High-stability low-power-consumption gas sensor

Abstract

A gas chamber of the high-stability low-power-consumption gas sensor comprises a bottom plate, an upper reflecting plate and an outer ring reflecting surface, the bottom plate is provided with a first low-power-consumption infrared light source, a first infrared detector and a second infrared detector, and the upper reflecting plate is provided with a first light splitting structure, a first off-axis parabolic reflecting surface and a second off-axis parabolic reflecting surface; the first low-power-consumption infrared light source is arranged corresponding to the first off-axis parabolic reflecting surface, the first infrared detector and the first light splitting structure, and the second infrared detector and the second off-axis parabolic reflecting surface respectively; the first light splitting structure is located on a reflection light path of the outer ring reflection surface. According to the utility model, the signal intensity of infrared light emitted by the same low-power-consumption infrared light source reaching the two infrared detectors is collected, the ratio of the measured signal intensity is not influenced by temperature, the concentration value obtained by inversion calculation conforms to the actual situation, the influence of temperature change on the detection result of the low-power-consumption gas sensor is solved, and the detection accuracy is improved. And the stability of the low-power-consumption gas sensor is improved.

Description

Technical Field

[0001] The utility model relates to the field of gas sensors, in particular to a high-stability and low-power consumption gas sensor. Background Art

[0002] The operating principle of a gas sensor is to exploit the absorption of light signals of specific wavelengths by the inherent vibration and rotational frequencies of gas molecules. The relationship between light absorption intensity and gas molecule concentration follows the Lambert-Beer law. Therefore, by detecting changes in light absorption intensity at specific wavelengths following the interaction between light and gas molecules, the concentration of a specific gas can be detected.

[0003] Among them, the low-power gas sensor has the characteristics of low power consumption because it uses low-power LED light source, low-power MCU and related low-power circuits. It can be powered by batteries. Therefore, the low-power gas sensor does not require any external cables, and there is no need to lay cables in advance on site, etc., making it more convenient to install and use.

[0004] The principle of low-power gas sensor to detect gas concentration is to calculate the light intensity measured by its internal infrared detector, and the gas absorption causes the detected light intensity to change within the range of 0.5-1 times. However, low-power LED light sources are particularly sensitive to temperature. The higher the temperature, the lower the luminous efficiency and the lower the luminous intensity. For example, in the operating temperature range of -40℃ to +70℃, under the influence of temperature changes, the maximum luminous intensity of the LED light source can reach more than 7 times the minimum value. Figure 6 By comparison, the sensor signal changes due to temperature changes are much greater than those due to gas absorption. Therefore, when existing low-power gas sensors detect gas concentration, changes in ambient temperature significantly impact the luminous efficiency of the low-power LED light source. The gas concentration calculated from the measured light signal intensity no longer matches the actual gas concentration, resulting in poor stability and inaccurate detection results. Utility Model Content

[0005] In order to solve the problem that the existing low-power gas sensor is affected by temperature, resulting in inaccurate gas concentration detection results, the utility model provides a high-stability low-power gas sensor.

[0006] The technical solution of this utility model is as follows:

[0007] A high-stability, low-power gas sensor comprises a shell and an air chamber located inside the shell, the air chamber comprising a bottom plate and an upper reflector arranged in parallel, the upper reflector being provided with a plurality of vents; the bottom plate being provided with a first low-power infrared light source, a first infrared detector and a second infrared detector, the upper reflector being further provided with a first spectroscopic structure, a first off-axis parabolic reflector, and a second off-axis parabolic reflector, the first low-power infrared light source and the first off-axis parabolic reflector, the first infrared detector and the first spectroscopic structure, the second infrared detector and the second off-axis parabolic reflector being respectively arranged in correspondence; an outer ring reflector is provided between the bottom plate and the upper reflector, and the first spectroscopic structure is located on the reflected light path of the outer ring reflector, the outer ring reflector being used to receive the reflected light from the first off-axis parabolic reflector and reflect the light four times before emitting it toward the second off-axis parabolic reflector.

