Thermal conductivity sensor for detecting a gas

Abstract

A thermal conductivity sensor is disclosed.SOLUTION: The thermal conductivity sensor comprises a first portion having at least one heating element and a second portion having at least one sensing element. The first portion and the second portion are positioned such that the at least one heating element and the at least one sensing element are spaced apart by a gas channel between the first portion and the second portion, the gas channel being configured to allow gas to pass through the gas channel so as to pass between the at least one heating element and the at least one sensing element. The at least one sensing element is configured to measure a change in temperature of the gas to detect the presence of the gas having the higher thermal conductivity.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to hydrogen sensors, and more particularly to thermal conductivity sensors for detecting gases. [Background technology]

[0002] Hydrogen sensors are an essential component in thermal conductivity measurements and play a multifaceted role in ensuring accuracy, safety, and control within experimental setups involving hydrogen gas. Conventional thermal conductivity sensors function by generating heat, which increases the temperature of the gas surrounding the sensor, and then measuring the temperature. When the gas contains a contaminant, such as hydrogen, which has a higher thermal conductivity than the bulk gas, the higher thermal conductivity of the contaminant gas results in more heat loss and a lower temperature. The temperature drop is then measured to determine the concentration of the gas in the surrounding environment. However, the accuracy of current thermal conductivity sensors can be compromised by mismanagement of heat distribution within the thermal conductivity sensor assembly. Furthermore, conventional thermal conductivity sensors have poor heat dissipation or inefficient insulation, which can lead to temperature fluctuations. Such temperature fluctuations affect the performance of both the heating and sensing elements, thus resulting in inaccurate readings.

[0003] The inventors have identified numerous areas for improvement in existing technologies and processes, which are the subject of the embodiments described herein. Through exerted effort, ingenuity, and innovation, many of these deficiencies, challenges, and problems have been overcome by developing solutions contained in the embodiments of the present disclosure, some examples of which are described in detail herein. Summary of the Invention

[0004] The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosure. This summary is not an extensive overview and is not intended to identify key or critical elements or to delineate the scope of such elements. Its purpose is to present some concepts of the described features in a simplified form as a prelude to the more detailed description that is presented later.

[0005] In one exemplary embodiment, a thermal conductivity sensor for detecting gas is disclosed. The thermal conductivity sensor includes a first portion having at least one heating element and a second portion having at least one sensing element. The first and second portions are positioned such that the at least one heating element and the at least one sensing element are spaced apart by a gas channel or gap between the first and second portions, and the gas channel or gap is configured to allow gas to pass between the at least one heating element and the at least one sensing element. The at least one sensing element is configured to measure a change in temperature of the gas to detect the presence of a gas having a higher thermal conductivity.

[0006] In some embodiments, the first and second portions of the thermal conductivity sensor are arranged in a plurality of orientations, further comprising at least one of a vertical orientation and a horizontal orientation.

[0007] In some embodiments, in the vertical orientation, the at least one heating element is positioned above or below the at least one sensing element and separated via a gas channel such that gas passes around the at least one heating element and the at least one sensing element.

[0008] In some embodiments, in a horizontal orientation, at least one heating element is positioned beside at least one sensing element, and the at least one heating element and the at least one sensing element are positioned on separate elevated structures separated by a gap such that gas passes around the at least one heating element and the at least one sensing element, hi some embodiments, gas passes over and under the at least one heating element and the at least one sensing element.

[0009] In some embodiments, the at least one sensing element is configured to measure changes in temperature of the gas to monitor heat transfer within the gas surrounding the thermal conductivity sensor, wherein the changes in heat transfer within the gas surrounding the thermal conductivity sensor correspond to changes in thermal properties of the gas.

[0010] In some embodiments, in a vertical orientation, the first portion corresponds to the top cap and the second portion corresponds to the base. Further, each end of the top cap is bonded to a corresponding end of the base with an adhesive such that a gas channel is provided between the top cap and the base. The adhesive includes at least one of a frit bond, an anodic bond, an epoxy adhesive, and a eutectic bond. The adhesive depends on the materials of the top cap and the base.

[0011] In some embodiments, the top cap comprises a set of vent holes configured to allow diffusion of gas into and through the gas channels of the thermal conductivity sensor, and the top cap and base are made from one or more materials including at least one of silicon, glass, or plastic.

[0012] In some embodiments, the thermal conductivity sensor further comprises an ambient temperature sensing element configured to measure the temperature of the gas passing through the gas channel in real time.

[0013] In some embodiments, the at least one sensing element comprises at least one of a resistor, a diode, or a thermopile. In some embodiments, the at least one heating element is made from a group of materials including at least one of iron-nickel (NiFe) / Permalloy, platinum (Pt), chromium (Cr), doped silicon (Si) or polysilicon, nichrome (NiCr), nickel (Ni), platinum silicide (PtSi) and other metal silicides, tungsten (W), titanium nitride (TiN), aluminum nitride (AlN), tungsten nitride (WN), or any combination thereof. In some embodiments, the at least one sensing element is made from a group of materials including at least one of NiFe / Permalloy, Pt, Cr, doped Si or polysilicon, NiCr, Ni, PtSi and other metal silicides, W, TiN, AlN, WN, or any combination thereof.

[0014] In another embodiment, a method is disclosed that includes positioning a first portion of a thermal conductivity sensor having at least one heating element and a second portion of the thermal conductivity sensor having at least one sensing element such that the at least one heating element and the at least one sensing element are spaced apart by a gas channel or gap between the first and second portions, the gas channel or gap being configured to allow gas to pass through the gas channel or gap so that the gas passes between the at least one heating element and the at least one sensing element, and the at least one sensing element being configured to measure a change in temperature of the gas to detect the presence of a gas having a higher thermal conductivity.

