Determining Sensor Operational Status via Sensor Interrogation

Abstract

To provide a method for predicting a future failure in an electrochemical gas sensor.SOLUTION: A method of operating a gas sensor for a gas analyte including a sensing component includes, as a first mode, interrogating the sensor by periodically applying an electrical signal to the sensing component of the sensor, measuring sensor response to the electrical signal which is indicative of a sensitivity of the sensor each time the electrical signal is applied to the sensing component, determining whether one or more thresholds are exceeded based upon the sensor response determined each time the electrical signal is applied to the sensing component, and entering a second mode different from the first mode in analysis of the sensor response to the periodically applied electrical signals, if one or more thresholds are exceeded.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 62 / 738,190, filed September 28, 2018, the disclosure of which is incorporated herein by reference.

[0002] background The following information is provided to aid the reader in understanding the technology disclosed below and the environments in which such technology may typically be used. Terms used herein are not intended to be limited to any particular narrow interpretation unless expressly specified otherwise in this document. References listed herein may facilitate understanding of the technology or its background. The disclosures of all references cited herein are incorporated by reference.

[0003] Gas sensors, such as electrochemical sensors, have proven effective for decades in detecting gases, such as toxic gases, in workplace environments. For example, the low cost, response speed, and selectivity of electrochemical gas sensors are just a few of the features that make them attractive for safety-related products. However, one of the necessary requirements for using electrochemical and other gas sensors is frequent calibration. For example, the sensitivity of electrochemical sensors is affected by the water content of their electrolytes, which varies as a result of fluctuations in ambient relative humidity, such as with seasons and geographic location. Such fluctuations in relative humidity lead to decreased sensitivity in arid regions and dry seasons and increased sensitivity in humid regions and wet seasons.

[0004] Therefore, prudence dictates that gas detection instruments containing electrochemical and / or other gas sensors be periodically tested for functionality. For example, frequent calibration with a test gas having a known concentration of analyte or target gas (including non-zero and zero concentrations) is required to adjust for the sensitivity variations described above. For example, it is common to routinely perform a "bump check" or functionality check of portable gas detectors. The purpose of this test is to verify the functionality of the entire gas detection system, commonly referred to as an instrument. Periodic bump checks or functionality checks may also be performed on permanent gas detectors, for example, to extend the interval between full calibrations. A gas detection system includes at least one gas sensor and electronic circuitry (including a power source) for driving the sensor, interpreting its response, and displaying the response to the user. The system further includes a housing to enclose and protect these components. A bump check typically involves a) applying a test gas of interest (usually a known concentration of the target or analyte gas the instrument is intended to detect, or a simulant gas for which the instrument is responding), b) collecting and interpreting the sensor response, and c) indicating to the end user the functional status of the system (i.e., whether the instrument is functioning properly).

[0005] Traditionally, bump tests have been performed periodically, typically daily. Bump checks provide a relatively high degree of assurance to the user that the gas detection device is operating properly. A bump check performs all necessary functions of all parts of the gas detection device in a similar manner as required to detect alarm levels of hazardous gases. In this regard, a bump check ensures efficient gas delivery from outside the device through any transport pathways (e.g., including any protective and / or diffusion membranes) to contact the active sensor components. A bump check also verifies that the sensing surface of the sensor itself is functioning properly and that the sensor provides an appropriate response function or signal. A bump check further verifies that the sensor is properly connected to its associated power source and electronic circuitry and that the sensor signal is being properly interpreted. Furthermore, a bump check verifies that the gas detector's indicator(s) and user interface(s) (e.g., display and / or notification functions) are functioning as intended.

[0006] However, periodic / daily bump checks have many significant drawbacks. For example, such bump checks are time-consuming, especially in facilities such as industrial facilities that contain several gas detection systems or instruments. Bump checks also require the use of expensive and potentially hazardous calibration or test gases. Furthermore, bump checks typically require specialized gas delivery systems, including pressurized gas bottles, pressure-reducing regulators, and tubing and adapters to properly deliver the calibration or test gas to the instrument. The need for specialized gas delivery systems often means that opportunities to bump check personal gas detection devices are limited to certain locations and times due to the availability of gas delivery equipment.

[0007] Recently, several systems and methods have been proposed to reduce the number of required bump tests. Such systems may include, for example, electronic interrogation of sensors in the absence of a test gas. Sensitivity variations in electrochemical gas sensors resulting from moisture loss or gain across multiple sensors occur gradually but predictably as the average relative humidity slowly changes. Similarly, sensor response to electronic interrogation (when a test gas containing a known concentration of the analyte gas or its surrogate is not present or applied) similarly varies. Electronic interrogation can be used, for example, to measure sensitivity changes and correct for them. Such electronic interrogation techniques and resulting electrochemical gas sensor corrections are disclosed, for example, in U.S. Patent Nos. 7,413,645, 7,959,777, 9,784,755, 9,528,957, and U.S. Patent Application Publication Nos. 2013 / 0186777 and 2017 / 0219515, the disclosures of which are incorporated herein by reference. In such electronic interrogation approaches, an electrical signal, such as a potential pulse, is typically applied to a sensing element or component of the sensor, and the resulting response is measured and recorded. The response may be measured, for example, in the form of a maximum peak (current) value (MPV) and / or another parameter. These responses are compared to values ​​obtained during previous gas test / pulse cycles. Changes from the calibration value may be correlated with changes in the sensitivity of the sensor.

[0008] Various electronic interrogation techniques have also been developed for sensors other than electrochemical sensors (such as combustible gas sensors). For example, U.S. Patent Application Publication No. 2014 / 0273263, the disclosure of which is incorporated herein by reference, discloses periodic measurements of a variable related to the reactance of a sensing element of a combustible gas sensor to determine the operational state of the sensing element. U.S. Patent Application Nos. 15 / 597,933 and 15 / 597,859 disclose electronic interrogation techniques for combustible gas sensors in which a variable related to the mass of the sensing element (e.g., an electrical property such as resistance) is periodically measured to determine, for example, whether a substance such as an inhibitor or poison has been deposited on the sensing element. Summary of the Invention [Problem to be solved by the invention]

[0009] Current testing or interrogation techniques are useful in determining whether an individual sensor is in working condition at the time of testing, but have relatively little success in predicting future failure of such sensors. [Means for solving the problem]

[0010] summary In one aspect, a method of operating a gas sensor for a gas analyte including a sensing component includes, as a first mode, interrogating the sensor by periodically applying an electrical signal to the sensing component of the sensor, measuring a sensor response to the electrical signal indicative of the sensitivity of the sensor each time the electrical signal is applied to the sensing component, determining whether one or more thresholds are exceeded based on the sensor response determined each time the electrical signal is applied to the sensing component, and entering a second mode, different from the first mode, in analyzing the sensor response to the periodically applied electrical signal if the one or more thresholds are exceeded.

[0011] In some embodiments, the sensor response to the periodically applied electrical signal in the second mode is analyzed to determine whether the sensor response to the periodically applied electrical signal has stabilized. The method may further include determining a rate of change of the sensor response during the second mode, for example, to determine whether the sensor response to the periodically applied electrical signal has stabilized. In some embodiments, at least one of a magnitude and a direction of the rate of change of the sensor response is determined. In some embodiments, the method further includes modifying one or more thresholds after determining that the sensor response to the periodically applied electrical signal has stabilized. It is not necessary to apply a test gas during the electronic sensor interrogation. In this regard, the sensor response may be determined without applying a test gas to the sensor. In some embodiments, at least one of a magnitude and a direction of the rate of change of the sensor response is determined.

[0012] The sensor may be, for example, an electrochemical gas sensor, and the sensing component may be, for example, a working electrode of the electrochemical gas sensor. The value of the sensor response may be determined, for example, based on at least one defined parameter of the sensor response. In some embodiments, the at least one defined parameter of the sensor response is selected from the group of a maximum current peak value, an area under the current curve, a minimum peak value, a peak-to-peak value, an area under the inversion curve, a baseline value of the sensor response, or one or more functions thereof (e.g., a product, ratio, or more complex function of one or more such parameters). The value of the sensor response at each periodically applied electronic interrogation may be, for example, a change in the value of the at least one defined parameter of the sensor response measurements at each periodically applied electronic interrogation from a value determined during calibration of the sensor.

