System and method for gas detection using an electrochemical gas sensor

Abstract

An electrochemical gas sensor for multi-gas analysis of a fluid sample comprises an electrochemical gas sensing element and a data collection component. The data collection component cyclically operates the electrochemical gas sensing element between a first excitation value and a signal detection value and a second excitation value and a signal detection value with a predetermined time constant, and is configured to measure the response of the electrochemical gas sensor to the fluid sample at the first excitation value and the signal detection value and at the second excitation value and the signal detection value. The response of the electrochemical gas sensor to the fluid sample at the first excitation value and the signal detection value and at the second excitation value and the signal detection value indicates the identity, respective concentrations, or combinations thereof of at least two analyte gases in the fluid sample.

Description

Technical Field

[0001] Description of Research and Development Funded by the Federal Government This invention was made with government support under Contract No. CWMD2004 awarded by ACC-NJ to the CWMD Consortium. The government has certain rights in this invention.

[0002] The subject matter disclosed herein generally relates to gas sensing, and more particularly to gas sensing using electrochemical gas sensors.

Background Art

[0003] Typically, an electrochemical gas sensor is operated by applying a specific bias voltage between electrodes and measuring the resulting current. The current resulting from the measurement is the single output response of the electrochemical gas sensor. This single output response is proportional to the concentration of one or more gases. Thus, in the conventional method of operating an electrochemical gas sensor as a single-output gas sensor, when the sensor responds to two or more gases, it is not possible to distinguish between different gases. Such a general response of an electrochemical gas sensor to two or more gases is known as gas cross-sensitivity and is unsuitable for distinguishing a single-output electrochemical gas sensor between multiple gases. Therefore, in order to improve the ability to distinguish multiple gases, it may be desirable to develop new electrochemical gas sensors and / or new methods of operating electrochemical gas sensors.

Summary of the Invention

Problems to be Solved by the Invention

[0004] With the above in mind, the present embodiment relates to a system and method for multi-gas detection using an electrochemical gas sensor. In contrast to the design of conventional electrochemical gas sensors, embodiments of the electrochemical gas sensors disclosed herein have the bias voltage of the electrochemical gas sensor periodically switched (e.g., cycled or modulated) before the sensor's current output reaches a steady state, utilizing techniques for cycling between bias voltages. Such operation of an electrochemical gas sensor involving periodic switching between at least two bias voltage levels provides the ability to distinguish between different gases. In some embodiments, the electrochemical gas sensor may also receive situational data (e.g., ambient temperature, relative humidity, atmospheric pressure, wind speed, wind direction, location, information about the surroundings, etc.), and then determine the identity and / or concentration of the gases present in the fluid sample based on some combination of the response of the electrochemical gas sensor and the situational data. The disclosed gas sensors and gas detection methods unexpectedly provide desirable characteristics such as the ability to distinguish between multiple gases not available from existing electrochemical gas sensors.

Means for Solving the Problems

[0005] For example, in one embodiment, an electrochemical gas sensor for multi-gas analysis of a fluid sample includes an electrochemical gas sensing element and a data collection component. The data collection component cycles the electrochemical gas sensing element between a first excitation value and a signal detection value and a second excitation value and a signal detection value with a predetermined time constant, and is configured to measure the response of the electrochemical gas sensor to the fluid sample at the first excitation value and signal detection value and at the second excitation value and signal detection value, wherein the response of the electrochemical gas sensor to the fluid sample at the first excitation value and signal detection value and at the second excitation value and signal detection value indicates the identity, respective concentrations, or a combination thereof of at least two analyte gases in the fluid sample.

[0006] In one embodiment, a method of operating an electrochemical gas sensor includes exposing an electrochemical gas sensing element of the electrochemical gas sensor to a fluid sample, cycling the electrochemical gas sensing element between a first operating condition and a second operating condition at a predetermined time constant via a data collection component, and measuring a response of the electrochemical gas sensor to the fluid sample at the first operating condition and the second operating condition, wherein the responses of the electrochemical gas sensor to the fluid sample at the first operating condition and the second operating condition indicate the identity, respective concentrations, or combinations thereof of at least two analyte gases in the fluid sample.

[0007] In one embodiment, an electrochemical gas sensor for multi-gas analysis of a fluid sample includes an electrochemical gas sensing element and a data collection component. The data collection component receives situation data indicating humidity, pressure, ambient temperature, one or more wind conditions, location, or any combination thereof, cycles the electrochemical gas sensing element between a first excitation value and signal detection value and a second excitation value and signal detection value at a predetermined time constant, and is configured to measure the response of the electrochemical gas sensor to the fluid sample at the first excitation value and signal detection value and the second excitation value and signal detection value. The electrochemical gas sensor is configured to determine the identity, respective concentrations, or combinations thereof of at least two analyte gases in the fluid sample based on the situation data and the responses of the electrochemical gas sensor to the fluid sample at the first excitation value and signal detection value and the second excitation value and signal detection value.

Brief Description of the Drawings

[0008] These and other features, aspects, and advantages of the present disclosure will be better understood by reading the following detailed description with reference to the accompanying drawings. In the accompanying drawings, like reference numerals represent like parts throughout the drawings.

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DETAILED DESCRIPTION OF THE INVENTION

[0009] This embodiment relates to a system and method for multi-gas detection that utilizes an electrochemical gas sensor that is cycled periodically between bias voltages before the measured current of the electrochemical gas sensor reaches a steady state.

[0010] By selecting the bias voltage and the time constant for the cycling operation or switching between different bias levels, the electrochemical gas sensor may be configured to detect multiple specific gases in a fluid sample. In some embodiments, the multi-gas sensor may also be configured to receive situational data (e.g., ambient temperature, relative humidity, atmospheric pressure, wind speed, wind direction, location, information about the surroundings, etc.) and to take the situational data into account when processing the output from the electrochemical gas sensor. Conventionally, electrochemical gas sensors have switched between different bias voltages using a time constant that is large enough, at least five minutes or more, such that the measured current of the electrochemical gas sensor reaches a steady state before switching the bias voltage. As a result, the gas sensor is not effective in distinguishing between multiple detected gases in a fluid sample. Thus, this embodiment unexpectedly demonstrates that cycling the electrochemical gas sensor between bias voltages before the measured current of the electrochemical gas sensor reaches a steady state can improve the ability of the electrochemical gas sensor to identify multiple gases in a fluid sample using a single sensor. As used herein, the time constant of the cycling operation of the sensor response is defined as the time for the sensor to alternate between two bias voltages.

[0011] An electrochemical gas sensor may also be configured to detect a plurality of specific gases in a fluid sample by performing measurements under direct current (DC) measurement conditions and / or impedance measurement conditions. By analyzing the response of the same electrochemical gas sensor to a fluid sample under DC measurement conditions and / or impedance measurement conditions, the detected gases may be distinguished using a multivariate data analysis algorithm. In one embodiment, multi-gas discrimination may be achieved by a single electrochemical gas sensor having impedance measurement values under two or more bias conditions. By analyzing the response of the same electrochemical gas sensor to a fluid sample using impedance measurement values under two or more bias conditions, the detected gases may be distinguished using a multivariate data analysis algorithm. In another embodiment, multi-gas discrimination may be achieved by a single electrochemical gas sensor having impedance measurement values only under DC and one bias condition. By analyzing the response of the same electrochemical gas sensor to a fluid sample using impedance measurement values only under DC and one bias condition, the detected gases may be distinguished using a multivariate data analysis algorithm.