[0015] The foregoing summary has been provided merely for the purpose of summarizing some exemplary embodiments to provide a basic understanding of some aspects of the present invention. Accordingly, it should be understood that the above-described embodiments are merely examples and should not be construed as narrowing the scope or spirit of the present invention in any way. It should be understood that the scope of the present invention encompasses many potential embodiments in addition to those summarized herein, some of which are further described below. [Brief explanation of the drawings]

[0016] Having thus described in general terms certain exemplary embodiments of the present disclosure, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and in which: [Figure 1] FIG. 1B is a cross-sectional side view of a thermal conductivity sensor in a vertical orientation according to an exemplary embodiment of the present disclosure. [Figure 2] FIG. 1B is a top view of a thermal conductivity sensor in a vertical orientation according to an exemplary embodiment of the present disclosure. [Figure 3A] FIG. 2 is a cross-sectional side view of a thermal conductivity sensor in a horizontal orientation according to an exemplary embodiment of the present disclosure. [Figure 3B] FIG. 1B is a top view of a thermal conductivity sensor in a horizontal orientation according to an exemplary embodiment of the present disclosure. [Figure 4A] FIG. 10 is a cross-sectional side view of another thermal conductivity sensor in a horizontal orientation, according to an exemplary embodiment of the present disclosure. [Figure 4B] FIG. 10 illustrates a filter media associated with another thermal conductivity sensor in a horizontal orientation, according to an exemplary embodiment of the present disclosure. [Figure 5] 10 is a graphical representation of a simulation of a thermal conductivity sensor in a vertical orientation, according to an exemplary embodiment of the present disclosure. [Figure 6] 1 is a graphical representation of the effect of temperature on at least one sensing element, according to an exemplary embodiment of the present disclosure. [Figure 7] 10 is a graphical representation of the change in sensed temperature corresponding to a 1% change in thermal conductivity of a gas, according to an exemplary embodiment of the present disclosure. [Figure 8] 10 is a graphical representation of a preliminary parallel plate simulation of changes in sensed temperature due to changes in thermal conductivity sensors, according to an exemplary embodiment of the present disclosure. [Figure 9] 10 is a graphical representation of another parallel plate preliminary simulation of a thermal conductivity sensor, according to an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0017] Certain embodiments will now be described in more detail below with reference to the accompanying drawings, in which some, but not all, embodiments are shown. Indeed, various embodiments 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.

[0018] The components shown in the drawings represent components that may or may not be present in various embodiments of the invention described herein, and thus an embodiment may include fewer or more components than those shown in the drawings without departing from the scope of the invention. Some components may be omitted from one or more figures or shown with dashed lines for visibility of the underlying components.

[0019] The present disclosure provides various embodiments of a thermal conductivity sensor. An embodiment may include a first portion having at least one heating element and a second portion having at least one sensing element. In various embodiments, the first portion and the second portion are positioned such that the at least one heating element and the at least one sensing element are spaced apart by a gas channel between the first portion and the second portion. In various embodiments, the gas channel is configured to allow gas to pass between the at least one heating element and the at least one sensing element. In various embodiments, the at least one sensing element is configured to measure a change in temperature of a gas to detect the presence of a gas having a higher thermal conductivity.

[0020] 1 illustrates a side cross-sectional view of a thermal conductivity sensor 100 in a vertical orientation according to an exemplary embodiment of the present disclosure. The thermal conductivity sensor 100 can comprise a first portion 102 and a second portion 104.

[0021] In some embodiments, the first portion 102 may include at least one heating element 106. The at least one heating element 106 may be configured to heat a gas flowing through the thermal conductivity sensor 100. The first portion 102 may correspond to a thick film having the at least one heating element 106. In some embodiments, the thick film may facilitate improving the reliability of the first portion 102 of the thermal conductivity sensor 100 when the at least one heating element 106 is heated. In some embodiments, the at least one heating element 106 may be made from a group of materials. In one example, the group of materials may preferably include at least one of Permalloy (81:19 iron-nickel (NiFe)) and 60:40 NiFe. A thin film of Permalloy may have a temperature coefficient of resistance of 3600 parts per million per degree Celsius (ppm / °C) to 4100 ppm / °C. In another example, the group of materials may include at least one of platinum (Pt), chromium (Cr), doped silicon (Si) or polysilicon, nichrome (NiCr), nickel (Ni), platinum silicide (PtSi) and other metal silicides, tungsten (W), titanium nitride (TiN), aluminum nitride (AlN), tungsten nitride (WN), or any combination thereof.

[0022] In some embodiments, the second portion 104 may include at least one sensing element 108. The at least one sensing element 108 may be configured to measure a change in temperature of the gas to detect the presence of a gas having a higher thermal conductivity. In one example, the gas may correspond to hydrogen gas. Furthermore, the at least one sensing element 108 may be configured to measure a change in temperature of the gas to monitor heat transfer within the gas surrounding the thermal conductivity sensor 100. In one embodiment, the change in heat transfer within the gas surrounding the thermal conductivity sensor 100 may correspond to a change in the thermal properties of the gas. Furthermore, the at least one sensing element 108 may be configured to measure a change in temperature of the gas within a range corresponding to the sensing region 116. Within the sensing region 116, the at least one sensing element 108 may be configured to monitor heat transfer within the gas surrounding the thermal conductivity sensor 100.