[0013] In some embodiments, one or more thresholds for the sensor response are determined by tracking the value of the sensor response over time and determining upper and lower thresholds for reference operation for the sensor. In some embodiments, one or more thresholds for the sensor response are determined by tracking the sensor response over time for a plurality of similar sensors and determining upper and lower group thresholds for reference operation for the plurality of sensors. In some embodiments in which a group threshold is determined, one or more other thresholds are determined by tracking the sensor response of each of the plurality of similar sensors over time and determining individual upper and lower thresholds for reference operation for each of the plurality of similar sensors. The second mode can be entered, for example, based on comparing the sensor response of each of the plurality of similar sensors to the upper and lower group thresholds and the individual upper and lower thresholds for each of the plurality of similar sensors.

[0014] The sensors of a plurality of similar sensors herein may exhibit at least one common characteristic other than being similar sensors, for example. The at least one common characteristic may be, for example, a geographic region in which they are deployed or a range of manufacture. In embodiments, groups and subgroups of similar sensors may be established.

[0015] In some embodiments, data from the sensor is transmitted to a remote processor system for processing and / or analysis. In some embodiments, data or information from a second gas sensor for a second gas analyte different from the gas analyte, or data from a third sensor for an environmental condition, is transmitted to the gas sensor.

[0016] In another aspect, a system includes a sensor including a sensing component having at least one characteristic sensitive to an analyte and a circuit operatively connected to the sensing component. The circuit is configured to, in a first mode, interrogate the sensor by periodically applying an electrical signal to the sensing component, measuring a sensor response to the electrical signal indicative of the sensitivity of the sensor each time the electrical signal is applied to the sensing component, and comparing the sensor response to one or more thresholds. The circuit is further configured to determine, based on the comparison of the sensor response to the one or more thresholds, whether to enter a second mode, different from the first mode, in analyzing the sensor response to the periodically applied electrical signal if the one or more thresholds are exceeded.

[0017] In some embodiments, the circuit is configured to analyze the sensor response to the periodically applied electrical signal in a second mode to determine whether the sensor response to the periodically applied electrical signal has stabilized. The circuit may be further configured to determine a rate of change of the sensor response during the second mode, for example, to determine whether the sensor response to the periodically applied electrical signal has stabilized. For example, at least one of a magnitude and a direction of the rate of change of the sensor response may be determined. In some embodiments, the circuit is further configured to modify one or more thresholds after determining that the sensor response to the periodically applied electrical signal has stabilized. For example, the circuit may be configured to determine the sensor response without applying a test gas to the sensor.

[0018] In some embodiments, the sensor is an electrochemical gas sensor, and the sensor component is a working electrode of the electrochemical gas sensor. As described above, the value of the sensor response is determined based on at least one defined parameter of the sensor response. In some embodiments, the at least one defined parameter of the sensor response is selected from the group consisting of a maximum current peak value, an area under the current curve, a minimum peak value, a peak-to-peak value, an area under the inversion curve, a baseline value of the sensor response, a function, or one or more functions described above. The value of the sensor response at each periodically applied electronic interrogation can be, for example, a change in the at least one defined parameter of the sensor response measurement at each periodically applied electronic interrogation from a value determined during sensor calibration.

[0019] In some embodiments, one or more thresholds for the sensor response are determined by tracking the value of the sensor response over time and determining upper and lower thresholds for reference operation for the sensor. In some embodiments, one or more thresholds for the sensor response are determined by tracking the sensor response for a plurality of similar sensors over time and determining a group upper threshold and a group lower threshold for reference operation for the plurality of sensors. Each of the plurality of similar sensors may include a communication system for, for example, transmitting data regarding the sensor response in response to a periodically applied electronic query and receiving data regarding the group upper threshold and the group lower threshold for reference operation for the plurality of sensors. In some embodiments in which a group threshold is determined, one or more other thresholds are determined by tracking the sensor response of each of the plurality of similar sensors over time and determining individual upper and lower thresholds for reference operation for each of the plurality of similar sensors. A second mode may be entered for each of the plurality of similar sensors, for example, based on comparing the sensor response of each of the plurality of similar sensors to the group upper and lower thresholds and the individual upper and lower thresholds.

[0020] In some embodiments where multiple similar sensors are tracked, each of the multiple similar sensors has at least one common characteristic other than being similar sensors, which may be, for example, a geographic region in which they are deployed or a range of time periods in which they are manufactured.

[0021] Data from the sensor may be transmitted, for example, to a remote processor system for processing and / or analysis. Data or information from a second gas sensor for a second gas analyte different from the gas analyte, or data from a third sensor for an environmental condition, may be transmitted to the gas sensor.

[0022] In a further aspect, a method of operating a system including a plurality of similar gas sensors, each of the plurality of similar gas sensors including a sensing component, includes interrogating each of the plurality of similar gas sensors in a first mode by periodically applying an electrical signal to the sensing component of the sensor, determining a sensor response to the electrical signal indicative of sensitivity for each of the plurality of similar gas sensors each time the electrical signal is applied to the sensing component, and analyzing the sensor response of each of the plurality of similar gas sensors to the periodically applied electrical signal based on baseline responses of the plurality of similar gas sensors to the periodically applied electrical signal determined over time. The method may further include determining whether each of the plurality of similar gas sensors enters a second mode different from the first mode in analyzing the sensor response to the periodically applied electrical signal based, for example, on a comparison of the sensor response of each of the plurality of similar gas sensors to the baseline responses of the plurality of similar gas sensors in the first mode. The method may be further characterized as described above.

[0023] In yet another aspect, a system includes a plurality of similar gas sensors, each of the plurality of similar gas sensors including a sensing component and an electronic circuit operable with the sensing component. The electronic circuit is configured to interrogate each of the plurality of similar gas sensors in a first mode by periodically applying an electrical signal to the sensor's sensing component, measure a sensor response to the electrical signal indicative of a sensitivity for each of the plurality of similar gas sensors each time the electrical signal is applied to its sensing component, and analyze the sensor response to the periodically applied electrical signal based on baseline responses of the plurality of similar gas sensors to the periodically applied electrical signal determined over time. The electronic circuit of each of the plurality of similar sensors can be further configured to determine whether to enter a second mode, different from the first mode, in analyzing the sensor response to the periodically applied electrical signal, e.g., based on a comparison of the sensor response to the baseline responses of the plurality of similar gas sensors in the first mode. This system can be further characterized as described above.

[0024] The present devices, systems, and methods, together with their attributes and attendant advantages, will be best appreciated and understood in consideration of the following detailed description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0025] [Figure 1A] FIG. 1A is a schematic diagram of one embodiment of an electrochemical sensor herein. [Figure 1B] FIG. 1B is a schematic circuit diagram of one embodiment of the sensor herein. [Figure 1C] FIG. 1C shows a typical response to an electronic interrogation of an electrochemical gas sensor. [Figure 1D] FIG. 1D shows the response of FIG. 1C on an enlarged scale. [Figure 2] FIG. 2 shows the change in sensor response (maximum peak (current) value or MPV) to electronic interrogation over time after initial calibration. [Figure 3]FIG. 3 shows the change in sensor response (MPV) to electronic interrogation over time for multiple sensors after initial calibration. [Figure 4] FIG. 4 shows the change in sensor response (shown as the difference between the change in MPV and the average change in MPV) to electronic interrogation over time for multiple sensors after initial calibration. [Figure 5] FIG. 5 shows the change in sensor response (MPV) to electronic interrogation over time for a single sensor after initial calibration, briefly falling below the −3 standard deviation threshold and then recovering. [Figure 6] FIG. 6 shows the change in sensor response (described as the difference between the change in MPV and the average change in MPV) to electronic interrogation over time for several sensors after initial calibration, with the output of one of the sensors changing differently than the others, but still within a nominal range. [Figure 7] FIG. 7 illustrates an exemplary embodiment of a system for data communication, processing, and analysis for sensor data from one or more facilities or locations. DETAILED DESCRIPTION OF THE INVENTION

[0026] Detailed Description It will be readily understood that the components of the embodiments, as generally described and illustrated in the Figures herein, may be arranged and designed in a wide variety of different configurations in addition to the exemplary embodiments described. Thus, the following more detailed description of the exemplary embodiments, as illustrated in the Figures, is not intended to limit the scope of the embodiments as claimed, but is merely illustrative of the exemplary embodiments.

[0027] References herein to "one embodiment" or "one embodiment" (or the like) mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment. Thus, appearances of the phrase "in one embodiment" or "in one embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment.