[0012] With the above in mind, FIG. 1 is a schematic diagram of one embodiment of a gas sensor 10 for multi-gas analysis of a fluid sample according to the present technology. In different embodiments, the gas sensor 10 may be a wearable multi-gas sensor, an ingestible gas sensor, a tattoo-type gas sensor, etc. for personal (e.g., patient) monitoring. In certain embodiments, the gas sensor 10 may be an industrial environment sensor, an asset monitoring sensor, an industrial process monitoring gas sensor, a consumer sensor, a transportation sensor, a security sensor, or any combination thereof. In a further embodiment, the sensor may be part of a wireless sensor network.

[0013] In the embodiment shown in FIG. 1, the gas sensor 10 generally includes an electrochemical gas sensor 12 (or other gas sensing element), a control circuit 14, and one or more output devices 16. The electrochemical gas sensor 12 includes a substrate 18, a first electrode 20 and a second electrode 22 disposed on the substrate 18, and a gas sensing material 24 disposed on the substrate 18 between and / or on the electrodes 20, 22. A data collection component 26, which may include a bias controller and / or an impedance detector, is electrically coupled across the first electrode 20 and the second electrode 22 and is configured to provide a bias voltage across the first electrode 20 and the second electrode 22 during multi-gas analysis of the fluid sample 28. The impedance response and / or direct current (DC) response of the electrochemical gas sensor 12 measured by the data collection component 26 (e.g., via an impedance detector) when the fluid sample 28 is exposed can indicate the gases present in the fluid sample 28. For example, a transfer function, multiplier coefficient, look-up table, model, etc. may be applied to the data collected from the impedance response and / or DC response of the electrochemical gas sensor 12 to identify one or more gases present in the fluid sample 28. The fluid sample 28 may include, for example, a gas, liquid, gas-liquid mixture, solid material, particles or particulate matter, etc. containing one or more gases, including analyte gases and / or interfering gases. In another embodiment, the fluid may be a gas or fuel such as a hydrocarbon-based fuel. For example, the fluid may be natural gas or hydrogen gas supplied to a power system (e.g., a manned vehicle, an unmanned vehicle, an aircraft engine, or a stationary generator set) for consumption. Further, the fluid sample 28 may include gasoline, diesel fuel, jet fuel or kerosene, biofuel, petroleum diesel-biodiesel fuel blend, natural gas (liquid or compressed), and / or fuel oil. In other embodiments, the fluid sample 28 may be a sample of ambient air indoors or outdoors. For example, the sample can be from an industrial, residential, military, construction, urban, or any other known location.Furthermore, the ambient air sample may include relatively low concentrations of chemical agents such as benzene, naphthalene, carbon monoxide, ozone, formaldehyde, nitrogen dioxide, sulfur dioxide, ammonia, hydrofluoric acid, hydrochloric acid, phosphine, ethylene oxide, carbon dioxide, hydrogen sulfide, nerve agents, vesicants, blood agents, and choking agents, hydrocarbons, and / or other environmental factors. In other embodiments, the fluid sample 28 may be a disinfectant such as alcohol, aldehyde, chlorine dioxide, hydrogen peroxide, etc. In other embodiments, the fluid sample 28 may be a combustible gas such as methane, ethane, propane, butane, hydrogen, and / or other gases at relatively low, medium, and / or high concentrations and may be mixed with the ambient air from around the gas sensor 10. The ambient air may have certain measurable or distinguishable characteristics such as relative humidity, temperature, atmospheric pressure, and the concentration of other gases. In a further embodiment, the fluid sample 28 may include at least one gas dissolved in an industrial liquid such as transformer oil, bioprocess media, fermentation media, wastewater, etc. The fluid sample 28 may also include at least one gas dissolved in a consumer liquid such as milk, non-alcoholic beverages, alcoholic beverages, cosmetics, etc. In other embodiments, the fluid sample 28 may include at least one gas dissolved in a body fluid such as blood, sweat, tears, saliva, urine, feces, bile, etc.

[0014] In certain embodiments, the fluid sample 28 may contain an analyte gas that is a toxic industrial material or a toxic industrial chemical. A non-limiting list of exemplary toxic industrial materials and chemicals includes, but is not limited to, ammonia, arsine, boron trichloride, boron trifluoride, carbon disulfide, chlorine, diborane, ethylene oxide, fluorine, formaldehyde, hydrogen bromide, hydrogen chloride, hydrogen cyanide, hydrogen fluoride, hydrogen sulfide, nitric acid (fuming nitric acid), phosgene, phosphorus trichloride, sulfur dioxide, sulfuric acid, and tungsten hexafluoride. In certain embodiments, the fluid sample 26 may contain an analyte gas that is a toxic substance with a moderate hazard index. A non-limiting list of exemplary toxic substances with a moderate hazard index includes, but is not limited to, acetone cyanohydrin, acrolein, acrylonitrile, allyl alcohol, allylamine, allyl chloroformate, boron tribromide, carbon monoxide, carbonyl sulfide, chloroacetone, chloroacetonitrile, chlorosulfonic acid, diketene, 1,2-dimethylhydrazine, ethylene dibromide, hydrogen selenide, methanesulfonyl chloride, methyl bromide, methyl chloroformate, methyl chlorosilane, methylhydrazine, methyl isocyanate, methyl mercaptan, nitrogen dioxide, phosphine, phosphorus oxychloride, phosphorus pentafluoride, selenium hexafluoride, silicon tetrafluoride, stibine, sulfur trioxide, sulfuryl chloride, sulfuryl fluoride, tellurium hexafluoride, n-octyl mercaptan, titanium tetrachloride, trichloroacetyl chloride, and trifluoroacetyl chloride.

[0015] In certain embodiments, the fluid sample 28 may contain an analyte gas that is a low-hazard-index toxic substance. A non-limiting list of exemplary low-hazard-index toxic substances includes, but is not limited to, allyl isothiocyanate, arsenic trichloride, bromine, bromine chloride, bromine pentafluoride, bromine trifluoride, carbonyl fluoride, chlorine pentafluoride, chlorine trifluoride, chloroacetaldehyde, chloroacetyl chloride, crotonaldehyde, cyanogen chloride, dimethyl sulfate, diphenylmethane-4,4'-diisocyanate, ethyl chloroformate, ethyl chlorothioformate, ethyl phosphonous dichloride, ethyl phosphonous dichloride, ethyleneimine, hexachlorocyclopentadiene, hydrogen iodide, pentacarbonyliron, isobutyl chloroformate, isopropyl chloroformate, isopropyl isocyanate, n-butyl chloroformate, n-butyl isocyanate, nitric oxide, n-propyl chloroformate, parathion, perchloromethyl mercaptan, sec-butyl chloroformate, tert-butyl isocyanate, tetraethyl lead, tetraethyl pyrophosphate, tetramethyl lead, toluene 2,4-diisocyanate, and toluene 2,6-diisocyanate.