[0023] In some embodiments, the at least one sensing element 108 may comprise at least one of a resistor, a diode, or a thermopile. In some embodiments, the at least one sensing element 108 may be made of a material group or a material pair from a material group. In one example, the thermocouple material group may preferably include at least one of chromium (Cr) and permalloy (80 / 20 NiFe) or Cr and 60 / 40 NiFe. In another thermocouple example, the material group may include at least one of polysilicon and aluminum (Al), n-type polysilicon and p-type polysilicon, Ni-Fe alloy and chromium disilicide, chromium nitride and copper (Cu), chromium nitride and Al, chromium nitride and p-type polysilicon, and copper (Cu) and a Cu-Ni alloy. In one exemplary embodiment, the pair of materials forms a thermocouple. In one exemplary embodiment, the resistor may be made of a material from the above-mentioned material group. In another exemplary embodiment, the resistor may be made from a group of materials such as platinum (Pt), nichrome (NiCr), platinum silicide (PtSi), other metal silicides, tungsten (W), and other materials known in the art. Additionally, the diode may correspond to either a pn junction or a metal-semiconductor junction.

[0024] In some embodiments, the first portion 102 and the second portion 104 of the thermal conductivity sensor 100 may be positioned such that the at least one heating element 106 and the at least one sensing element 108 are spaced apart by a gas channel 110 between the first portion 102 and the second portion 104. The gas channel 110 may be configured to allow gas to pass between the at least one heating element 106 and the at least one sensing element 108. In some embodiments, the at least one heating element 106 may be spaced apart from the at least one sensing element 108 such that the at least one heating element 106 and the at least one sensing element 108 are on opposite sides of the gas channel 110. Thus, the at least one sensing element 108 may not be heated by the at least one heating element 106 to the elevated temperature of the at least one heating element 106, but may instead be heated directly by the gas.

[0025] In some embodiments, the first portion 102 and the second portion 104 of the thermal conductivity sensor 100 may be arranged in multiple orientations. Furthermore, the multiple orientations may include at least a perpendicular orientation. In some embodiments, in the perpendicular orientation, the at least one heating element 106 may be positioned above the at least one sensing element 108 and separated via a gas channel 110 such that gas passes around the at least one heating element 106 and the at least one sensing element 108. In one example, passing gas around the at least one heating element 106 and the at least one sensing element 108 may correspond to passing gas under or over the at least one heating element 106 and the at least one sensing element 108. In some embodiments, positioning the at least one heating element 106 above the at least one sensing element 108 and having gas between the at least one heating element 106 positioned above the at least one sensing element 108 may result in a significant improvement in the sensitivity of the thermal conductivity sensor 100 for detecting thermal conductivity. In some alternative embodiments, in a vertical orientation, the at least one heating element 106 may be positioned below the at least one sensing element 108 and separated by a gas channel 110 .

[0026] In some embodiments, the thermal conductivity sensor 100 may rely on the use of heat and heat transfer. Additionally, a temperature difference may exist between the at least one heating element 106 and the at least one sensing element 108 in the gas. Additionally, heat transfer may vary through the gas to which the at least one heating element 106 and the at least one sensing element 108 are exposed. Furthermore, the change in heat transfer may correspond to a change in the thermal properties of the gas. The change in heat transfer may change the output of the thermal conductivity sensor 100 and may be directly related to the composition of the gas.

[0027] In some embodiments, in a vertical orientation, the first portion 102 may correspond to a top cap. Further, the top cap may include a set of vent holes 112. The set of vent holes 112 may be configured to allow gas present in the gas channel 110 to diffuse into and through the gas channel 110. In one exemplary embodiment, the top cap may be made of one or more materials. The one or more materials may include at least one of silicon, glass, or plastic. In some embodiments, the second portion 104 may correspond to a base. In one exemplary embodiment, the base may be made of one or more materials. The one or more materials may preferably include at least one of silicon. Further, the one or more materials may include at least one of glass or plastic. Further, each end of the top cap may be bonded to a corresponding end of the base with an adhesive such that the gas channel 110 is provided between the top cap and the base. In one exemplary embodiment, the adhesive may include at least one of a frit bond, an anodic bond, an epoxy adhesive, and a eutectic bond. In one example, silicon-to-silicon bonding can be performed with frit bonding and eutectic bonding. In another example, glass-to-silicon bonding can be performed using anodic bonding and frit bonding. In yet another example, plastic, glass, and silicon can each be bonded to silicon with an adhesive, such as silicone, epoxy adhesive, or cyanoacrylate.

[0028] Additionally, the thermal conductivity sensor 100 may include an ambient temperature sensing element 114. The ambient temperature sensing element 114 may be configured to measure the temperature of the gas passing through the gas channel 110 in real time. In some embodiments, the ambient temperature sensing element 114 and the at least one sensing element 108 may be positioned adjacent to one another. In some embodiments, the ambient temperature sensing element 114 may include at least one of a temperature sensing resistor or a temperature diode. The at least one sensing element 108 and the ambient temperature sensing element 114 may be positioned in one or more combinations. The one or more combinations may include at least one of a temperature resistor and a resistor, a temperature diode and a diode, or a temperature resistor and a thermopile.