[0028] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to provide a thorough understanding of the embodiments. However, one skilled in the art will understand that various embodiments can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations have not been shown or described in detail to avoid obscuration.

[0029] As used in this specification and the appended claims, the singular forms a, an, and the include plural references unless the context clearly dictates otherwise. Thus, for example, a reference to a "processor" includes a plurality of such processors and equivalents thereof known to those skilled in the art, and a reference to "the processor" is a reference to one or more such processors and equivalents known to those skilled in the art. The recitation of ranges of values ​​herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise stated herein, each separate value and intermediate range is incorporated herein as if individually set forth herein. All methods described herein may be performed in any suitable order unless otherwise indicated herein or otherwise expressly contraindicated by the context.

[0030] As used herein, the terms "electronic circuit," "electronic circuit," or "circuit" include, but are not limited to, hardware, firmware, software, or a combination of each for performing a function or operation. For example, based on desired functionality or needs, a circuit may include a software-controlled microprocessor, discrete logic such as an application-specific integrated circuit (ASIC), or other programmed logic device. A circuit may also be fully embodied as software. As used herein, "circuit" is considered synonymous with "logic." As used herein, the term "logic" includes, but is not limited to, hardware, firmware, software, or a combination of each for performing a function or operation or causing a function or operation from other components. For example, based on desired functionality or needs, logic may include a software-controlled microprocessor, discrete logic such as an application-specific integrated circuit (ASIC), or other programmed logic device. Logic may also be fully embodied as software.

[0031] As used herein, the term "processor" includes, but is not limited to, one or more of virtually any number of processor systems or stand-alone processors, such as microprocessors, microcontrollers, central processing units (CPUs), and digital signal processors (DSPs), in any combination. A processor may be associated with various other circuits that support the operation of the processor, such as random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), clocks, decoders, memory controllers, or interrupt controllers. These support circuits may be internal or external to the processor or its associated electronic packaging. The support circuits are in operative communication with the processor. The support circuits are not necessarily shown in block diagrams or other figures separately from the processor.

[0032] As used herein, the term "controller" includes, but is not limited to, any circuit or device that coordinates and controls the operation of one or more input and / or output devices. A controller may include, for example, a device having one or more processors, microprocessors, or central processing units that can be programmed to perform functions.

[0033] As used herein, the term "logic" encompasses, but is not limited to, hardware, firmware, software, or combinations thereof for performing a function or operation or causing a function or operation from another element or component. Based on a particular application or need, logic may include, for example, software-controlled microprocessors, discrete logic such as application-specific integrated circuits (ASICs), or other programmed logic devices. Logic may also be embodied entirely as software. As used herein, the term "logic" is considered synonymous with the term "circuitry."

[0034] As used herein, the term "software" includes, but is not limited to, one or more computer-readable or executable instructions that cause a computer or other electronic device to function, operate, or behave in a desired manner. The instructions may be embodied in various forms, such as a routine, algorithm, module, or program, including separate applications or code from dynamically linked libraries. Software may also be implemented in various forms, such as a standalone program, a function call, a servlet, an applet, instructions stored in memory, part of an operating system, or other type of executable instructions. Those skilled in the art will appreciate that the form of software will depend, for example, on the requirements of the desired application, the environment in which it will be executed, or the desires of the designer / programmer.

[0035] Although some embodiments herein are described in the context of electrochemical gas sensors and their electronic interrogation, the devices, systems, and methods of the present invention are applicable to any type of sensor in which diagnostic testing or electronic interrogation of a sensing component is performed.

[0036] As mentioned above, recent developments for electronic interrogation of electrochemical sensors have reduced the need for frequent calibration with test gases. In electronic interrogation, an electrical signal is applied to the sensing component of the sensor, which interacts with the target or analyte gas. For example, the electrical signal may be applied to the working electrode of an electrochemical sensor that includes an electrocatalyst that catalyzes a reduction or oxidation reaction with the analyte gas. Similarly, an electrical signal may be applied to the sensing element of a combustible gas sensor, which may or may not include a catalyst that promotes combustion of the sensed gas (e.g., by providing a reaction pathway with a lower activation energy than the reaction without the catalyst) upon heating the sensing element to an appropriate temperature.

[0037] For electrochemical gas sensors, electronic interrogation can be fairly short, for example, to minimize the total time the sensor performs offline sensor test diagnostics (i.e., between sensor electronic interrogation cycles). For example, some exemplary embodiments of electrochemical gas sensor devices, systems, and / or methods for electronic interrogation may enable an electrochemical sensor herein to return to normal (gas sensing) mode operation in less than 10 seconds, less than 5 seconds, or less than 1 second. Devices, systems, and methods for electronic interrogation of sensors not only allow an instrument containing one or more sensors to remain “online,” but also provide active, automatic sensor status monitoring as a background operation without the need for user activation. Electronic interrogation herein is performed periodically. As used herein, the term “periodically” refers to electronic interrogation that occurs from time to time or multiple times over time, but not necessarily at a fixed interval or frequency. The frequency of electronic interrogation can be constant or variable. For example, interrogating a sensor several times per hour can provide near-constant sensor life and health monitoring.

[0038] In electrochemical gas sensors, the gas to be measured typically passes through a sensor housing from the surrounding atmosphere or environment through a gas-porous or gas-permeable membrane to a first or working electrode (also called a sensing electrode) where a chemical reaction occurs. A complementary chemical reaction occurs at a second electrode, known as the counter electrode (or auxiliary electrode). Electrochemical sensors generate an analytical signal through the generation of a current that results directly from the oxidation or reduction of the analyte gas (i.e., the gas being detected) at the working electrode. A comprehensive description of electrochemical gas sensors is also provided in Cao, Z. and Stetter, JR, “The Properties and Applications of Amperometric Gas Sensors,” Electroanalysis, 4(3), 253 (1992), the disclosure of which is incorporated herein by reference.

[0039] The combination of the working and counter electrodes produces an electrical signal that is (1) related to the concentration of the analyte gas and (2) strong enough to provide a signal-to-noise ratio suitable for distinguishing between concentration levels of the analyte gas over the entire range of interest. In other words, the current flow between the working and counter electrodes should be measurably proportional to the concentration of the analyte gas over the concentration range of interest.

[0040] In addition to the working and counter electrodes, electrochemical sensors often contain a third electrode, commonly referred to as a reference electrode. The reference electrode is used to maintain the working electrode at a known voltage or potential. The reference electrode should be physically and chemically stable in the electrolyte.

[0041] The electrical connection between the working electrode and the counter electrode is maintained through an electrolyte. The electrolyte's functions include (1) efficiently carrying ionic current, (2) solubilizing the analyte gas, (3) supporting both the counter electrode and working electrode reactions, and (4) forming a stable reference potential with the reference electrode. Criteria for an electrolyte include, for example, (1) electrochemical inertness, (2) ionic conductivity, (3) chemical inertness, (4) temperature stability, (5) low cost, (6) low toxicity, (7) low flammability, and (8) appropriate viscosity.

[0042] Generally, the electrodes of an electrochemical cell provide the surfaces on which oxidation or reduction (redox) reactions occur, thereby providing the mechanism by which ionic conduction in the electrolyte solution couples with electronic conduction in the electrodes to provide a complete circuit for electrical current. The measurable current resulting from a cell reaction in an electrochemical cell is directly proportional to the extent of the reaction occurring at the electrodes. Therefore, high reaction rates are preferably maintained within the electrochemical cell. To this end, the counter and / or working electrodes of an electrochemical cell generally contain a suitable electrocatalyst on their surfaces to support the reaction rate.

[0043] As a result of electrostatic forces, the volume of solution very close to the working electrode surface adopts a highly ordered structure. This structure is important for understanding electrode processes. The volume of solution very close to the electrode surface is variously referred to as the diffusion layer, diffuse layer, and / or Helmholtz layer, or plane.

[0044] The magnitude of resistance and capacitance present in an electrochemical cell is a result of the nature and identity of the materials used in its manufacture. The resistance of an electrolyte is a result of the number and type of ions dissolved in the solvent. The capacitance of an electrode is primarily a function of the active surface area of ​​the electrocatalyst. Ideally, these quantities remain constant. However, the solution resistance present in an amperometric gas sensor utilizing an aqueous (water-based) electrolyte can change, for example, as a result of exposure to different ambient relative humidity levels. As water evaporates from the sensor, the chemical concentration of the ionic electrolyte increases. This concentration change can result in an increase or decrease in the electrolyte's resistivity, depending on the actual electrolyte used.