[0008] By adopting the above technical solution, the infrared light emitted by the first low-power infrared light source is first emitted to the first off-axis parabolic reflector, and the first off-axis parabolic reflector collimates the infrared light so that the divergent infrared light becomes parallel reflected light; the first off-axis parabolic reflector reflects the light to the outer ring reflector, and the light reaching the outer ring reflector will be reflected multiple times. The first spectroscopic structure is set on the reflected light path of the outer ring reflector. When the light reaches the first spectroscopic structure, part of the light is reflected by the first spectroscopic structure to the first infrared detector, and the remaining part of the light continues to propagate along the reflected light path of the outer ring reflector through the first spectroscopic structure. After being reflected four times by the outer ring reflector, the light is emitted to the second off-axis parabolic reflector, reflected by the second off-axis parabolic reflector and converged to the second infrared detector.

[0009] The utility model according to the above scheme is characterized in that it also includes an air chamber skeleton for connecting the base plate and the upper reflective plate, the air chamber skeleton includes a hollow plate and an outer plate arranged at the edge of the hollow plate, the inner side wall of the outer plate is plated with a reflective surface to form the outer ring reflective surface, and the hollow plate is provided with a plurality of hollow openings, which respectively correspond to the first low-power infrared light source, the first infrared detector and the second infrared detector.

[0010] By adopting the above technical solution, the emitted light of the first low-power infrared light source enters the space of the outer ring reflective surface through the corresponding hollow opening, the reflected light of the first spectroscopic structure enters the first infrared detector through the corresponding hollow opening, and the reflected light of the second off-axis parabolic reflective surface enters the second infrared detector through the corresponding hollow opening.

[0011] Furthermore, the upper reflective plate is provided with a limiting boss, the top edge of the peripheral plate is provided with a limiting groove, and the limiting boss is connected to the limiting groove in a limiting manner.

[0012] Furthermore, the first light splitting structure is provided at the rear end of the first reflection point, or the rear end of the second reflection point, or the rear end of the third reflection point of the reflection light path of the outer ring reflection surface.

[0013] The utility model according to the above scheme is characterized in that the base plate is also provided with a second low-power infrared light source, a third infrared detector and a fourth infrared detector, and the upper reflecting plate is also provided with a second splitting structure, a third off-axis parabolic reflecting surface and a fourth off-axis parabolic reflecting surface; the second low-power infrared light source and the third off-axis parabolic reflecting surface, the second infrared detector and the second splitting structure, the fourth infrared detector and the fourth off-axis parabolic reflecting surface are respectively arranged correspondingly; an inner ring reflecting surface is provided between the base plate and the upper reflecting plate, and the second low-power infrared light source, the third infrared detector, the fourth infrared detector, the second splitting structure, the third off-axis parabolic reflecting surface and the fourth off-axis parabolic reflecting surface are all located within the projected circular area of ​​the inner ring reflecting surface.

[0014] By adopting the above technical solution, the infrared light emitted by the second low-power infrared light source first reaches the third off-axis parabolic reflector, is collimated by the third off-axis parabolic reflector and becomes parallel reflected light that is emitted to the second spectroscopic structure. Part of the light is reflected by the second spectroscopic structure to the third infrared detector, and the remaining light passes through the second spectroscopic structure to the inner ring reflector. The light is reflected only once on the inner ring reflector and then emitted to the fourth off-axis parabolic reflector. The light is reflected by the fourth off-axis parabolic reflector and converges to the fourth infrared detector.

[0015] Furthermore, it also includes an air chamber skeleton provided with the outer ring reflective surface, the air chamber skeleton includes a hollow plate, the hollow plate is provided with an outer plate and an inner plate in a concentric circle structure, and the inner side walls of the outer plate and the inner plate are coated with a reflective film to form the outer ring reflective surface and the inner ring reflective surface respectively.

[0016] Furthermore, the first spectroscopic structure and the second spectroscopic structure both have a metal reflective plate, and the metal reflective plate is provided with a plurality of light-transmitting holes. The ratio of the area of ​​all the light-transmitting holes to the area of ​​the metal reflective plate is the transmittance of the metal reflective plate, and the ratio of the area of ​​the metal reflective plate after removing all the light-transmitting holes to the area of ​​the metal reflective plate is the reflectivity of the metal reflective plate.

