Systems and methods for using a variety of solid electrolyte sensors for selective, low-resolution formaldehyde detection

Abstract

The present application relates to systems and methods for using a variety of solid electrolyte sensors for selective, low resolution formaldehyde detection. A method for determining a concentration of a second target gas in the presence of a first target gas is disclosed, the method comprising: operating a first sensor under a first operating condition, wherein the first sensor is part of a sensor assembly, wherein the first sensor comprises a filter for filtering the first target gas; operating a second sensor under a second operating condition, wherein the second sensor is part of the sensor assembly; detecting at least the first target gas by the first sensor; detecting the second target gas by the second sensor; processing a signal output from the first sensor and a signal output from the second sensor; and determining a concentration of the first target gas and determining a concentration of the second target gas based on the processed output signals.

Description

[0001] This application is a divisional application of National Patent Application No. 201780097246.7, which was filed on October 26, 2017, and is entitled "System and method for using multiple solid electrolyte sensors for selective, low-resolution formaldehyde detector".

[0002] Cross-references to related applications

[0003] not applicable.

[0004] Statement regarding federally sponsored research or development

[0005] not applicable.

[0006] References to microfilm attachments

[0007] not applicable. Background Technology

[0008] When monitoring the presence of various gases, other gases (e.g., carbon monoxide (CO)) may be present that can react within the sensor. For example, the sensor electrodes may include a catalyst that catalyzes the reaction between the target gas and the interfering gas (e.g., carbon monoxide). Therefore, the presence of the interfering gas can create cross-sensitivity in the sensor, leading to the illusion that the level of the target gas present in the ambient gas is greater than its actual presence. Due to the danger posed by the presence of various target gases, the threshold level used to trigger an alarm can be relatively low, and the cross-sensitivity caused by the presence of interfering substances can be high enough to cause false alarms from the target gas sensor. Summary of the Invention

[0009] In one embodiment, a method for determining the concentration of a second target gas in the presence of a first target gas may include: operating a first sensor under first operating conditions, wherein the first sensor is part of a sensor assembly; operating a second sensor under second operating conditions, wherein the second sensor is part of a sensor assembly, and wherein the second operating conditions are different from the first operating conditions; detecting at least one target gas by the first sensor; detecting at least one target gas by the second sensor; processing a signal output from the first sensor and a signal output from the second sensor; and determining the concentration of at least one of the first target gas and the second target gas based on the processed output signal.

[0010] In one embodiment, a sensor assembly configured to detect a second target gas in the presence of a first target gas may include: a first sensor including a first operating condition; a second sensor including a second operating condition, wherein the first operating condition differs from the second operating condition; and a processor configured to receive a first output signal from the first sensor; receive a second output signal from the second sensor; process the received output signals by comparing them; and determine the concentration of at least one of the first target gas and the second target gas based on the processed output signals.

[0011] In one embodiment, a method for determining formaldehyde concentration in the presence of carbon monoxide may include: operating a first sensor under first operating conditions, wherein the first sensor is part of a sensor assembly; operating a second sensor under second operating conditions, wherein the second sensor is part of a sensor assembly, and wherein the second operating conditions are different from the first operating conditions; detecting at least one of carbon monoxide and formaldehyde using the first sensor; detecting at least one of carbon monoxide and formaldehyde using the second sensor; processing a signal output from the first sensor and a signal output from the second sensor; and determining the concentration of at least one of carbon monoxide and formaldehyde based on the processed output signal. Attached Figure Description

[0012] To gain a more complete understanding of this disclosure, reference is now made to the following brief description in conjunction with the accompanying drawings and detailed embodiments, wherein similar reference numerals denote similar parts.

[0013] Figure 1 A schematic diagram of a sensor according to an embodiment of the present disclosure is shown.

[0014] Figure 2 A sensor assembly according to an embodiment of this disclosure is shown.

[0015] Figures 3A to 3B An exploded view of the first and second sensors according to an embodiment of the present disclosure is shown. Detailed Implementation

[0016] First, it should be understood that although exemplary embodiments of one or more implementations are shown below, the disclosed systems and methods can be implemented using any number of techniques, whether currently known or not yet available. This disclosure should in no way be limited to the exemplary embodiments, drawings, and techniques shown below, but modifications can be made within the scope of the appended claims and their equivalents.

