies that the calibration constants, the baseline j and the sensitivity coefficient k, are adequate with respect to the temperature and humidity level of the external fluidic medium 10 as well as with respect to the aging of the electrochemical sensor 6.

[0049] In practice, the measuring device 1 is fixedly mounted in the external fluidic medium 10 and the amperometric mode Al forms a current measurement mode which provides a user with a series of time measurements of one or more electroactive gases 11. The calibration phase Pcal is implemented by the user or automatically to recalibrate the electrochemical sensor 6 after a certain time of use.

[0050] With reference to Figures 2 and 5, the Pcal calibration phase begins with the implementation of the amperometric mode Al in which: • The control unit 7 commands the regulating device 3 to admit the external fluidic medium 10 into chamber 2, for example via a first signal SI activating the pump or fan. At the end of this step, chamber 2 defines an open volume into which the external fluidic medium 10 is admitted and discharged to the outside. • The control unit 7 then commands the electrochemical sensor 6 to take an initial electrical measurement 11 at a given measurement time. During this step, the electrochemical sensor 6 is electrically powered and consumes the electroactive gas 11 in the open volume of chamber 2. • The control unit 7 then determines a first measurement of the concentration Cl of the electroactive gas 11 in the chamber 2. This step is implemented from the first electrical measurement il and the predetermined calibration constants j, k stored in the database 8 according to the relation: Cl=(il-j) / k, where j designates the baseline and k the sensitivity coefficient of the electrochemical sensor 6.

[0051] With reference to Figures 3, 4 and 5, the Pcal calibration phase then continues with the coulometric mode A2 in which: • The control unit 7 commands the regulating device 3 to stop the admission of the external fluidic medium 10 into chamber 2, for example via a second signal S2 to stop the pump or fan. At the end of this step, chamber 2 defines a closed volume containing a sample of the fluidic medium 10. • the control unit 7 then commands the electrochemical sensor 6 aA set of second electrical measurements i2 is taken within the closed volume of chamber 2. These second electrical measurements i2 are acquired during a predetermined time interval At, corresponding to the time required for the electrochemical sensor 6 to completely consume the electroactive gas 11 present in the closed volume of chamber 2 (see [Fig. 4]). The time interval At depends on the volume V of chamber 2 and the sensitivity of the electrochemical sensor 6. At the end of this step, the fluidic medium sample 10 trapped in chamber 2 no longer contains any electroactive gas IL. The control unit 7 then determines a second concentration measurement C2 of the electroactive gas 11 from the second electrical measurements i2. To do this, with reference to [Fig. 4], the control unit 7 determines a measurement curve H from the second electrical measurements i2, for example, by interpolation.The control unit 7 then determines the quantity of charge Q (expressed in coulombs) generated by the total consumption of the electroactive gas 11 by integrating the measurement curve H over the predetermined time interval At. Next, the second concentration measurement C2 is determined from the quantity of charge Q and the volume V of chamber 2. Applying Faraday's laws of electrolysis, the control unit 7 then measures a first difference el between the first concentration measurement Cl and the second concentration measurement C2, for example, in the form el = IC2 - Cil. If the first difference el exceeds a predetermined maximum threshold a, the control unit 7 then adjusts the predetermined sensitivity coefficient k to reduce this difference.The second concentration measurement C2 advantageously does not depend on temperature and humidity level, unlike the first concentration measurement CL. Thus, if the first concentration measurement Cl differs from the second concentration measurement C2 by more than the first maximum threshold a, the value of the sensitivity coefficient k is readjusted. The first threshold a is preferably between 1% and 10%. Preferably, the control element 7 also commands the electrochemical sensor 6 to take a third electrical measurement i3 after the predetermined time interval At. The control element 7 then measures a second deviation e2 between the third electrical measurement i3 and the predetermined baseline j, for example in the form e2 = Ii3 - jl. If the second deviation e2 is greater than a second predetermined maximum threshold X, the control element 7 then modifies the predetermined baseline j, preferably by replacing it with the third electrical measurement i3. The third electrical measurement i3 is generated at a measurement instant following the interval of time At, in the closed volume of chamber 2 when the sample no longer contains electroactive gas 11. The second threshold / . is preferably between 1% and 10%. • At the end of the coulometric mode A2, the values ​​of the calibration constants j, k were checked and readjusted if necessary. A new measurement phase Pmes can then be started by implementing the amperometric mode Al.

[0052] According to a preferred aspect, the second electrical measurement i2 is acquired at close intervals with the first electrical measurement il in order to ensure that the concentration of the electroactive gas 11 has not changed between the two measurements. According to another preferred aspect, the baseline j is corrected with the sensitivity coefficient k.

[0053] In the preceding example, the coulometric mode A2 is implemented after the amperometric mode A1. However, the order of the steps and modes A1, A2 could be different as long as: • The control step of the first electrical measurement (il) of the amperometric mode (Al) is consecutive to the control step of the regulation device (3) to admit the external fluidic medium (10), and • The control step for the third electrical measurement i3 of the coulometric mode A2 is subsequent to the control step for the second electrical measurements i2, itself subsequent to the control step for the regulation device 3 to stop the admission of the external fluidic medium 10. This block of steps could thus be implemented before the amperometric mode AL

[0054] According to another embodiment of the invention illustrated in [Fig. 6], the measuring device 1 further comprises an auxiliary sensor 9 of the electroactive gas 11 in the chamber 2, preferably of the metal oxide semiconductor type (known as a "MOS sensor") or of the photoionization type (known as a "PID sensor"). Such sensors are known to those skilled in the art. The auxiliary sensor 9 has a predetermined auxiliary baseline j9 which is also stored in the data storage element 8.

