Thermal conductivity detector-based gas sensor and associated method

Abstract

A sensing device is provided. For example, a sensing device may include a conductive element, a DC voltage source, a voltage measurement device, a first switching circuit for selectively connecting the DC voltage source to the conductive element, and a processor controlling the first switching circuit. The conductive element includes a first dissimilar material and a second dissimilar material arranged such that there is a first bond between the dissimilar materials and a second bond between the dissimilar materials. The processor controls the first switching circuit to connect the DC voltage source to the conductive element to apply a DC voltage for a first time period, and to disconnect the DC voltage source to measure a voltage for a second time period.

Description

Technical Field

[0001] Embodiments of the present disclosure relate generally to sensing devices, and more particularly to thermal conductivity detector (TCD) based sensing devices. Background Art

[0002] Heating sensing devices such as thermal conductivity gas sensing devices raise the sensing element to a desired operating temperature. In many such devices, there is a heating element separate from the sensing element to raise the sensing element to a desired operating temperature.

[0003] Such heated sensing devices are plagued by technical challenges and limitations.Through effort, ingenuity, and innovation, many of these identified problems have been addressed by developing solutions, including in the embodiments of the present disclosure, many examples of which are described in detail herein. Summary of the invention

[0004] Various embodiments described herein relate to sensing devices and associated methods for sensing thermally conductive gas and / or air flow.

[0005] According to various embodiments of the present disclosure, a sensing device is provided. In some embodiments, the sensing device includes: a substrate; a conductive element, the conductive element is positioned on the substrate and includes a first dissimilar material and a second dissimilar material, the first dissimilar material and the second dissimilar material are arranged so that there is a first joint between the first dissimilar material and the second dissimilar material and a second joint between the first dissimilar material and the second dissimilar material; a direct current (DC) voltage source; a voltage measuring device; a first switching circuit, the first switching circuit is used to selectively connect the DC voltage source to the first connection terminal and the second connection terminal of the conductive element; and a processor, the processor controls the first switching circuit. The conductive element also includes a first connection terminal and a second connection terminal. The processor controls the first switching circuit to selectively connect the DC voltage source to the first connection terminal and the second connection terminal of the conductive element to apply a DC voltage on the first connection terminal and the second connection terminal of the conductive element within a first time period, and selectively disconnect the DC voltage source from the first connection terminal and the second connection terminal of the conductive element to measure the voltage on the first connection terminal and the second connection terminal within a second time period.

[0006] In some embodiments, the first and second dissimilar materials of the conductive element are arranged such that a plurality of first junctions exist between the first and second dissimilar materials and a plurality of second junctions exist between the first and second dissimilar materials.

[0007] In some embodiments, the substrate includes a first portion and a second portion that is thinner than the first portion, the plurality of first bonding portions are positioned on the first portion of the substrate, and the plurality of second bonding portions are positioned on the second portion of the substrate.

[0008] In some embodiments, the first time period is long enough for the voltage across the first connection terminal and the second connection terminal to reach a steady-state voltage, and the second time period is long enough for the temperature of the first junction and the temperature of the second junction to decrease by a measurable amount.

[0009] In some embodiments, the processor determines a steady-state voltage across the first connection terminal and the second connection terminal, and uses the determined steady-state voltage to determine (i) the presence and / or concentration of a thermally conductive gas adjacent to the conductive element and / or (ii) the presence and / or amount of air flow over the conductive element.

[0010] In some embodiments, the processor determines a time constant of the voltage across the first connection terminal and the second connection terminal during a second time period, and uses the determined time constant to determine (i) the presence and / or concentration of a thermally conductive gas adjacent to the conductive element and / or (ii) the presence and / or amount of air flow over the conductive element.

[0011] In some embodiments, the first dissimilar material and the second dissimilar material include a first dissimilar conductive or semiconductive material and a second dissimilar conductive or semiconductive material.

[0012] In some embodiments, the first dissimilar material and the second dissimilar material include a chromium-nickel alloy and a nickel-aluminum alloy, respectively.

[0013] In some embodiments, the processor causes a DC voltage source to apply a plurality of different voltages across a first connection terminal and a second connection terminal of a conductive element, each different voltage being applied a first time with a first polarity and a second time with an opposite second polarity, and after applying each of the plurality of different voltages, the processor causes a voltage measuring device to measure the voltage across the first connection terminal and the second connection terminal of the conductive element, and the processor detects when a time constant of the voltage across the first connection terminal and the second connection terminal changes abruptly, and determines a temperature consistent with the abrupt change in the time constant of the voltage across the first connection terminal and the second connection terminal, which is the dew point.

[0014] In some embodiments, the DC voltage source includes one or more batteries.

[0015] According to various embodiments of the present disclosure, a method for sensing thermally conductive gas and / or air flow is provided. In some embodiments, the method includes a processor of a sensing device causing a first switching circuit to selectively connect a direct current (DC) voltage source to a first connection terminal and a second connection terminal of a conductive element; the DC voltage source applies a DC voltage to the first connection terminal and the second connection terminal of the conductive element within a first time period; the processor of the sensing device causes the first switching circuit to selectively disconnect the DC voltage source from the first connection terminal and the second connection terminal of the conductive element; and a voltage measuring device measures the voltage on the first connection terminal and the second connection terminal within a second time period. The conductive element includes a first dissimilar material and a second dissimilar material, and the first dissimilar material and the second dissimilar material are arranged so that there is a first joint between the first dissimilar material and the second dissimilar material and a second joint between the first dissimilar material and the second dissimilar material.