[0045] Furthermore, even substances that are typically considered insoluble in a particular solvent have a small, finite concentration of the substance in the solvent. For example, the concentration of metal from an electrode dissolved in the electrolyte of an electrochemical sensor is very small, but finite. This small concentration of dissolved metal is in constant flux; that is, metal atoms are constantly dissolving from the electrode and being re-plated somewhere else. The net effect of this process is to reduce the effective surface area of ​​the electrode. This has the effect of reducing the sensor capacitance over time. Both of the above effects have the net effect of changing the sensitivity of the sensor over its lifetime.

[0046] 1A shows a schematic diagram of a representative embodiment of an electrochemical sensor 10 that can be used in the devices, systems, and methods herein. The sensor 10 includes a housing 20 having a gas inlet 30 for introducing one or more target or analyte gases into the sensor 10. In the illustrated embodiment, electrolyte saturated wick materials 40a, 40b, and 40c separate the working electrode 50 from the reference electrode 70 and counter electrode 80 in the sensor 10 and / or provide ionic conduction therebetween via an electrolyte 44 in the housing 20 and absorbed within the wick materials 40a, 40b, and 40c. Electronic circuitry 100, as known in the art, is provided for, for example, maintaining a desired potential difference between the working electrode 50 and the reference electrode 70, varying or pulsing the potential difference as described herein, and processing the output signal from the sensor 10.

[0047] In the illustrated embodiment, the working electrode 50 may be formed, for example, by depositing a first layer of catalyst 54 (e.g., using catalyst deposition techniques known in the sensor art) on the diffusion membrane 52. Gases are readily transported or transferred through the diffusion membrane 52 (e.g., via diffusion), but the electrolyte 44 is not readily transported or transferred through the diffusion membrane 52. The working electrode 50 may be attached (e.g., via heat sealing) to the inner surface of the top, cap, or lid 22 of the housing 20.

[0048] The electronic circuit 100 may include a processor or controller system 102 including, for example, one or more processors or microprocessors for controlling various aspects of the operation of the sensor 10. A memory system 104 may be disposed in operative or communicative connection with the processor system 102 and may store software for controlling the sensor 10 and / or analyzing its output, as described herein. A user interface system (e.g., including a display, speaker, etc.) may also be disposed in operative or communicative connection with the processor system 102. A communication system 108, such as a transceiver, may be disposed in operative or communicative connection with the processor system 102 for wired and / or wireless communication. A power source 110 (e.g., a battery system) may provide power to the electronic circuit 100.

[0049] FIG. 1B shows a schematic diagram of an embodiment of a portion or part of an electronic or control circuit 100 used in some studies of the present sensors. The portion of the electronic circuit 100 shown in FIG. 1B is also referred to as a potentiostatic circuit. In a three-electrode sensor such as that shown in FIG. 1A, a predetermined potential difference or voltage is maintained between the reference electrode 70 and the sensing or working electrode 50 to control the electrochemical reaction and provide an output signal proportional to the current generated by the sensor. As described above, the working electrode 50 responds to the analyte or target gas by oxidizing or reducing the gas. The redox reaction generates a current proportional to the gas concentration. The current is supplied to the sensor 10 via the counter electrode 80. A redox reaction opposite to that at the working electrode occurs at the counter electrode 80, completing a circuit with the working electrode 50. The potential of the counter electrode 80 is allowed to float. When a gas is detected, the cell current rises and the counter electrode 80 polarizes relative to the reference electrode 70. The potential of the counter electrode 80 is not important as long as the circuit provides sufficient voltage and current to maintain the correct potential of the working electrode 50 .

[0050] For example, as described in U.S. Patent Application Publication No. 2017 / 0219515, in some exemplary embodiments, the measurement circuit of electrical / electronic circuit 100 includes a single-stage operational amplifier, i.e., op-amp IC1. The sensor current is reflected by gain resistor 120 (which has a resistance of 5 kΩ in the illustrated embodiment) to generate an output voltage. Load resistor 122 (which has a resistance of 56 Ω in the illustrated embodiment) may be selected, for example, via a balance between the fastest response time and the best signal-to-noise ratio.

[0051] Control op-amp IC2 provides potentiostatic control and provides current to counter electrode 80 to balance the current required by working electrode 50. The inverting input to IC2 is connected to the reference electrode, but no significant current flows from the reference electrode.

[0052] During electronic interrogation of an electrochemical gas sensor herein, such as sensor 10, a non-faradaic current can be induced (e.g., via application of energy to the working electrode 50). For example, an electrical signal can be applied to the working electrode 50 to generate a step change in potential that generates a non-faradaic current. The generated non-faradaic current, as a result of charging of the electrodes, can be used to monitor the operational state, functionality, or health status of the sensor. However, as described above, the sensor is then returned to its normal bias potential or potential range for normal operation in sensing a target or analyte gas. The process of returning the sensor to its operating bias or operating potential difference (which may be zero) generates a current peak (charge accumulation) in the opposite direction. The current peak generated upon returning to the operating potential difference can take many seconds to dissipate.

[0053] Information regarding the health, operating state, or operating status of the sensor may be obtained from, for example, (i) maximum peak value (MPV), which is the maximum current observed upon application of a potential pulse; (ii) area under the curve (AUC), which is the integrated current response of the working electrode after application of the potential pulse (which corresponds to the charging response of the sensor); (iii) minimum peak value (mPV), which is the minimum current obtained upon removal or reversal of the potential pulse. This is typically obtained as the difference between the current observed immediately before and immediately after removal or reversal of the potential pulse and may also be tabulated and used as the difference between the minimum current and the baseline; (iv) peak-to-peak value (PP), which is the algebraic difference between the maximum and minimum of the observed current; (v) reversal area under the curve (rAUC), or more precisely, the inverse area under the curve, which is the charging current obtained by integrating the current response after removal or reversal of the potential pulse; and (vi) the response to a measured electronic query in the form of a change in baseline or baseline output and a function thereof (e.g., a product, ratio, and / or more complex function of one, two, or more such parameters). The operating conditions of the sensing component (e.g., the working electrode of an electrochemical gas sensor, or the sensing element of a combustible gas sensor) and the sensor / sensor device are typically determined by relating such and / or other parameters to changes in the sensor's sensitivity, which refers to the ratio between the output signal (e.g., current) and the measured physical quantity (e.g., concentration of the analyte or target gas).

[0054] Measuring / analyzing a single data point or multiple data points over a short period of time provides a response / current versus time curve for a representative electrochemical gas sensor for hydrogen sulfide or HS, as shown, for example, in FIGS. 1C and 1D. Rapid discharge of the relatively large current peaks that occur when inducing a non-faradaic current in sensor 10 (or another sensor herein) and / or returning sensor 10 (or another sensor herein) to its operating potential difference can also be achieved through active control of the sensor electronics or electronic circuit 100 (e.g., by lowering the load resistance of electronic circuit 100 between working electrode 50 and the point at which the output / response is measured after the test potential difference is applied). In some embodiments, the load resistance between working electrode 50 and the output of operational amplifier IC1 is lowered to a low value. Subsequently, the load resistance between working electrode 50 and the output of operational amplifier IC1 is restored to its normal resistance or operating load resistance (or within the operating range of the load resistance) after the charge has substantially or completely dissipated.

[0055] In some embodiments, load resistor 122 (see FIG. 1B) is bypassed to reduce the load resistance between working electrode 50 and the inverting terminal of operational amplifier IC1. Bypass circuit 124 may be provided, for example, to bypass load resistor 122. In some embodiments, a field effect transistor (FET) 126 was used as a switch in bypass circuit 124 to controllably bypass or short around load resistor 122. In some embodiments, a metal oxide semiconductor FET or MOSFET was used.