[0017] The following brief terminology definitions should apply throughout the application:

[0018] The term "comprising" means including but not limited to, and should be interpreted in the manner commonly used in the patent context;

[0019] The phrases “in one embodiment”, “according to one embodiment”, etc., generally mean that the specific feature, structure or characteristic following the phrase may be included in at least one embodiment of the invention, and may be included in more than one embodiment of the invention (importantly, such phrases do not necessarily refer to the same embodiment).

[0020] If the instruction manual describes something as "exemplary" or "example," it should be understood as referring to a non-exclusive example;

[0021] The terms “approximately” or “about,” when used with numbers, may refer to a specific number, or alternatively, a range close to that specific number as understood by those skilled in the art; and

[0022] If the specification states that a component or feature "may," "can," "should," "will," "preferably," "possibly," "usually," "optionally," "for example," "often," or "may" (or other such words) be included or have that characteristic, then that particular component or feature is not necessarily included or has that characteristic. Such components or features may be optionally included in some embodiments or may be excluded.

[0023] Implementations of this disclosure include systems and methods for detecting formaldehyde without cross-sensitivity to carbon monoxide. With the growth of the housing market, the demand for household formaldehyde detectors (for personal use) is likely to increase, as people in certain areas may suffer health damage due to exposure to low levels of formaldehyde, particularly in newly built homes (due to the presence of formaldehyde in building materials and paint). Current formaldehyde detectors often exhibit cross-sensitivity to carbon monoxide (CO), where CO may be present at higher concentrations (compared to formaldehyde levels). This cross-sensitivity can cause false alarms and hinder effective formaldehyde detection. Furthermore, currently available high-quality detectors (which may not suffer from these cross-sensitivity issues) may be prohibitively expensive.

[0024] Embodiments of this disclosure may employ two solid electrolyte sensors (SECS) operating under two different conditions. For example, the sensors may operate at two different bias potentials and / or with two different filters. The responses of these two sensors to formaldehyde exposure may differ from their responses to CO (and other cross-sensitive gases), thus isolating and detecting formaldehyde-related responses. The low cost of SECS allows for wider household use, providing users with an affordable selective formaldehyde detector. Furthermore, by comparing the outputs from the two sensors, noise in the signals can be eliminated, achieving high resolution in the detected signals. This improved resolution enables the detection of lower concentrations of formaldehyde.

[0025] It is known in the art that gas detectors use multiple sensors to provide selectivity. However, the disclosed embodiments include two sensors that operate under different conditions, which can provide additional detection benefits, as described herein. For example, a formaldehyde detector may include two different bias voltages applied to the two sensors. As another example, a formaldehyde detector may include different filters for the two sensors, which can provide improved resolution and selectivity for formaldehyde. These two examples with different operating conditions may be used individually and / or simultaneously in the same formaldehyde detector.

[0026] A dual-sensor design can be utilized by identifying the difference in response between two sensors. Sensor responses may vary due to differences in bias voltage, which can result in differences in sensitivity, response time, and noise for gases such as formaldehyde, CO, and other organic gases. The difference in response between the two sensors can be interpreted to identify one or more gases. Noise in the signal can also be eliminated to achieve selectivity and high resolution.

[0027] Now refer to Figure 1 An exemplary embodiment of sensor 100 is shown, wherein sensor 100 may include multiple layers attached to substrate 102. Substrate 102 may include an alumina ceramic material and may include one or more diffusion channels 112 extending through the thickness of the substrate, wherein diffusion channels 112 may allow gas to flow from the surrounding environment into sensor 100. In some embodiments, sensor 100 may include a first layer 104 (e.g., which may be a catalytic layer and / or an electrode layer) configured to allow gas transfer to sensor 100 and other layers of sensor 100. In some embodiments, first layer 104 may include platinum (Pt) and ionic solution materials. Although Figure 1The schematic diagram shows only one electrode layer (i.e., the catalyst layer, first layer 104), but the sensor 100 may include two or three electrodes that are coplanar with each other. In some embodiments, the first layer 104 may include between one and three electrodes, which may include a sensing (or operating) electrode, a counter electrode, and / or a reference electrode.