[0029] In some embodiments, the gas may pass through a set of vents 112 to reach the gas channel 110. Furthermore, at least one heating element 106 may be configured to heat the gas. Simultaneously, at least one sensing element 108 may be configured to read a temperature difference of the gas. The temperature difference may correspond to the difference between the temperature of the gas as it passes through the set of vents 112 and the temperature of the gas as it is heated by the at least one heating element 106. Furthermore, due to the temperature difference, there may be a change in heat transfer through the gas. Furthermore, the change in heat transfer may correspond to a change in the thermal properties of the gas. The change in heat transfer may provide a thermal conductivity of the gas. The thermal conductivity may then be directly related to the composition of the gas.

[0030] 2 shows a top view of a thermal conductivity sensor 100 in a vertical orientation according to an exemplary embodiment of the present disclosure. FIG. 2 will be described in conjunction with FIG.

[0031] The thermal conductivity sensor 100 may include a plurality of bond pads 202 on the first portion 102 and the second portion 104. In one example, the bond pads 202 on the first portion 102 may be bonded to the bond pads 202 on the second portion 104 via a plurality of wire bonds 204. The wire bonds 204 may link the bond pads 202 on the first portion 102 and the second portion 104, enabling the transmission of electrical signals and data across the thermal conductivity sensor 100. This link may ensure seamless operation and functionality of the thermal conductivity sensor 100, as the wire bonds 204 enable the exchange of information necessary for accurate temperature measurement or control. In another example, the bond pads 202 may be bonded through silicon vias or through glass.

[0032] In some embodiments, the bond pads 202 may be separated from the gas channel 110 by the first portion 102. The bond pads 202 may be configured to electrically connect the at least one heating element 106 to the second portion 104. The bond pads 202 may serve as connection points for electrical signal and data transmission between the at least one heating element 106 and the second portion 104. The bond pads 202 may be separated to protect the thermal conductivity sensor 100 from potential interference or contamination by gas passing through the gas channel 110. Isolating the bond pads from the gas channel 110 may maintain the integrity and reliability of the electrical connections in the thermal conductivity sensor 100 and minimize the risk of malfunction or damage due to environmental factors. Furthermore, the separation may indicate that the at least one heating element 106 may play an important role in the operation of the thermal conductivity sensor 100, such as facilitating accurate temperature measurement or regulation.

[0033] In some embodiments, the bond pads 202 may serve as a way for the thermal conductivity sensor 100 to be connected to the outside of the thermal conductivity sensor 100 via other wire bonds that may be connected to a printed circuit board (PCB) or another die. Additionally, electrical connections from the first portion 102 to the second portion 104 may be made using silicon or glass vias within the first portion 102. In some embodiments, the wire bonds 204 attached to the bond pads 202 may be further protected with an insulating encapsulant.

[0034] As depicted in FIG. 1 , the first portion 102 may include at least one heating element 106 and a set of vent holes 112. The set of vent holes 112 may be configured to allow gas present in the gas to diffuse into and through the gas channels 110. Gas can enter the thermal conductivity sensor 100 from a supply through the set of vent holes 112, initiating a process in which the gas is heated and / or circulated. Additionally, the set of vent holes 112 may be configured to allow diffusion of gas out of the gas channels 110. The set of vent holes 112 may facilitate diffusion of gas from within the gas channels 110 to the external environment. The allowed diffusion of gas into and out of the gas channels 110 may complete a cycle within the thermal conductivity sensor 100.

[0035] In some embodiments, thermal conductivity sensor 100 may operate over a temperature range. The temperature range may correspond to a range of -25 degrees Celsius (°C) to 85°C. Additionally, thermal conductivity sensor 100 may operate over a pressure range. The pressure range may correspond to a range from sea level to 12,000 feet (ft.) above sea level. Those skilled in the art will appreciate that the above-described components of thermal conductivity sensor 100 are provided for illustrative purposes only without departing from the scope of the present disclosure.

[0036] 3A illustrates a side cross-sectional view of a thermal conductivity sensor 300 in a horizontal orientation, according to an exemplary embodiment of the present disclosure. The thermal conductivity sensor 300 can include a first portion 302 and a second portion 304.

[0037] In some embodiments, the first portion 302 may include at least one heating element 306 and at least one sensing element 308. In some embodiments, the first portion 302 may be disposed on a second portion 304 having a recessed cavity 310. In one example, the second portion 304 may correspond to a base. In some embodiments, the at least one heating element 306 and the at least one sensing element 308 may be positioned such that the at least one heating element 306 and the at least one sensing element 308 are spaced apart by a gap 314 inside the recessed cavity 310. The gap 314 may be configured to allow a gas 312 to pass through the gap 314, such that the gas 312 passes through the recessed cavity 310 between the at least one heating element 306 and the at least one sensing element 308. In some embodiments, the at least one heating element 306 may be spaced apart from the at least one sensing element 308 such that the gas 213 under analysis is between the at least one heating element 306 and the at least one sensing element 308. As a result, the at least one sensing element 308 may not be heated by the at least one heating element 306 to the high temperature of the at least one heating element 306, but instead may be heated directly by the gas 312.

[0038] In some embodiments, the at least one heating element 306 and the at least one sensing element 308 of the thermal conductivity sensor 300 may be arranged in multiple orientations. Furthermore, the multiple orientations may include at least a horizontal orientation. In some embodiments, in the horizontal orientation, the at least one heating element 306 may be positioned beside the at least one sensing element 308. In one example, the at least one heating element 306 may be positioned to the left of the at least one sensing element 308. In another example, the at least one heating element 306 may be positioned to the right of the at least one sensing element 308. Furthermore, the at least one heating element 306 and the at least one sensing element 308 may be positioned on respective elevated structures 318, 320 above the first portion 302, separated by a gap 314 such that the gas 312 passes around the at least one heating element 306 and the at least one sensing element 308. In one example, passing of the gas 312 around the at least one heating element 306 and the at least one sensing element 308 may correspond to passing of the gas 312 over or under the at least one heating element 306 and the at least one sensing element 308. Furthermore, there may be a gap between the overhead structure 318 and the overhead structure 320 to allow the gas 312 to pass between the at least one heating element 306 and the at least one sensing element 308. The description relating to each of the overhead structures 318, 320 is provided in conjunction with FIG. 3B.