[0016] In certain embodiments, the fluid sample 28 may contain an analyte gas that is an indoor pollutant. A non-limiting list of exemplary indoor pollutants includes, but is not limited to, acetaldehyde, formaldehyde, 1,3-butadiene, benzene, chloroform, methylene chloride, 1,4-dichlorobenzene, perchloroethylene, trichloroethylene, naphthalene, and polycyclic aromatic compounds. In certain embodiments, the fluid 26 may contain an analyte gas that is an outdoor pollutant.A non-limiting list of exemplary outdoor pollutants includes, but is not limited to, ozone, nitrogen dioxide, sulfur dioxide, and carbon monoxide.

[0017] In the illustrated embodiment, the first electrode 20 and the second electrode 22 of the electrochemical gas sensor 12 are electrically coupled to the data collection component 26 of the control circuit 14 of the gas sensor 10. In some embodiments, the data collection component 26 may be a detector designed to measure the response of the electrochemical gas sensing material 24 with one or more of the bias voltages. In certain embodiments, the data collection component 26 may be able to measure the DC response (e.g., current response) of the electrochemical gas sensor 12. In certain embodiments, the data collection component 26 may measure both the AC response and the DC response of the electrochemical gas sensor 12. Thus, in some embodiments, the data collection component 26 may be an impedance detector or may include an impedance detector. The data collection component 26 is configured to measure the response of the electrochemical gas sensing material 24 to exposure to the fluid sample 28 while the data collection component 26 applies one or more bias voltages across the first electrode 20 and the second electrode 22 (e.g., via a bias controller). The response of the electrochemical gas sensing material 24 can indicate the gaseous state of the fluid sample 28 (e.g., the identity and / or concentration of the gas present). In other embodiments, the data collection component 26 may detect multiple gases in the fluid sample by performing measurements under DC measurement conditions and / or impedance measurement conditions. By analyzing the response of the electrochemical gas sensor 12 to the fluid sample 28 under DC measurement conditions and impedance measurement conditions, the electrochemical gas sensor 12 may be able to distinguish the gases within the fluid sample 28, for example, by using a multivariate data analysis algorithm. As used herein, the term impedance is a non-limiting term for any electrical response of the electrochemical gas sensing material 24 to exposure to the fluid sample 28 while the data collection component 26 applies one or more bias voltages across the first electrode 20 and the second electrode 22 (e.g., via a bias controller). In some embodiments, such responses may be measured as different electrical properties.Non-limiting examples of these different electrical responses may include, for example, impedance, admittance, reactance, susceptance, etc. In this specification, examples of responses are shown as impedance, but other electrical responses are also contemplated.

[0018] The control circuit 14 of the illustrated gas sensor 10 includes a data processing unit 32 (also referred to herein as a data processing circuit) communicatively coupled to a data collection component 26 to receive an excitation response measured by the data collection component 26 (e.g., via an impedance detector). The data processing unit 32 may include an on-board data processor 34 and a memory 36 storing a gas analysis model 38 including an analyte gas classification model 40, an analyte gas quantification model 42, or any combination thereof. The gas analysis model 38 may be a mathematical model that models the relationship between a sensor response (e.g., while the data collection component 26 maintains one or more bias voltages between the first electrode 20 and the second electrode 22, e.g., via a bias controller, in response to exposure to a fluid sample 28) and a specific classification or concentration of an analyte gas in the fluid sample 28. For example, the gas classification model 40 may model the relationship between the response to exposure to the fluid sample 28 while the data collection component 26 maintains one or more bias voltages between the first electrode 20 and the second electrode 22 and a specific classification of the analyte gas, and the gas quantification model 42 may model the relationship between the response to exposure to the fluid sample 28 while the data collection component 26 maintains one or more bias voltages between the first electrode 20 and the second electrode 22 and the response to a specific concentration of the analyte gas. In other embodiments, the gas analysis model may model the relationship between the impedance measured at two bias conditions, and / or the DC measurement and the impedance at one bias condition, and a specific classification or concentration of an analyte gas in the fluid sample 28. In some embodiments, the gas analysis model may also take into account situational data received from the sensor or some other source (e.g., ambient temperature, relative humidity, atmospheric pressure, wind speed, wind direction, location, information about the surroundings, etc.). In a particular embodiment, the gas analysis model 38 may include one or more coefficients determined experimentally and stored in the memory 36.

[0019] As used herein, “resolving” or “differentiating” two or more analyte gases of a fluid sample, or “providing resolution” between two or more analyte gases of a fluid sample, refers to determining a respective classification for each of the analyte gases of the fluid sample, determining the respective concentration of each of the analyte gases of the fluid sample, or determining both the respective classification and the respective concentration of each of the analyte gases of the fluid sample. As used herein, “classifying” or “determining a classification of” an analyte gas refers to determining the exact chemical identity of the analyte gas (e.g., ethanol, acetone, hydrogen), or determining the chemical classification to which each analyte gas belongs (e.g., hydrocarbon, alcohol, phenol, ether, aldehyde, ketone, carboxylic acid, ester, etc.). As used herein, an “unselected” response refers to an excitation response that is measured by the data acquisition component 26 and not used by the on-board data processor 34 during the analysis for resolving the analyte gases of the fluid sample 28. In certain embodiments, the memory 36 may be integrated with the data processor 34. In certain embodiments, the data processor 34 may be a multi-core processor. For example, in some embodiments, the on-board data processor 34 may be a multi-core processor on a single integrated circuit having two or more distinct processing units (or cores) each of which reads and executes program instructions. In certain embodiments, the multi-core processor may include only a single central processing unit (CPU) and a plurality of additional cores. In embodiments where the data processor 34 is a multi-core processor, different gas analysis models 38 and / or different signal processing algorithms may be executed independently by different cores to reduce the power consumption of the data processing unit 32 and / or the gas sensor 10.

[0020] In the illustrated embodiment, the gas sensor 10 includes one or more output devices 16. In certain embodiments, the output device 16 may include one or more display devices 44 configured to present information regarding ambient conditions and multi-gas analysis such as the classification and / or concentration of two or more analyte gases of the fluid sample 28. In some embodiments, other output devices 16 (e.g., speakers, light emitting diodes (LEDs), tactile feedback devices) may be included. Thus, the output device 16 may be configured to generate an alarm (e.g., visual alarm, audible alarm, tactile alarm, etc.) when a particular condition is detected. In certain embodiments, the output device 16 includes one or more communication devices 46 (e.g., wired communication interface, wireless communication interface) that enable the gas sensor 10 to communicate with other computing systems such as a desktop computer, a mobile computing device (e.g., laptop, smartphone), a remote server (e.g., Internet server, cloud server), or other sensors of a multi-sensor monitoring system (e.g., gas sensor, temperature sensor, vibration sensor, health monitor). For example, in certain embodiments, information determined by the on-board data processor 34 regarding the resolution of two or more analyte gases in the fluid sample 28 may be provided to an external computing system that functions as a controller for a network of sensors including the gas sensor 10. In some embodiments, the gas sensor 10 may additionally or alternatively use the communication device 46 to provide excitation response measurements to an external computing system, such that the external computing system can use these measurements to calculate one or more coefficient values for one or more of the gas analysis models and return these coefficient values to the gas sensor 10 for storage in the memory 36.