[0028] In some embodiments, sensor 100 may include a second layer 106 (e.g., a humidifying layer) configured to absorb any moisture within sensor 100, preventing electrolyte from third layer 108 from flooding the electrodes located within first layer 104. In some embodiments, second layer 106 may include silica (SiO2) and an ion solution material. In some embodiments, sensor 100 may include a third layer 108 (e.g., an electrolyte layer) configured to provide an electrolyte to facilitate ion conduction between electrodes. Optionally, third (electrolyte) layer 108 may also be configured to provide a reservoir of water to enable sensor operation within a certain humidity range. In some embodiments, third layer 108 may comprise a mixture of sulfuric acid (H2SO4) and / or polyvinylpyrrolidone (PVPY), wherein PVPY can be used to immobilize the sulfuric acid electrolyte.

[0029] In some embodiments, sensor 100 may include a fourth layer 110 (e.g., which may include a sealing layer) configured to seal against substrate 102 to provide an hermetically tight seal for sensor 100. The sealing layer 110 prevents air from flowing into sensor 100 except at diffusion channel 112. In some embodiments, the sealing layer 110 may include a silicone material. In some embodiments, sensor 100 may include one or more electrical contacts 120 extending out of sensor 100 to provide electrical connection to other elements of the gas detector. In some embodiments, sensor 100 may include up to three electrical contacts 120 for each of the three electrodes located within the first layer 104.

[0030] Reference Figure 2The diagram illustrates a sensor assembly 200, which may include at least a portion of a formaldehyde gas detector. The sensor assembly 200 may include at least two sensors 202 and 204 located within the sensor assembly 200. In some embodiments, sensors 202 and 204 may include electrochemical sensors. In some embodiments, a first sensor 202 may operate under a first condition, and a second sensor 204 may operate under a second condition, wherein the outputs from the first sensor 202 and / or the second sensor 204 can be adjusted by adjusting the operating conditions. In some embodiments, the sensor assembly 200 may include a power supply 212 (e.g., a battery) configured to power elements of the sensor assembly 200. In some embodiments, the sensor assembly 200 may include one or more other components, such as component 214, which may include additional sensor elements, communication elements, electrical elements, and / or any other components 214 that may be located within the sensor assembly 200.

[0031] In some implementations, the different operating conditions applied to the first sensor 202 and the second sensor 204 may include differences in bias voltage, differences in filtration conditions, and / or combinations of both. Gas concentration can be predicted by comparing the signals output from the two sensors 202 and 204 without requiring sensors 202 and 204 to reach a steady state. Additionally, any common-mode signals (e.g., transients in temperature, pressure, and / or humidity, and / or electrical interference) in the signals output from each of sensors 202 and 204 can be canceled out by comparing the signals.

[0032] Sensor assembly 200 may include a printed circuit board (PCB) 210, which may include one or more electrical connection elements configured to connect to sensors 202 and 204. In some embodiments, PCB 210 may be configured to apply one or more controls to one or more of sensors 202 and 204 (i.e., PCB 210 may control one or more operating conditions of sensors 202 and 204). For example, PCB 210 may include one or more elements configured to apply a bias voltage to one or both of sensors 202 and 204. PCB 210 may include a processor, memory, and other elements known to those skilled in the art.

[0033] In some embodiments of sensor assembly 200, first sensor 202 may include a first bias voltage, while second sensor 204 may include a second bias voltage, wherein the second bias voltage is different from the first bias voltage. When the two sensors 202 and 204 operate at different bias voltages, the relative sensitivity of the sensors to different gases can be adjusted and compared. As an example, sensors 202 and 204 may include sensors configured to detect a first gas, wherein the sensor's response to the first gas may not change with changes in bias voltage (e.g., due to diffusion limitations). However, the response of sensors 202 and 204 to other gases or a second gas can be changed by adjusting the bias voltage applied to the sensors. In some embodiments, sensitivity to other gases can be increased by increasing the bias voltage. If two different bias voltages are applied to two different sensors 202 and 204, the signals from the two sensors 202 and 204 can be compared and / or processed to determine the response caused by a gas other than the first gas (i.e., the second gas). This information can be used to determine the concentration of the second gas. Algorithms that can be used to process sensor outputs may take into account the specific type of sensor, the gas flow rate at the sensor, the effect of the bias voltage applied to the sensor, operating conditions (e.g., temperature, pressure, humidity), and other factors. Furthermore, the transient behavior of sensors 202 and 204 may differ due to different operating conditions (i.e., different bias voltages), so time dependence can be considered in algorithms that process signals from both sensors 202 and 204.