[0016] The above exemplary invention content and other exemplary objects and / or advantages of the present disclosure and the manner of achieving these objects and / or advantages are further explained in the following detailed description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The description of the exemplary embodiments may be read in conjunction with the accompanying drawings. It will be appreciated that, for simplicity and clarity of illustration, the elements shown in the figures are not necessarily drawn to scale unless otherwise described. For example, the dimensions of some of the elements may be exaggerated relative to other elements unless otherwise described. Embodiments incorporating the teachings of the present disclosure are shown and described with respect to the drawings presented herein, in which:

[0018] Figure 1 A block diagram showing an exemplary sensing device according to an exemplary embodiment of the present disclosure is shown;

[0019] Figure 2 shows a model of an exemplary sensing device according to an exemplary embodiment of the present disclosure;

[0020] Figure 3 shows a model of an exemplary sensing element of an exemplary sensing device according to an alternative exemplary embodiment of the present disclosure;

[0021] Figure 4 is a graph showing a voltage response of a sensing element of an exemplary sensing device according to an exemplary embodiment of the present disclosure; and

[0022] Figure 5 is a flow chart illustrating an exemplary method for operating an exemplary sensing device according to an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION

[0023] Some embodiments of the present disclosure will be described more fully below with reference to the accompanying drawings, which show some, but not all, embodiments of the present disclosure. In fact, these disclosures can 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 the present disclosure satisfies applicable legal requirements. The same reference numerals refer to the same elements throughout.

[0024] As used herein, terms such as "front," "rear," "top," "bottom," "left," "right," and the like are used for illustrative purposes in the examples provided below to describe the relative positions of certain components or portions of components. Additionally, as will be apparent to one of ordinary skill in the art from this disclosure, the terms "substantially" and "approximately" indicate that the referenced element or associated description is accurate within an applicable engineering tolerance.

[0025] As used herein, the term "comprising" means including but not limited to, and should be interpreted in the manner in which it is typically used in a patent context. The use of broader terms such as "comprising," "including," and "having" should be understood to provide support for narrower terms such as "consisting of," "consisting essentially of," and "composed essentially of."

[0026] The phrases "in one embodiment," "according to one embodiment," "in some embodiments," and the like generally mean that the particular feature, structure, or characteristic following the 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 are not necessarily referring to the same embodiment).

[0027] Phrases such as "in one example," "according to one example," "in some examples," and the like generally mean that a particular feature, structure, or characteristic following the phrase may be included in at least one example of the present disclosure, and may be included in more than one example of the present disclosure (importantly, such phrases do not necessarily refer to the same example).

[0028] If the specification states that a component or feature "may", "can", "could", "should", "will", "preferably", "likely", "usually", "optionally", "for example", "as an example", "in some examples", "often" or "might" (or other such language) be included or have a property, the specific component or feature is not required to be included or have that property. Such components or features may be optionally included in some examples, or may be excluded.

[0029] As used herein, the word “example” or “exemplary” means “serving as an example, instance, or illustration.” Any implementation described herein as “example” or “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations.

[0030] The terms “electrically coupled,” “electrically coupled,” “in communication with,” “in electronic communication with,” or “connected” in this disclosure refer to two or more elements or components that are connected by wired means and / or wireless means such that signals, voltage / current, data and / or information can be transmitted to and / or received from these elements or components.

[0031] The term "component" may refer to an article, device, or apparatus that may include one or more surfaces, parts, layers, and / or elements. For example, an exemplary component may include one or more substrates that may provide one or more underlying layers for the component, and may include one or more elements that form part of atop a substrate and / or one or more elements that may be disposed on top of a substrate. In the present disclosure, the term "element" may refer to an article, device, or apparatus that may provide one or more functions.

[0032] The term "sensing device" may refer to an article, device, or apparatus that measures a physical input from its environment and converts that input into data that can be interpreted by a person or machine. Sensing devices can be used in a variety of applications, including detecting dangerous gases in an environment. Sensing devices can be mounted in a fixed location or can be portable so as to be carried by a user. Portable sensing devices are typically powered by batteries. One common type of sensing device is a thermal conductivity gas sensing device, which can measure the concentration of a gas based on the difference in thermal conductivity of different gases relative to air.

[0033] The terms "sensor", "sensor circuit", "sensing circuit", "sensing element", "sensing element", etc. may refer to one or more components, integrated circuits, etc. within a sensing device that interact with the environment, detect an input to be detected (e.g., whether a hazardous gas is present), and provide an output (e.g., a voltage) to another component in the sensing device for interpretation. In some conventional thermal conductivity gas sensing devices, the sensing circuit includes a resistive heating element and one or more thermopiles. When power is applied to the resistive heating element, a temperature gradient is generated across the thermopiles, thereby generating an output voltage corresponding to the temperature difference. When exposed to a gas with a higher thermal conductivity than air (e.g., hydrogen), the heat loss from the resistive heating element is greater, and the temperature is therefore lower. This temperature difference varies with gas concentration and can be detected, measured, and used to provide an alarm.

[0034] In order to address the challenges and limitations associated with conventional sensing devices, various examples of the present disclosure may be provided. For example, various examples of the present disclosure may provide exemplary sensing devices, apparatuses, methods, and systems having sensing elements that do not include a separate heating element compared to some conventional sensing devices. The exemplary sensing devices include sensing elements that utilize the Peltier effect and the Seebeck effect as described herein. The Peltier effect states that a voltage applied to a thermocouple causes a temperature difference between the junctions of different materials in the thermocouple. The Seebeck effect states that a temperature difference between two dissimilar electrical conductors or semiconductors produces a voltage difference between the two materials.