[0056] 1C and 1D show the output of a representative sensor 10 including a working electrode 50 designed to detect hydrogen sulfide or HS. In the embodiment studied in FIGS. 1C and 1D, the working electrode 50 was formed by depositing an iridium catalyst on a diffusion membrane, the reference electrode 70 was formed by depositing an iridium catalyst on a diffusion membrane, and the counter electrode 80 was formed by depositing an iridium catalyst on a diffusion membrane. The bias potential or working potential difference of the sensor was 0 mV. As illustrated in FIG. 1C, an electronic interrogation procedure is initiated at point A. After 0.5 seconds (represented by point B), a test potential difference is applied. In the illustrated study, a test potential of +10 mV was applied. The maximum peak value (MPV) of the output was recorded 1 / 16 seconds after application of the test potential, as represented by point C. At that point, the potential was also returned to the 0 mV working potential difference. Upon bypassing the load resistor 122, the FET 126 was activated approximately simultaneously with the return of the potential to the operating potential difference. The significantly lowered load resistance resulted in a large negative current spike (which, in normal operating mode, would result in a very negative gas ppm reading). However, the rapid discharge that occurs upon bypassing the load resistor 122 returns the sensor output to baseline in a very short time (i.e., less than one second). To better illustrate this result, Figure 1D is scaled. However, if the load resistor 122 were not bypassed, it would take several seconds for the output to return to the baseline output. As shown in Figure 1C, when the FET 126 is deactivated, as represented by point D, and the 56 Ω load resistor 122 is restored back into the circuit in approximately 0.95 seconds, the output current falls below a value identified by the end user. This value is typically in the range of approximately 0 to ±2 ppm of the target gas.

[0057] Information regarding the health or state of the sensor may be obtained, for example, by applying an electrical signal in the form of a very small and / or short-duration electrode potential change and measuring / analyzing a single data point or multiple data points over a short time span in the resulting response / current curve, using the above-mentioned maximum peak (current) value (MPV) and / or another parameter. In some exemplary embodiments herein, the MPV is used to characterize the sensing element / working electrode of an electrochemical sensor. As described above, the rapid discharge of the relatively large current peaks that occur when inducing a non-faradaic current in sensor 10 (or another electrochemical sensor herein) and / or returning sensor 10 (or another sensor herein) to its working potential difference can be achieved through active control of the sensor electronics / electronic circuitry 100 (e.g., by reducing the load resistance of electronic circuitry 100 between the working electrode 50 and the point at which the output / response is measured after the test potential difference is applied). In some embodiments, the load resistance between the working electrode 50 and the output of operational amplifier IC1 is reduced to a low value. The load resistance between the working electrode 50 and the output of the operational amplifier IC1 is then restored to its normal resistance or operating load resistance (or within the operating range of the load resistance) after the charge has substantially or completely dissipated.

[0058] For example, fluctuations in the sensitivity of electrochemical sensors as a result of moisture loss or gain occur gradually, but generally in a predictable manner as the average relative humidity changes slowly. Sensor response to gas-free electronic interrogation, as described above, similarly changes. Electronic interrogation can be used to track and correct for sensitivity changes, as described, for example, in U.S. Patent Nos. 7,413,645, 7,959,777, 9,784,755, and 9,528,957, and U.S. Patent Application Publication Nos. 2013 / 0186777 and 2017 / 0219515. As described above, potential pulses are typically applied to the sensor's sensing component, and the resulting response is recorded, for example, in the form of a maximum peak (current) value and / or one or more other parameters. These responses can be compared to values ​​obtained during previous gas test / pulse cycles. Changes from calibration correlate with changes in operating conditions / sensor sensitivity. In this way, the health of the sensor at the time of interrogation is assessed. The sensitivity can then be adjusted to compensate for such changes. While such a method provides a real-time status of the sensor's health state at the time of interrogation, it does not address future sensor performance.

[0059] In some embodiments of the devices, systems, and methods herein, multiple consecutive interrogation events are performed in a first mode or first interrogation mode, for example, to determine whether the sensor response to the electronic interrogation is outside of a baseline operating range. For example, changes in the value of one or more variables based on or determined from one or more parameters, such as MPV, AUC, and / or other parameters, may be used to evaluate if the sensor is in need of further / altered analysis and / or maintenance. If, for example, the sensor response to the interrogation is outside of baseline, normal, or expected variation (e.g., expected variation as a result of normal, slowly changing relative humidity), the sensor may be identified or flagged as requiring attention.

[0060] In some embodiments herein, a second mode, second interrogation mode, or observation mode is entered when the sensor exhibits a response to the electronic interrogation that is outside a response baseline. In the second mode, analysis of the sensor response to the electronic interrogation differs from the first mode. In the second mode, the sampling rate of one or more parameters may be altered and / or the identity of one or more measured parameters may be changed. In some embodiments, if the sensor response to the electronic interrogation is stable or stabilized, a determination is made over one or more periods from the response measured in the second mode to periodic electronic interrogation (i.e., multiple electronic interrogations over time). For example, it may be determined over one or more periods in the second mode whether the sensor response is approaching an average rate of change within a predetermined threshold over one or more periods in the second mode or whether it remains within a predetermined or defined response range over one or more periods in the second mode. In some embodiments, the rate of change of the measurement variable (based on or derived from one or more parameters) can be determined over one or more time periods in the second mode, for example, to determine whether the sensor response is stabilized. A determination regarding sensor response stability (e.g., determined from the magnitude / direction of the rate of change over one or more time periods in the second mode) can be used to determine, for example, whether sensor settings should be changed (e.g., changing the baseline range of response, changing the sensitivity correction, etc.), whether the sensor needs to be recalibrated, or whether the sensor needs to be replaced. In the devices, systems, and methods described herein, the health or operating state (i.e., sensitivity) of the sensor is not only measured upon electronic interrogation, but its future health state is estimated using a set of health measurements (i.e., measured responses to electronic interrogation).

[0061] The baseline range of sensor response to electronic interrogation can be derived in several ways. A simple method for determining the baseline range of response is to track the sensor response over time and determine the baseline or normal variation. Limits (e.g., upper and lower thresholds) can then be set to identify or flag deviations in sensor operation. Such limits can be redetermined over time, for example, as additional electronic interrogations are performed. The baseline limits or thresholds, and whether such baseline limits are exceeded (thereby triggering entry into the second mode), can be determined, for example, via software stored in memory system 104 and executable by processor system 102. Figure 2 shows an example plot of the change in MPV value from the initial calibration point (at the time of manufacture) over 80 days.

[0062] In FIG. 2, the sensor exhibiting baseline behavior is labeled sensor 10a(i). In the results of FIG. 2, the average over 80 days is 26 counts, with a standard deviation of 107 counts. Limits or thresholds can be set, for example, using a multiple of the standard deviation (e.g., ±1 to ±3 sigma). In the illustrated embodiment, limits were set using ±3 times the standard deviation, capturing 99.7% of the baseline distribution. Such limits (upper and lower thresholds) are shown by the upper and lower dashed traces in FIG. 2. In the first mode described above, delta MPV is tracked over time and compared to baseline delta MPV values ​​(upper and lower thresholds of the baseline delta MPV value). Once the delta MPV moves beyond one of these limits, the system can enter, for example, a second or observation mode, in which analysis of the electronic query responses differs from that in the first mode. As described above, the rate of change of delta MPV may be tracked over one or more time periods in the second mode to determine whether the sensor response to the electronic interrogation has stabilized. Thus, in some embodiments of the second mode, the electronic interrogation continues as described above, and although the delta MPV is still tracked, the rate of change of delta MPV (dΔMPV / dt) is tracked as well.

[0063] Two representative examples of tracking the rate of change of delta MPV are shown in FIG. 2. The data trace for sensor 10a(ii) shows that the sensor experienced a gradual change in MPV value. Once the delta MPV exceeds the -3 sigma value / limit, the rate of change is monitored in the second operating mode as described above. Additionally, a warning or notification may (but is not required) be provided to the user to alert them that the sensor has entered the second mode. However, the user is not required to take any action at that time. Providing the second or observation mode described herein may provide a significant advantage because it reduces the amount of user interaction required compared to currently available sensors by reducing unnecessary two-way maintenance. Depending on the control software stored in the sensor's memory system 104, the sensor can, for example, modify compensation, increase the frequency of pulse / electronic interrogation tests, measure one or more additional parameters, and change the range of the baseline sensor response in the second mode. Such operations may be automated or may not require user intervention.