[0034] As an example, the first gas may include CO, and the second gas may include formaldehyde. The sensor assembly may be configured to detect CO and formaldehyde based on the outputs of the two sensors 202 and 204. The bias voltage applied to the two sensors may be between zero (i.e., no bias voltage) and approximately 300 mV.

[0035] In some embodiments, only one sensor may have an applied bias voltage. In some embodiments, two sensors may have applied bias voltages, wherein the applied bias voltages are different for the two sensors. In some embodiments, sensor assembly 200 may include more than two sensors (i.e., multiple sensors), wherein each of the multiple sensors may include a different bias voltage, and wherein the number of gases detectable by sensor assembly 200 may be equal to the number of sensors.

[0036] Each of two (or more) of sensors 202 and 204 may include a gas passage configured to allow gas to flow from the external environment into sensors 202 and 204 (e.g., similar to...). Figure 1(Diffusion channel 112 as described in the text). In some embodiments, the gas channels leading to sensors 202 and 204 may be separate from each other. In some embodiments, the gas channels leading to sensors 202 and 204 may be configured to provide equal airflow to each of the sensors.

[0037] In some embodiments of sensor assembly 200, sensors 202 and 204 may include different filtering elements configured to filter certain gases from the gas flow entering the sensors. For example, the first sensor 202 may include a first filter, while the second sensor 204 may include a second filter, wherein the first filter is configured to filter differently from the second filter. As another example, one of the first sensor 202 and the second sensor 204 may include a filter, while the other does not.

[0038] As an example, sensors 202 and 204 may include sensors configured to detect a first gas, and sensor assembly 200 may be configured to also detect a second gas. To perform the detection of the second gas, the first sensor 202 may include a filter configured to capture / block the second gas, while the second sensor 204 does not include a filter. Therefore, the first sensor 202 may generate a signal in response to the first gas, and the second sensor 204 may generate a signal in response to both the first and second gases.

[0039] During operation, the output of the first sensor 202 (excluding the second gas) can be compared with the output of the second sensor 204 (including the second gas) to determine the concentration of the second gas. In some embodiments, the signals generated by sensors 202 and 204 in response to the first gas may be significantly higher than the signals generated by sensors 202 and 204 in response to the second gas. In some embodiments, the first gas may typically be present at a much higher concentration than the second gas. As an example, the determined formaldehyde concentration may be about 100 times lower than the carbon monoxide concentration. As an example, the carbon monoxide to formaldehyde concentration ratio may be about 100:1. As another example, the carbon monoxide to formaldehyde concentration ratio may be about 500:1. In some embodiments, filtering the first gas into sensors 202 and 204 may be more difficult than filtering the second gas.

[0040] Algorithms used to process sensor outputs may take into account the specific type of sensor, the gas flow rate at the sensor, the effect of the bias voltage applied to the sensor, operating conditions (e.g., temperature, pressure, humidity), and other factors. Testing can be performed on a prototype sensor assembly to determine the preferred or optimal algorithm processing. Furthermore, due to different operating conditions (i.e., different filtration conditions), the transient behavior of sensors 202 and 204 may differ, so time dependence can be considered in algorithms processing signals from both sensors 202 and 204. For example, when the first sensor 202 includes a filter while the second sensor 204 does not, the gas flowing into the first sensor 202 may flow more slowly than the gas flowing into the second sensor 204.