[0035] Various embodiments of the present disclosure provide an exemplary sensing device having a sensing element, the sensing element comprising a first dissimilar conductive or semiconductive material and a second dissimilar conductive or semiconductive material, the first dissimilar conductive or semiconductive material and the second dissimilar conductive or semiconductive material being arranged such that there is at least a first junction between the first dissimilar material and the second dissimilar material and at least a second junction between the first dissimilar material and the second dissimilar material. In various embodiments, a direct current (DC) voltage is applied to the terminals of the sensing element for a first predetermined time period, which causes one or more of the junctions to become hotter than the ambient air according to the Peltier effect, and causes one or more of the junctions to become cooler than the ambient air. In various embodiments, when the DC voltage is removed from the terminals of the sensing element, the junctions are at different temperatures, and a voltage is generated on the terminals of the sensing element due to the temperature difference according to the Seebeck effect. In various embodiments, the voltage on the terminals of the sensing element is measured for a second predetermined time period. In various embodiments, which of the junctions becomes hotter and which becomes colder can be changed by reversing the polarity of the applied DC voltage.

[0036] In various implementations, after the DC voltage is removed from the terminals of the sensing element, the temperature difference between the junctions will decrease by a measurable amount. In various implementations, after the DC voltage is removed from the terminals of the sensing element, the temperature of each of the junctions will reach the ambient air temperature.

[0037] In various embodiments, a DC voltage is applied across the terminals of the sensing element by closing the first switch assembly, and the DC voltage is removed from the terminals of the sensing element by opening the first switch assembly. In various embodiments, a processor controls closing and opening of the first switch assembly.

[0038] In various embodiments, in the presence of a gas with a higher thermal conductivity than air (hydrogen or helium) and / or with increased air flow over the sensing element, the rate at which heat is dissipated from the junction to the surrounding air will increase. Under such conditions, the time for the junction temperature to reach equilibrium will decrease. Generally speaking, the time to reach thermal equilibrium decreases by about one percent for every one percent increase in hydrogen concentration in the air.

[0039] In various embodiments, the shape and characteristics of the measured voltage signal change as the temperature difference dissipates. In various embodiments, the shape and characteristics of the measured voltage signal can be related to the presence and / or concentration of a gas having a higher thermal conductivity than air and / or to the presence and amount of air flow over the sensing element.

[0040] In various embodiments, a voltage measuring device (e.g., a voltmeter) is selectively connected to the sensing element to measure the voltage across the terminals of the sensing element. In various embodiments, the voltage measuring device is connected to the sensing element by closing the second switch assembly, and the voltage measuring device is disconnected from the sensing element by opening the second switch assembly. In various embodiments, the processor controls the closing and opening of the second switch assembly.

[0041] In various embodiments, the sensing element is mounted on a substrate. In various embodiments, the sensing element includes a plurality of thermocouples forming a thermopile such that a plurality of first junctions exist between a first dissimilar material and a second dissimilar material and a plurality of second junctions exist between the first dissimilar material and the second dissimilar material. In various embodiments, the substrate includes a thinner portion and a thicker portion such that the plurality of first junctions are positioned on the thinner portion of the substrate and the plurality of second junctions are positioned on the thicker portion of the substrate.

[0042] Embodiments of the present disclosure may be used with any suitable sensing device including, but not limited to, gas detection sensors, air flow sensors, and dew point / humidity sensors.

[0043] Reference now Figure 1 , a block diagram of an exemplary sensing device 100 according to various embodiments of the present disclosure is provided. Figure 1 As shown, in some embodiments, the sensing device 100 includes a processor or processing circuit 102, a memory circuit 104, an input / output circuit 106, a communication circuit 108, a sensing circuit 110, and a power supply 118. In some embodiments, the sensing device 100 is configured to perform and carry out the operations described herein.

[0044] Although these components are described with respect to functional limitations, it should be understood that at least some of the specific implementations necessarily include the use of specific computing hardware. It should also be understood that in some embodiments, certain components described herein include similar or common hardware. For example, in some embodiments, two sets of circuits utilize the use of the same processor, memory, circuits, etc. to perform their associated functions, so that each set of circuits does not require duplicate hardware.

[0045] The processing circuit 102 may be embodied in a variety of different ways. In various embodiments, the use of the term "processor" or "processing circuit" should be understood to include a single-core processor, a multi-core processor, multiple processors within the sensing device 100, and / or one or more remote or "cloud" processors external to the sensing device 100. In some exemplary embodiments, the processing circuit 102 may include one or more processing devices configured to execute independently. Alternatively or additionally, the processing circuit 102 may include one or more processors configured in series via a bus to enable independent execution of operations, instructions, pipelining, and / or multithreading.

[0046] In an exemplary embodiment, the processing circuit 102 may be configured to execute instructions stored in the memory circuit 104 or otherwise accessible by the processor. Alternatively or additionally, the processing circuit 102 may be configured to perform hard-coded functions. Therefore, whether configured by hardware methods or software methods, or by a combination thereof, the processing circuit 102 may represent an entity (e.g., physically embodied in circuit form) that is capable of performing operations according to the embodiments of the present disclosure while being configured accordingly. Alternatively or additionally, the processing circuit 102 may be embodied as an executor of software instructions, and these instructions may specifically configure the processing circuit 102 to perform various algorithms embodied in one or more operations described herein when executing such instructions. In some embodiments, the processing circuit 102 includes hardware, software, firmware, and / or a combination thereof that performs one or more operations described herein.

[0047] In some embodiments, the processing circuit 102 (and / or a coprocessor or any other processing circuit that assists the processor or is otherwise associated with the processor) communicates with the memory circuit 104 via a bus for transferring information between components of the sensing device 100.