[0039] In one exemplary embodiment, the first portion 302 and the second portion 304 may be made of one or more materials. The one or more materials may include at least one of silicon or glass. Furthermore, the first portion 302 may be bonded to the second portion 304 with an adhesive, with a gap 314 provided between the first portion 302 and the second portion 304. In one exemplary embodiment, the adhesive may include at least one of a frit bond, an anodic bond, an epoxy adhesive, and a eutectic bond. In one example, the silicon-to-silicon bonding may be performed with a frit bond and a eutectic bond. In another example, the glass-to-silicon bonding may be performed with an anodic bond and a frit bond. In yet another example, each of the glass and the silicon may be bonded to the silicon with an adhesive, such as a silicone, an epoxy adhesive, or a cyanoacrylate.

[0040] In some embodiments, at least one heating element 306 positioned near the at least one sensing element 308 and accompanying the gas 312 can provide significant sensitivity improvements for the thermal conductivity sensor 300 with respect to detecting the thermal conductivity of the gas 312. In some embodiments, the thermal conductivity sensor 300 may rely on the use of heat and heat transfer. Furthermore, a temperature difference may exist between the at least one heating element 306 and the at least one sensing element 308 in the gas 312, causing changes in heat transfer through the gas 312 to which the at least one heating element 306 and the at least one sensing element 308 are exposed. Furthermore, changes in heat transfer may correspond to changes in the thermal properties of the gas 312, such as from the gas 312 to the gas 312 + hydrogen. Changes in heat transfer can change the output of the thermal conductivity sensor 300 and can be directly related to the composition of the gas 312.

[0041] In some embodiments, the at least one heating element 306 may be made from a group of materials. In one example, the group of materials may preferably include at least one of Permalloy (81:19 iron-nickel (NiFe)) and 60:40 NiFe. Thin films of Permalloy may have a temperature coefficient of resistance of 3600 parts per million per degree Celsius (ppm / °C) to 4100 ppm / °C. In another example, the group of materials may include at least one of platinum (Pt), chromium (Cr), doped silicon (Si) or polysilicon, nichrome (NiCr), nickel (Ni), platinum silicide (PtSi) and other metal silicides, tungsten (W), TiN, aluminum nitride (AlN), tungsten nitride (WN), or any combination thereof.

[0042] In some embodiments, the at least one sensing element 308 may be configured to measure a change in temperature of the gas 312 to detect the presence of a gas 312 having a higher thermal conductivity. In one example, the gas 312 may correspond to hydrogen gas. Furthermore, the at least one sensing element 308 may be configured to measure a change in temperature of the gas 312 to monitor heat transfer within the gas 312 around the thermal conductivity sensor 300. In one embodiment, a change in heat transfer within the gas 312 around the thermal conductivity sensor 300 may correspond to a change in the thermal properties of the gas 312. In some embodiments, the at least one sensing element 308 may comprise at least one of a resistor, a diode, or a thermopile. In some embodiments, the at least one sensing element 308 may be made from a group of materials. In one example, the group of materials may preferably include at least one of chromium (Cr) and permalloy (80 / 20 NiFe) and Cr and 60 / 40 NiFe. In another example, the group of materials may include at least one of polysilicon and aluminum (Al), n-type polysilicon and p-type polysilicon, Ni-Fe alloy and chromium disilicide, chromium nitride and copper (Cu), chromium nitride and Al, chromium nitride and p-type polysilicon, and copper (Cu) and a Cu-Ni alloy. In one exemplary embodiment, the resistor may be made from the group of materials described above. In another exemplary embodiment, the resistor may be made from a group of materials such as Pt, NiCr, PtSi, other metal silicides, W, and other materials known in the art. Furthermore, the diode may correspond to either a pn junction or a metal-semiconductor.

[0043] Additionally, the thermal conductivity sensor 300 may include an ambient temperature sensing element 316 on the first portion 302. The ambient temperature sensing element 316 may be configured to measure the temperature of the gas 312 passing through the gap 314 in real time. In one example, the ambient temperature sensing element 316 and the at least one heating element 306 may be positioned adjacent to one another. In another example, the ambient temperature sensing element 316 and the at least one sensing element 308 may be positioned adjacent to one another. In some embodiments, the ambient temperature sensing element 316 may include at least one of a temperature sensor or a temperature diode. The at least one sensing element 308 and the ambient temperature sensing element 316 may be positioned in one or more combinations. The one or more combinations may include at least one of a temperature resistor and a resistor, a temperature diode and a diode, or a temperature resistor and a thermopile.

[0044] 3B illustrates a top view of the thermal conductivity sensor 300 in a horizontal orientation according to an exemplary embodiment of the present disclosure. FIG. 3B will be described in conjunction with FIG. 3A.

