Gas sensor and method of forming the same

Abstract

Various embodiments may relate to a gas sensor. The gas sensor may include a thermal emitter. The gas sensor may also include a pyroelectric detector spaced apart from the thermal emitter such that a gap between the thermal emitter and the pyroelectric detector is equal to or less than 10 mm.

Description

GAS SENSOR AND METHOD OF FORMING THE SAMECROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority of Singapore application No. 10202303046U filed October 27, 2023, the contents of it being hereby incorporated by reference in its entirety for all purposes.TECHNICAL FIELD

[0002] Various embodiments of this disclosure may relate to a gas sensor. Various embodiments of this disclosure may relate to a method of forming a gas sensor.BACKGROUND

[0003] The use of hydrogen (H2) as a clean and renewable energy has been increasing due to the desire to reduce carbon footprint. In addition, high concentration, high resolution H2 sensors are required to monitor H2 gas purity and concentration for in-line applications such as for fuel cells and in the food industry.

[0004] Currently, there are no miniature H2 sensors to detect high concentration H2 with 0.1% resolution. Further, in terms of design for thermal conductivity sensors, conventional thermal conductivity H2 gas sensors are based on heated resistive tungsten wires, which can create sparks when too hot, and may lead to explosion if H2 gas is between 4% to 76%. Another reported sensor for carbon dioxide (CO2) sensing uses germanium (Ge) substrate as a thermal pathway with both the emitter and the detector facing down towards the substrate.SUMMARY

[0005] Various embodiments may relate to a gas sensor. The gas sensor may include a thermal emitter. The gas sensor may also include a pyroelectric detector spaced apart from the thermal emitter such that a gap between the thermal emitter and the pyroelectric detector is equal to or less than 10 mm.

[0006] Various embodiments may relate to a method of forming a gas sensor. The method may include providing a thermal emitter. The method may also include providing a pyroelectric detector spaced apart from the thermal emitter such that a gap between the thermal emitter and the pyroelectric detector is equal to or less than 10 mm.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily drawn to scale, emphasis instead generally being placed upon illustrating the principles of various embodiments. In the following description, various embodiments of the invention are described with reference to the following drawings.FIG. 1 is a general illustration of a gas sensor according to various embodiments.FIG. 2 is a general illustration of a method of forming a gas sensor according to various embodiments.FIG. 3A shows a schematic illustrating the side view of a portion of the gas sensor according to various embodiments looking in from a gas hole (i.e , a gas inlet hole or a gas outlet hole).FIG. 3B shows a perspective three-dimensional (3D) view of a portion of the gas sensor according to various embodiments that contains the enclosed space between the thermal emitter and the pyroelectric detector.FTG. 3C shows a planar view of the portion of the gas sensor according to various embodiments corresponding to FIG. 3B (i.e., when viewed from the thermal emitter or the pyroelectric detector).FIG. 3D shows a cross-sectional schematic of the gas sensor according to various embodiments. FIG. 3E shows a perspective three-dimensional (3D) cut view of the gas sensor according to various embodiments.FIG. 4 shows a plot of voltage (in milli-Volts or mV) as a function of time (in minutes or min) illustrating gas sensing response of the gas sensor according to various embodiments using helium (He) gas.FIG. 5 shows a plot of voltage (in milli-Volts or mV) as a function of time (in minutes or min) showing a magnified or zoom-in view of the gas sensing response of the gas sensor according to various embodiments at 95% helium (He), 95.5 % He, 95.6% He and 96% He.FIG. 6 shows a plot of voltage (in milli-Volts or mV) as a function of time (in seconds or s) illustrating gas sensing response of the gas sensor according to various embodiments using hydrogen (H2) gas.FIG. 7 shows a plot of voltage (in milli-Volts or mV) as a function of time (in seconds or s) illustrating the voltage change when nitrogen (N2) gas of different flow rates is passed through the gas sensor according to various embodiments.FIG. 8 A shows a plot of voltage (in milli-Volts or mV) as a function of time (in minutes or min) illustrating the gas sensing response of a gas sensor in which the thermal emitter and the pyroelectric detector are spaced by a distance of 40 mm according to various embodiments. FIG. 8B show s a plot of voltage (in milli-Volts or mV) as a function of time (in minutes or min) illustrating the gas sensing response of a gas sensor in which the thermal emitter and the pyroelectric detector are spaced by a distance of 20 mm according to various embodiments.FTG. 9A shows an arrangement common in conventional gas sensors that use optical gas sensing.FIG. 9B shows a possible arrangement of the gas sensor according to various embodiments which may employ thermal conductivity gas sensing.DESCRIPTION