[0041] As an example, Figures 3A to 3B A first sensor 302 and a second sensor 304 (which may be similar to sensors 202 and 204) are shown, each with different filtration conditions. The first sensor 302 and the second sensor 304 may include a bottom housing 320 and a top housing 322, wherein the top housing 322 includes an air inlet 323. The first sensor 302 and the second sensor 304 may also include a substrate 102 (e.g., as shown in the image). Figure 1 The substrate 102 includes one or more diffusion channels 112 and one or more electrical contacts 120. The bottom housing 320 may include components configured to hold the substrate 102 (and...). Figure 1 The cavity 330 (other layers described in the text). In some embodiments, the first sensor 302 and / or the second sensor 304 may include a dust filter 324 configured to prevent particulate matter from entering through the air inlet 323.

[0042] Additionally, the first sensor 302 may include a filter 326 (configurable to filter a second (target) gas) located in the airflow path from the inlet 323 to the diffusion channel 112. The filter 326 may include one or more materials (as described above) configured to filter the second gas. As an example, the filter 326 may include a sheet of glass fiber impregnated with potassium permanganate. In some embodiments, the first sensor 302 may also include a membrane 328 configured to hold the filter 326 in place so that it does not move within the sensor housings 320 and 322.

[0043] Some embodiments of this disclosure may include a method for detecting a second target gas in the presence of a first target gas. One method may include detecting at least one target gas via a first sensor of a sensor assembly, wherein the first sensor may include a first operating condition. Another method may include detecting at least one target gas via a second sensor, wherein the second sensor includes a second operating condition, and the second operating condition is different from the first operating condition. The method may include comparing and / or processing output signals from the first and second sensors to determine the concentration of at least one target gas. In some embodiments, the method may include determining the concentration of the first target gas and determining the concentration of the second target gas. In some embodiments, the method may include determining the concentration of the second target gas in the presence of the first target gas. In some embodiments, the first target gas may include CO, while the second target gas may include volatile organic compounds (VOCs). In some embodiments, the second target gas may include formaldehyde.

[0044] Various apparatuses and methods have been described herein, and exemplary embodiments or aspects may include, but are not limited to:

[0045] In a first embodiment, a method for determining the concentration of a second target gas in the presence of a first target gas may include: operating a first sensor under first operating conditions, wherein the first sensor is part of a sensor assembly; operating a second sensor under second operating conditions, wherein the second sensor is part of the sensor assembly and wherein the second operating conditions are different from the first operating conditions; detecting at least one target gas by the first sensor; detecting at least one target gas by the second sensor; processing a signal output from the first sensor and a signal output from the second sensor; and determining the concentration of at least one of the first target gas and the second target gas based on the processed output signal.

[0046] The second implementation may include the method described in the first implementation, wherein the first target gas includes carbon monoxide.

[0047] The third embodiment may include the method described in the first or second embodiment, wherein the second target gas includes volatile organic compounds.

[0048] The fourth embodiment may include the method described in any one of the first to third embodiments, wherein the second target gas includes formaldehyde.

[0049] The fifth embodiment may include the method described in any one of the first to fourth embodiments, wherein the first operating condition includes a first bias voltage and the second operating condition includes a second bias voltage.

[0050] The sixth embodiment may include the method of the fifth embodiment, wherein one of the first bias voltage and the second bias voltage includes a zero bias voltage.

[0051] The seventh embodiment may include the method described in the fifth or sixth embodiment, wherein one of the first bias voltage and the second bias voltage comprises about 300mV.

[0052] The eighth embodiment may include the method described in any one of the fifth to seventh embodiments, wherein one of the first bias voltage and the second bias voltage includes a bias voltage between about 0 mV and about 500 mV.

[0053] The ninth embodiment may include the method described in any one of the first to eighth embodiments, wherein the first operating condition includes a first filtering condition and the second operating condition includes a second filtering condition.

[0054] The tenth embodiment may include the method of the ninth embodiment, wherein one of the first sensor and the second sensor includes a filter.

[0055] In an eleventh embodiment, a sensor assembly configured to detect a second target gas in the presence of a first target gas may include: a first sensor including a first operating condition; a second sensor including a second operating condition, wherein the first operating condition is different from the second operating condition; and a processor configured to receive a first output signal from the first sensor; receive a second output signal from the second sensor; process the received output signals by comparing them; and determine the concentration of at least one of the first target gas and the second target gas based on the processed output signals.