[0045] 3A , at least one heating element 306 and at least one sensing element 308 may be positioned on respective elevated structures separated by a gap 314 such that gas 312 passes underneath the at least one heating element 306 and at least one sensing element 308. Thermal conductivity sensor 300 may include elevated structure 318 and elevated structure 320. At least one heating element 306 may be positioned on elevated structure 318 separated by a gap 314 such that gas 312 passes underneath the at least one heating element 306. At least one sensing element 308 may be positioned on elevated structure 320 separated by a gap 314 such that gas 312 passes underneath the at least one sensing element 308. In some embodiments, the elevated structure 318 and the elevated structure 320 may separate the at least one heating element 306 from the at least one sensing element 308 so that the gas 312 under analysis is between the at least one heating element 306 and the at least one sensing element 308. As a result, the at least one sensing element 308 is not heated by the at least one heating element 306 to the high temperature of the at least one heating element 306, but instead may be heated directly by the gas 312.

[0046] In some embodiments, thermal conductivity sensor 300 may operate over a temperature range. The temperature range may correspond to a range of -25 degrees Celsius (°C) to 85°C. Additionally, thermal conductivity sensor 300 may operate over a pressure range. The pressure range may correspond to a range from sea level to 12,000 feet (ft.) above sea level. Those skilled in the art will appreciate that the above-described components of thermal conductivity sensor 300 are provided for illustrative purposes only without departing from the scope of the present disclosure.

[0047] 4A shows a schematic diagram of another thermal conductivity sensor 400 in a horizontal orientation, according to an exemplary embodiment of the present disclosure. The thermal conductivity sensor 400 can include a first portion 402 and a second portion 404.

[0048] In some embodiments, the first portion 402 may comprise at least one heating element 406 and at least one sensing element. The first portion 402 may be disposed on a second portion 404 having a recessed cavity 408. The at least one sensing element may include a first sensing element 410 and a second sensing element 412. In one example, the second portion 404 may correspond to a base. In some embodiments, the at least one heating element 406 and the at least one sensing element may be positioned such that the at least one heating element 406 and the at least one sensing element are spaced apart by a gap 416 inside the recessed cavity 408. Furthermore, the at least one heating element 406 and the at least one sensing element may be positioned such that the at least one heating element 406 is between the first sensing element 410 and the second sensing element 412. The gap 416 may be configured to allow the gas 414 to pass through the gap 416, such that the gas 414 passes around the first sensing element 410, the at least one heating element 406, and the second sensing element 412. In some embodiments, the first sensing element 410, the at least one heating element 406, and the second sensing element 412 may be spaced apart from one another such that the gas 414 under analysis is between the first sensing element 410, the at least one heating element 406, and the second sensing element 412. As a result, the first sensing element 410 and the second sensing element 412 may not be heated by the at least one heating element 406 to the high temperature of the at least one heating element 406, but instead may be heated directly by the gas 414.

[0049] In some embodiments, the at least one heating element 406 and the at least one sensing element of the thermal conductivity sensor 400 may be arranged in multiple orientations. Furthermore, the multiple orientations may include at least a horizontal orientation. In some embodiments, in the horizontal orientation, the at least one heating element 406 may be positioned between the first sensing element 410 and the second sensing element 412. Furthermore, the at least one heating element 406, the first sensing element 410, and the second sensing element 412 may be positioned on respective elevated structures (not labeled) on the first portion 402, separated by a gap 416 such that gas 414 passes around the first sensing element 410, the at least one heating element 406, and the second sensing element 412. In one example, passing the gas 414 through the first sensing element 410, the at least one heating element 406, and the second sensing element 412 may correspond to passing the gas 414 over or under the first sensing element 410, the at least one heating element 406, and the second sensing element 412. Additionally, there may be gaps between the elevated structures to allow the gas 414 to pass between the at least one heating element 406, the first sensing element 410, and the second sensing element 412.

[0050] In some embodiments, at least one heating element 406 positioned between the first sensing element 410 and the second sensing element 412 and accompanying the gas 414 can provide significant sensitivity improvements for the thermal conductivity sensor 400 in detecting thermal conductivity. In some embodiments, the thermal conductivity sensor 400 may rely on the use of heat and heat transfer. Furthermore, a temperature difference may exist between the first sensing element 410, the at least one heating element 406, and the second sensing element 412 in the gas 414, causing heat transfer to change through the gas 414 to which the first sensing element 410, the at least one heating element 406, and the second sensing element 412 are exposed. Furthermore, the change in heat transfer may correspond to a change in the thermal properties of the gas within the gas 414, such as from gas 414 to gas 414 + hydrogen. The change in heat transfer can change the output of the thermal conductivity sensor 400 and can be directly related to the composition of the gas 414.

[0051] In some embodiments, the at least one heating element 406 may be made from a group of materials. In one example, the group of materials may preferably include at least one of Permalloy (81:19 iron-nickel (NiFe)) and 60:40 NiFe. Thin films of Permalloy may have a temperature coefficient of resistance of 3600 parts per million per degree Celsius (ppm / °C) to 4100 ppm / °C. In another example, the group of materials may include at least one of platinum (Pt), chromium (Cr), doped silicon (Si) or polysilicon, nichrome (NiCr), nickel (Ni), platinum silicide (PtSi) and other metal silicides, tungsten (W), TiN, aluminum nitride (AlN), tungsten nitride (WN), or any combination thereof.

