Method, apparatus, and system for compensating baseline drift in a gas sensor

Abstract

Methods, apparatuses, and systems are provided for calculating a compensated reading of a gas sensing device. Example methods include: causing a first supply operating voltage to a sensing circuit of the gas sensing device; determining a first output of the sensing circuit; causing a second supply excitation voltage to the sensing circuit; determining a second output of the sensing circuit; and calculating a compensated reading of the gas sensing device based at least in part on the first output and the second output.

Description

Technical Field

[0001] The present disclosure generally relates to methods, devices, and systems for improving the accuracy of gas sensor readings, and more particularly to methods, devices, and systems for calculating compensated readings that account for baseline drift in a lower explosive limit gas sensor. Background Art

[0002] A gas sensor is a device that can detect the presence and / or concentration level of a gas substance (e.g., including combustible gases, flammable gases, and / or toxic gases). For example, a lower explosive limit (LEL) gas sensor can measure the concentration level of combustible and / or flammable gas substances (such as, for example, propane and methane) up to one hundred percent (100%) of the lower explosive limit of the gas substance. The term "lower explosive limit" refers to the minimum concentration level at which a gas substance supports combustion in air when an ignition source is present.

[0003] Many factors can affect the accuracy of LEL gas sensor readings, including, for example, mechanical shock and wear and tear of components through use. For example, a sudden force can be applied to the LEL gas sensor (e.g., when the LEL gas sensor is dropped to the ground), and the sudden force can affect the performance of various components within the LEL sensor. As another example, after long-term exposure to high temperatures, the performance of various components within the LEL sensor can change, resulting in inaccuracies in the readings. Summary of the Invention

[0004] The various embodiments described herein relate to methods, devices, and systems for improving the accuracy of gas sensor readings. Specifically, the various embodiments relate to calculating a compensated reading of a gas sensing device.

[0005] According to various examples of the present disclosure, methods for calculating a compensated reading of a gas sensing device are provided. The gas sensing device can include a sensing circuit, and the sensing circuit can include a first circuit branch and a second circuit branch electrically connected in parallel.

[0006] In some examples, the method can include: causing a first supply operating voltage to be applied to the sensing circuit; determining a first output of the sensing circuit; causing a second supply excitation voltage to be applied to the sensing circuit; determining a second output of the sensing circuit; and calculating the compensated reading of the gas sensing device based at least in part on the first output and the second output. The first output can correspond to a first voltage difference between the first circuit branch and the second circuit branch in response to the operating voltage, and the second output can correspond to a second voltage difference between the first circuit branch and the second circuit branch in response to the excitation voltage. The excitation voltage can be less than the operating voltage. The compensated reading can correspond to the concentration level of the gas substance in contact with the gas sensing device.

[0007] In some examples, the detector element and the compensator element can be electrically coupled on a first circuit branch, and the first resistor and the second resistor can be electrically coupled on a second circuit branch.

[0008] In some examples, the detector element includes a first metal coil covered in a catalytic material, and the compensator element includes a second metal coil covered in a non-catalytic material.

[0009] In some examples, the operating voltage causes a gas species to react on the detector element, and the excitation voltage causes the gas species to remain inert on the detector element.

[0010] In some examples, before causing a second supply of the excitation voltage, the method further includes: calculating a first reading of the gas sensing device based at least in part on the first output; and determining that the first reading does not meet a threshold.

[0011] In some examples, the operating voltage is between 2 volts (inclusive) and 4.5 volts (inclusive), and the excitation voltage is between 0.1 volts (inclusive) and 0.2 volts (inclusive). In some examples, the operating voltage is 3 volts and the excitation voltage is 0.2 volts.

[0012] According to various examples of the present disclosure, a system for calculating a compensated reading is provided. The system can include a sensing circuit, a processing circuit in electronic communication with the sensing circuit, and a memory circuit in electronic communication with the processing circuit. The sensing circuit can include a first circuit branch and a second circuit branch electrically coupled in parallel. The memory circuit can store computer program instructions. Using the processing circuit, the computer program instructions can be configured to cause the system to: cause a first supply of an operating voltage to the sensing circuit; determine a first output of the sensing circuit; cause a second supply of an excitation voltage to the sensing circuit; determine a second output of the sensing circuit; and calculate a compensated reading of the gas sensing device based at least in part on the first output and the second output. In some examples, the first output corresponds to a first voltage difference between the first circuit branch and the second circuit branch in response to the operating voltage. In some examples, the second output corresponds to a second voltage difference between the first circuit branch and the second circuit branch in response to the excitation voltage. In some examples, the excitation voltage is less than the operating voltage. In some examples, the compensated reading corresponds to a concentration level of a gas species in contact with the sensing circuit.

[0013] According to various examples of the present disclosure, a computer program product is provided. The computer program product may include at least one non-transitory computer-readable storage medium having computer-readable program code portions stored therein. The computer-readable program code portions include executable portions configured to: cause a first supply of a working voltage to a sensing circuit of a gas sensing device; determine a first output of the sensing circuit; cause a second supply of an excitation voltage to the sensing circuit; determine a second output of the sensing circuit; and calculate a compensated reading of the gas sensing device based at least in part on the first output and the second output. The sensing circuit may include a first circuit branch and a second circuit branch electrically connected in parallel. The first output may correspond to a first voltage difference between the first circuit branch and the second circuit branch in response to the working voltage. The second output may correspond to a second voltage difference between the first circuit branch and the second circuit branch in response to the excitation voltage. The excitation voltage may be less than the working voltage. The compensated reading may correspond to a concentration level of a gas substance in contact with the gas sensing device.