[0064] For sensors whose response to electronic interrogation is found to stabilize in the second mode (e.g., via electronic or electrical circuitry 100), the response may stabilize within the original range of the baseline response, or within another range of the baseline response, or within an offset range of the baseline response. One or more limits or thresholds for acceptable / baseline response may be defined for the sensor. If the sensor stabilizes in a response range that exceeds such limits or thresholds, the sensor may be flagged for service or replacement, for example. For sensor 10a(ii), the rate of change stabilizes, and the system predicts that the future state of sensor 10a(ii) will be stable within a new acceptable baseline range, although offset from the original range or baseline response. The system may, for example, trigger a "recalibrate sensor" display or warning and / or reset the system to the new state. In the case of a "new" calibration, for example, the sensor may determine a delta MPV from a new "anchor" value determined during the new calibration. The sensor may also (alternatively or additionally) continue to determine the delta MPV from a manufacturing calibration.

[0065] Meanwhile, the data trace for sensor 10a(iii) indicates a catastrophic failure of sensor 10a(iii). Again, if the delta MPV exceeds the -3 sigma lower limit, the rate of change can be monitored, for example, in a second mode over one or more time periods to determine whether the sensor response to electronic interrogation stabilizes. In the case of sensor 10a(iii), the sensor response (in this example, the delta MPV) continues to change rapidly, and the system predicts that sensor 10a(iii) will rapidly move from its useful state for gas detection. The system can trigger, for example, a "replace sensor" alert. After making such a determination, quantification can be performed, and an alert can be provided to remove the sensor from operation permanently or for a period of time (e.g., 24 hours or several days) if repair is possible. If the out-of-service period is unduly dangerous or burdensome, the sensor can be replaced during that period.

[0066] The range of "group" criteria for response to an electronic query can also be determined using, for example, data distribution across a population of sensors (e.g., multiple similar sensors) that may share at least one common characteristic other than being similar sensors. As used herein, the term "similar" refers to sensors manufactured in a similar or identical manner. Generally, such sensors are manufactured to sense the same analyte and contain sensing components manufactured in the same manner. For example, similar electrochemical gas sensors for a particular gas analyte may include a working electrode manufactured in a similar manner and may contain the same electrolyte. The counter electrode, reference electrode, and / or electronic circuitry of such sensors may also be manufactured in a similar or identical manner. Such electrochemical gas sensors may be, for example, two- or three-electrode sensors known in the art. Similar combustible gas sensors may include, for example, a sensing element, a compensating element, and / or an electronic circuitry manufactured in a similar or identical manner.

[0067] In terms of common characteristics (other than being similar sensors), a population of sensors may share, for example, the same local environment and / or a common range of manufacturing dates and times. Such sensors may be units all used in the same location for a particular customer, or all units used in a larger region (e.g., a city or county). Distributions may also be based, for example, on sensor manufacturing date codes and may cover global and / or localized populations. Groups and subgroups of similar sensors may be established based on different shared or common characteristics. Results from each unit may be compiled, and the distribution for the entire population may be used as a reference data set.

[0068] Figure 3 shows a representative example of data from 15 sensors in the same local environment. As described above, the change in MPV values ​​from the initial calibration point is plotted for all sensors over 80 days. The average value over 80 days was 5 counts, with a standard deviation of 117 counts. In the representative example of Figure 3, group limits or thresholds can be established, for example, using multiples of sigma. In the illustrated embodiment, upper and lower group thresholds were established using ±3 times the standard deviation to capture 99.7% of the reference distribution. Group limits can be determined, for example, via a processor system external to the multiple similar sensors that communicates with and receives data / information from each of the multiple similar sensors. The determined group limits can be transmitted, for example, from the external processing system to each of the multiple similar sensors. Such group limits are indicated by the upper and lower dashed lines in Figure 3. When the measured delta MPV for a particular sensor moves beyond these limits, the sensor system can enter a second or observation mode. As mentioned above, in some embodiments, the rate of change of delta MPV for a sensor in the second mode may be tracked to determine whether the sensor response stabilizes. Similar to Figure 2, two examples are shown in Figure 3: a sensor step change (sensor 10a(ii)) and a catastrophic sensor failure (sensor 10a(iii)). Actions for such individual sensors (e.g., adjusting baseline thresholds or initiating notifications / alerts, such as "recalibration alert" and "replace sensor" alerts) may be the same as those described above in connection with the single sensor example of Figure 2.

[0069] Referring again to Figure 3, it is clear that the local population of sensors studied responds in a similar manner to daily changes in the local environment. This result suggests an additional step: using local population data to compare each sensor's daily delta MPV value to the daily average delta MPV for all sensors in that local population. In this way, baseline behavior for the population is normalized for each interrogation event, and deviations from baseline behavior become more apparent. Figure 4 illustrates this approach. Over 80 days, the average is 0 counts, but the standard deviation is only 55 counts. Again, ±3 times the standard deviation can be used to set group limits, capturing 99.7% of the baseline distribution. These are shown by the dotted lines in Figure 4. This data processing removes some of the daily noise in the delta MPV values ​​and allows the two deviating cases to be easily distinguished from the other sensors.

[0070] Some sensors may exhibit more inherent noise than the general population. A sensor flagged by the population processing described in connection with FIG. 3 (i.e., comparing the sensor response to one or more electronic queries against a group limit or threshold determined for a population / multiple similar sensors) still performs above baseline when compared to its own history (i.e., comparing the sensor response to one or more electronic queries against an individual limit or threshold determined for the individual sensor). In other cases, the processing described in connection with FIG. 3 can be combined with the single-sensor processing described in connection with FIG. 2. In the representative example of FIG. 4, sensor 10a(iv) exhibits several instances of falling below the -3 standard deviation / threshold line for the group / multiple similar sensors being monitored. Sensor 10a(iv) may be identified as flagged for, for example, a single treatment or evaluation for follow-up. FIG. 5 illustrates single-sensor processing (e.g., as described in connection with FIG. 2 above) for sensor 10a(iv). As shown in FIG. 5, sensor 10a(iv) temporarily falls below the individual sensor's -3 standard deviation limit but then recovers. By combining both the group, population or distribution treatments described herein and the individual sensor treatments, a more comprehensive assessment can be obtained and sensor 10a(iv), for example, can be deemed to be functioning properly.

[0071] For example, when assessing trends for a population of similar sensors that share at least one common characteristic (i.e., a common characteristic other than being similar sensors, e.g., geographic location, range of manufacturing dates, etc.), data analysis other than determining whether measurements are outside of a normative range may be performed. For example, while a particular sensor should be stabilized or follow a certain trend (based on data from the sensor population), it may be expected that the particular sensor may exhibit a different output than its peers or other sensors in the monitored population. Such differences may be indicated in ways other than, for example, the output of a particular value / parameter (e.g., MPV or delta MPV) outside a threshold range (e.g., outside of + / - 3 standard deviations). For example, the magnitude of the response, the magnitude of the rate of change, and / or the direction of change of each sensor relative to its peers may be determined / analyzed. As shown in FIG. 6, sensor 10a(v) exhibits a rate of change in delta MPV that is opposite to the other sensors in the surveyed population. A sensor 10a(v) may be identified or flagged and placed into a second or observation mode for further / alternative analysis and / or evaluation based on such trends that differs from its peers, for example, even if the delta MPV behavior is within the norm for the population of sensors and / or for the individual sensor 10a(v).

[0072] In some embodiments, for example, if it is determined in the second mode that a particular sensor should be recalibrated and / or its baseline response range should be offset by at least a defined or predetermined amount from the baseline range of the population / plurality of similar sensors of which the particular sensor is a member, it may be determined, for example, that the particular sensor should not be tracked as a member of the population / plurality of similar sensors. If the particular sensor stabilizes within or is slightly offset from the baseline range of the population / plurality of similar sensors, it may be determined, for example, that the particular sensor should continue to be tracked as a member of the population / plurality of similar sensors, and its response may continue to be considered in determining the baseline threshold for the population / group of multiple similar sensors.

[0073] When monitoring a population / plurality of similar sensors, a sensor response or response trend that differs from other sensors in the population / plurality of similar sensors or other monitored populations / plurality of similar sensors may not indicate that the sensor in question is malfunctioning, but may indicate that the sensor should not be a member of the monitored population / plurality of similar sensors. Such a different response may result, for example, from a different microenvironment at a particular location. For example, a sensor in a monitored population / plurality of similar sensors that exhibits a different response / trend may be located within a structure at a particular location, while other sensors in the population / plural of similar sensors may be located outside a door. Similarly, a sensor in a monitored population / plural of similar sensors that exhibits a different response / trend may be located in direct sunlight, while other sensors in the population / plural of similar sensors are not. Thus, a sensor response that differs from the responses of its peers in the population / plural of similar sensors may trigger an investigation into whether the sensor is properly included in the population / plural of similar sensors. For example, it may be determined that the sensor under investigation should be monitored only individually or within another population / plural of similar sensors.