[0048] The memory or memory circuit 104 may be non-transitory and may include, for example, one or more volatile and / or non-volatile memories. In some embodiments, the memory circuit 104 includes or embodies an electronic storage device (e.g., a computer-readable storage medium). In some embodiments, the memory circuit 104 is configured to store information, data, content, applications, instructions, etc. for enabling the sensing device 100 to perform various operations and / or functions according to exemplary embodiments of the present disclosure.

[0049] Input / output circuit 106 may be included in sensing device 100. In some embodiments, input / output circuit 106 may provide output to a user and / or receive input from a user. Input / output circuit 106 may communicate with processing circuit 102 to provide such functions. Input / output circuit 106 may include one or more user interfaces. In some embodiments, the user interface may include a display including an interface presented as a web user interface, an application user interface, a user device, a back-end system. In some embodiments, input / output circuit 106 also includes a keyboard, a mouse, a joystick, a touch screen, a touch area, a soft key, a microphone, a speaker, or other input / output mechanisms. Processing circuit 102 and / or input / output circuit 106 may be configured to control one or more operations and / or functions of one or more user interface elements by computer program instructions (e.g., software and / or firmware) stored on a memory (e.g., memory circuit 104, etc.) accessible by a processor. In some embodiments, input / output circuit 106 includes or utilizes a user-oriented application to provide input / output functions to a computing device and / or other display associated with a user.

[0050] The communication circuit 108 may be included in the sensing device 100. The communication circuit 108 may include any device, such as a device or circuit embodied in hardware or a combination of hardware and software, which is configured to receive and / or transmit data from / to a network and / or any other device, circuit or module that communicates with the sensing device 100. In some embodiments, the communication circuit 108 includes, for example, a network interface for implementing communication with a wired or wireless communication network. Additionally or alternatively, the communication circuit 108 may include one or more network interface cards, antennas, buses, switches, routers, modems and supporting hardware, firmware and / or software, or any other device suitable for implementing communication via one or more communication networks. In some embodiments, the communication circuit 108 may include a circuit for interacting with an antenna and / or other hardware or software to cause a signal to be transmitted via an antenna and / or to process a signal received via an antenna. In some embodiments, the communication circuit 108 enables data to be transmitted and / or received to and / or from a user device, one or more sensors and / or other external computing devices that communicate with the sensing device 100.

[0051] The sensing circuit 110 may include any suitable circuitry to provide the desired sensing functionality. In the case of a thermal conductivity gas sensing device, the sensing circuit 110 includes a DC voltage source 112 , a sensing element 114 (including one or more thermopiles), and a voltage measurement device 116 .

[0052] The power source 118 provides power to the sensing device 100, including providing power to the sensing circuit 110. The power source 118 may include any suitable power source, and for a portable sensing device, may include one or more batteries.

[0053] In some embodiments, two or more of the groups of circuits 102-110 are combinable. Alternatively or additionally, one or more of the groups of circuits 102-110 perform some or all of the operations and / or functions described herein as being associated with another circuit. In some embodiments, two or more of the groups of circuits 102-110 are combined into a single module embodied in the form of hardware, software, firmware, and / or a combination thereof.

[0054] Although the above description provides an exemplary sensing device 100, it should be noted that the scope of the present disclosure is not limited to the above description. In some examples, the exemplary sensing device 100 according to the present disclosure can be in other forms. In some examples, the exemplary sensing device 100 may include one or more additional and / or alternative elements, and / or may be used with Figure 1 The shown structures are different.

[0055] Now refer to Figure 2, which is a model of an exemplary sensing device according to an exemplary embodiment of the present disclosure. Figure 2 The exemplary sensing device 200 includes a processing circuit 202, a DC voltage source 212, a sensing element (e.g., a thermocouple) 214, a voltage measuring device 216, a first switch component S1, and a second switch component S2. Similar to the above, the DC voltage source 212 is selectively connected to the sensing element 214 via the first switch component S1, and the voltage measuring device 216 (e.g., a voltmeter) is selectively connected to the sensing element 214 via the second switch component S2. Figure 2 In the simplified model of , the sensing element 214 includes a single thermocouple having two dissimilar materials (one material is represented by shading and the other material is represented by cross-hatching). The two dissimilar materials are arranged so that there are two junctions J1 and J2 between the two dissimilar materials. In various embodiments, the thermocouple of the sensing element 214 is exposed to ambient air so that the sensing device 200 can detect a gas having a higher thermal conductivity than air based on the rate at which heat is dissipated from the junctions J1 and J2 to the surrounding air. Because the rate at which heat is dissipated from the junctions J1 and J2 also increases with the increase of the air flow over the sensing element, in some embodiments, the sensing element 214 in the device to be used as a gas sensor will be positioned in a housing having a structure (e.g., a baffle) that allows ambient air to reach the sensing element 214 but shields the sensing element 214 from the flow of air. Conversely, an embodiment of the sensing element 214 in the device to be used as a flow sensor will be positioned in a housing having a structure (e.g., a tunnel) that allows flow of air to reach the sensing element 214.

[0056] exist Figure 2 In the illustrated embodiment of the present invention, the processing circuit 202 sends control signals to the first switch component S1 and the second switch component S2 to control the closing and opening of the switches thereof. The processing circuit 202 causes the first switch component S1 to close and the second switch component S2 to open to connect the DC voltage source 212 to the sensing element 214 and disconnect the voltage measuring device 216 from the sensing element 214. Due to the two dissimilar materials, the voltage applied to the sensing element 214 will increase the temperature of one junction (e.g., J1) to above the ambient temperature and reduce the temperature of the other junction (e.g., J2) to below the ambient temperature due to the Peltier effect. Which junction experiences a temperature increase and which junction experiences a temperature decrease depends on the polarity of the applied DC voltage and can be changed by changing the polarity of the applied DC voltage.