[0014] The foregoing illustrative matter, as well as other exemplary objects and / or advantages of the present disclosure and the manner in which they are achieved, are further explained in the following detailed description and its accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The description of the illustrative embodiments may be read in conjunction with the accompanying drawings. It will be understood that, for simplicity and clarity of illustration, elements shown in the drawings are not necessarily drawn to scale. For example, the dimensions of some elements may be exaggerated relative to other elements unless otherwise described. Embodiments including teachings of the present disclosure are shown and described relative to the accompanying drawings herein, in which:

[0016] Figure 1 A perspective view of an example gas sensing device in accordance with various embodiments of the present disclosure is shown;

[0017] Figure 2 A perspective view of various components of an example gas sensing device in accordance with various embodiments of the present disclosure is shown;

[0018] Figure 3 A perspective view of various components of an example gas sensing device in accordance with various embodiments of the present disclosure is shown;

[0019] Figure 4 A diagram of various components of an example gas sensing device in accordance with various embodiments of the present disclosure is shown;

[0020] Figure 5 A diagram of various components of an example gas sensing device in accordance with various embodiments of the present disclosure is shown;

[0021] Figure 6Shows an example circuit diagram of an example sensing circuit according to various embodiments of the present disclosure;

[0022] Figure 7 Shows an example flowchart according to various embodiments of the present disclosure; and

[0023] Figure 8 Shows an example flowchart according to various embodiments of the present disclosure. Detailed Description

[0024] Some embodiments of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments of the present disclosure are shown. In fact, these disclosures may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Throughout the specification, like reference numerals refer to like elements.

[0025] The phrases "in one embodiment", "according to one embodiment" and similar phrases generally mean that the particular feature, structure or characteristic after the said phrase may be included in at least one embodiment of the present disclosure and may be included in more than one embodiment of the present disclosure (importantly, such phrases do not necessarily refer to the same embodiment).

[0026] The word "example" or "exemplary" used herein means "serving as an example, instance, or illustration". Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

[0027] If the specification states that a component or feature "may", "should", "preferably", "possibly", "usually", "optionally", "for example", "often" or "maybe" (or other such language) is included or has a feature, it is not required that the specific component or feature be included or have the said feature. Such a component or feature may optionally be included in some embodiments, or it may be excluded.

[0028] As described above, many factors can affect the accuracy of gas sensor readings, which can lead to "baseline drift". The term "baseline drift" refers to an incorrect positive or negative reading from a LEL gas sensor when there is no combustible gas substance (which can indicate the presence of a combustible gas substance). In this regard, various embodiments of the present disclosure can overcome the technical challenges associated with the compensation for baseline drift and can improve the accuracy in sensor readings, for example, by calculating a compensated reading, the details of which are described hereinafter.

[0029] Now refer to Figure 1, shows an example gas sensing device 100 in accordance with various embodiments of the present disclosure. In particular, the example gas sensing device 100 can be a lower explosive limit (LEL) sensor configured to detect and measure the concentration level of a combustible gas species.

[0030] As shown in Figure 1 , the example gas sensing device 100 can include a cover member 103, a housing member 105, a mounting member 107, and one or more connection wires 109, 111, and 113.

[0031] The cover member 103 can be made of a material having fire-resistant properties and can include a porous structure, such as, for example, sintered stainless steel or sintered metal fibers. The cover member 103 can be in contact with the gas species that the example gas sensing device 100 is configured to detect and / or measure. The porous structure of the cover member 103 can allow the gas species to pass through the cover member 103 and into the example gas sensing device 100. The fire-resistant properties of the cover member 103 can prevent any combustion and / or flame occurring within the example gas sensing device 100 from spreading outside the gas sensing device 100.

[0032] The housing member 105 of the example gas sensing device 100 can be made of a metal alloy, such as stainless steel or carbon steel. In some examples, the housing member 105 can be shaped similarly to a hollow cylindrical shape. In some examples, the housing member 105 can be other shapes, such as but not limited to a hollow hexagonal prism shape, a hollow cube shape, without departing from the scope of the present disclosure.

[0033] The housing member 105 together with the cover member 103 can form an enclosure that houses various components of the example gas sensing device 100, such as but not limited to a header plate. The header plate can include two or more bead-shaped members that are disposed on the surface of the header plate and are in contact with the gas species passing through the cover member 103. Each of the bead-shaped members can include a metal coil that can be coated with a material to form a bead shape. Example details of an example header plate are shown and described below in connection with Figure 3 Example details of an example bead-shaped member are shown and described below in connection with Figure 5 .

[0034] The mounting member 107 of the exemplary gas sensing device 100 can be attached to the housing member 105 and can provide a mechanical connection between the exemplary gas sensing device 100 and other device(s) to which the exemplary gas sensing device 100 can be connected. For example, the mounting member 107 can be mounted in a collection cone to facilitate the detection and measurement of combustible gas substances by the exemplary gas sensing device 100. In some examples, the mounting member 107 can be shaped like a hollow cylinder. In some examples, the mounting member 107 can be other shapes, such as but not limited to a hollow hexagonal prism shape, a hollow cube shape, without departing from the scope of the present disclosure.

[0035] In some examples, the exemplary gas sensing device 100 can include one or more connection lines 109, 111, and 113. The connection lines 109, 111, and 113 can be connected to the electronic component(s) within the exemplary gas sensing device 100 (such as, for example, the metal coil of the bead-shaped member disposed on the manifold board), and can transmit the electronic signals associated with these electronic component(s) to one or more other circuits, such as the signal adapter 115.