[0056] The twelfth embodiment may include the sensor assembly described in the eleventh embodiment, wherein the processor is configured to determine the difference between two output signals.

[0057] The thirteenth embodiment may include the sensor assembly described in the eleventh or twelfth embodiment, wherein the first operating condition allows the first sensor to detect the first target gas, and wherein the second operating condition allows the second sensor to detect the first target gas in combination with the second target gas.

[0058] The fourteenth embodiment may include the sensor assembly described in any of the eleventh to thirteenth embodiments, wherein the first sensor includes a first filter, and wherein the second filter includes a second filter different from the first filter.

[0059] The fifteenth embodiment may include the sensor assembly described in any of the eleventh to fourteenth embodiments, wherein the first sensor includes a first bias voltage, and wherein the second filter includes a second bias voltage different from the first filter.

[0060] In a sixteenth embodiment, a method for determining formaldehyde concentration in the presence of carbon monoxide may include: operating a first sensor under first operating conditions, wherein the first sensor is part of a sensor assembly; operating a second sensor under second operating conditions, wherein the second sensor is part of the sensor assembly and wherein the second operating conditions are different from the first operating conditions; detecting at least one of carbon monoxide and formaldehyde using the first sensor; detecting at least one of carbon monoxide and formaldehyde using the second sensor; processing a signal output from the first sensor and a signal output from the second sensor; and determining the concentration of at least one of carbon monoxide and formaldehyde based on the processed output signal.

[0061] The seventeenth embodiment may include the method of the sixteenth embodiment, wherein processing the signal output from the first sensor and the signal output from the second sensor includes determining the difference between the two output signals.

[0062] The eighteenth embodiment may include the method described in the sixteenth or seventeenth embodiment, wherein the first operating condition includes a first filtering condition and the second operating condition includes a second filtering condition.

[0063] The nineteenth embodiment may include the method described in any one of the sixteenth to eighteenth embodiments, wherein the first operating condition includes a first bias voltage and the second operating condition includes a second bias voltage.

[0064] The twentieth embodiment may include the method described in any one of the sixteenth to nineteenth embodiments, wherein the ratio of the concentration of carbon monoxide to the concentration of formaldehyde is approximately 100:1.

[0065] Although various embodiments based on the principles disclosed herein have been shown and described above, modifications can be made by those skilled in the art without departing from the spirit and teachings of this disclosure. The embodiments described herein are representative only and not intended to be limiting. Many variations, combinations, and modifications are possible and are within the scope of this disclosure. Alternative embodiments resulting from the merging, integration, and / or omission of features of one or more embodiments are also within the scope of this disclosure. Therefore, the scope of protection is not limited by the description given above, but is defined by the following claims, which include all equivalents of the subject matter of the claims. Each claim is incorporated into the specification as further disclosure, and the claims are for one or more embodiments of the invention. Furthermore, any of the foregoing advantages and features may relate to specific embodiments, but the application of such published claims should not be limited to methods and structures that achieve any or all of the above advantages or have any or all of the above features.

[0066] Furthermore, the section headings used herein are intended to align with or provide organizational clues for the recommendations of 37 CFR 1.77. These headings should not limit or characterize one or more inventions that can be set forth in any of the claims disclosed in this disclosure. Specifically, and by way of example, although a heading may refer to “technical field,” the claims should not be limited by the language chosen under that heading to describe a so-called field. Moreover, the description of the technology in the “Background Art” section should not be construed as an admission that a particular technology is prior art to any one or more inventions of this disclosure. “Summary of the Invention” should also not be considered a limiting characterization of one or more inventions set forth in the published claims. Furthermore, any reference to the singular form “invention” in this disclosure should not be used to prove that there is only one novel point in this disclosure. Multiple inventions may be set forth according to the limitations of the multiple claims disclosed in this disclosure, and such claims accordingly define one or more inventions protected by them, as well as their equivalents. In all cases, the scope of these claims should be considered in accordance with the advantages of the claims themselves, and should not be limited by the headings set forth herein.