[0017] Furthermore, a distance between a straight line on which the optical path from the first off-axis parabolic reflective surface to the outer ring reflective surface lies and a center point of the outer ring reflective surface is equal to square root of two of the radius of the outer ring reflective surface.

[0018] By adopting the above technical solution, the first off-axis parabolic reflector is directed toward the outer ring reflector at a specific angle, so that the light path formed by the reflection of the light within the outer ring reflector is a square light path, which is conducive to ensuring that there is ample space inside the square light path for setting the inner ring reflector.

[0019] The utility model according to the above solution is characterized in that the shell includes an outer protective cover and a bottom shell, the top of the outer protective cover is provided with an air inlet, and the bottom shell is penetrated by a plurality of sensor pins.

[0020] The utility model according to the above scheme is characterized in that it also includes a low-power circuit board, which is arranged under the base plate, and the pins of several low-power infrared light sources and several infrared detectors in the air chamber are welded to the low-power circuit board after passing through the base plate.

[0021] The utility model according to the above solution has the following beneficial effects:

[0022] The utility model arranges a first low-power infrared light source, a first infrared detector, a second infrared detector, a first spectroscopic structure, a first off-axis parabolic reflector and a second off-axis parabolic reflector in a gas chamber. When detecting gas concentration, the signal intensity of infrared light emitted by the same low-power infrared light source reaching two infrared detectors with the same filter band is collected, and the signal intensity ratio of the two infrared detectors is measured. Since the ratio is not affected by temperature, the concentration value obtained by inverting and calculating the ratio is consistent with the actual situation, thereby solving the influence of temperature changes on the detection results of the low-power gas sensor and improving the stability of the low-power gas sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is an exploded view of the structure of the present utility model;

[0024] Figure 2 This is a schematic structural diagram of the air chamber skeleton of the utility model;

[0025] Figure 3 Schematic diagram of the structure of the upper reflector;

[0026] Figure 4 This is a schematic diagram of the optical path of the utility model;

[0027] Figure 5 This is a curve diagram of the detection light intensity ratio changing with temperature of the utility model;

[0028] Figure 6 This is a graph showing how the light intensity detected by an existing low-power gas sensor changes with temperature.

[0029] In the figure,

[0030] 1. Air chamber frame; 11. Outer ring reflective surface; 12. Inner ring reflective surface; 13. Hollow opening; 14. Limiting groove;

[0031] 20. Base plate; 2. First low-power infrared light source; 3. First infrared detector; 4. Second infrared detector; 5. Second low-power infrared light source; 6. Third infrared detector; 7. Fourth infrared detector;

[0032] 8. Upper reflector; 81. First off-axis parabolic reflector; 82. Second off-axis parabolic reflector; 83. Third off-axis parabolic reflector; 84. Fourth off-axis parabolic reflector; 85. First light splitting structure; 86. Second light splitting structure; 87. Vent; 88. Position limiting boss;

[0033] 9. Low-power circuit board; 10. Outer protective cover; 101. Air inlet. DETAILED DESCRIPTION

[0034] To better understand the purpose, technical solutions, and technical effects of the present invention, the present invention is further explained below with reference to the accompanying drawings and embodiments. It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. It should also be noted that the embodiments described below are intended only to illustrate the present invention and are not intended to limit the present invention.

[0035] It should be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may also be an intermediate element; when an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0036] The indicated orientation or position relationship is based on the orientation or position relationship shown in the accompanying drawings, or the orientation or position relationship in which the product of the application is typically placed when in use, or the orientation or position relationship commonly understood by those skilled in the art, or the orientation or position relationship commonly placed when the product of the application is in use. It is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0037] The terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features. "Several" means two or more, unless otherwise expressly specified.