[0036] In some examples, the signal adapter 115 can be mounted on a printed circuit board, such as the electronic signals transmitted by the connection lines can be analyzed by the processing circuit, the details of which are described below in conjunction with Figures 6 - 8 description.

[0037] Although Figure 1 the exemplary gas sensing device 100 is shown as having three connection lines, in some examples, the exemplary gas sensing device can have fewer than three or more than three connection lines without departing from the scope of the present disclosure.

[0038] Additionally or alternatively, the exemplary gas sensing device 100 can include one or more metal pins that are connected to the electronic component(s) within the exemplary gas sensing device 100 (such as, for example, the metal coil of the bead-shaped member disposed on the manifold board), and can transmit the electronic signals associated with these electronic component(s) to one or more other circuits.

[0039] Now referring to Figure 2 and Figure 3 , various example components of the exemplary gas sensing device are shown. In particular, Figure 2 shows an example housing 200 of the exemplary gas sensing device, and Figure 3 shows an example manifold board 300 of the exemplary gas sensing device.

[0040] As shown in Figure 2The exemplary housing 200 shown in FIG. may include a cover member 202, a housing member 204, and a mounting member 206. In some examples, the cover member 202 may be similar to the cover member 103 described above in connection with Figure 1 In some examples, the housing member 204 may be similar to the housing member 105 described above in connection with Figure 1 In some examples, the mounting member 206 may be similar to the mounting member 107 described above in connection with Figure 1 Now referring to

[0041] FIG. Figure 3 shows an exemplary manifold plate 300. The manifold plate 300 may include a pair of bead members 301 and 303, a mounting disk 305, and a printed circuit board 307.

[0042] As described above in connection with Figure 1 the bead members 301 and 303 may be disposed on the surface of the manifold plate 300 and be in contact with a gas substance passing through the cover member of the exemplary gas sensing device (e.g., the cover member 103 of the exemplary gas sensing device 100 described above in connection with Figure 1 Each of the bead members 301 and 303 may include a metal coil, such as a platinum coil. When a voltage is supplied to the metal coil, the metal coil may generate heat, causing the temperature of the bead member to rise.

[0043] In some examples, each of the bead members 301 and 303 may include a (plurality of) materials covering the metal coil and forming a bead shape. In particular, one of the bead members (e.g., the bead member 301) may include a porous alumina material and / or other catalytic materials covering the metal coil (such a bead member may also be hereinafter referred to as a "detector element"). In contrast, the other bead member (e.g., the bead member 303) may include a non-catalytic material (such a bead member may also be hereinafter referred to as a "compensator element").

[0044] In some examples, the metal coil of the bead member 301 may have the same resistance as the metal coil of the bead member 303. In some examples, the bead members 301 and 303 may be of the same shape. In some examples, the shape of the bead member 301 may be different from the shape of the bead member 303.

[0045] As shown in Figure 3 the bead member 301 and the bead member 303 may be disposed on the mounting disk 305 of the manifold plate 300. In particular, each of the bead member 301 and the bead member 303 may be disposed in a separate hole on the surface of the mounting disk 305. In some examples, the mounting disk 305 may include a (plurality of) heat-resistant materials, such as, for example, polytetrafluoroethylene (PTFE).

[0046] The printed circuit board 307 can be disposed below the mounting plate 305. The printed circuit board 307 can mechanically support and electrically connect various electronic components (such as, for example, various electronic components for a sensing circuit). Further, the bead-shaped member 301 and the bead-shaped member 303 can be connected to various electronic components on the printed circuit board 307, such as a sensing circuit, for example, by metal leads. Example metal leads are shown and described below in connection with Figure 4 Example sensing circuits are shown and described below in connection with Figure 6 Example sensing circuits are shown and described below in connection with

[0047] Now referring to Figure 4 and Figure 5 example diagrams are provided that illustrate various example structures associated with example bead-shaped members.

[0048] In an embodiment as shown in Figure 4 the bead-shaped member 402 can be connected to a pair of metal leads 410. In particular, the metal leads 410 can be connected to a metal coil within the bead-shaped member 402, and the metal leads 410 can include a material such as platinum.

[0049] In some examples, the ends of the metal leads 410 can be connected to various electronic components, such as, for example, a sensing circuit as shown in Figure 6 In other words, the bead-shaped member 402 can be connected to the sensing circuit by the metal leads 410.

[0050] Further, the bead-shaped member 402 can be housed within a container member 406. The container member 406 can be made of metal and can also include holes that allow the bead-shaped member 402 to contact the gas substance to be detected. In some examples, the container member 406 can be fastened to the manifold plate 408 by a sealing ring 404. The sealing ring 404 can include an elastic material such as, for example, rubber and / or silicone.

[0051] Now referring to Figure 5 an example internal structure of an example bead-shaped member is shown. In particular, Figure 5 a half-sectional view is provided showing a metal coil 503 disposed within a cover member 501.

[0052] As described above, an example gas sensing device can include two bead-shaped members. One of the bead-shaped members (“the detector element”) can have a cover member 501 that includes a catalytic material. The catalytic material can allow catalytic combustion or oxidation to occur. In this regard, when a voltage is supplied to the metal coil 503, the metal coil 503 can heat the bead-shaped member. When the voltage is high enough, the high temperature of the bead-shaped member can cause a combustible gas substance to react (such as catalytic oxidation) on the detector element.

[0053] Another bead-shaped member (“compensator element”) may have a cover member 501 that includes a non-catalytic material and may otherwise be similar to the detector element. In other words, the compensator element does not trigger catalytic combustion or oxidation, and combustible gas species may remain inert on the compensator element.