[0021] Furthermore, the illustrated gas sensor 10 includes a battery 48 that is electrically coupled to supply power to various components of the gas sensor 10, including a control circuit 14 and an output device 16. It will be understood that the battery 48 may have a capacity suitable for supplying power to all components of the gas sensor 10. For example, this may include providing a bias voltage between a first electrode 20 and a second electrode 22, measuring the response of the electrochemical gas sensing material 24, analyzing the measured response to exposure to a fluid sample 28 while a bias controller 26 maintains one or more bias voltages between the first electrode 20 and the second electrode 22, and presenting the results of the analysis via a suitable output device 16. In certain embodiments, the battery 48 may have a capacity sufficient to operate the gas sensor 10 for at least 10 hours. For example, the battery 48 may have a capacity in the range of 1 milliampere-hour (mAh) to 500 mAh, 1 mAh to 200 mAh, or 1 mAh to 100 mAh, or other ranges. In certain embodiments, such as those where the gas sensor 10 is designed to be particularly thin (e.g., for ingestible or tattoo-type embodiments of the gas sensor 10), the battery 48 may have a thickness of less than about 5 millimeters (mm). In some embodiments, all of the components of the gas sensor 10 may be coupled to or at least partially disposed within a package or housing suitable for a particular gas sensing application. For example, for personal monitoring applications, the packaging of the gas sensor 10 may be made of a biocompatible polymer that can be worn externally, injected subcutaneously, or ingested to perform multi-gas analysis on an individual or patient.

[0022] In some embodiments, the multi-gas sensor 10 system may be worn by an operator or may be a wearable device that can otherwise be moved from place to place. In such embodiments, the multi-gas sensor 10 may be disposed within a helmet, hat, glove, or other equipment of clothing / devices or may be an integral part thereof. For example, the multi-gas sensor 10 may be disposed within a wearable or non-wearable transportable object such as the frame of military or industrial eyeglasses, a wearable pulse oximeter, a safety vest or harness, clothing items, a mobile device (e.g., a mobile phone, a tablet, etc.). The wearable device may be integrated into the fabric of the clothing and can be placed on the clothing such as in a pocket, an armband, a wrist, or other limbs. The wearable multi-gas sensor 10 can be manufactured using complementary metal-oxide semiconductor electronics, flexible electronics, flexible hybrid electronics, and other manufacturing techniques based on other methods for providing a conformal and flexible design, implementation, and use. Optionally, the system may be a fixed device, may be independently movable (e.g., removable from the operator and movable independently of the operator), or may be floating in the air, etc.

[0023] In one or more embodiments, the multi-gas sensor 10 may be a wearable sensor system and may be held within a wearable and / or non-wearable transportable object (e.g., the frame of military or industrial eyeglasses). The wearable multi-gas sensor 10 may be worn by a human or animal or robot, etc., and may be removably coupled or integrated to an article worn by the subject (e.g., a shirt, pants, a safety vest, safety protective clothing, glasses, a hat, a helmet, an auditory device, etc.), or may be any alternative device such as movable so that the multi-gas sensor 10 can be moved between different positions, stationary or substantially stationary.

[0024] The multi-gas sensor 10 may be in contact with a fluid sample 28 in the form of a fluid container having a controlled volume or open area, such as an indoor facility (e.g., a room, hall, house, school, hospital, confined space, etc.) or an outdoor facility (e.g., a stadium, gas production site, filling station, gasoline filling station, hydrogen filling station, compressed natural gas filling station, liquefied natural gas filling station, gas distribution site, fuel distribution site, coast, forest, city, urban environment, marine environment, etc.). In some embodiments, the multi-gas sensor 10 may provide continuous monitoring of the fluid sample 28 in a reservoir or flow path. In one or more embodiments, the multi-gas sensor 10 may be an impedance gas sensor, an electromagnetic sensor, an electronic sensor, a hybrid sensor, or another type of sensor. Optionally, the multi-variable gas sensor 10 may be a sensor array.

[0025] The wearable multi-gas sensor 10 may be worn or carried by different subjects or individuals, such as, but not limited to, soldiers, medical professionals, athletes, system operators, students, or active or inactive individuals. Optionally, the wearable multi-gas sensor 10 may be coupled to, integrated with, or disposed on an asset such as a mobile system like a drone or a fixed system. The wearable multi-gas sensor 10 may be disposed on an article worn by the subject, such as a helmet, pocket (e.g., shirt, pants, bag, etc.), glove, wristband, earpiece, etc., or may be directly attached or otherwise coupled to the subject or asset, such as around the wrist or ankle.

[0026] Figure 2 is a flow diagram showing one embodiment of a process 100 in which a gas sensor 10 performs a multi-gas analysis of a fluid sample 28. Process 100 begins by exposing an electrochemical gas sensing material 24 (block 102) of the gas sensor to a fluid sample 28 having at least two gases, including one or more analyte gases and / or one or more interfering gases. For example, the entire gas sensor 10, or only the electrochemical gas sensing material 24 of the gas sensor 10, may be exposed to the fluid sample 28. In block 104, a data collection component 26 (e.g., via a bias controller) cycles a bias voltage across the first electrode 20 and the second electrode 22 at a set time constant. For example, the time constant may be set such that the bias voltage switches before the measured current of the electrochemical gas sensor 12 reaches a steady state. In other embodiments, the time constant may be selected such that the time constant is less than half of a second time constant related to an expected rate of change of the concentration of one of the analyte gases. In some embodiments, the bias voltage may be set based on the characteristics of the analyte gas being measured. For example, the time constant may be between 0.01 seconds and 1 second, or any value therebetween. In other embodiments, the time constant may be between 1 second and 5 seconds, or anywhere therebetween. In further embodiments, the time constant may be between 5 seconds and 10,000 seconds, or anywhere therebetween. In the embodiments disclosed herein, the bias voltage includes a first and second voltage, although embodiments in which the bias voltage includes three or more voltages are envisioned. For example, the bias voltage may include 3, 4, 5, 6, 7, 8, 9, 10, or more voltages. Further, the data collection component 26 (e.g., via a bias controller) may cycle between the bias voltages according to a step function, sine wave, square wave, sawtooth pattern, or some other function. In block 106, a data collection component (e.g., via an impedance detector) measures the response of the electrochemical gas sensing material 24 to exposure to the fluid sample 28 while the data collection component 26 (e.g., via a bias controller) cycles between the bias voltages. As will be described in more detail below, the response can indicate the identity and / or concentration of the analyte gas within the fluid sample 28.

[0027] In block 108, while the data processor 34 of the gas sensor 10 performs data analysis of the response of the electrochemical gas sensing material 24 to exposure to the fluid sample 28, the data collection component 26 (e.g., via a bias controller) cycles between bias voltages based on at least one of the stored gas analysis models 38 to determine whether the baseline excitation conditions should be adjusted and, if adjusted, selects the adjusted excitation conditions. For the electrochemical gas sensor 12, the data processor 34 may adjust the bias voltage across the first electrode 20 and the second electrode 22 and / or the time constant at which the bias controller cycles between bias voltages. The adjusted excitation conditions may then be communicated to the data collection component 26. In some embodiments, the data processor 34 may receive one or more situation data 110, such as ambient temperature, humidity, pressure, other gases present, etc., and may then adjust the excitation conditions based on the received situation data and / or the received response data. Thus, the gas sensor may be capable of adapting to various conditions that can affect the operation of the sensor, such as rain, heat, snow / cold. In some embodiments, the gas sensor 10 may also be equipped with a dynamic gain controller, whereby the data processor 34 may adjust the gain based on the measured response, enabling real-time adjustment of the sensitivity and resolution of the sensor response to the environment. In embodiments where the data processor 34 adjusts the excitation conditions of the electrochemical gas sensor 12, new data may be collected and analyzed at the new excitation conditions. In some cases, the gas sensor 10 may pass through multiple iterations of the excitation conditions before stabilizing at an appropriate combination of excitation conditions.