[0074] In addition to providing further information / guidance in analyzing one or more sensor responses, tracking the responses of a population / multiple similar sensors to periodic electronic interrogations may provide information regarding, for example, systematic problems with the sensors of the population / multiple similar sensors. Such sensors may have been manufactured, for example, within a determined date / time or manufacturing code range. A particular defect (e.g., a defect in electrolyte composition) may not be discovered at the time of manufacture, but may result in an abnormal response to a subsequent electronic interrogation. Tracking such multiple similar sensor responses to electronic interrogations may result in the detection of systematic problems with the sensors, for example, even before such defects become otherwise apparent.

[0075] Changes in the maximum peak value and / or one or more other parameters from the time of sensor manufacture (and / or from other starting or anchor points, such as the next calibration) to later in the sensor's life can be analyzed to determine, for example, the type of environmental conditions (e.g., low humidity or dry conditions) experienced by the sensor during that historical period. Based on such historical data, one or more parameters of sensor operation can be altered. Software algorithms stored in memory and executable by one or more processors can, for example, apply different temperature compensation. An algorithm can, for example, apply different sensitivity compensation based on such historical data. Algorithms herein (based on such historical data) can be used, for example, to alter the response range of a baseline based on such historical data.

[0076] Data from sensors that are not like sensors, or from sensors that have characteristics that are significantly different from one or more sensors being monitored / analyzed, can also be used to determine the operational state of sensors in the devices, systems, and methods herein. Such sensors that are not like sensors can be, for example, sensors for analytes other than the sensor whose operational state is being determined. Such sensors that are not like sensors can be, for example, sensors of a different type (e.g., a combustible gas sensor when the like sensor is an electrochemical gas sensor).

[0077] Additionally, sensors for environmental conditions, such as pressure sensors, humidity sensors, altitude sensors, or altimeters, may also or alternatively be used to determine operating conditions. Data from temperature and / or humidity sensors may be used, for example, in determining appropriate reference ranges for measured parameters (e.g., delta MPV, as described in the exemplary embodiments herein). Sensor placement in cool, dry locations may have different setpoints than in warm, humid locations. Altitude may be related, for example, to oxygen concentrations, which affect the output of oxygen sensors and combustible gas sensors. At high altitudes, oxygen concentrations are lower (fewer oxygen molecules per unit volume) than at sea level. Below sea level, for example, in underground mines, the environment may be oxygen-rich.

[0078] For example, when the operational state of one or more combustible gas sensors is tracked under the methods herein, an oxygen sensor can be used to determine whether the combustible gas sensor is / are operating under oxygen-deficient or oxygen-excessive conditions over a particular period of time. Such an oxygen sensor can be, for example, an electrochemical gas sensor. Similarly, sensors for inhibitors and / or poisons of combustible gas sensors (e.g., sulfur-containing compounds, halogens, silicon-containing compounds, etc.) can be detected by, for example, electrochemical sensors and / or other sensors.

[0079] When the operational status of one or more electrochemical gas sensors is tracked under the methods herein, a combustible gas sensor or other sensor can be used, for example, to detect interfering gases with the electrochemical gas sensor. Alcohols, for example, can be detected via a combustible gas sensor. For example, speciation, such as that disclosed in U.S. Pat. No. 10,234,412, the disclosure of which is incorporated herein by reference, can be used to detect alcohol species. Alcohols can affect certain electrochemical gas sensors, such as carbon monoxide or CO sensors. Even a slight increase in the combustible gas sensor output can eventually be associated with an abnormal output from an electrochemical gas sensor for a CO sensor, or with such a sensor going offline. Alkenes can also be detected via a combustible gas sensor. Alkenes are similarly interferents with electrochemical gas sensors for CO. Data from one or more combustible gas sensors can be used to determine whether an alkene is present that is causing a response in one or more CO sensors.

[0080] History or time spans of data from one or more gas sensors, pressure sensors, humidity sensors, temperature sensors, etc. may be analyzed to determine how such data history may affect the performance of one or more sensors monitored under the methods herein. Location data (e.g., from GPS or other systems) and the location of a monitored sensor or sensors within a facility may be correlated with, for example, gas test data, anomalies, alarms, upscale measurements, downscale measurements, etc. Determination and / or analysis of non-standard conditions or events may be associated with the output of one or more sensors monitored.

[0081] Various types of gas sensors may include one or more filters, for example, to limit or prevent contact or exposure of the gas sensing element to inhibitors, poisons, interferents, etc. Changes in the transport properties of such filters due to exposure to such inhibitors, poisons, interferents, etc. can affect the sensor response. Sensors sensitive to inhibitors, poisons, interferents, etc. of a sensor or sensors monitored using the methodology herein may be used, for example, in interpreting trends in the output of such sensors. Similarly, such sensors sensitive to inhibitors, poisons, interferents, etc. may be used to monitor or track the operational status of filters for one or more sensors monitored using the methodology herein.

[0082] FIG. 7 illustrates a representative embodiment of a system for collecting, communicating, and analyzing data from one or more sensors, which may be located at a single facility or distributed across multiple facilities, for example. In some embodiments herein, facility 200a (e.g., an oil refinery, an offshore drilling rig, a manufacturing facility, an industrial chemical plant, etc.) includes one or more sensors 10a(i)-10a(vii) of the present specification, while one or more other facilities, represented by facility 200b, include one or more other sensors 10b(i)-10b(vii) of the present specification. While seven sensors are shown in each of facilities 200a and 200b, facilities may include fewer or more sensors. Some facilities may include, for example, 100 or more sensors. The operation of the system components of facility 200b (and / or other facilities) with respect to data collection, communication, and / or processing is very similar to the components of facility 200a. Accordingly, data communication and / or processing in the systems herein is primarily described below with reference to facility 200a.

[0083] As described above, each sensor 10a(i) herein includes a communication system (e.g., a transceiver), which may be wired or wireless. Data from sensors 10a(i)-10a(vii) can be communicated directly to, for example, a remote processing system 500, which is described further below. Alternatively, data from sensors 10a(i)-10a(vii) can be transmitted to remote system 500 via local system 250a. In some embodiments, data can be communicated from sensors 10a(i)-10a(vii) to local system 250a via local network 220a, including, for example, a 4-20 mA transmission system, an Ethernet-based network, and / or a wireless network known in the art. Data can be collected and transmitted to remote system 500 in real time, for example, for analysis. Data transfer can occur continuously or discontinuously / batch-wise. For example, raw or processed sensor data may be transmitted by local system 250a to remote system 500 for processing (or further processing) and / or analysis by remote system 500. Remote system 500 may receive data from several local systems 250a, 250b, etc. (i.e., from several different facilities). Local system 250a may include, for example, processing system 252a (e.g., including one or more processors or microprocessors), an associated memory system 254a in communication with processor system 252a, and a communication system 256a in communication with processor system 252a. Processing / analysis may be distributed, for example, among the sensor's processing system, the local system, and the remote system 500 (e.g., in determining upper and lower threshold values ​​for a group). Transmission from sensors 10a(i) to 10a(vii) and / or local system 250a to remote system 500 occurs over network 400, which may include wired and / or wireless communication protocols (e.g., data over cellular transmission protocols, internet transmission protocols, telephone line protocols, etc.).

[0084] The remote system 500 may include, for example, a central processing system or a distributed processing system, which may include, for example, one or more computers, servers, or server systems 510. The computer, server, or server system 510 may include, for example, one or more processors or processor systems 512 communicatively coupled to one or more memories or memory systems 514, as known in the computer arts. The memory systems 514 may include one or more databases 516 stored therein. The local systems 250a, 250b, etc. may communicate with the communication system or systems 520 of the remote system 500 via one or more wired or wireless communication channels 400 (e.g., landline telephone, wireless telephone, broadband Internet connection, and / or other communication channels), as described above. Software stored in the memory system 514, or one or more other memory systems communicatively coupled to the processor 512, may be used to process or analyze data from the local systems 250a, 250b, etc.

[0085] The foregoing description and accompanying drawings presently describe several representative embodiments. It should be understood that various modifications, additions, and alternative designs will become apparent to those skilled in the art in light of the foregoing teachings without departing from the scope of the present specification, which is set forth not by the foregoing description, but by the claims that follow. All changes and variations that come within the meaning and range of equivalency of the claims are intended to be embraced within their scope.