[0054] In some examples, the length D1 of the bead-shaped member is one millimeter (1 mm). In some examples, the length D1 may be other suitable values without departing from the scope of the present disclosure.

[0055] Now referring to Figure 6 , an example circuit diagram is shown that illustrates an example sensing circuit of an example gas sensing device.

[0056] As described above, the metal coil of the bead-shaped member of the example gas sensing device may be connected to the sensing circuit. As shown in Figure 6 , the metal coil of the detector element (i.e., the bead-shaped member having a catalytic material) may have a resistance , and the metal coil of the compensator element (i.e., the bead-shaped member having a non-catalytic material) may have a resistance .

[0057] In an embodiment as shown in Figure 6 , the sensing circuit may include a Wheatstone bridge circuit. In particular, the Wheatstone bridge circuit may include a first circuit branch and a second circuit branch connected in parallel. As shown in Figure 6 , the detector element and the compensator element may be connected on the first circuit branch of the Wheatstone bridge circuit, and a first resistor and a second resistor may be connected on the second circuit branch of the Wheatstone bridge circuit.

[0058] Further, a voltage ( ) may be supplied to provide power to the Wheatstone bridge circuit. In some examples, the value of the voltage ( ) may be adjustable and / or controllable. For example, a processing circuit may communicate with an adjustable power supply to cause different voltages to be supplied to provide power to the Wheatstone bridge circuit. Example voltages may include, for example, an operating voltage ( ) and an excitation voltage ( ), the details of which are described below in connection with Figure 7 and Figure 8 .

[0059] Referring again to Figure 6 , the voltage difference ( ) between the first circuit branch and the second circuit branch (i.e., between point A and point B of the Wheatstone bridge circuit) may be calculated based on the following equation:

[0060]

[0061] In some examples, the resistor and the resistor may have the same resistance value. The detector element and the compensator element may each include a metal coil having the same resistance value. When the detector element and the compensator element are at the same temperature (e.g., when there is no catalytic combustion or oxidation), and have the same value. In other words, when there is no combustible gas substance:

[0062]

[0063] When there is a combustible gas substance, the combustible gas substance may cause catalytic oxidation of the detector element (but not the compensator element, as described above). The oxidation may further increase the temperature of the detector element, while the temperature of the compensator element is not affected by the presence of the combustible gas substance. The increase in the temperature of the detector element may cause a change in the resistance of the detector element. Therefore, the difference in temperature between the detector element and the compensator element may be represented as a difference in the corresponding resistances. In other words, when there is a combustible gas substance:

[0064]

[0065] Further, the new resistance of the detector element due to the increase in temperature ( ) may be calculated based on the following equation:

[0066]

[0067] In an example where the resistor and the resistor have the same resistance value, the new resistance of the detector element ( ) may be calculated based on the following equation:

[0068]

[0069] As described above, when there is no combustible gas substance, the voltage difference ( ) should be close to zero. However, even when there is no combustible gas substance, many factors (such as mechanical shock and wear and tear of resistor components) may cause the voltage difference ( ) to deviate from zero, resulting in a "baseline drift".

[0070] In some examples, when baseline drift is observed, a calibration process may be performed to adjust the resistance of the Wheatstone bridge circuit, for example, by adjusting the resistance of the variable resistor in the Wheatstone bridge circuit (as in Figure 6as shown in). For example, calibration gas (i.e., fresh air without any combustible gas substance) can be supplied to the gas sensing device, and the variable resistor can be adjusted so that the voltage difference ( ) is set to zero.

[0071] However, this calibration process can have some drawbacks. For example, when the gas sensing device is immovably fastened in a specific location (e.g., in an environment with combustible gas substances), it can be challenging to supply calibration gas to the gas sensing device to perform this calibration process. As another example, a user may incorrectly apply an air bottle mixed with a combustible gas substance under the mistaken belief that there is no combustible gas substance in the bottle, which can lead to further inaccuracies.

[0072] Various embodiments of the present disclosure provide example methods, systems, and devices that can overcome the above drawbacks. In some example embodiments, when calculating the compensated reading of a gas detection device, there may be no need for calibration gas. Thus, some example embodiments of the present disclosure can improve the accuracy of gas sensor readings.

[0073] Now refer to Figure 7 and Figure 8 , which show some example methods related to calculating the compensated reading of a gas sensing device according to various embodiments.

[0074] In some examples, each block of the flowchart and combinations of blocks in the flowchart can be implemented in various ways (such as, hardware, firmware, circuits, and / or other means related to executing software, the software including one or more computer program instructions).

[0075] In some examples, one or more of the steps described in the figures can be implemented by computer program instructions that can be stored in a memory circuit (such as, non-transitory memory) of a system employing embodiments of the present disclosure and executed by a processing circuit (such as, a processor) of the system. These computer program instructions can direct the system to act in a specific manner such that the instructions stored in the memory circuit produce a manufacture, and the execution of the instructions implements the functions specified in the (multiple) flowchart blocks. Further, the system can include one or more other circuits, such as, for example, the sensing circuit described above in connection with Figure 6 . The various circuits of the system (such as, the sensing circuit, the processing circuit, and the memory circuit) can communicate electronically with each other and / or within each other to transfer data to and / or receive data from each other.

[0076] In some examples, an embodiment may take the form of a computer program product on a non-transitory computer-readable storage medium storing computer-readable program instructions (e.g., computer software). Any suitable computer-readable storage medium may be used, including a non-transitory hard disk, CD-ROM, flash memory, optical storage device, or magnetic storage device.

[0077] In some examples, each block of the flowchart and combinations of blocks in the flowchart may be performed manually.