[0028] When determined by the data processor 34 that the excitation conditions are acceptable, in block 112, the data processor 34 performs data analysis of the response of the electrochemical gas sensing material 24 to exposure to the fluid sample 28, while the data collection component 26 (e.g., via a bias controller) cycles between bias voltages based on at least one of the stored gas analysis models 38 to provide real-time resolution of the analyte gas in the fluid sample 28. That is, in block 112, the system may output a respective classification 114 of two or more analyte gases in the fluid sample and / or a respective concentration 116 of two or more analyte gases in the fluid sample. In this context, "real-time" refers to the on-board data processor 34 of the gas sensor 10 that can locally and rapidly elucidate the analyte gas in the fluid sample without the need to provide the measured excitation response to an external computing system for processing. In some embodiments, the data processing unit 32 may generate or select a transfer function, a multiplication factor, a look-up table, a model, etc., and apply it to the data collected from the response of the gas sensing material 24 during exposure to the fluid sample.

[0029] Figure 3 is a flow diagram showing one embodiment of a process 200 in which a gas sensor 10 performs a multi - gas analysis of a fluid sample 28. Process 200 begins by exposing an electrochemical gas sensing material 24 (block 202) of the gas sensor to a fluid sample 28 having at least two gases, including one or more analyte gases and / or one or more interfering gases. In block 204, a data collection component 26 (e.g., via a bias controller) applies one or more bias voltages across the first electrode 20 and the second electrode 22. In some embodiments, the data collection component 26 (e.g., via a bias controller) may cycle between two bias voltages across the first electrode 20 and the second electrode 22. In such embodiments, impedance measurements at the two bias voltages can indicate at least two analyte gases in the fluid sample 28. In other embodiments, the data collection component 26 (e.g., via a bias controller) may maintain a single bias voltage across the first electrode 20 and the second electrode 22. In such embodiments, DC and impedance measurements at the bias voltage can indicate at least two analyte gases within the fluid sample 28. In some embodiments, the bias voltage may be set based on the characteristics of the analyte gas being measured. However, embodiments are envisioned in which the bias voltage includes three or more voltages. For example, the bias voltage can include 3, 4, 5, 6, 7, 8, 9, 10, or more voltages, and the data collection component 26 (e.g., via a bias controller) may cycle between the bias voltages according to a step function, sine wave, square wave, saw - tooth pattern, or some other function. In block 206, the data collection component (e.g., via an impedance detector) measures the impedance and / or DC response of the electrochemical gas sensing material 24 to exposure to the fluid sample 28 while the data collection component 26 (e.g., via a bias controller) is cycling to apply the bias voltage. As will be described in more detail below, the response can indicate the identity and / or concentration of the analyte gas within the fluid sample 28.

[0030] In block 208, the data processor 34 of the gas sensor 10 may perform data analysis of the response of the electrochemical gas sensing material 24 to exposure to the fluid sample 28, while the data collection component 26 (e.g., via a bias controller) determines whether to apply a bias voltage based on at least one of the stored gas analysis models 38 to adjust the baseline excitation conditions and selects the adjusted excitation conditions. For the electrochemical gas sensor 12, the data processor 34 may adjust the bias voltage across the first electrode 20 and the second electrode 22 and / or the time constant when the bias controller cycles between bias voltages. The adjusted excitation conditions may then be communicated to the data collection component 26. In some embodiments, the data processor 34 may receive one or more situation data 110, such as ambient temperature, humidity, pressure, other gases present, etc., and then adjust the excitation conditions based on the received situation data and / or the received response data. Thus, the gas sensor may be capable of adapting to various conditions that can affect the operation of the sensor, such as rain, heat, snow / cold. In some embodiments, the gas sensor 10 may also be equipped with a dynamic gain controller, whereby the data processor 34 may adjust the gain based on the measured response, enabling real-time adjustment of the sensitivity and resolution of the sensor response to the environment. In embodiments where the data processor 34 adjusts the excitation conditions of the electrochemical gas sensor 12, new data may be collected and analyzed with the new excitation conditions. In some cases, the gas sensor 10 may pass through multiple iterations of the excitation conditions before stabilizing to an appropriate combination of excitation conditions.

[0031] When determined by the data processor 34 that the excitation conditions are acceptable, in block 210, the data processor 34 performs data analysis of the response of the electrochemical gas sensing material 24 to exposure to the fluid sample 28, while the data collection component 26 (e.g., via a bias controller) applies a bias voltage based on at least one of the stored gas analysis models 38 to provide real-time resolution of the analyte gas in the fluid sample 28. That is, in block 210, the system may output the respective classification 114 of two or more analyte gases in the fluid sample and / or the respective concentration 116 of two or more analyte gases in the fluid sample. The impedance response and / or DC response of the electrochemical gas sensor 12 when the fluid sample 28 is exposed can indicate the gas present in the fluid sample 28. For example, a transfer function, multiplier coefficient, look-up table, model, etc. may be applied to the data collected from the impedance response and / or DC response of the electrochemical gas sensor 12 to identify one or more gases present in the fluid sample 28. In this context, "real-time" refers to the on-board data processor 34 of the gas sensor 10 that can locally and rapidly elucidate the analyte gas of the fluid sample without the need to provide the measured excitation response to an external computing system for processing. In some embodiments, the data processing unit 32 may generate or select a transfer function, multiplier coefficient, look-up table, model, etc. and apply it to the data collected from the response of the gas sensing material 24 during exposure to the fluid sample.

[0032] The multivariate data processing principle is applied to quantify the diversity of responses of a multivariate sensor to different gases. A multivariate transfer function may be constructed to quantify different gases. These constructed multivariate transfer functions may be implemented to quantify different gases within new measurement data from this multivariate sensor. Non-limiting examples of the multivariate data processing principle include techniques for performing gas classification / cluster analysis and quantification. Classification / cluster analysis can be performed to determine the type of analyte gas. Quantification can be performed to determine the concentration of the analyte gas. Examples of classification / cluster analysis algorithms include, but are not limited to, principal component analysis (PCA), hierarchical cluster analysis (HCA), independent component analysis (ICA), linear discriminant analysis (LDA), and support vector machine (SVM) algorithms. Non-limiting examples of methods for performing analyte quantification to determine the concentration of a specific analyte gas include principal component regression (PCR), independent component regression (ICR), non-linear regression analysis (NRA), discriminant function analysis (DFA), or artificial neural network analysis (ANN). In certain aspects of the subject matter of the invention described herein, a quantification algorithm can follow a classification algorithm.

[0033] [[ID=z3]] The analyte gas may include a wide range of materials and / or chemicals with various hazard indices. Materials having a "high" hazard index may include, for example, ammonia, arsine, boron trichloride, boron trifluoride, carbon disulfide, chlorine, diborane, ethylene oxide, fluorine, formaldehyde, hydrogen bromide, hydrogen chloride, hydrogen cyanide, hydrogen fluoride, hydrogen sulfide, nitric acid, fuming, phosgene, phosphorus trichloride, sulfur dioxide, sulfuric acid, and tungsten hexafluoride.