[0038] Example 1

[0039] like Figures 1 to 5 As shown, a high-stability, low-power gas sensor comprises a housing and an air chamber within the housing. The air chamber comprises a parallel bottom plate 20 and an upper reflector 8. The upper reflector 8 is provided with several vents 87, through which gas can enter the chamber. The bottom plate 20 is provided with a first low-power infrared light source 2, a first infrared detector 3, and a second infrared detector 4. The upper reflector 8 is provided with a first beam splitting structure 85, a first off-axis parabolic reflector 81, and a second off-axis parabolic reflector 82. The first low-power infrared light source 2 is positioned corresponding to the first off-axis parabolic reflector 81, the first infrared detector 3 is positioned corresponding to the first beam splitting structure 85, and the second infrared detector 4 is positioned corresponding to the second off-axis parabolic reflector 82. An outer ring reflective surface 11 is positioned between the bottom plate 20 and the upper reflector 8. The outer ring reflective surface 11 receives light reflected from the first off-axis parabolic reflector 81 and reflects it four times before projecting it toward the second off-axis parabolic reflector 82. The first beam splitting structure 85 is located in the reflected light path of the outer ring reflective surface 11.

[0040] like Figure 4 As shown, the infrared light emitted by the first low-power infrared light source 2 is first emitted to the first off-axis parabolic reflector 81. The first off-axis parabolic reflector 81 collimates the infrared light, so that the divergent infrared light becomes parallel reflected light. In order to ensure that the first off-axis parabolic reflector can efficiently utilize and reflect the light energy emitted by the first low-power infrared light source, the center of the light-emitting surface of the first low-power infrared light source is vertically positioned directly above the focal point of the first off-axis parabolic reflector. The distance between the center of the light-emitting surface and the focal point of the first off-axis parabolic reflector depends on the size and divergence angle of the light-emitting surface. The reverse extension line of the light emitted at the edge of the light-emitting surface at the maximum divergence angle coincides with the focal point of the first off-axis parabolic reflector.

[0041] The first off-axis parabolic reflector 81 reflects light onto the outer ring reflector 11. Because the outer ring reflector 11 forms a closed loop of internal reflection, light reaching the outer ring reflector 11 undergoes multiple reflections, achieving a longer optical path within a confined or effective space. A first beam splitter structure 85 is positioned within the reflected optical path of the outer ring reflector 11. When light reaches the first beam splitter structure 85, a portion of the light is reflected by the first beam splitter structure 85 toward the first infrared detector 3. The remaining light passes through the first beam splitter structure 85 and continues along the reflected optical path of the outer ring reflector 11. After four reflections from the outer ring reflector 11, the light is directed toward the second off-axis parabolic reflector 82, where it is reflected and converges onto the second infrared detector 4.

[0042] like Figure 2 and Figure 3As shown, in this embodiment, the low-power gas sensor also includes an air chamber skeleton 1 for connecting the bottom plate 20 and the upper reflective plate 8. The air chamber skeleton 1 includes a hollow plate and a peripheral plate. The peripheral plate is arranged at the edge of the hollow plate, and the inner side wall of the peripheral plate is plated with a reflective surface to form an outer ring reflective surface 11. The hollow plate is provided with a plurality of hollow openings 13, which correspond to the first low-power infrared light source 2, the first infrared detector 3 and the second infrared detector 4 respectively. The emitted light of the first low-power infrared light source 2 enters the space of the outer ring reflective surface 11 through the corresponding hollow openings, the reflected light of the first spectroscopic structure 85 enters the first infrared detector 3 through the corresponding hollow openings, and the reflected light of the second off-axis parabolic reflective surface 82 enters the second infrared detector 4 through the corresponding hollow openings.

[0043] The upper reflective plate 8 is provided with a limiting boss 88, and the top edge of the peripheral plate is provided with a limiting groove 14. The limiting boss 88 is connected to the limiting groove 14 to limit the position, which can quickly position and install the hollow plate and the upper reflective plate 8. In other optional embodiments, the upper reflective plate 8 is provided with a limiting groove, and the peripheral plate on the hollow plate is provided with a matching limiting boss.

[0044] In this embodiment, a first low-power infrared light source 2, a first off-axis parabolic reflector 81, an outer ring reflector 11, a first beam splitting structure 85, a first infrared detector 3, a second off-axis parabolic reflector 82, and a second infrared detector 4 form an optical path for detecting the gas to be measured in the gas chamber. The center wavelength of the first low-power infrared light source and the detection wavelengths of the first and second infrared detectors are both within the absorption band of the gas to be measured. The first and second infrared detectors have the same filter band, ensuring that their detection bands are the same.