[0078] Now referring Figure 7 to, there is shown an example method 700 in accordance with some embodiments of the present disclosure. In particular, example method 700 illustrates an example embodiment for calculating various parameters for calculating a compensated reading.

[0079] In some examples, method 700 may be performed by a processing circuit (such as, but not limited to, an application specific integrated circuit (ASIC), a central processing unit (CPU)). In some examples, the processing circuit may be electrically coupled to and / or in electronic communication with other circuits of an example gas sensing device, such as, but not limited to, a sensing circuit (e.g., as shown in Figure 6 ), a memory circuit (such as, for example, a random access memory (RAM) for storing computer program instructions), and / or a display circuit (for presenting device readings on a display).

[0080] Method 700 begins at block 702. At block 704, the processing circuit may cause a working voltage ( ) to be supplied to a sensing circuit of an example gas sensing device, such as the sensing circuit described above in connection with Figure 6 . The working voltage ( ) may be a default working voltage for the sensing circuit. In some examples, the working voltage ( ) may cause a combustible gas species to react on the detector element, as described above in connection with Figure 6 .

[0081] In some examples, the working voltage ( ) may be a constant voltage between 2 V (inclusive) and 4.5 V (inclusive). In some examples, the working voltage ( ) may be selected from the following values: 2.3 V, 2.5 V, 2.8 V, 3 V, 3.5 V, and 4.25 V. In some examples:

[0082]

[0083] At the working voltage ( )After being supplied to the sensing circuit, the processing circuit may record an output at block 706 based on a constant non-transitory signal received from the sensing circuit under a "zero condition"( ), and may record an output at block 708 based on a constant non-transitory signal from the sensing circuit under a "span condition"( ).

[0084] The term "zero condition" refers to the condition when no combustible gas substance is in contact with the gas sensing device. In other words, under the zero condition, there is no combustible gas substance (e.g., fresh air without any combustible gas substance) in contact with the detector element of the sensing circuit (as described above in connection with Figure 6 ).

[0085] The term "span condition" refers to the condition when a combustible gas substance with a known concentration level( ) is in contact with the gas sensing device. As a non-limiting example, the span condition may be methane gas at fifty percent (50%) of its lower explosive limit in contact with the gas sensing device. In other words, under the span condition, the detector element of the sensing circuit (as described above in connection with Figure 6 ) may be in contact with a combustible gas with a known concentration level( ), and the resistance of the detector element may change, as described above at least in connection with Figure 6 .

[0086] In some examples, each of the output( ) and the output( ) may correspond to the voltage difference in the Wheatstone bridge circuit of the sensing circuit under the corresponding condition. For example, the processing circuit may record the output( ), and may record the output( ), where the output( ) corresponds to the voltage difference( ) of the Wheatstone bridge circuit (as shown in Figure 6 ) under the zero condition and in response to the operating voltage( ), and the output( ) corresponds to the voltage difference( ) of the Wheatstone bridge circuit (as shown in Figure 6 ) under the span condition and in response to the operating voltage( ). Further, any change in the resistance of the detector element may be calculated based at least in part on the voltage difference( ), as described above at least in connection with Figure 6 .

[0087] In some examples, the processing circuit may compare the output( ) and( ) The value of is stored in a memory circuit that is in electronic communication with the processing circuit.

[0088] In some examples, block 706 may be executed before block 708. In other words, the processing circuit may receive and record the output from the sensing circuit under zero conditions ( ) before receiving and recording the output from the sensing circuit under cross conditions ( ).

[0089] In some examples, block 706 may be executed after block 708. In other words, the processing circuit may receive and record the output from the sensing circuit under cross conditions ( ) after receiving and recording the output from the sensing circuit under zero conditions ( ).

[0090] After recording the values of the outputs ( ) and ( ), the processing circuit may calculate the sensitivity of the gas sensing device ( ) at block 710. The sensitivity ( ) indicates how much the output of the sensing circuit (e.g., the voltage difference ( )) of the sensing circuit changes when the measured input quantity (e.g., the concentration level of a combustible gas species) changes.

[0091] As described above, a combustible gas species may affect the resistance of the detector element in the sensing circuit but not the resistance of the compensator element in the sensing circuit. The higher the concentration level of the combustible gas species, the greater the difference in resistance between the detector element and the compensator element, resulting in a greater voltage difference ( ) in the Wheatstone bridge circuit of the sensing circuit.

[0092] In some examples, the sensitivity ( ) may be calculated based at least in part on the outputs ( ) and ( ). In some examples, the sensitivity ( ) may be calculated based on the following equation:

[0093]

[0094] where, is the output under cross conditions, is the output under zero conditions, and is the concentration level of the combustible gas species at cross conditions.

[0095] At block 712, the processing circuit may cause an excitation voltage ( )Supplied to the sensing circuit of the exemplary gas sensing device (such as the sensing circuit described above in connection with Figure 6 ).

[0096] In some examples, the excitation voltage ( ) is less than the operating voltage ( ). In some examples, the excitation voltage ( ) may not cause any combustible gas species to react on the detector element. In other words, the excitation voltage ( ) may be low enough to avoid overheating of the detector element (e.g., temperature below 200 °C), and thus may cause the gas species to remain inert on the detector element.

[0097] In some examples, the excitation voltage ( ) may be a constant voltage between 0.1 V (inclusive) and 0.2 V (inclusive). In some examples:

[0098]

[0099] After the excitation voltage ( ) is supplied to the sensing circuit, the processing circuit may record the value of the output ( ) at block 714 based on the constant non - transient signal received from the sensing circuit.