[0055] Still with reference to [Fig.6], the coulometric mode A2 also includes the following steps: • the control unit 7 commands the auxiliary sensor 9 to take a fourth electrical measurement i4 at the end of the predetermined time interval At of total consumption of the electroactive gas 11 in chamber 2, and • The control unit 7 then measures a third deviation e3 between the fourth electrical measurement i4 and the predetermined auxiliary baseline j9, for example in the form e3 = i4 — j9. If the third deviation e3 is greater than one At the third predetermined maximum threshold 0, the control unit 7 then modifies the predetermined auxiliary baseline j9, preferably by replacing it with the fourth electrical measurement i4. This allows for the recalibration of the electrochemical sensor 6, as well as an auxiliary sensor 9 mounted in chamber 2.

[0056] Advantageously, the self-calibrating measuring device 1 according to the invention makes it possible to measure an electroactive gas 11 using an electrochemical sensor 6 and to recalibrate the electrochemical sensor 6 by combining two different types of measurement: an amperometric mode A1 and a coulometric mode A2. The measuring device 1 is thus reliable and accurate, regardless of temperature, humidity level, or the aging of the electrochemical sensor. Furthermore, the measuring device 1 does not require another sensor or a filtering element to recalibrate the electrochemical sensor 6, which allows for simple, fast, and inexpensive calibration.

Claims

Demands

1. A measuring device (1) for at least one electroactive gas (11) in an external fluidic medium (10), the measuring device (1) being self-calibrating and comprising: • a chamber (2) having a predetermined volume (V), • at least one control device (3) configured to admit the external fluidic medium (10) into the chamber (2), • at least one electrochemical sensor (6), positioned in the chamber (2), configured to be electrically powered and to provide an electrical measurement by consumption of said at least one electroactive gas (11) in the chamber (2), • at least one control element (7) configured, in an amperometric mode (Al), for: • control the regulating device (3) to allow the admission of the external fluidic medium (10) into the chamber (2), • command the electrochemical sensor (6) to perform a first electrical measurement (il), and • determine a first concentration measurement (Cl) of said at least one electroactive gas (11) in the chamber (2), from the first electrical measurement (il), a predetermined baseline (j) and a predetermined sensitivity coefficient (k), • said control element (7) being configured, in a coulometric mode (A2), for: • control the regulating device (3) to stop the admission of the external fluidic medium (10) into the chamber (2), • command the electrochemical sensor (6) to take a plurality of second electrical measurements (i2) during a predetermined time interval (At) of total consumption of said at least one electroactive gas (11) in the chamber (2), • determine a second concentration measurement (C2) of said at least one electroactive gas (11) in the chamber (2), from the plurality of second electrical measurements (i2), of the predetermined time interval (At) and of the predetermined volume (V) of the chamber (2), • measure a first difference (el) between the first concentration measurement (Cl) and the second concentration measurement (C2), and • modify the predetermined sensitivity coefficient (k) if the first deviation (el) is greater than a first predetermined maximum threshold (a).

2. Measuring device (1) according to claim 1, wherein the control element (7) is also configured, in coulometric mode (A2), for: • command the electrochemical sensor (6) to take a third electrical measurement (i3) at the end of the predetermined time interval (At) of total consumption of said at least one electroactive gas (11) in the chamber (2), • measure a second deviation (e2) between the third electrical measurement (i3) and the predetermined baseline (j), and • modify the predetermined baseline (j) if the second deviation (e2) is greater than a second predetermined maximum threshold (X).

3. Measuring device (1) according to any one of claims 1 and 2, wherein the control element (7) is configured, in coulometric mode (A2), for: • determine a measurement curve (H) from the plurality of second electrical measurements (i2), • determine a quantity of electric charge (Q) by integrating the measurement curve (H) over the predetermined time interval (At), and • determine the second concentration measurement (C2) of said at least one electroactive gas (11) in the chamber (2) from the quantity of electric charge (Q) and the predetermined volume (V) of the chamber (2).

4. Measuring device (1) according to any one of claims 1 to 3, wherein the predetermined volume (V) of the chamber (2) is less than 10mL, and preferably greater than 0.5mL.

5. Measuring device (1) according to any one of claims 1 to 4, wherein the regulating device (3) is in the form of a pump or a fan.

6. Measuring device (1) according to any one of claims 1 to 5, comprising at least one conduit (4) for supplying the chamber (2) with external fluidic medium (10), preferably having a diameter less than 5mm, and preferably at least five times less than a length of the conduit (4).

7. A measuring device (1) according to any one of claims 1 to 6, comprising at least one auxiliary sensor (9) of said at least one electroactive gas (11) in the chamber (2) having a predetermined auxiliary baseline (j9), the control member (7) also being configured, in coulometric mode (A2), to: • command the auxiliary sensor (9) to take a fourth electrical measurement (i4) at the end of the predetermined time interval (At) of total consumption of said at least one electroactive gas (11) in the chamber (2), • measure a third deviation (e3) between the fourth electrical measurement (i4) and the predetermined auxiliary baseline (j9), and • modify the predetermined auxiliary baseline (j9) if the third deviation (e3) is greater than a third predetermined maximum threshold (0).

8. Measuring device (1) according to claim 7, wherein the auxiliary sensor (9) is in the form of a metal oxide semiconductor sensor or a photoionization sensor.

9. Method of using the measuring device (1) according to any one of claims 1 to 8, comprising at least one calibration phase (Pcal) in which the control element (7) implements the amperometric mode (A1) and the coulometric mode (A2).

10. Method of use according to claim 9, comprising at least one measurement phase (Pmes) in which the control element (7) only implements the amperometric mode (Al).