[0057] The processing circuit 202 causes the second switch assembly S2 to close and the first switch assembly S2 to disconnect, so as to connect the voltage measuring device 216 to the sensing element 214 and disconnect the DC voltage source 212 from the sensing element 214. After the DC voltage is disconnected from the sensing element 214, the temperature of the two joints will begin to balance and return to the ambient temperature over time. Due to the two different materials, the temperature difference between the two different electrical conductors or semiconductors produces a voltage difference between the two materials due to the Seebeck effect. The voltage will decrease over time as the temperature difference decreases. As the temperature difference decreases and the voltage decreases accordingly, the voltage measuring device 216 measures the voltage within a period of time. Therefore, in some embodiments, the same sensing element (that is, the same thermocouple) is used to generate the temperature difference, and then the voltage generated by the temperature difference is measured as the temperature difference decreases. In this regard, a separate heating element is not required in various embodiments of the present invention.

[0058] In some embodiments, the first dissimilar material and the second dissimilar material of the sensing element are conductive or semiconductive materials. For example, the first dissimilar material and the second dissimilar material may include chrome-nickel alloy and nickel-aluminum alloy, respectively. Chrome-nickel alloy is an alloy of nickel and chromium plus nine other elements. Nickel-aluminum alloy is an alloy containing nickel, manganese, aluminum, silicon and nine other elements. However, any suitable dissimilar conductive or semiconductive material may be used. For example, in various embodiments, any of the materials listed in Figure 11 of U.S. Patent No. 11,747,184, entitled THERMOPILE-BASED FLOW SENSING DEVICE, issued on September 5, 2023, may be used as the first dissimilar material and / or the second dissimilar material described herein. The contents of U.S. Patent No. 11,747,184 are incorporated herein in their entirety.

[0059] exist Figure 2 In the illustrated embodiment of the present invention, the processing circuit 202 is connected to the voltage measuring device 216 to receive the measured voltage. In some embodiments, the processing circuit 202 processes the measured voltage (as further described below) to determine the presence and / or concentration of thermally conductive gas adjacent to the sensing element 214 and / or the presence and / or amount of air flow over the sensing element 214. In some embodiments, the processing circuit 202 generates an output signal to send the determined gas concentration and / or air flow to, for example, a display element and / or a central monitoring device for display to a user.

[0060] Now refer to Figure 3 , which is a model of an exemplary sensing element of an exemplary sensing device according to an exemplary embodiment of the present disclosure. Figure 3 The exemplary sensing device 300 includes a DC voltage source 312, a sensing element 314 and a first switch component S1. For simplicity, Figure 3 The voltage measuring device, processing circuit and second switch assembly are omitted. Figure 3 In the illustrated embodiment, the sensing element 314 includes a plurality of thermocouples connected in series, such that there are multiple segments of two dissimilar materials (one material represented by shading and the other material represented by cross-hatching), with multiple first junctions J1 (five are shown) and multiple second junctions J2 (four are shown). Having multiple thermocouples connected in series causes a greater temperature difference when a voltage is applied by the DC voltage source 312, and a greater voltage is generated by the temperature difference between the dissimilar materials, thereby providing a voltage that is easier to measure.

[0061] In various embodiments, the sensing element is mounted on a (typically planar) substrate such as a silicon substrate. In various embodiments, a thinner substrate is preferred so that the substrate itself does not conduct too much heat away from the sensing element, and the primary source of heat loss is through thermal conduction of the gas surrounding the sensing element, rather than through thermal conduction of the substrate.

[0062] In some embodiments, the substrate has a thinner portion and a thicker portion. Figure 3 In the illustrated embodiment of , the substrate includes a thinner portion 320 on which the second bonding portion J2 is mounted and a thicker portion 322 on which the first bonding portion J1 is mounted.

[0063] As described above, when a DC voltage is applied to the terminals of the sensing element of the thermal conductivity gas sensing device as described herein, a temperature gradient is generated across the thermopile, which generates an output voltage corresponding to the temperature. Figure 4 , which is a graph 400 illustrating a voltage response of an exemplary thermal conductivity gas sensing device. Figure 4 Graph 400 of illustrative embodiments shows the voltage (V(sensing), y-axis) at the terminals of an exemplary sensing element of an exemplary sensing device over time (t, x-axis). In graph 400, time t(s) is the time after the DC voltage has been applied and the temperature difference (and therefore the voltage) has reached its maximum value (this may be referred to as the "steady-state time"), time t(1) is the time when the DC voltage has been removed from the terminals of the exemplary sensing element and (after a short delay) the temperature and corresponding voltage first begin to change, time t(2) is the end of the measurement period, V(e) is the voltage on the sensing element at time t(2), and V(s) is the initial or steady-state voltage (during time t(s)). The end of the measurement period t(2) may be, for example, when the steady-state voltage V(s) has decreased by 50%, when the voltage V(sensing) has reached zero (indicating that the temperature of the junction has equilibrated), or any other suitable time.

[0064] Due to the faster temperature dissipation as described above, the presence of a gas with a higher thermal conductivity than air or the presence of air flow will cause the steady-state voltage V(s) to be lower and will cause the voltage V(sensing) to decrease faster after the voltage is removed from the sensing element. Therefore, the steady-state voltage V(s) is proportional to the concentration of the gas with a higher thermal conductivity than air and is proportional to the air flow. Similarly, the time constant (τ) of the voltage V(sensing) curve is also proportional to the concentration of the gas with a higher thermal conductivity than air and is proportional to the air flow. Therefore, in various embodiments, the measured steady-state voltage V(s) and / or the time constant (τ) of the voltage V(sensing) curve can be used to determine the presence of a gas with a higher thermal conductivity than air and / or the presence of air flow.