[0100] In some examples, the value of the output ( ) may correspond to the voltage difference in a Wheatstone bridge circuit. For example, referring again to Figure 6 , the value of the output ( ) may correspond to the voltage difference ( ) of the Wheatstone bridge circuit (as shown in Figure 6 ) in response to the excitation voltage ( ). In some examples, the processing circuit may store the recorded value of the output ( ) in a memory circuit that is in electronic communication with the processing circuit.

[0101] As described above, in some examples, the excitation voltage ( ) may cause the gas species to remain inert on the detector element. Thus, the value of the output ( ) may only indicate the voltage difference (or corresponding resistance difference) between the detector element and the compensator element that is not caused by any combustible gas species that may or may not be present.

[0102] At block 716, the processing circuit may calculate the coefficient ( ) and intercept ( ) of the sensing circuit (such as the sensing circuit described above in connection with Figure 6 ). The coefficient ( ) and the intercept ( ) can indicate the amount of baseline drift of the sensing circuit, which is caused, for example, by mechanical shock and wear and tear of the detector element and the compensator element. In some examples, the coefficient ( ) can be calculated based on the following equation:

[0103]

[0104] where, is the output when the operating voltage is supplied under zero conditions, is the output when the excitation voltage is supplied, is the operating voltage, and is the excitation voltage.

[0105] In some examples, the intercept ( ) can be calculated based on the following equation:

[0106]

[0107] where, is the output when the operating voltage is supplied under zero conditions, is the output when the excitation voltage is supplied, is the operating voltage, and is the excitation voltage.

[0108] After calculating the coefficient ( ) and the intercept ( ), the processing circuit can store the coefficient ( ) and the intercept ( ) in the memory circuit at block 718, the memory circuit being in electronic communication with the processing circuit. The coefficient ( ) and the intercept ( ) can be used to calculate the compensated readings of the gas sensing device, examples of which are shown and described below in connection with Figure 8 .

[0109] Method 700 ends at block 720.

[0110] Now referring to Figure 8 , an example method 800 in accordance with some embodiments of the present disclosure is shown. In particular, example method 800 shows an example embodiment of calculating the compensated readings for a gas sensing device.

[0111] In some examples, method 800 may be performed by a processing circuit (such as, but not limited to, an application specific integrated circuit (ASIC), a central processing unit (CPU)). In some examples, the processing circuit may be electrically coupled to, and / or in electronic communication with, other circuits of the example gas sensing device, such as, but not limited to, a sensing circuit (e.g., as shown in Figure 6 ), a memory circuit (such as, for example, a random access memory (RAM) for storing computer program instructions), and / or a display circuit (for presenting device readings on a display).

[0112] Method 800 begins at block 801. At block 803, the processing circuit may cause a first supply operating voltage ( ) to be provided to the sensing circuit of the example gas sensing device, such as the sensing circuit described above in connection with Figure 6 . As described above, the operating voltage ( ) may be a default operating voltage for the sensing circuit and may cause a combustible gas species to react on the detector element, as described above in connection with Figure 6 .

[0113] In some examples, the operating voltage ( ) may be a constant voltage between 2 V (inclusive) and 4.5 V (inclusive). In some examples, the operating voltage ( ) may be selected from the values: 2.3 V, 2.5 V, 2.8 V, 3 V, 3.5 V, and 4.25 V. In some examples:

[0114]

[0115] In some examples, Figure 8 the operating voltage ( ) at block 803 of Figure 7 may be the same as the operating voltage ( ) at block 704 of

[0116] After the operating voltage ( ) is provided to the sensing circuit, the processing circuit may, at block 805, determine and record a first output ( ) based on a constant non - transient signal received from the sensing circuit.

[0117] In some examples, the first output ( ) may correspond to a first voltage difference of the sensing circuit in response to the operating voltage ( ). For example, referring again to Figure 6 , the sensing circuit may include a Wheatstone bridge circuit, and the processing circuit may determine and record the first output ( ), the first output ( ) corresponds to the voltage difference in the Wheatstone bridge circuit of the sensing circuit ( ).

[0118] In some examples, when the operating voltage ( ) is supplied to the sensing circuit, the sensing circuit can be in contact with the combustible gas substance detected by the gas sensing device. In such examples, the first voltage difference can be caused, for example, by the baseline shift of the gas sensing device (e.g., a change in the resistance of the detector element not due to the detection of the combustible gas substance) and the reaction of the combustible gas substance on the detector element.

[0119] At block 807, the processing circuit can calculate a first reading ( ) of the gas sensing device. The first reading ( ) of the gas sensing device can correspond to the concentration level of the combustible gas substance (as determined by the gas sensing device) and can be calculated at least in part based on the first output ( ). In some examples, the first reading ( ) can be calculated based on the following equation:

[0120]

[0121] Where, is in response to the analog voltage from the first output of the sensing circuit, is the output recorded under zero conditions and when the analog voltage is supplied (e.g., as described in block 706 in connection with Figure 7 ), and is the sensitivity of the sensing circuit (e.g., as described in block 710 in connection with Figure 7 ).

[0122] At block 809, the processing circuit can determine whether the first reading ( ) meets a threshold. For example, the circuit can determine whether the first reading ( ) meets the following mathematical inequality related to the threshold ( ):

[0123]

[0124] In some examples, the processing circuit can set the threshold ( ) based on the combustible gas substance that the gas sensing device is configured to measure. For example, the processing circuit can set the threshold ( )Set to one percent (1%) of the lower explosive limit of the combustible gas substance. In some examples, the processing circuit may set the threshold based on other parameters (e.g., safety threshold parameters of the safety system). )

[0125] At block 809, if the processing circuit determines that the first reading ( ) meets the threshold (e.g., when the first reading ( ) is not greater than the threshold ( ) and not less than the negative threshold ( ), then the processing circuit may proceed to block 819 and method 800 ends. In other words, the processing circuit may determine that the first reading ( ) can be used to calculate the concentration level of the combustible gas substance and that there is little or no baseline drift in the sensing circuit.