[0067] It should be understood that the use of broad terms such as “comprising,” “including,” and “having” provides support for narrower terms such as “consisting of,” “substantially composed of,” and “substantially constitutes.” The use of terms such as “optionally,” “may,” “possibly,” etc., for any element of an embodiment indicates that the element is not required, or alternatively, that the element is required, both alternatives being within the scope of one or more embodiments. Furthermore, references to examples are for illustrative purposes only and are not intended to be exclusive.

[0068] While several embodiments are provided in this disclosure, it should be understood that the disclosed systems and methods may be embodied in many other specific forms without departing from the spirit or scope of this disclosure. The examples of the invention should be considered illustrative rather than restrictive, and the invention is not limited to the details set forth herein. For example, various elements or components may be combined or integrated into another system, or certain features may be omitted or not implemented.

[0069] Furthermore, without departing from the scope of this disclosure, technologies, systems, subsystems, and methods described and illustrated as separate or independent in the various embodiments may be combined or integrated with other systems, modules, technologies, or methods. Other items shown or discussed as directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, means, or intermediate component, whether such coupling or communication is carried out electrically, mechanically, or otherwise. Other examples of variations, substitutions, and modifications that can be identified by those skilled in the art without departing from the spirit and scope of the disclosure herein will also be provided.

Claims

1. A method for determining the concentration of a second target gas in the presence of a first target gas, the method comprising: A first sensor is operated under first operating conditions, wherein the first sensor is part of a sensor assembly, and wherein the first sensor includes a first filter configured to filter the first target gas from an airflow entering the first sensor, and a membrane configured to retain the first filter. The second sensor is operated under a second operating condition, wherein the second sensor is part of the sensor assembly, wherein the second sensor includes a second filter configured to filter the second target gas from the gas flow entering the second sensor, wherein the first operating condition includes a first bias voltage, and wherein the second operating condition includes a second bias voltage different from the first bias voltage. At least the first target gas is detected by the first sensor; The second target gas is detected by the second sensor; Processing the signal output from the first sensor and the signal output from the second sensor; and The concentrations of the first target gas and the second target gas are determined based on the processed output signal. The first operating condition includes a first filtering condition and the second operating condition includes a second filtering condition. The first filtering condition is different from the second filtering condition, and the second filter is different from the first filter.

2. The method according to claim 1, wherein the first target gas comprises carbon monoxide.

3. The method according to claim 1, wherein the second target gas comprises a volatile organic compound.

4. The method according to claim 1, wherein the second target gas comprises formaldehyde.

5. The method of claim 1, wherein the filter comprises a glass fiber sheet impregnated with potassium permanganate.

6. The method of claim 1, wherein at least one of the first sensor and the second sensor comprises a dust filter.

7. The method of claim 1, wherein one of the first bias voltage and the second bias voltage comprises a zero bias voltage.

8. The method of claim 1, wherein one of the first bias voltage and the second bias voltage comprises a bias voltage of 300mV.

9. The method of claim 1, wherein one of the first bias voltage and the second bias voltage comprises a bias voltage between 0 and 500 mV.

10. A sensor assembly configured to detect a second target gas in the presence of a first target gas, the sensor assembly comprising: A first sensor, the first sensor including a first operating condition; A second sensor, the second sensor including a second operating condition, wherein the first operating condition is different from the second operating condition, wherein the first sensor includes a first filter configured to filter a first target gas from an airflow entering the first sensor, and a membrane configured to retain the first filter, wherein the second sensor includes a second filter configured to filter the second target gas from an airflow entering the second sensor, wherein the first operating condition includes a first bias voltage, and wherein the second operating condition includes a second bias voltage different from the first bias voltage; Processor, the processor being configured to: Receive a first output signal from the first sensor; Receive the second output signal from the second sensor; They are processed by comparing the received output signals; and The concentrations of the first target gas and the second target gas are determined based on the processed output signal. The first operating condition includes a first filtering condition and the second operating condition includes a second filtering condition. The first filtering condition is different from the second filtering condition, and the second filter is different from the first filter.

11. The sensor assembly of claim 10, wherein the first operating condition allows the first sensor to detect the first target gas, and wherein the second operating condition allows the second sensor to detect the second target gas in combination with the first target gas.

12. The sensor assembly of claim 10, wherein the processor is configured to determine the difference between two output signals.

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