[0034] Examples of materials having a "medium" hazard index include, for example, acetone cyanohydrin, acrolein, acrylonitrile, allyl alcohol, allylamine, allyl chloroformate, boron tribromide, carbon monoxide, carbonyl sulfide, chloroacetone, chloroacetonitrile, chlorosulfonic acid, diketene, 1,2-dimethylhydrazine, ethylene dibromide, hydrogen selenide, methanesulfonyl chloride, methyl bromide, methyl chloroformate, methyl chlorosilane, methylhydrazine, methyl isocyanate, mercaptan, nitrogen dioxide, phosphine, phosphorus oxychloride, phosphorus pentafluoride, selenium hexafluoride, silicon tetrafluoride, stibine, sulfur trioxide, sulfuryl chloride, sulfuryl fluoride, tellurium hexafluoride, n-octyl mercaptan, titanium tetrachloride, trichloroacetyl chloride and trifluoroacetyl chloride.

[0035] Examples of materials with a "low" hazard index include, for example, allyl isothiocyanate, arsenic trichloride, bromine, bromine chloride, bromine pentafluoride, bromine trifluoride, carbonyl fluoride, chlorine pentafluoride, chlorine trifluoride, chloroacetaldehyde, chloroacetyl chloride, crotonaldehyde, cyanogen chloride, dimethyl sulfate, diphenylmethane - 4,4'-diisocyanate, ethyl chloroformate, ethyl chlorothioformate, ethyl phosphonous dichloride, ethyl phosphonous dichloride, ethyleneimine, hexachlorocyclopentadiene, hydrogen iodide, pentacarbonyl iron, isobutyl chloroformate, isopropyl chloroformate, isopropyl isocyanate, n - butyl chloroformate, n - butyl isocyanate, nitrogen monoxide, n - propyl chloroformate, parathion, perchloromethyl mercaptan, sec - butyl chloroformate, tert - butyl isocyanate, tetraethyl lead, tetraethyl pyrophosphate, tetramethyl lead, toluene 2,4 - diisocyanate, and toluene 2,6 - diisocyanate, and may include. The analyte gas may also include a series of indoor environmental agents such as acetaldehyde, formaldehyde, 1,3 - butadiene, benzene, chloroform, methylene chloride, 1,4 - dichlorobenzene, perchloroethylene, trichloroethylene, naphthalene, polycyclic aromatic compounds, and outdoor environmental agents such as ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide. Further, the analyte gas may include industrial chemicals such as combustibles, confined space hazards, etc.

[0036] In the embodiments of processes 100, 200 shown in FIGS. 2 and 3, after elucidating the analyte gas of fluid sample 28, gas sensor 10 may output, using one or more output devices 16, each classification 114 of the analyte gas of the fluid sample, each concentration 116 of the analyte gas of the fluid sample, or some combination thereof. For example, one or more output devices 16 of gas sensor 10 may present or display each classification 114, each concentration 116 of the analyte gas of fluid sample 28, or some combination thereof. In certain embodiments, gas sensor 10 may provide each classification 114 of the analyte gas, each concentration 116, or some combination thereof, to an external computing system via one or more suitable communication devices 46 (e.g., a wireless communication interface) of gas sensor 10.

[0037] To experimentally demonstrate the disclosed technology, three types of experiments were conducted. In the first type of experiment, as illustrated and described with respect to FIG. 2, dynamic bias modulation of a single electrochemical gas sensor was used for multi-gas detection and discrimination of a fluid sample. In the second type of experiment, as illustrated and described with respect to FIG. 3, impedance detection by an electrochemical gas sensor at two bias conditions was used for multi-gas detection and discrimination of a fluid sample. In the third type of experiment, as illustrated and described with respect to FIG. 3, impedance detection by an electrochemical gas sensor at DC and one bias condition was used for multi-gas detection and discrimination of a fluid sample.

[0038] In the first type of experiment conducted, while the electrochemical gas sensor was being exposed to various test gases, the electrochemical gas sensor was cycled between two bias voltages at the set time constant. FIG. 4 is a plot 300 of experimental data collected when the electrochemical gas sensor 12 was cycled between bias voltages at the set time constant while being exposed to fluid samples 28 having various concentrations of test gas as well as a control fluid sample. In these experiments, the control fluid sample was a sample of clean humid air in which no test gas was present. The horizontal axis represents time in minutes. The vertical axis is the response amplitude (e.g., detector counts proportional to the current output from the sensor). As shown, the electrochemical gas sensor 12 was cycled between a first bias voltage of -400 mV and a second bias voltage of -100 mV at the time constant such that the electrochemical gas sensor 12 switched alternately between the two bias voltages every 30 seconds. During a first period 302, as a control, while the electrochemical gas sensor 12 was being exposed to clean humid air, the bias controller 26 cycled the electrochemical gas sensor 12 between the bias voltages at the set time constant. During a second period 304, while the electrochemical gas sensor 12 was being exposed to fluid samples having decreasing oxygen gas (O2) concentrations of 15%, 10%, and 5%, the bias controller 26 cycled the electrochemical gas sensor 12 between the bias voltages at the set time constant. During a third period 306, while the electrochemical gas sensor 12 was being exposed to fluid samples having increasing hydrogen gas (H2) concentrations of 0.3%, 0.6%, and 0.9%, the bias controller 26 cycled the electrochemical gas sensor 12 between the bias voltages at the set time constant. As shown, the response of the electrochemical gas sensor 12 to various concentrations of O2 and H2 can be observed from plot 300 even though the bias controller 26 cycled the electrochemical gas sensor 12 before reaching a steady state for each cycle.

[0039] Principal component analysis (PCA) was used to analyze the test data shown in Figure 4. Figure 5 shows a plot of the contributions of the sensor responses to the first principal component (PC1) and the second principal component (PC2), determined by PCA of the test data. PCA is a robust unsupervised pattern recognition tool for the classification of multivariate data. PCA reduces a multidimensional dataset to facilitate its interpretation by calculating orthogonal principal components oriented in the directions of the maximum variance within the dataset. The first principal component contains the highest degree of variance, followed by the other PCs in order of decreasing variance. Thus, PCA concentrates the most important characteristic of the data (variance) in a low-dimensional space. Using the responses of this single sensor at two bias levels, a multivariate model was constructed using the PCA tool.

[0040] As shown, Figure 5 includes a plot 416 of the PC1 score on the horizontal axis versus the PC2 score on the vertical axis. The PC1 vs. PC2 plot 416 shows a good distinction between the data points of the control fluid 418, the data points (420) for three concentrations of O2 gas, and the data points (422) for three concentrations of H2 gas. The PC plot 416 visualizes the response patterns of sensor 10 to different gases during dynamic modulation of the sensor at two bias levels. As shown, the plot 416 starts with the response to the control fluid sample 418 (e.g., clean humid air) and extends in different directions depending on the type of gas detected (e.g., O2 420 and H2 422). Thus, the distribution of the data points in the PCA score plot enables visualization of the relationship between the original responses of the sensor at two bias levels with respect to the distinction between the three concentrations of the two gases (e.g., O2 420 and H2 422) and the control 418.