[0045] During use, when the gas to be measured is introduced into the gas chamber, the inherent vibration and rotation frequency of the gas molecules absorb infrared light signals of a specific wavelength. The first infrared detector 3 and the second infrared detector 4 can both detect changes in the absorption intensity of light of a specific wavelength after the infrared light interacts with the gas molecules. The details are as follows:

[0046] The optical path length from the first low-power infrared light source 2 to the first infrared detector 3 is L1, and the optical path length from the first low-power infrared light source 2 to the second infrared detector 4 is L2; ​​when the ambient temperature is T1, and there is no gas to be measured, the light intensity detected by the first infrared detector 3 is I 01 The light intensity detected by the second infrared detector 4 is I 02 When there is a gas to be measured, the light intensity detected by the first infrared detector 3 is I 11 The light intensity detected by the second infrared detector 4 is I 12 , according to Lambert-Beer law:

[0047]

[0048] Where α(υ) is the absorption coefficient of the gas to be measured, C is the concentration of the gas to be measured, and e is a constant;

[0049] Dividing formula (2) by formula (1) yields:

[0050] Therefore, the low-power gas sensor can measure the ratio of the signal intensities of the two infrared detectors after the gas with concentration C is introduced at temperature T1; 01 , I 02 is the value measured without the gas to be measured, is a constant.

[0051] When the ambient temperature changes to T2, the brightness of the first low-power infrared light source 2 is k times that when the ambient temperature is T1. Therefore, when there is no gas to be measured, the light intensity I detected by the first infrared detector 3 is 03 =k·I 01 , the light intensity I detected by the second infrared detector 4 04 =k·I 02 When there is a gas to be measured, the light intensity detected by the first infrared detector 3 is I 13 The light intensity detected by the second infrared detector 4 is I 14 , according to Lambert-Beer law:

[0052]

[0053] Dividing formula (5) by formula (4) yields: ;

[0054] Because I 03 =k·I 01 , I 04 =k·I 02 , then we can get:

[0055] Comparing formula (3) and formula (6), we can see that I 14 / I 13 =I 12 / I 11 Therefore, the ratio of the signal intensities of the two infrared detectors is only related to the gas absorption coefficient, the gas concentration, and the equivalent optical path (L2-L1) of the gas detection optical path to be measured, and is not affected by temperature. The concentration of the gas to be measured is calculated by ratio inversion to eliminate the influence of temperature changes on the gas concentration detection of the low-power gas sensor.

[0056] like Figure 5As shown, the light signal intensity received by the first infrared detector is divided by the light signal intensity of the second infrared detector and multiplied by 10000 to obtain the normalized detection signal intensity. It can be seen that the normalized detection signal intensity is not affected by changes in the external ambient temperature. When the external ambient temperature changes from -40 degrees to 70 degrees, the normalized detection signal intensity remains basically constant.

[0057] It should be noted that the method of inverting the signal intensity ratio of two infrared detectors to calculate the concentration of the gas to be measured is an existing technology. Before the low-power gas sensor is put into use, a gas with a known concentration gradient is first introduced into the low-power gas sensor. For gases with different concentrations, different signal intensity ratios can be obtained. This ratio can be defined as the normalized detection signal intensity; the normalized detection signal intensities corresponding to different concentrations are recorded, and a nonlinear curve fitting is used to obtain an exponential function f(x)=e x The calculation formula is written into the low-power gas sensor chip. When in use, the low-power gas sensor is placed in an environment with a gas of unknown concentration. A normalized detection signal strength can be measured, and the chip automatically calculates the corresponding gas concentration based on the calculation formula.

[0058] In the present invention, the first spectroscopic structure 85 can be arranged behind the first reflection point of the outer ring reflection surface 11, or behind the second reflection point of the outer ring reflection surface 11, or behind the third reflection point of the outer ring reflection surface 11, and the first infrared detector 3 is correspondingly arranged directly below the first spectroscopic structure 85 to ensure that the reflected light from the first spectroscopic structure 85 is received.