[0008] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the invention. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to fonn new embodiments.

[0009] Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments. Features that are described in the context of an embodiment may correspondingly be applicable to the other embodiments, even if not explicitly described in these other embodiments. Furthermore, additions and / or combinations and / or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

[0010] In the context of various embodiments, the articles “a”, “an” and “the” as used with regard to a feature or element include a reference to one or more of the features or elements.

[0011] In the context of various embodiments, the term “about” or “approximately” as applied to a numeric value encompasses the exact value and a reasonable variance, e g. within 10% of the specified value.

[0012] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0013] By “comprising” it is meant including, but not limited to, whatever follows the word “comprising”. Thus, use of the term “comprising” indicates that the listed elements are required or mandatory, but that other elements are optional and may or may not be present.

[0014] By “consisting of’ is meant including, and limited to, whatever follows the phrase “consisting of’. Thus, the phrase “consisting of’ indicates that the listed elements are required or mandatory, and that no other elements may be present.

[0015] Embodiments described in the context of one of the gas sensors are analogously valid for the other gas sensors, embodiments described in the context of a method are analogously valid for a gas sensor, and vice versa.

[0016] Various embodiments may address one or more shortcomings of conventional gas sensors. FIG. 1 is a general illustration of a gas sensor according to various embodiments. The gas sensor may include a thermal emitter 102. The gas sensor may also include a pyroelectric detector 104 spaced apart from the thermal emitter 102 such that a gap between the thermal emitter 102 and the pyroelectric detector 104 is equal to or less than 10 mm.

[0017] In other words, various embodiments may include a gas sensor with a thermal emitter 102 and a pyroelectric detector 104 such that a distance between the thermal emitter 102 and the pyroelectric detector 104 is equal to or less than 10 mm.

[0018] For avoidance of doubt, FIG.l is intended to illustrate the features of the sensor according to various embodiments, and is not intended to limit, for instance, the dimensions, size, shapes etc. of the various features.

[0019] The gap between the thermal emitter 102 and the pyroelectric detector 104 may be measured between an exposed emitting or heating surface or area of the thermal emitter 102 and an exposed sensing surface or area of the pyroelectric detector 104.

[0020] Unlike conventional gas sensors which typically use heated tungsten or platinum (Pt) wire, various embodiments may include the thermal emitter 102, which is not typically used in gas sensors as they may be dependent on thermal conductivity changes in gases and rate of heat transfer. Conventional gas sensors may also be optical gas sensors in which the source and the detector are placed far apart, typically in centimeters or meters. In contrast, in various embodiments, the gap between the thermal emitter 102 and the pyroelectric detector 104 may be equal or less than 10 mm.

[0021] In various embodiments, the gap or the distance between the thermal emitter 102 and the pyroelectric detector 104 may be of a value selected from a range from 0.1 mm to 10 mm.

[0022] The thermal emitter 102 (alternatively referred to as a thermal emitter source or an emitter source) may be configured to emit infrared radiation. The thermal emitter may be a thermal source such as a thermal micro-electromechanical systems (MEMS) based infrared source or a MEMS emitter. The thermal emitter 102 may, for instance, be a MEMS microhotplate.