[0041] Another experiment was conducted using the same two bias voltages (-400 mV and -100 mV), but varying the time constant such that the bias controller switched the electrochemical gas sensor 12 between the two bias voltages every 6 seconds while the sensor was exposed to the same test gases (controlled clean humid air, O2 gas, H2 gas). Figure 6 is a plot 500 of experimental data collected while the electrochemical gas sensor was cycled between two bias voltages at the set time constant while exposing the sensor to fluid samples having clean humid air, O2 gas, and H2 gas. The horizontal axis represents time in minutes. The vertical axis indicates the response amplitude. As shown, the electrochemical gas sensor 12 was cycled between -400 mV and -100 mV at the time constant such that the electrochemical gas sensor 12 switched between the two bias voltages every 6 seconds. During the first period 502, while the electrochemical gas sensor 12 was exposed to clean humid air, the bias controller 26 cycled the electrochemical gas sensor 12 between the bias voltages at the set time constant. During the second period 504, while the electrochemical gas sensor 12 was exposed to fluid samples having decreasing O2 concentrations, 15%, 10%, and 5%, the bias controller 26 cycled the electrochemical gas sensor 12 between the bias voltages at the set time constant. During the third period 506, while the electrochemical gas sensor 12 was exposed to fluid samples having increasing concentrations of H2, 0.3%, 0.6%, and 0.9%, the bias controller 26 cycled the electrochemical gas sensor 12 between the bias voltages at the set time constant. As shown, the response of the electrochemical gas sensor 12 to various concentrations of O2 and H2 can be observed from plot 500 even though the bias controller 26 cycled the electrochemical gas sensor 12 before reaching a steady state for each cycle.

[0042] Similar to the experiments shown and described with respect to FIGS. 4 and 5, the test data was analyzed using PCA. FIG. 7 includes a plot 616 of the PC1 score on the horizontal axis versus the PC2 score on the vertical axis. The PC1 vs. PC2 plot shows a good distinction between the data points for the control fluid 618, the data points for three concentrations of O2 gas (620), and the data points for three concentrations of H2 gas (622). Thus, similar to FIG. 5, FIG. 7 shows that the distribution of data points in the PCA score plot enables visualization of the relationship between the original response of sensor 10 at two bias levels for two gases (e.g., O2 gas 620 and H2 gas 622) and the control 618 when measurements were made at time constants of 30 seconds and 6 seconds while the sensor was exposed to the same test gases (control 618 of clean humid air, O2 gas 620, H2 gas 622).

[0043] In the second type of experiment conducted, impedance detection was performed using the electrochemical gas sensor 12 under two bias conditions while the sensor was exposed to various test gases. Specifically, the electrochemical gas sensor 12 was exposed to fluid samples containing three types of ethanol with increasing concentrations (22.2 ppm, 44.4 ppm, 66.6 ppm), and then to fluid samples containing two types of H2 with increasing concentrations (111 ppm and 222 ppm). For all fluid samples, the carrier gas was air with a relative humidity of approximately 10%. In this experiment, the bias voltages were set to 0 mV and -100 mV. For impedance measurement, the monitored frequency was 100 kHz. FIG. 8 shows a plot 700 of the measured impedance responses of the electrochemical gas sensor 12 to exposure to various fluid samples at a bias voltage of 0 mV and a frequency of 100 kHz. Thus, feature 704 shows the measured impedance response of the electrochemical gas sensor 12 to 22.2 ppm ethanol, feature 706 shows the measured impedance response of the electrochemical gas sensor 12 to 44.4 ppm ethanol, feature 708 shows the measured impedance response of the electrochemical gas sensor 12 to 66.6 ppm ethanol, feature 710 shows the measured impedance response of the electrochemical gas sensor 12 to 111 ppm H2, and feature 712 shows the measured impedance response of the electrochemical gas sensor 12 to 222 ppm H2. As shown in FIG. 8, when the bias voltage is 0 mV, a clear pattern can be seen in the responses to different gases. For example, the response to a fluid sample with 66.6 ppm ethanol (708) had a larger amplitude than the response to a fluid sample with 111 ppm H2 (710).

[0044] Figure 9 shows a plot 800 of the measured impedance response of the electrochemical gas sensor 12 to exposure to various fluid samples at a bias voltage of -100 mV and a frequency of 100 kHz. Thus, during a first period 802, feature 804 shows the measured impedance response of the electrochemical gas sensor 12 to 22.2 ppm of ethanol, feature 806 shows the measured impedance response of the electrochemical gas sensor 12 to 44.4 ppm of ethanol, feature 808 shows the measured impedance response of the electrochemical gas sensor 12 to 66.6 ppm of ethanol, feature 810 shows the measured impedance response of the electrochemical gas sensor 12 to 111 ppm of H2, and feature 812 shows the measured impedance response of the electrochemical gas sensor 12 to 222 ppm of H2. Similar to FIG. 8, a distinct pattern is seen in the responses to different gases at a bias voltage of 0 mV shown in FIG. 9. For example, the response to a fluid sample having 66.6 ppm of ethanol (808) had a smaller amplitude than the response to a fluid sample having 111 ppm of H2 (810).

[0045] As a result of the operation of the electrochemical gas sensor at 0 mV and -100 mV biases and impedance detection at 100 kHz, there are distinct differences in the responses between the two bias voltages shown in FIGS. 8 and 9. For example, at a bias voltage of 0 mV, the response to a fluid sample having 66.6 ppm of ethanol (708) had a larger amplitude than the response to a fluid sample having 111 ppm of H2 (710). However, at a bias voltage of -100 mV, the response to a fluid sample having 66.6 ppm of ethanol (808) had a smaller amplitude than the response to a fluid sample having 111 ppm of H2 (810). Such differences enable the discrimination between the two gases using multivariate statistical methods. Thus, by varying the bias voltage and impedance detection, multi-gas discrimination can be achieved.

[0046] Figure 10 shows a plot 900 of the measured DC response (measured as current) of the electrochemical gas sensor 12 to exposure to various fluid samples at a bias voltage of 0 mV. Thus, during period 902, feature 904 shows the measured DC response of the electrochemical gas sensor 12 to 22.2 ppm of ethanol, feature 906 shows the measured DC response of the electrochemical gas sensor 12 to 44.4 ppm of ethanol, feature 908 shows the measured DC response of the electrochemical gas sensor 12 to 66.6 ppm of ethanol, feature 910 shows the measured DC response of the electrochemical gas sensor 12 to 111 ppm of H2, and feature 912 shows the measured DC response of the electrochemical gas sensor 12 to 222 ppm of H2. As shown in Figure 10, there is a clear pattern in the responses to different gases at a bias voltage of 0 mV and in the measured DC response measured as current. For example, the response to a fluid sample having 66.6 ppm of ethanol (908) had a smaller amplitude than the response to a fluid sample having 111 ppm of H2 (910).

[0047] Comparing the plot of the impedance response at 0 mV bias shown in Fig. 8 with the DC response at 0 mV bias shown in Fig. 10 may reveal some differences. For example, the amplitude of the DC response to 66.6 ppm ethanol (908) was smaller than the amplitude of the DC response to 111 ppm H2 (910). However, the amplitude of the impedance response to 66.6 ppm ethanol (708) at 100 kHz was larger than the amplitude of the impedance response to 111 ppm H2 (710). Such differences enable the discrimination between the two gases using multivariate statistical methods. Therefore, comparing the impedance response and the DC response at the same bias voltage may also be useful for discriminating gases. Sensor operation with periodic switching between two bias voltages can utilize a switching circuit and provide the ability to discriminate gases. Furthermore, sensor operation using the impedance response and the DC response at the same bias voltage also provides the ability to discriminate the same or different gases and / or to achieve gas detection resolution and sensitivity.