[0065] In some implementations, the time constant (τ) of the voltage V(sensing) curve can be determined using the following equation:

[0066]

[0067] Once the time constant (τ) is determined, V(sense) at any time (t) can be calculated using the following equation:

[0068]

[0069] In some embodiments, a steady-state voltage (V(s)) and / or a time constant (τ) when only air is present (i.e., no gas having a higher thermal conductivity than ambient air) and / or when no air flow is present is determined and stored for use in gas and / or air flow detection. Such advance determination of the steady-state voltage (V(s)) and / or the time constant (τ) when only air is present and / or when no air flow is present may be performed in any suitable manner and at any suitable time. For example, in some embodiments, the steady-state voltage (V(s)) and / or the time constant (τ) when only air is present and / or when no air flow is present is determined during calibration of the device. Such calibration may occur, for example, during a manufacturing process. In some embodiments, the steady-state voltage (V(s)) and / or the time constant (τ) are also determined at multiple different gas concentrations and / or air flow rates and stored for use in gas and / or air flow detection. In this regard, in some embodiments, the measured steady-state voltage (V(s)) and / or time constant (τ) are compared to stored values ​​for the steady-state voltage (V(s)) and / or time constant (τ) to determine gas concentration and / or air flow.

[0070] In some implementations, the time constant can be determined by measuring the time it takes for the voltage to decrease by a predetermined amount.

[0071] In some embodiments, the voltage is not required to reach steady state during the powering period. If it is known how long the DC voltage has been applied and how hot it has reached, then the apparatus as described herein can still be used, albeit with more complex signal processing. Keeping the powering portion of the process as short as possible has the benefit of minimizing power consumption.

[0072] In some embodiments, the substrate has a uniform thickness. For example, in some embodiments, the substrate may include planar silicon that is approximately 10 to 15 thousandths of an inch thick. In some embodiments, all of the binding portions of the sensing element are thermally isolated from the substrate. In some embodiments, some of the binding portions of the sensing element (such as the first binding portion J1) are thermally isolated from the substrate, while other binding portions (such as the second binding portion J2) are not thermally isolated from the substrate. An embodiment in which all of the binding portions of the sensing element are thermally isolated from the substrate may be referred to as "symmetrical", such that applying a voltage to the sensing element causes one group of binding portions (such as the first binding portion J1) to become hotter than the substrate and another group of binding portions (such as the second binding portion J2) becomes colder. An embodiment in which some of the binding portions of the sensing element are thermally isolated from the substrate and other binding portions are not thermally isolated from the substrate may be referred to as "asymmetric", such that one group of binding portions (such as the first binding portion J1) remains close to the substrate temperature and another (floating) group of binding portions (such as the second binding portion J2) is heated or cooled relative to the substrate. In some embodiments, the thermally isolated binding portions are thermally isolated because the binding portions are positioned on a relatively thin substrate.

[0073] In some symmetrical embodiments, the polarity of the applied DC voltage is changed with each measurement cycle, so that the hot and cold junctions of the device are swapped on each alternating measurement cycle, and the resulting temperature gradient, and therefore the thermopile output voltage, is reversed on each alternating measurement cycle. In such embodiments, offset voltage errors in the electronics can cancel each other out.

[0074] For a device to be classified as "intrinsically safe", the maximum temperature of the device must be maintained below the temperature at which flammable gases can be ignited. Depending on the flammable gases present, this maximum temperature can be as low as 100C. By heating one end of the device and cooling the other end (symmetrical sensor), twice the temperature difference can be generated for the same upper temperature limit. For an asymmetrical sensor, the floating end can be cooled relative to the substrate rather than heated so that the maximum temperature of the device remains below the ambient temperature. In this regard, in some embodiments of the present invention, excessive temperature rise beyond the gradient can be avoided.

[0075] In some asymmetric embodiments, in dry air, the output signal due to the thermal conductivity of the air should be the same, regardless of whether the floating end is heated or cooled relative to the environment (except for the opposite polarity). Similarly, the output voltage signal should be proportional only to the applied voltage, and the instantaneous signal should remain constant with the applied voltage because the heat loss from the device is the same under all conditions. However, if the floating end is cooled to below the dew point of the air, there will be a sudden change in heat loss due to condensation occurring on the floating end, so the signal is very different from the signal measured at other voltages or when the floating end is heated. Therefore, in practice, by taking multiple measurements at different applied voltages and polarities and noting when a sudden change in heat loss occurs, the device of some embodiments of the present disclosure can act as a thermal conductivity device and is similar to a cooled mirror dew point meter. In some embodiments, the measured dew point can be used to calculate the absolute humidity, which can then be used to apply compensation to the gas thermal conductivity measurement.

[0076] Now we will see Figure 5 , which provides a flowchart showing exemplary steps, procedures, processes and / or operations according to various embodiments of the present disclosure. The various methods described herein (including, for example, Figure 5 The method shown) may provide various technical benefits and / or improvements.

[0077] See now Figure 5 , showing an exemplary method 500. In some embodiments, the exemplary method includes a method of sensing a thermally conductive gas and / or air flow. At step / operation 501, a processor (such as but not limited to the above combined Figure 1 The processing circuit 102 of the exemplary sensing device 100 described above causes the first switch component to be closed and the second switch component to be open. As described above, closing such a first switch component switches a DC voltage source (such as, but not limited to, the above combined Figure 1 The exemplary sensing device 100 is provided with a DC voltage source 112 connected to a sensing element (such as, but not limited to, the above-described Figure 1 The sensing element 114 of the exemplary sensing device 100 is shown.