[0023] The pyroelectric detector 104 may include any suitable pyroelectric material, such as scandium aluminum nitride (ScAIN), lithium tantalate (LiTaOs), aluminum nitride (AIN), hafnium oxide (HfCh) or lead zirconate titanate (PZT).

[0024] In various embodiments, the gas sensor may also include a gas chamber (alternatively referred to as a gas cell enclosure) such that the thermal emitter 102 and the pyroelectric detector 104 are on opposite sides of the gas chamber. In other words, the gas chamber 102 may be between the thermal emitter 102 and the pyroelectric detector 104. The thermal emitter 102 and the pyroelectric detector 104 may be adjacent or may adjoin the gas chamber. The gas chamber may include or be made of any suitable material or materials. For instance, the gas chamber may include or be made of a suitable metal such as aluminum (Al)or stainless steel In various embodiments, the gas chamber may include or may be made of Teflon coated stainless steel.

[0025] In various embodiments, the gas chamber may include a gas inlet hole and a gas outlet hole. The gas inlet hole and the gas outlet hole may directly face each other. The gas sensor may include a gas inlet coupled to the gas chamber. The gas inlet and the gas outlet may be adjacent or adjoin the gas chamber. The gas inlet may be coupled to the gas inlet hole of the gas chamber. The gas sensor may also include a gas outlet coupled to the gas chamber such that the gas inlet and the gas outlet are directly facing each other. The gas outlet may be coupled to the gas outlet hole of the gas chamber. The gas inlet may be a tube, pipe or channel that carries the gas into the gas chamber, while the gas outlet may be another tube, pipe or channel that carries the gas out of the gas chamber. The gas inlet and / or the gas outlet may include a suitable metal. The gas inlet and / or the gas outlet may have a cross-section of any suitable shape, e.g., a circular cross-section. Correspondingly, the gas inlet hole and / or the gas outlet hole may be of any suitable shape, e.g., a circle. By having the gas inlet hole and the gas outlet hole face each other, the gas sensor may have a shorter distance between the thermal emitter 102 and the pyroelectric detector 104. Various embodiments may employ thermal conductivity gas sensing. For thermal conductivity gas sensing, as the distance between the thermal emitter 102 and the pyroelectric detector 104 decreases, the higher the sensitivity.

[0026] The gas chamber may be configured to carry a gas from the gas inlet to the gas outlet. The gas inlet and the gas outlet may be in fluidic connection with each other via the gas chamber.

[0027] During operation, the gas may flow from the gas inlet to the gas outlet between the thermal emitter 102 and the pyroelectric detector 104. The thermal emitter 102 may heat up the region between the thermal emitter 102 and the pyroelectric detector 104. The gas (with high thermal conductivity, e.g., H2) in contact with the pyroelectric detector 104 (i.e., the exposedsensing surface or area of the pyroelectric detector 104) may then take heat away from the pyroelectric detector 104. The pyroelectric detector 104 may sense a temperature drop and may register a drop in signal or voltage. Various embodiments may be used for in-line sensing.

[0028] In various embodiments, a diameter of the gas inlet or the gas inlet hole may be smaller than the gap between the thermal emitter 102 and the pyroelectric detector 104. In various embodiments, a diameter of the gas outlet or the gas outlet hole may be smaller than the gap between the thermal emitter 102 and the pyroelectric detector 104. In various embodiments, the diameter of the gas inlet / gas inlet hole and / or the diameter of the gas outlet / gas outlet hole may be in millimeters, e.g., less than 10 mm.

[0029] A diameter of the gas chamber may be greater than a diameter of the gas inlet or the gas inlet hole. The diameter of the gas chamber may be greater than the diameter of the gas outlet or the gas outlet hole. The diameter of the gas chamber may extend substantially perpendicular to a length of the gas inlet and / or a length of the gas outlet.