[0126] At block 809, if the processing circuit determines that the first reading ( ) does not meet the threshold (e.g., when the first reading ( ) is greater than the threshold ( ) or less than the negative threshold ( ), then the processing circuit may proceed to block 811. In other words, the processing circuit may determine that there is baseline drift in the sensing circuit and that the first reading ( ) may include inaccuracies due to baseline drift.

[0127] Although block 809 shows an example embodiment of using a threshold to determine whether to calculate a compensated reading of the gas sensing device, it should be noted that other embodiments may determine whether to calculate the compensated reading based on other parameters. For example, the processing circuit may determine that the gas sensing device has been in contact with the combustible gas substance for a predetermined amount of time (e.g., 3 hours) and may trigger the operation shown in block 811.

[0128] At block 811, the processing circuit may cause an excitation voltage to be supplied to the sensing circuit of the example gas sensing device (such as the sensing circuit described above in connection with Figure 6 ).

[0129] As described above, the excitation voltage ( ) is less than the operating voltage ( ) and may not cause any combustible gas substance to react on the detector element. For example, the excitation voltage ( ) may be low enough to avoid overheating of the detector element (e.g., temperature below 200 °C) and may thus cause the gas substance to remain inert on the detector element.

[0130] In some examples, the excitation voltage ( ) can be a constant voltage between 0.1 V (inclusive) and 0.2 V (inclusive). In some examples:

[0131]

[0132] In some examples, Figure 8 the excitation voltage of block 811 ( ) can be the same as Figure 7 the excitation voltage of block 712 ( ).

[0133] After the excitation voltage ( ) is supplied to the sensing circuit, the processing circuit can determine and record a second output ( ) at block 813 based on the constant non - transient signal received from the sensing circuit.

[0134] In some examples, the second output ( ) can correspond to the voltage difference of the sensing circuit in response to the excitation voltage ( ). For example, referring again to Figure 6 , the processing circuit can record the second output ( ), which corresponds to the voltage difference of the sensing circuit ( ). The sensing circuit can include a Wheatstone bridge circuit, and the processing circuit can determine and record the second output ( ), which corresponds to the voltage difference in the Wheatstone bridge circuit of the sensing circuit ( ).

[0135] In some examples, when the excitation voltage ( ) is supplied to the sensing circuit, the sensing circuit can be in contact with the same combustible gas substance (described above in connection with block 805) detected by the gas sensing device. Compared with the first output ( ) of block 805, the second output ( ) can only correspond to the voltage difference caused by the baseline shift of the gas sensing device, because there is no reaction of the combustible gas substance due to the low voltage of the excitation voltage ( ) on the detector element.

[0136] In some examples, the processing circuit can store the second output ( ) in a memory circuit that is in electronic communication with the processing circuit.

[0137] At block 815, the processing circuit can calculate a value ( ), the value ( )For example, consider the possible baseline drift of the gas sensing device when an analog voltage is supplied. In particular, the processing circuit can calculate a value ) based at least in part on a second output . For example, the value ( ) can be calculated based on the following equation:

[0138]

[0139] where is a coefficient, and is an intercept (as described above in connection with Figure 7 in boxes 716 and 718), is the operating voltage, is the output when an analog voltage is supplied under zero conditions (e.g., as described in Figure 7 in box 706), is the output when an excitation voltage is supplied.

[0140] At block 817, the processing circuit can calculate a compensated reading ( ) based at least in part on a first output value ( ) and a value ( ) that is calculated in part based on a second output ( ). For example, the compensated reading ( ) can be calculated based on the following equation:

[0141]

[0142] where is the output from the sensing circuit when an analog voltage is supplied, and is the sensitivity of the sensing circuit (e.g., as described in box 710).

[0143] Comparing the calculation of the first reading ( ) at block 807 with the calculation of the compensated reading ( ), it should be noted that the calculation of the compensated reading ( ) uses a value ( ) that can account for any possible baseline drift of the gas sensing device. Thus, the compensated reading ( ) can indicate the concentration level of the gas species with improved accuracy compared to the first reading ( ). )

[0144] In some examples, the compensated reading ( ) can be implemented in various environments, scenarios, and industries, for example, to improve workplace safety and / or prevent injuries. For example, an exemplary gas sensing device according to various embodiments of the present disclosure can be suitable as part of a safety system in an oil drilling environment, for example, to detect whether a combustible gas substance is at or near a hazardous level. In some examples, the gas sensing device can transmit a compensated reading ( ) to a processing circuit that can be within the gas sensing device, or to a processing circuit external to the gas sensing device via a wireless external communication network using any of a variety of protocols (such as, for example, Bluetooth®, ZigBee). The processing circuit can determine whether the concentration level indicated by the compensated reading ( ) meets a hazardous threshold. If so, the processing circuit can trigger an alarm (such as an audio alarm through a speaker element connected to the processing circuit) to warn the user that the combustible gas substance has reached a hazardous level.

[0145] Method 800 ends at block 819.

[0146] It should be understood that the present disclosure is not limited to the specific embodiments disclosed, and modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, unless otherwise described, these terms are used only in a general and descriptive sense and not for purposes of limitation.