[0078] At step / operation 503, a DC voltage source (such as but not limited to the above combined Figure 1The DC voltage source 112 of the exemplary sensing device 100 described herein applies a DC voltage to the sensing element. The applied DC voltage may have any suitable magnitude and duration. In some exemplary embodiments, a DC voltage in the range of millivolts to volts is applied for tens of milliseconds, depending on the physical size of the sensing element (generally speaking, the larger the sensing element, the longer the DC voltage must be applied to reach a steady-state voltage). The voltage should generally be at a level that can cause a significant temperature difference (e.g., about 100 degrees Celsius) across the junction.

[0079] At step / operation 505, a processor (such as but not limited to the above combined Figure 1 The processing circuit 102 of the exemplary sensing device 100 described above causes the first switch component to be opened and the second switch component to be closed. As described above, opening such a first switch component disconnects the DC voltage source, and closing such a second switch component disconnects the voltage measuring device (such as, but not limited to, the above-mentioned combination Figure 1 The voltage measuring device 116 of the exemplary sensing device 100 is connected to the sensing element.

[0080] At step / operation 507, a voltage measuring device (such as but not limited to the above combined Figure 1 The voltage measurement device 116 of the exemplary sensing device 100 measures the voltage across the sensing element. As described above, when the second switch assembly is initially closed, the temperature difference between the junctions will be at its maximum, there will be a short delay, and then the temperature difference between the junctions will begin to balance and the measured voltage will begin to decay toward zero.

[0081] Although not in Figure 5 As shown in , but as described above, the measured voltage when the second switch assembly is initially closed (ie, the steady state voltage) can be used to determine the presence and / or concentration of the thermally conductive gas and / or the presence and / or amount of air flow.

[0082] At step / operation 509, a processor (such as but not limited to the above combined Figure 1 The processing circuit 102 of the exemplary sensing device 100 determines the time constant of the voltage curve as described above.

[0083] At step / operation 511, a processor (such as but not limited to the above combined Figure 1 The processing circuit 102 of the exemplary sensing device 100 uses the determined time constant of the voltage curve to determine the presence and / or concentration of a thermally conductive gas and / or the presence and / or amount of air flow, as described above.

[0084] In some embodiments, the method repeats steps / operations 501-511 continuously or periodically.

[0085] The operations and processes described herein support a combination of means for performing the specified functions and a combination of operations for performing the specified functions. It will be understood that one or more operations and a combination of operations can be implemented by a computer system based on dedicated hardware that performs the specified functions or a combination of dedicated hardware and computer instructions.

[0086] In some example embodiments, some of the operations herein may be modified or further amplified as described below. In addition, in some embodiments, additional optional operations may also be included. It should be understood that each of the modifications, optional additions, or amplifications described herein may be included in the operations herein, either individually or in combination with any other features described herein.

[0087] The foregoing method and process descriptions are provided only as illustrative examples, and are not intended to require or imply that the steps of the various embodiments must be performed in the order presented. As will be appreciated by those skilled in the art, the order of steps in the above-described embodiments may be performed in any order. Words such as "afterwards," "then," "next," and the like are not intended to limit the order of the steps; these words are simply used to guide the reader through the description of the method. In addition, for example, any reference to a claim element in the singular form using the articles "a," "an," or "the" should not be construed as limiting the element to the singular and, in some cases, may be construed in the plural.

[0088] Although various embodiments according to the principles disclosed herein have been shown and described above, modifications may be made thereto by those skilled in the art without departing from the teachings of the present disclosure. The embodiments described herein are representative only and are not intended to be limiting. Many variations, combinations and modifications are possible and are within the scope of the present disclosure. Alternative embodiments obtained by merging, integrating and / or omitting the features of the embodiments are also within the scope of the present disclosure. Therefore, the scope of protection is not limited by the description given above, but 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 embodiments of the present disclosure. In addition, any of the above 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.

[0089] In addition, the section headings used herein are intended to be consistent with the recommendations of 37 CFR § 1.77 or to provide organizational clues. These headings should not limit or characterize the disclosures set forth in any claims that may be published from this disclosure. For example, the description of the technology in the "background technology" should not be interpreted as an admission that a certain technology is prior art to any disclosure in this disclosure. "Summary of the invention" should also not be considered as a limiting characterization of the disclosure set forth in the published claims. In addition, any reference to the singular "disclosure" or "embodiment" in this disclosure should not be used to prove that there is only one novel point in this disclosure. According to the limitations of multiple claims published from this disclosure, multiple embodiments of the disclosure may be set forth, and such claims accordingly define the disclosures protected by them and their equivalents. In all cases, the scope of these claims should be considered in accordance with the present disclosure on the merits of the claims themselves, and should not be limited by the titles set forth herein.

[0090] Moreover, without departing from the scope of the present disclosure, the systems, subsystems, devices, techniques and methods described and shown in a discrete or separate manner in various embodiments may be combined or integrated with other systems, modules, techniques or methods. Other devices or components shown or discussed as being connected or communicating with each other may be indirectly connected through some intermediate devices or components, whether such connection is made electrically, mechanically or otherwise. Other examples of changes, substitutions and modifications may be determined by those skilled in the art and may be made without departing from the scope disclosed herein.