[0030] In various embodiments, the gas chamber may be cylindrical. A cylindrical enclosed area may allow gas to only flow in from the gas inlet and out from the gas outlet. In various other embodiments, the gas chamber may be of any other suitable shape.

[0031] In various embodiments, the flow of the gas may be substantially parallel to the thermal emitter 102 (i.e., an exposed emitting or heating surface or area of the thermal emitter 102) and / or the pyroelectric detector 104 (i.e., an exposed sensing surface or area of the pyroelectric detector 104). The flow of the gas may be substantially perpendicular to the direction from the thermal emitter 102 to the pyroelectric detector 104. The flow of the gas may be substantially perpendicular to the diameter of the gas chamber. In the current context, the term “substantially” may refer to a variance equal to or less than 5° (i.e., < ± 5°).

[0032] In various embodiments, the gas sensor may be configured to determine a concentration or a flow rate of the gas. In various embodiments, the gas sensor or thepyroelectric detector 104 may be configured to generate a lower voltage with an increase in concentration or the flow rate of the gas.

[0033] The gas may be any suitable gas, e g., a gas with high thermal conductivity. For instance, the gas may be hydrogen (H2), helium (He) or nitrogen (N2).

[0034] In various embodiments, the gas sensor may be able to achieve 0.1% (1000 ppm) resolution when detecting a gas such as H2 or He at a high gas concentration, e g., from 80% to 100 % H2 or He. This resolution may be achieved by a combination of factors, such as the small gap between the thermal emitter 102 and the pyroelectric detector 104, the cylindrical gas chamber and / or the small gas inlet hole and the small gas outlet hole facing each other.

[0035] In various embodiments, the gas chamber or the gas sensor may further include a window The window may separate the gas chamber from the thermal emitter. The window may be configured to prevent direct contact of the gas with the thermal emitter 102. The window may include any suitable material, such as barium fluoride (BaF2), zinc selenide (ZnSe) or germanium (Ge).

[0036] FIG. 2 is a general illustration of a method of forming a gas sensor according to various embodiments. The method may include, in 202, providing a thermal emitter. The method may also include, in 204, providing a pyroelectric detector spaced apart from the thermal emitter such that a gap between the thermal emitter and the pyroelectric detector is equal to or less than 10 mm.

[0037] In other words, various embodiments may relate to a method of forming a gas sensor including a thermal emitter and a pyroelectric detector, such that the thermal emitter and the pyroelectric detector are spaced by a gap of 10 mm or less.

[0038] For avoidance of doubt, FIG. 2 is not intended to limit the sequence of the various steps. For instance, step 202 may occur before, after or at the same time as step 204.

[0039] Tn various embodiments, the method may further include providing a gas chamber such that the thermal emitter and the pyroelectric detector are on opposite sides of the gas chamber.

[0040] In various embodiments, the method may include coupling a gas inlet to the gas chamber. The method may also include coupling a gas outlet to the gas chamber such that the gas inlet and the gas outlet are directly facing each other. The gas inlet may be coupled to a gas inlet hole of the gas chamber, while the gas outlet may be coupled to a gas outlet hole of the gas chamber.

[0041] In various embodiments, a diameter of the gas inlet or the gas inlet hole may be smaller than the gap between the thermal emitter and the pyroelectric detector. A diameter of the gas outlet or the gas outlet hole may be smaller than the gap between the thermal emitter and the pyroelectric detector.

[0042] The gas chamber may be configured to carry a gas from the gas inlet hole to the gas outlet hole. In various embodiments, a diameter of the gas chamber may be greater than a diameter of the gas inlet or the gas inlet hole. In various embodiments, the diameter of the gas chamber may be greater than the diameter of the gas outlet or the gas outlet hole.

[0043] In various embodiments, the flow of the gas may be substantially parallel to the thermal emitter or the pyroelectric detector.

[0044] In various embodiments, the gas sensor may be configured to determine a concentration or a flow rate of the gas.