[0052] In some embodiments, the first portion 402 may include at least one sensing element having a first sensing element 410 and a second sensing element 412. The at least one sensing element may be configured to measure a change in temperature of the gas 414 to detect the presence of a gas 414 having a higher thermal conductivity. In one example, the gas 414 may correspond to a hydrogen-containing gas. Furthermore, the at least one sensing element may be configured to measure a change in temperature of the gas 414 to monitor heat transfer within the gas 414 around the thermal conductivity sensor 400. In one embodiment, the change in heat transfer within the gas 414 around the thermal conductivity sensor 400 may correspond to a change in the thermal properties of the gas. In some embodiments, the at least one sensing element may include at least one of a resistor, a diode, or a thermopile. In some embodiments, the at least one sensing element may be made from a group of materials. In one example, the group of materials may preferably include at least one of chromium (Cr) and permalloy (80 / 20 NiFe) and Cr and 60 / 40 NiFe. In another example, the group of materials may include at least one of polysilicon and aluminum (Al), n-type polysilicon and p-type polysilicon, Ni-Fe alloy and chromium disilicide, chromium nitride and copper (Cu), chromium nitride and Al, chromium nitride and p-type polysilicon, and copper (Cu) and a Cu-Ni alloy. In one exemplary embodiment, the resistor may be made from the group of materials described above. In another exemplary embodiment, the resistor may be made from a group of materials such as Pt, NiCr, PtSi, other metal silicides, W, and other materials known in the art. Furthermore, the diode may correspond to either a pn junction or a metal-semiconductor.

[0053] Additionally, the thermal conductivity sensor 400 may include an ambient temperature sensing element 418 on the first portion 402. The ambient temperature sensing element 418 may be configured to measure the temperature of the gas 414 passing through the gap 416 in real time. In one example, the ambient temperature sensing element 418 and the first sensing element 410 may be positioned adjacent to one another. In another example, the ambient temperature sensing element 418 and the second sensing element 412 may be positioned adjacent to one another. In some embodiments, the ambient temperature sensing element 418 may include at least one of a temperature sensor or a temperature diode. The first sensing element 410 and the ambient temperature sensing element 418, or the second sensing element 412 and the ambient temperature sensing element 418, may be positioned in one or more combinations. The one or more combinations may include at least one of a temperature resistor and a resistor, a temperature diode and a diode, or a temperature resistor and a thermopile.

[0054] Figure 4B shows a filter media 420 associated with another thermal conductivity sensor 400 in a horizontal orientation, according to an exemplary embodiment of the present disclosure. Figure 4B will be described in conjunction with Figure 4A.

[0055] In some embodiments, the first portion 402 may include at least one heating element 406 and at least one sensing element. The first portion 402 may be disposed on the second portion 404 having the recessed cavity 408. Additionally, at least one package 422 having a filter media 420 may be disposed on the first portion 402. The at least one package 422 may correspond to the location of the filter media 420. The filter media 420 may form a layer on the first portion 402. The filter media 420 may be configured to allow the gas 414 to diffuse evenly throughout the gap 416. The filter media 420 may be configured to allow the gas 414 to diffuse evenly to reduce temperature changes as the gas 414 passes through the first sensing element 410, the at least one heating element 406, and the second sensing element 412. When the gas 414 diffuses evenly between the first sensing element 410, the at least one heating element 406, and the second sensing element 412, the filter media 420 can minimize temperature changes, thereby optimizing the performance and accuracy of the thermal conductivity sensor 400.

[0056] In some embodiments, thermal conductivity sensor 400 may operate over a range of temperatures. The temperature range may correspond to a range of -25 degrees Celsius (°C) to 85°C. Additionally, thermal conductivity sensor 400 may operate over a range of pressures. The pressure range may correspond to a range from sea level to 12,000 feet (ft.) above sea level. Those skilled in the art will appreciate that the above-described components of thermal conductivity sensor 400 are provided for illustrative purposes only without departing from the scope of the present disclosure.

[0057] In some embodiments, thermal conductivity sensor 100, thermal conductivity sensor 300, and thermal conductivity sensor 400 can retain the same functionality without departing from the scope of the present disclosure.

[0058] 5 shows a graphical representation 500 of a simulation of the thermal conductivity sensor 100 in a vertical orientation, according to an exemplary embodiment of the present disclosure. FIG. 5 will be described in conjunction with FIG.

[0059] In some embodiments, graphical representation 500 may represent the transfer of heat by at least one heating element 106 onto at least one sensing element 108, as indicated by 502. The x- and y-axes of graphical representation 500 may represent the distance between the at least one heating element 106 and the at least one sensing element 108 in micrometers (μm). In one example, the at least one heating element 106 radiates heat having a temperature in the range of 298 Kelvin (K) to 369 K, as indicated by temperature scale 504. As the distance between the at least one sensing element 108 and the at least one heating element 106 increases, the temperature decreases.

[0060] In some embodiments, the heat radiated from the at least one heating element 106 decreases to different degrees across the vertical direction of the at least one heating element 106 and across the horizontal direction of the at least one heating element 106. In one example, the gas temperature in the vertical direction of the at least one heating element 106 at a distance of 15-20 μm ranges from 320-297.6 K. In another example, the gas temperature in the horizontal direction of the at least one heating element 106 at the same distance of 15-20 μm ranges from 360.7-359.8 K. In some embodiments, the distance of the at least one sensing element 108 from the at least one heating element 106 may be 20 μm and exposed to a lower temperature of 300-306.5 K, resulting in the at least one heating element 106 having no effect on the at least one sensing element.

[0061] 6 illustrates a graphical representation 600 of the effect of temperature on at least one sensing element, according to an exemplary embodiment of the present disclosure. FIG. 6 will be described in conjunction with FIG.