[0048] The technical effect of the present disclosure includes multi-gas detection using an electrochemical (E-chem) sensor that is cycled between bias voltages before the electrochemical gas sensor reaches a steady state. By selecting a bias voltage and a time constant for the electrochemical gas sensor, the electrochemical gas sensor may be configured to detect multiple specific gases in a fluid sample. In some embodiments, the multi-gas sensor may receive or be configured to receive situational data (e.g., ambient temperature, relative humidity, atmospheric pressure, wind speed, wind direction, location, information about the surroundings, etc.), and may or be configured to consider the situational data when processing the output from the electrochemical gas sensor to identify the multiple gases present in the fluid sample. Conventionally, electrochemical gas sensors utilize a large time constant such that the electrochemical gas sensor reaches a steady state before switching the bias voltage. As a result, the gas sensor is slow to react to changes in the fluid sample and is not very effective at detecting multiple gases in the fluid sample. Accordingly, the present embodiment demonstrates, contrary to expectation, that by cycling the electrochemical gas sensor between bias voltages before the electrochemical gas sensor reaches a steady state, the response time to changes in the fluid sample can be shortened, and the ability of the electrochemical gas sensor to identify multiple gases in the fluid sample can be improved without sacrificing the accuracy of the electrochemical gas sensor. Using the disclosed technology, electrochemical gas sensors can be designed, manufactured, and used to elucidate multiple gases in a fluid sample more quickly, accurately, and over a wider range of conditions than previously possible.

[0049] This specification uses examples to disclose the invention, including the best mode, and to enable any person skilled in the art to make and use the invention, including making and using any device or system and performing any incorporated method. The patentable scope of the invention is defined by the claims and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements that do not differ from the literal language of the claims.

Claims

1. An electrochemical gas sensor for multi-gas analysis of a fluid sample, an electrochemical gas sensing element, and a data collection component configured to operate the electrochemical gas sensing element in a cycle between a first excitation value and a signal detection value and a second excitation value and a signal detection value with a predetermined time constant, and measure the response of the electrochemical gas sensor to the fluid sample at the first excitation value and signal detection value and at the second excitation value and signal detection value, wherein the response of the electrochemical gas sensor to the fluid sample at the first excitation value and signal detection value and at the second excitation value and signal detection value indicates the identity, respective concentrations, or combinations thereof of at least two analyte gases in the fluid sample, a data collection component; An electrochemical gas sensor for multi-gas analysis of a fluid sample, comprising:

2. The electrochemical gas sensor according to claim 1, wherein the first excitation value comprises a first bias level of the electrochemical gas sensor and the second excitation value comprises a second bias level of the electrochemical gas sensor.

3. The electrochemical gas sensor according to claim 1, wherein the first signal detection value is based on a direct current (DC) measurement value and the second signal detection value is based on an impedance measurement value of the electrochemical gas sensor.

4. The electrochemical gas sensor according to claim 3, wherein the DC measurement value and the impedance measurement value of the electrochemical gas sensor are under a common bias condition.

5. The electrochemical gas sensor according to claim 1, wherein the first signal detection value is based on a first impedance measurement value of the electrochemical gas sensor and the second signal detection value is based on a second impedance measurement value of the electrochemical gas sensor.

6. The electrochemical gas sensor according to claim 5, wherein the first impedance measurement value is under a first bias condition and the second impedance measurement value is under a second bias condition.

7. The electrochemical gas sensor according to claim 5, wherein the first impedance measurement value is at a first frequency and the second impedance measurement value is at a second frequency.

8. The electrochemical gas sensor according to claim 7, wherein the first frequency and the second frequency are selected based on the identity of the at least two analyte gases, the identity of one or more interfering gases, or a combination thereof.

9. The electrochemical gas sensor according to claim 1, further comprising a data processor configured to determine the identity, respective concentrations, or a combination thereof of the at least two analyte gases in the fluid sample based on the response of the electrochemical gas sensor to the fluid sample at the first excitation value and signal detection value and the second excitation value and signal detection value.

10. The electrochemical gas sensor according to claim 1, wherein the predetermined time constant is less than half of the expected rate of change of the concentration of one of the at least two analyte gases in the fluid sample.

11. The gas sensor according to claim 1, wherein the cyclic operation between the first excitation value and signal detection value and the second excitation value and signal detection value includes a cyclic operation between a first bias voltage value and a second bias voltage value.

12. The electrochemical gas sensor according to claim 11, wherein the cyclic operation between the first bias voltage value and the second bias voltage value follows a sine wave, a square wave, a sawtooth pattern, or any combination thereof.

13. The electrochemical gas sensor according to claim 11, wherein the first bias voltage value and the second bias voltage value are selected based on the identity of the at least two analyte gases, the identity of one or more interfering gases, or a combination thereof.

14. The gas sensor according to claim 1, wherein the sensor is incorporated into a mobile electronic device.

15. A method of operating an electrochemical gas sensor, comprising: exposing an electrochemical gas sensing element of the electrochemical gas sensor to a fluid sample; cycling the electrochemical gas sensing element between a first operating condition and a second operating condition at a predetermined time constant via a data collection component; Measuring the response of the electrochemical gas sensor to the fluid sample under the first operating condition and the second operating condition, wherein the response of the electrochemical gas sensor to the fluid sample under the first operating condition and the second operating condition indicates the identity, respective concentrations, or a combination thereof of at least two analyte gases in the fluid sample; A method of operating an electrochemical gas sensor comprising.

16. The method according to claim 15, wherein the first operating condition corresponds to a first bias voltage value and the second operating condition corresponds to a second bias voltage value.

17. The method according to claim 16, wherein the first bias voltage value and the second bias voltage value are selected based on the identity of the at least two analyte gases.

18. The method according to claim 15, wherein the first operating condition corresponds to a first impedance measurement value at a first frequency and the second operating condition corresponds to a direct current (DC) measurement value or a second impedance measurement value at a second frequency.

19. The method according to claim 18, wherein the first frequency, or both the first and second frequencies, are selected based on the identity of the at least two analyte gases.

20. An electrochemical gas sensor for multi-gas analysis of a fluid sample, An electrochemical gas sensing element; A data collection component, Receiving situation data indicating humidity, pressure, ambient temperature, one or more wind conditions, location, or any combination thereof; Cyclically operating the electrochemical gas sensing element between a first excitation value and signal detection value and a second excitation value and signal detection value at a predetermined time constant; Measuring the response of the electrochemical gas sensor to the fluid sample at the first excitation value and signal detection value and the second excitation value and signal detection value; A data collection component configured to perform; Comprising The electrochemical gas sensor is configured to determine the identity, respective concentrations, or a combination thereof of at least two analyte gases in the fluid sample based on the situation data and the response of the electrochemical gas sensor to the fluid sample at the first excitation value and signal detection value and the second excitation value and signal detection value. An electrochemical gas sensor for multi-gas analysis of a fluid sample.

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