[0045] In various embodiments, the method may include providing a window between the thermal emitter and the gas chamber. The window may include barium fluoride (BaF?), zinc selenide (ZnSe) or germanium (Ge).

[0046] In various embodiments, the gap may be of a value selected from a range from 0.1 mm to 10 mm.

[0047] Various embodiments may relate to an arrangement of components to form a thermal conductivity sensor capable of sensing high concentration gases such as H2 at resolution of 0.1%. The components may include a thermal emitter source, a detector, a gas inlet, a gas outlet, and a gas cell enclosure or gas chamber, i.e., an enclosed space, where the gas flows through and between the thermal emitter source, the detector, the gas inlet and the gas outlet.

[0048] The gas cell may include a gas cell enclosure, i.e., a fully enclosed cylindrical gas cell made of aluminum (Al), stainless steel or Teflon-coated stainless steel. FIG. 3A shows a schematic illustrating the side view of a portion of the gas sensor according to various embodiments looking in from a gas hole (i.e., a gas inlet hole or a gas outlet hole). The gas sensor may include a thermal emitter 302 and a pyroelectric detector 304 placed opposite of each other. The thermal emitter 302 may be a thermal source such as a thermal MEMS infrared source or a MEMS emitter. The pyroelectric detector 304 may be a thermal emitter, such as a ScAlN-based pyroelectric detector. The gap between the emitter 302 and the detector 304 is denoted as “a” , where a < 10 mm. Generally speaking, as a decreases, the gas resolution detected may be higher. In addition, the higher the power emitted by the thermal emitter 302, the higher the gas resolution that may be detected. The gas hole may be arranged between the gap, and may have a diameter of millimeter dimensions. The diameter of the gas hole (i.e., the gas inlet hole or the gas outlet hole), b, may be less than a.

[0049] FIG. 3B shows a perspective three-dimensional (3D) view of a portion of the gas sensor according to various embodiments that contains the enclosed space between the thermal emitter 302 and the pyroelectric detector 304. FIG. 3C shows a planar view of the portion of the gas sensor according to various embodiments corresponding to FIG. 3B (i.e., when viewed from the thermal emitter 302 or the pyroelectric detector 304). The enclosed space may be referred to as a gas cell enclosure or gas chamber 306. The gas cell enclosure 306 may be circular, and may follow the shape of the emitting area of the thermal emitter 302 and / or thesensing area of the pyroelectric detector 304. The gas inlet hole and the gas outlet hole may be opposite each other. The gas sensor may also include a gas inlet 308a, which may be a tube coupled to the gas inlet hole. In addition, the gas sensor may include a gas outlet 308b, which may be another tube coupled to the gas outlet hole. Gas may flow in from the gas inlet 308a through the gas inlet hole into the gas cell enclosure 306, and may flow out from the gas cell enclosure 306 through the gas outlet hole to the gas outlet 308b. Accordingly, the gas to be sensed may flow continuously through the gas cell enclosure 306. The gas sensor may also include a housing or holder 310 that contains, holds or defines the gas cell enclosure 306. The housing or holder 310 may also hold or contain at least a portion of the gas inlet 308a and / or at least a portion of the gas outlet 308b. The housing or holder 310 may be made of or may include a suitable metal or plastic material In various embodiments, the housing or holder 310 may include or may be formed from a first transistor outline (TO) header and a second TO header. A TO header may be a package with small pin count to allow a device chip to be placed on it and be wire bonded to the respective pins. As indicated in FIG. 3C, the gas sensor may have a length of 20 mm and a breadth of 15 mm.