[0062] In some embodiments, graphical representation 600 may represent the effect of temperature on the at least one sensing element 108, as indicated by 602. The x-axis of graphical representation 600 may represent the vertical distance, in percentage, from the center of the at least one heating element 106 to the edge of the first portion 102. The y-axis of graphical representation 600 may represent the temperature of the heat from the at least one heating element 106 in K. In one example, when the at least one sensing element 108 is positioned 20 μm above the at least one heating element 106, the at least one sensing element 108 is exposed to a temperature of 300 K to 305 K. Furthermore, as the distance of the at least one sensing element 108 increases relative to the at least one heating element 106, the temperature decreases uniformly from 300 K to less than 295 K.

[0063] 7 shows a graphical representation 700 of the change in sensed temperature corresponding to a 1% change in the thermal conductivity of a gas, according to an exemplary embodiment of the present disclosure. FIG. 7 will be described in conjunction with FIG.

[0064] In some embodiments, graphical representation 700 may represent the change in sensed temperature corresponding to a 1% change in the thermal conductivity of the gas, as shown by 702. The x-axis of graphical representation 700 may represent the vertical distance from the center of the at least one heating element 106 to the edge of the first portion 102. The y-axis of graphical representation 700 may represent the change in sensed temperature. In one example, the change in sensed temperature increases as the distance from the center of the at least one heating element 106 to the edge of the first portion 102 decreases.

[0065] FIG. 8 illustrates a graphical representation 800 of a preliminary parallel plate simulation of changes in sensed temperature due to changes in thermal conductivity sensor 100, according to an exemplary embodiment of the present disclosure.

[0066] In some embodiments, graphical representation 800 may represent a preliminary parallel plate simulation of the change in sensed temperature of thermal conductivity sensor 100 as the thermal conductivity of the gas is changed, as shown by curves 802, 804, 806, and 808. The x-axis of graphical representation 800 may represent the vertical distance from the center of at least one heating element 106 to the edge of first portion 102. The y-axis of graphical representation 800 may represent the change in sensed temperature (i.e., the percentage temperature change). Additionally, thermal conductivity, denoted "k," may be expressed as "k o This value may correspond to the concentration of high thermal conductivity gas species in the gas. In one example, k=1.01k, as shown by curve 808. o In another example, k=1.02k, as shown by curve 806. o In yet another example, k=1.03k, as shown by curve 804. o In one example, k=1.04k, as shown by curve 802. o As the concentration of the high thermal conductivity gas species increases, the thermal conductivity of the gas mixture increases.

[0067] FIG. 9 shows a graphical representation 900 of another parallel plate preliminary simulation of the thermal conductivity sensor 100, according to an exemplary embodiment of the present disclosure.

[0068] In some embodiments, graphical representation 900 may represent another parallel plate preliminary simulation of thermal conductivity sensor 100 with varying thermal conductivity, as shown by curves 902, 904, 906, and 908. The x-axis of graphical representation 900 may represent the vertical distance from the center of at least one heating element 106 to the edge of first portion 102. The y-axis of graphical representation 900 may represent the rate of change of sensed temperature (i.e., % temperature change) corresponding to the change in thermal conductivity of the gas mixture. Additionally, thermal conductivity, denoted "k," may be expressed as "k o The value may correspond to the concentration of the gas. In one example, k=1.01k, as shown by curve 908. oIn another example, k=1.02k, as shown by curve 906. o In yet another example, k=1.03k, as shown by curve 904. o In one example, k=1.04k, as shown by curve 902. o As the concentration of the high thermal conductivity gas species increases, the thermal conductivity of the gas mixture increases.

[0069] In some embodiments, a method of a thermal conductivity sensor 100 is disclosed. The method may include positioning a first portion 102 of the thermal conductivity sensor 100 having at least one heating element 106 and a second portion 104 of the thermal conductivity sensor 100 having at least one sensing element 108 such that the at least one heating element 106 and the at least one sensing element 108 are spaced apart by a gas channel or gap between the first portion 102 and the second portion 104, the gas channel or gap being configured to allow gas to pass through the gas channel or gap. Furthermore, the at least one sensing element 108 may be configured to measure a change in temperature of the gas to detect the presence of a gas having a higher thermal conductivity.

[0070] Many modifications and other embodiments of the inventions described herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. It is therefore to be understood that the inventions are not limited to the specific embodiments disclosed, and that modifications and other embodiments are intended to be included within the scope of the appended claims. Furthermore, while the foregoing description and the associated drawings describe exemplary embodiments in the context of particular illustrative combinations of elements and / or functions, it is to be understood that different combinations of elements and / or functions may be provided in alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and / or functions than those explicitly described above are also contemplated as being recited within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. 1. A thermal conductivity sensor, comprising: a first portion having at least one heating element; a second portion having at least one sensing element; the first and second portions are positioned such that the at least one heating element and the at least one sensing element are spaced apart by a gas channel or gap between the first and second portions, the gas channel or gap being configured to allow gas to pass through the gas channel or gap to pass between the at least one heating element and the at least one sensing element; A thermal conductivity sensor, wherein the at least one sensing element is configured to measure a change in temperature of the gas to detect the presence of the gas having a higher thermal conductivity.

2. The thermal conductivity sensor of claim 1 , wherein the at least one sensing element is configured to measure changes in temperature of the gas to monitor heat transfer within the gas surrounding the thermal conductivity sensor.

3. The thermal conductivity sensor of claim 1 , further comprising an ambient temperature sensing element configured to measure the temperature of the gas passing through the gas channel in real time.

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