Claims

1. A method for calculating a compensated reading of a gas sensing device, the method comprising: causing a first supply operating voltage to a sensing circuit of the gas sensing device, wherein the sensing circuit includes a first circuit branch and a second circuit branch electrically connected in parallel; determining a first output of the sensing circuit, wherein the first output corresponds to a first voltage difference between the first circuit branch and the second circuit branch in response to the operating voltage; calculating a first reading of the gas sensing device based at least in part on the first output; causing a second supply excitation voltage to the sensing circuit, wherein the excitation voltage is less than the operating voltage, wherein a detector element and a compensator element are electrically connected on the first circuit branch, and wherein the operating voltage causes a gas substance to react on the detector element, and wherein the excitation voltage causes the gas substance to remain inert on the detector element; determining a second output of the sensing circuit, wherein the second output corresponds to a second voltage difference between the first circuit branch and the second circuit branch in response to the excitation voltage; and calculating a compensated reading of the gas sensing device based at least in part on the first output and the second output, wherein the compensated reading corresponds to a concentration level of a gas substance in contact with the gas sensing device.

2. The method according to claim 1, wherein a first resistor and a second resistor are electrically connected on the second circuit branch.

3. The method according to claim 2, wherein the detector element includes a first metal coil covered with a catalytic material, and wherein the compensator element includes a second metal coil covered with a non-catalytic material.

4. The method according to claim 1, wherein before causing the second supply excitation voltage, the method further includes: determining that the first reading does not meet a threshold.

5. The method according to claim 1, wherein the operating voltage is between 2 volts and 4.5 volts, and wherein the excitation voltage is between 0.1 volts and 0.2 volts.

6. The method according to claim 5, wherein the operating voltage is 3 volts, and wherein the excitation voltage is 0.2 volts.

7. A system for calculating a compensated reading, the system comprising: a sensing circuit, wherein the sensing circuit includes a first circuit branch and a second circuit branch electrically connected in parallel; a processing circuit in electronic communication with the sensing circuit; and a memory circuit in electronic communication with the processing circuit, wherein the memory circuit stores computer program instructions, and wherein, using the processing circuit, the computer program instructions are configured to cause the system to: cause a first supply operating voltage to the sensing circuit; determine a first output of the sensing circuit, wherein the first output corresponds to a first voltage difference between the first circuit branch and the second circuit branch in response to the operating voltage; calculate a first reading of a gas sensing device based at least in part on the first output; Cause a second supply excitation voltage to the sensing circuit, wherein the excitation voltage is less than the operating voltage, wherein a detector element and a compensator element are electrically coupled on the first circuit branch, and wherein the operating voltage causes a gas species to react on the detector element, and wherein the excitation voltage causes the gas species to remain inert on the detector element; Determine a second output of the sensing circuit, wherein the second output corresponds to a second voltage difference between the first circuit branch and the second circuit branch in response to the excitation voltage; and Calculate a compensated reading of the gas sensing device based at least in part on the first output and the second output, wherein the compensated reading corresponds to a concentration level of a gas species in contact with the sensing circuit.

8. The system according to claim 7, wherein, A first resistor and a second resistor are electrically coupled on the second circuit branch.

9. The system according to claim 8, wherein, The detector element includes a first metal coil covered with a catalytic material, and wherein the compensator element includes a second metal coil covered with a non-catalytic material.

10. The system according to claim 9, wherein, Before causing the second supply excitation voltage, using the processing circuit, the computer program instructions are further configured to cause the system to: Determine whether the first reading satisfies a threshold.

11. The system according to claim 7, wherein, The operating voltage is between 2 volts and 4.5 volts, and wherein the excitation voltage is between 0.1 volts and 0.2 volts.

12. The system according to claim 11, wherein, The operating voltage is 3 volts, and wherein the excitation voltage is 0.2 volts.

13. A computer program product including at least one non-transitory computer-readable storage medium having computer-readable program code portions stored therein, the computer-readable program code portions including executable portions configured to: Cause a first supply operating voltage to a sensing circuit of a gas sensing device, wherein, The sensing circuit includes a first circuit branch and a second circuit branch electrically coupled in parallel; Determine a first output of the sensing circuit, wherein the first output corresponds to a first voltage difference between the first circuit branch and the second circuit branch in response to the operating voltage; Calculate a first reading of the gas sensing device based at least in part on the first output; Cause a second supply excitation voltage to the sensing circuit, wherein the excitation voltage is less than the operating voltage, wherein a detector element and a compensator element are electrically coupled on the first circuit branch, and wherein the operating voltage causes a gas species to react on the detector element, and wherein the excitation voltage causes the gas species to remain inert on the detector element; Determine a second output of the sensing circuit, wherein the second output corresponds to a second voltage difference between the first circuit branch and the second circuit branch in response to the excitation voltage; and Compensated readings of the gas sensing device are calculated based at least in part on the first output and the second output, wherein the compensated readings correspond to a concentration level of a gas species in contact with the gas sensing device.

14. The computer program product according to claim 13, wherein, the detector element includes a first metal coil covered in a catalytic material, wherein the first circuit branch includes a compensator element having a second metal coil covered in a non-catalytic material.

15. The computer program product according to claim 13, wherein, before causing the second supply excitation voltage, the executable portion is further configured to: determine whether the first reading meets a threshold.

16. The computer program product according to claim 13, wherein, the operating voltage is between 2 volts and 4.5 volts, wherein the excitation voltage is between 0.1 volt and 0.2 volt.

17. The computer program product according to claim 16, wherein, the operating voltage is 3 volts, wherein the excitation voltage is 0.2 volt.

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