[0050] FIG. 3D shows a cross-sectional schematic of the gas sensor according to various embodiments. FIG. 3D shows the thermal emitter 302, the pyroelectric detector 304, the gas inlet 308a, the gas outlet 308b and the gas cell enclosure or gas chamber 306. The gas sensor may include gasket sealings between interfaces (e g., between metal-metal and / or metal-plastic) for sealing or confining the gas. For instance, there may be a gasket sealing for an interface between the gas inlet 308a and the gas cell enclosure or gas chamber 306, and another gasket sealing for an interface between the gas outlet 308b and the gas cell enclosure or gas chamber 306. Epoxy glue may be applied at other interfaces (e.g, emitter-plastic / metal, detector- plastic / metal) for securing the thermal emitter 302 and the pyroelectric detector 304 to the holder or housing 310. For instance, the gas sensor may include an epoxy glue layer attachingthe thermal emitter 302 to the first TO header, and another epoxy glue layer attaching the pyroelectric detector 304 to the second TO header.

[0051] FIG. 3E shows a perspective three-dimensional (3D) cut view of the gas sensor according to various embodiments. The gas sensor or the gas cell enclosure may include a transparent window 312 (including a material such as barium fluoride, zinc selenide or germanium) arranged in front of the thermal emitter 302. The transparent window 312 may prevent the heating surface of the thermal emitter 302 from being in direct contact with the gas. This may improve the safety of the gas sensor since the gas may be an explosive gas such as hydrogen gas.

[0052] FIG. 4 shows a plot of voltage (in milli-Volts or mV) as a function of time (in minutes or min) illustrating gas sensing response of the gas sensor according to various embodiments using helium (He) gas. The concentration of He may be varied from 90% to 96% and the voltage of the pyroelectric detector may be monitored. The results show a drop in voltage as the concentration of He increases.

[0053] FIG. 5 shows a plot of voltage (in milli-Volts or mV) as a function of time (in minutes or min) showing a magnified or zoom-in view of the gas sensing response of the gas sensor according to various embodiments at 95% helium (He), 95.5 % He, 95.6% He and 96% He. A voltage change of 0.0068 mV may be measured for a 0.1% He (1000 ppm) concentration difference from 95.5% He to 95.6% He. A greater voltage change may be expected for hydrogen (H2) gas as it has a higher thermal conductivity compared to He.

[0054] FIG. 6 shows a plot of voltage (in milli-Volts or mV) as a function of time (in seconds or s) illustrating gas sensing response of the gas sensor according to various embodiments using hydrogen (H2) gas. The concentration of the H2 may be varied from 1% (10,000 ppm) to 400 ppm, with cycling of intervals of the different concentrations of H2 with intervals of nitrogen (N2) gas.

[0055] The gas sensor may also be used to sense flow rate change. FIG. 7 shows a plot of voltage (in milli-Volts or mV) as a function of time (in seconds or s) illustrating the voltage change when nitrogen (N2) gas of different flow rates is passed through the gas sensor according to various embodiments. The changes may be observed from 1000 standard cubic centimeters per minute (seem) down to 50 seem.

[0056] FIG. 8A shows a plot of voltage (in milli-Volts or mV) as a function of time (in minutes or min) illustrating the gas sensing response of a gas sensor in which the thermal emitter and the pyroelectric detector are spaced by a distance of 40 mm according to various embodiments. FIG. 8B shows a plot of voltage (in milli-Volts or mV) as a function of time (in minutes or min) illustrating the gas sensing response of a gas sensor in which the thermal emitter and the pyroelectric detector are spaced by a distance of 20 mm according to various embodiments. FIGS. 8A - 8B are obtained from 90% He concentration and 100% He concentration. Thank you. For the distance of 40 mm between the emitter and the detector, the gas sensor shows a voltage difference of 0.01634 mV between 90% He and 100% He. For the distance of 20 mm between the emitter and the detector, the gas sensor shows a voltage difference of 0.0283 mV between 90% He and 100% He. A shorter distance between the emitter and the detector (i.e., 20 mm) may provide a greater change for a 10% change of He, indicating higher sensitivity when the emitter and the detector are closer together.