[0091] Those skilled in the art to which these embodiments belong will think of many modifications and other embodiments of the disclosure set forth herein, which have the benefit of the teachings presented in the foregoing description and the associated drawings. Although the drawings only show certain components of the devices and systems described herein, various other components can be used in combination with the components and structures disclosed herein. Therefore, 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. For example, various elements or components may be combined, rearranged or integrated into another system, or certain features may be omitted or not implemented. In addition, the steps in any of the above methods may not necessarily occur in the order depicted in the drawings, and in some cases, one or more of the depicted steps may occur substantially simultaneously, or may involve additional steps. Although specific terms are used herein, they are used only in a general and descriptive sense, not for restrictive purposes.

Claims

1. A sensing device, comprising: substrate; a conductive element positioned on the substrate, the conductive element comprising a first dissimilar material and a second dissimilar material, the first dissimilar material and the second dissimilar material being arranged such that a first joint exists between the first dissimilar material and the second dissimilar material and a second joint exists between the first dissimilar material and the second dissimilar material, the conductive element further comprising a first connecting terminal and a second connecting terminal; Direct current (DC) voltage source; Voltage measuring device; a first switching circuit for selectively connecting the DC voltage source to the first connection terminal and the second connection terminal of the conductive element; and a processor that controls the first switching circuit to selectively connect the DC voltage source to the first connection terminal and the second connection terminal of the conductive element to apply a DC voltage across the first connection terminal and the second connection terminal of the conductive element during a first time period, and selectively disconnect the DC voltage source from the first connection terminal and the second connection terminal of the conductive element to measure the voltage across the first connection terminal and the second connection terminal during a second time period.

2. The sensing device according to claim 1, wherein the first dissimilar material and the second dissimilar material of the conductive element are arranged such that a plurality of first junctions exist between the first dissimilar material and the second dissimilar material and a plurality of second junctions exist between the first dissimilar material and the second dissimilar material; wherein the substrate comprises a first portion and a second portion thinner than the first portion; wherein the plurality of first bonding portions are positioned on the first portion of the substrate; and The plurality of second bonding portions are positioned on the second portion of the substrate.

3. The sensing device according to claim 1, wherein the first time period is a time period long enough to allow the voltages on the first connection terminal and the second connection terminal to reach a steady-state voltage; and The second period of time is a period of time long enough to reduce the temperature of the first joint and the temperature of the second joint by a measurable amount.

4. The sensing device according to claim 3, wherein the processor determines the steady-state voltage on the first connection terminal and the second connection terminal; and The processor uses the determined steady-state voltage to determine (i) the presence and / or concentration of a thermally conductive gas adjacent to the conductive element and / or (ii) the presence and / or amount of air flow over the conductive element.

5. The sensing device according to claim 3, wherein the processor determines a time constant of the voltages on the first connection terminal and the second connection terminal during the second time period; and The processor uses the determined time constant to determine (i) the presence and / or concentration of a thermally conductive gas adjacent to the conductive element and / or (ii) the presence and / or amount of air flow over the conductive element.

6. The sensing device of claim 1 , wherein the processor causes the DC voltage source to apply a plurality of different voltages across the first and second connection terminals of the conductive element, each different voltage being applied a first time with a first polarity and a second time with an opposite second polarity; wherein after applying each of the plurality of different voltages, the processor causes the voltage measuring device to measure the voltages on the first connection terminal and the second connection terminal of the conductive element; and The processor detects when a time constant of the voltage across the first and second connection terminals changes abruptly, and determines a temperature consistent with the abrupt change in the time constant of the voltage across the first and second connection terminals, the temperature being the dew point.

7. A method of sensing a thermally conductive gas and / or air flow, the method comprising: causing, by a processor of the sensing device, a first switching circuit to selectively connect a direct current (DC) voltage source to a first connection terminal and a second connection terminal of a conductive element, the conductive element comprising a first dissimilar material and a second dissimilar material, the first dissimilar material and the second dissimilar material being arranged such that a first junction exists between the first dissimilar material and the second dissimilar material and a second junction exists between the first dissimilar material and the second dissimilar material; applying a DC voltage to the first connection terminal and the second connection terminal of the conductive element by the DC voltage source during a first time period; causing, by the processor of the sensing device, the first switching circuit to selectively disconnect the DC voltage source from the first connection terminal and the second connection terminal of the conductive element; as well as The voltage at the first connecting terminal and the second connecting terminal is measured by a voltage measuring device during a second time period.

8. The method according to claim 7, wherein the first time period is a time period long enough for the voltages on the first connection terminal and the second connection terminal to reach a steady-state voltage; wherein the second period of time is a period of time long enough to reduce the temperature of the first junction and the temperature of the second junction by a measurable amount; and The method further comprises: determining, by the processor of the sensing device, the steady-state voltages on the first connection terminal and the second connection terminal; as well as The determined steady state voltage is used by the processor of the sensing device to determine (i) the presence and / or concentration of a thermally conductive gas adjacent to the conductive element and / or (ii) the presence and / or amount of air flow over the conductive element.

9. The method according to claim 8, further comprising: determining, by the processor of the sensing device, a time constant of the voltages on the first connection terminal and the second connection terminal during the second time period; as well as The determined time constant is used by the processor of the sensing device to determine (i) the presence and / or concentration of a thermally conductive gas adjacent to the conductive element and / or (ii) the presence and / or amount of air flow over the conductive element.

10. The method according to claim 7, further comprising: applying a plurality of different voltages to the first connection terminal and the second connection terminal of the conductive element, each different voltage being applied a first time with a first polarity and a second time with an opposite second polarity; measuring the voltages at the first connection terminal and the second connection terminal of the conductive element after applying each of the plurality of different voltages; as well as A sudden change in the time constant of the voltage across the first and second connection terminals is detected, and a temperature consistent with the sudden change in the time constant of the voltage across the first and second connection terminals is determined, the temperature being the dew point.

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