Claims

1. 1. A gas sensor device for use in connection with a plurality of similar gas sensor devices, comprising: Each of the plurality of similar gas sensor devices comprises: a similar sensing component for detecting a gas analyte in a gas environment; analogous electronic circuitry operatively connected to said analogous sensing component; a similar communication system operatively connected to the similar electronic circuitry; The analogous electronic circuit of each of the plurality of analogous gas sensor devices, in a first mode, (i) interrogating the analog sensing component of the analog gas sensor device by periodically applying a first mode electrical signal to the analog sensing component of the analog gas sensor device during deployment of the analog gas sensor device to detect the gas analyte; (ii) determining a sensor response to the first mode electrical signal each time the first mode electrical signal is applied to the analog sensing component of the analog gas sensor device; It is structured as follows: the analogous communication system is configured to transmit data regarding the sensor response to the periodically applied first mode electrical signal and to receive data regarding a group reference response; The gas sensor device includes: a sensing component for detecting the gas analyte in the gas environment; an electronic circuit operatively connected to the sensing component; a communication system operatively connected to the electronic circuit; In a first mode, the electronic circuit (i) during deployment of the gas sensor device to detect the gas analyte, interrogating the sensing component of the gas sensor device by periodically applying a first mode electrical signal to the sensing component; (ii) determining a sensor response to the first mode electrical signal each time the first mode electrical signal is applied to the sensing component; (iii) analyzing the sensor response of the gas sensor device to the periodically applied first mode electrical signal based on information from group reference response data determined over time from response data to the periodically applied first mode electrical signal to the analogous sensing component of each of one or more of the plurality of analogous gas sensor devices. It is structured as follows: The communication system is further configured to transmit data regarding the sensor response to the periodically applied first mode electrical signal and to receive the information regarding the group reference response. Gas sensor device.

2. 2. The gas sensor device of claim 1, wherein the electronic circuitry is further configured to analyze the sensor response of the gas sensor device to the periodically applied first mode electrical signal based on a sensor baseline response of the gas sensor device over time.

3. 3. The gas sensor apparatus of claim 2, wherein the electronic circuitry is further configured to determine whether to enter the second mode based on at least one of a comparison of the sensor response to one or more of the periodically applied first mode electrical signals with the sensor reference response and a comparison of the sensor response to one or more of the periodically applied first mode electrical signals with the group reference response.

4. 4. The gas sensor apparatus of claim 3, wherein the electronic circuitry is further configured to: periodically apply a second mode electrical signal to the sensing component in the second mode; determine at least one of a magnitude and a direction of a rate of change of the sensor response to the periodically applied second mode electrical signal; and determine whether the sensor response to the periodically applied second mode electrical signal is stable.

5. 5. The gas sensor apparatus of claim 4, wherein the electronic circuitry is further configured to analyze the sensor response to the periodically applied first mode electrical signal in the first mode to determine whether at least one of one or more threshold values ​​has been exceeded based on the sensor response determined each time the first mode electrical signal is applied to the sensing component in the first mode, when determining whether to enter the second mode.

6. 6. The gas sensor device of claim 5, wherein the electronic circuitry is further configured to return the gas sensor device to the first mode when it is determined that the sensor response to the periodically applied second mode electrical signal has stabilized in the second mode.

7. 6. The gas sensor apparatus of claim 5, wherein the electronic circuitry is further configured to change the one or more thresholds after the sensor response to the periodically applied second mode electrical signal is determined to be stable.

8. 5. The gas sensor device of claim 4, wherein the sensor response to the periodically applied first mode electrical signal and the sensor response to the periodically applied second mode electrical signal are determined without applying a test gas having a known concentration of the gas analyte or a simulant thereof to the gas sensor device.

9. 5. The gas sensor device of claim 4, wherein the gas sensor device is an electrochemical gas sensor device and the sensing component is a working electrode.

10. 10. The gas sensor apparatus of claim 9, wherein the value of the sensor response to the periodically applied first mode electrical signal is determined based on at least one defined parameter of the sensor response, and the value of the sensor response to the periodically applied second mode electrical signal is determined based on at least one defined parameter of the sensor response.

11. 11. The gas sensor apparatus of claim 10, wherein the at least one defined parameter of the sensor response to the periodically applied electrical signal in a first mode and the at least one defined parameter of the sensor response to the periodically applied electrical signal in a second mode are independently selected from the group consisting of a maximum current peak value, an area under the current curve, a minimum peak value, a peak-to-peak value, an area under the inversion curve, a baseline value, or one or more functions thereof.

12. 12. The gas sensor device of claim 11 , wherein the value of the sensor response at each of the periodically applied first mode electrical signals is a change in a value of at least one defined parameter of the sensor response measured at each of the periodically applied first mode electrical signals from a value determined during calibration of the gas sensor device.

13. a plurality of thresholds for the sensor response to the periodically applied first mode electrical signal; two of the plurality of thresholds are determined by tracking values ​​of the sensor response to the periodically applied first mode electrical signal over time and determining upper and lower baseline operating thresholds for the gas sensor apparatus; the other two of the plurality of thresholds are determined by tracking the sensor responses to the periodically applied first mode electrical signal for the plurality of similar gas sensor devices over time and determining a baseline operating group upper threshold and a group lower threshold for the plurality of similar gas sensor devices.

6. The gas sensor device according to claim 5.

14. 10. The gas sensor device of claim 1, wherein the electronic circuitry is further configured to transmit data from the gas sensor device via the communication system to a remote processor system for analysis.

15. data from a second gas sensor regarding a second gas analyte different from the gas analyte or data from a third sensor regarding an environmental condition is transmitted to the gas sensor device; 10. The gas sensor device of claim 1, further comprising an electronic circuit configured to analyze at least one of data from the second gas sensor or data from the third sensor regarding the environmental condition to determine an operating state of the gas sensor device.

16. 1. A system comprising: A plurality of similar gas sensors is provided, each of the plurality of similar gas sensors comprising a sensing component for detecting a gas analyte in a gas environment; an electronic circuit operatively connected to the sensing component; and a communication system operatively connected to the electronic circuit; The electronic circuit of each of the plurality of similar gas sensors, in a first mode, (i) interrogating the sensing component of the analog gas sensor by periodically applying a first mode electrical signal to the sensing component of the analog gas sensor during deployment of the analog gas sensor to detect the gas analyte; (ii) determining a sensor response of the analog gas sensor to the first mode electrical signal each time the first mode electrical signal is applied to the sensing component of the analog gas sensor; (iii) analyzing the sensor responses of the similar gas sensors to the periodically applied first mode electrical signal based on group reference response information determined over time from data of respective responses of one or more of the plurality of similar gas sensors to the periodically applied first mode electrical signal. It is structured as follows: the communication system is configured to transmit data regarding the sensor response to the periodically applied first mode electrical signal and to receive the information regarding the group reference response. system.

17. 17. The system of claim 16, wherein the electronic circuitry is further configured to analyze the sensor response of the similar gas sensor to the periodically applied first mode signal based on a sensor baseline response of the similar gas sensor over time.

18. A gas sensor device, a sensing component responsive to a gas analyte; an electronic circuit operatively connected to the sensing component; The electronic circuitry includes: (i) interrogating the sensing component in a first mode by periodically applying a first mode electrical signal to the sensing component to measure a sensor response to the first mode electrical signal; analyzing the sensor response to the periodically applied first mode electrical signal in the first mode to determine whether at least one of one or more thresholds has been exceeded based on the sensor response to the periodically applied first mode electrical signal; and entering a second mode if at least one of the one or more thresholds has been exceeded in the first mode; (ii) periodically applying a second mode electrical signal to the sensing component in the second mode and measuring the sensor response to the second mode electrical signal, and analyzing the sensor response to the periodically applied second mode electrical signal in the second mode differently from analyzing the sensor response to the periodically applied first mode electrical signal in the first mode to determine whether the sensor response to the periodically applied second mode electrical signal in the second mode is stable. It is configured as follows: Gas sensor device.

19. 20. The gas sensor apparatus of claim 18, wherein the electronic circuitry is further configured to return the gas sensor apparatus to the first mode when the sensor response to the periodically applied second mode electrical signal in the second mode has stabilized.

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