[0057] FIG. 9A shows an arrangement common in conventional gas sensors that use optical gas sensing. As shown in FIG. 9A, the gas inlet hole and the gas outlet hole may not face each other. Consequently, the distance d between the emitter and the detector may increase. For optical gas sensors, the greater the distance d, the better for gas sensing due to more interaction of the emitter beam with the gas to be sensed. FIG. 9B shows a possible arrangement of the gas sensor according to various embodiments which may employ thermal conductivity gas sensing. In various embodiments, by having the gas inlet hole and the gas outlet hole face each other,the distance d between the thermal emitter and the pyroelectric detector may decrease. As demonstrated above, as the distance d between the thermal emitter and the detector decreases, the higher the sensitivity.

Claims

Claims1. A gas sensor comprising: a thermal emitter, and a pyroelectric detector spaced apart from the thermal emitter such that a gap between the thermal emitter and the pyroelectric detector is equal to or less than 10 mm.

2. The gas sensor according to claim 1, further comprising: a gas chamber such that the thermal emitter and the pyroelectric detector are on opposite sides of the gas chamber.

3. The gas sensor according to claim 2, further comprising: a gas inlet coupled to the gas chamber; and a gas outlet coupled to the gas chamber such that the gas inlet and the gas outlet are directly facing each other.

4. The gas sensor according to claim 3, wherein a diameter of the gas inlet is smaller than the gap between the thermal emitter and the pyroelectric detector; and wherein a diameter of the gas outlet is smaller than the gap between the thermal emitter and the pyroelectric detector.

5. The gas sensor according to claim 3, wherein the gas chamber configured to carry a gas from the gas inlet to the gas outlet;wherein a diameter of the gas chamber is greater than a diameter of the gas inlet; and wherein the diameter of the gas chamber is greater than the diameter of the gas outlet.

6. The gas sensor according to claim 5, wherein a flow of the gas is substantially parallel to the thermal emitter or the pyroelectric detector.

7. The gas sensor according to claim 5, wherein the gas sensor is configured to determine a concentration or a flow rate of the gas.

8. The gas sensor according to claim 2, wherein the gas chamber comprises a window.

9. The gas sensor according to claim 8, wherein the window comprises barium fluoride (BaFz), zinc selenide (ZnSe) or germanium (Ge).

10. The gas sensor according to claim 1, wherein the gap is of a value selected from a range from 0. 1 mm to 10 mm.

11. A method of forming a gas sensor, the method comprising: providing a thermal emitter; andproviding a pyroelectric detector spaced apart from the thermal emitter such that a gap between the thermal emitter and the pyroelectric detector is equal to or less than 10 mm.

12. The method according to claim 11, further comprising: providing a gas chamber such that the thermal emitter and the pyroelectric detector are on opposite sides of the gas chamber.

13. The method according to claim 12, further comprising coupling a gas inlet to the gas chamber; and coupling a gas outlet to the gas chamber such that the gas inlet and the gas outlet are directly facing each other.

14. The method according to claim 13, wherein a diameter of the gas inlet is smaller than the gap between the thermal emitter and the pyroelectric detector; and wherein a diameter of the gas outlet is smaller than the gap between the thermal emitter and the pyroelectric detector.

15. The method according to claim 13, wherein the gas chamber configured to carry a gas from the gas inlet to the gas outlet; wherein a diameter of the gas chamber is greater than a diameter of the gas inlet; and wherein the diameter of the gas chamber is greater than the diameter of the gas outlet.

16. The method according to claim 15, wherein a flow of the gas is substantially parallel to the thermal emitter or the pyroelectric detector.

17. The method according to claim 15, wherein the gas sensor is configured to determine a concentration or a flow rate of the gas.

18. The method according to claim 12, further comprising: providing a window between the thermal emitter and the gas chamber.

19. The method according to claim 18, wherein the window comprises barium fluoride (BaF2), zinc selenide (ZnSe) or germanium (Ge).

20. The method according to claim 11, wherein the gap is of a value selected from a range from 0. 1 mm to 10 mm.

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