[0059] like Figure 4 As shown, if the first spectroscopic structure 85 is arranged after the first reflection point of the outer ring reflection surface 11, the optical path length L1 from the first low-power infrared light source 2 to the first infrared detector 3 can be determined by the light propagation path, and its optical path is: first low-power infrared light source 2-first off-axis parabolic reflection surface 81-first reflection point of the outer ring reflection surface 11-first spectroscopic structure 85-first infrared detector 3.

[0060] If the first spectroscopic structure 85 is arranged after the second reflection point of the outer ring reflection surface 11, the optical path from the first low-power infrared light source 2 to the first infrared detector 3 is: first low-power infrared light source 2-first off-axis parabolic reflection surface 81-first reflection point of the outer ring reflection surface 11-second reflection point of the outer ring reflection surface 11-first spectroscopic structure 85-first infrared detector 3.

[0061] If the first spectroscopic structure 85 is arranged after the third reflection point of the outer ring reflection surface 11, the optical path from the first low-power infrared light source 2 to the first infrared detector 3 is: first low-power infrared light source 2-first off-axis parabolic reflection surface 81-first reflection point of the outer ring reflection surface 11-second reflection point of the outer ring reflection surface 11-third reflection point of the outer ring reflection surface 11-first spectroscopic structure 85-first infrared detector 3.

[0062] It can be seen that the placement of the first beam splitting structure 85 determines the optical path length L1 from the first low-power infrared light source 2 to the first infrared detector 3. However, regardless of where the first beam splitting structure 85 is positioned within the rectangular optical path of the outer ring reflective surface 11, the light propagation path from the first low-power infrared light source 2 to the second infrared detector 4 remains unchanged, and the optical path length L2 remains fixed. The optical path is: first low-power infrared light source 2 - first off-axis parabolic reflector 81 - first reflection point on the outer ring reflective surface 11 - second reflection point on the outer ring reflective surface 11 - third reflection point on the outer ring reflective surface 11 - fourth reflection point on the outer ring reflective surface 11 - second off-axis parabolic reflector 82 - second infrared detector 4. Therefore, different placement positions of the first beam splitting structure 85 can adjust the distance difference (L2 - L1) between the two infrared detectors and the first low-power infrared light source 2, thereby changing the equivalent optical path of the gas detection optical path. A longer equivalent optical path length increases the sensor's detection accuracy, while a shorter equivalent optical path length increases the sensor's range. According to actual needs, the user can adjust the position of the first light splitting structure 85 when producing the low-power infrared gas sensor to select higher detection accuracy or a larger range.

[0063] Example 2

[0064] like Figures 1 to 5 As shown, a low-power infrared gas sensor, compared to the first embodiment, has a gas chamber equipped with both a target gas detection optical path and an interfering gas detection optical path. This low-power gas sensor is used in gas detection environments where interfering gases are present. The target gas detection optical path can be used to detect the concentration of the target gas, while the interfering gas detection optical path is used to detect the concentration of the interfering gas. The interfering gas detection optical path operates on the same principle as the target gas detection optical path.

[0065] In this embodiment, the bottom plate 20 is provided with not only a first low-power infrared light source 2, a first infrared detector 3, and a second infrared detector 4, but also a second low-power infrared light source 5, a third infrared detector 6, and a fourth infrared detector 7. The upper reflector 8 is provided with not only a first light-splitting structure 85, a first off-axis parabolic reflector 81, and a second off-axis parabolic reflector 82, but also a second light-splitting structure 86, a third off-axis parabolic reflector 83, and a fourth off-axis parabolic reflector 84. The second low-power infrared light source 5 is provided in correspondence with the third off-axis parabolic reflector 83, the second infrared detector 4 is provided in correspondence with the second light-splitting structure 86, and the fourth infrared detector 7 is provided in correspondence with the fourth off-axis parabolic reflector 84.

[0066] like Figure 4 As shown, an inner ring reflective surface 12 is provided between the bottom plate 20 and the upper reflective plate 8. This inner ring reflective surface 12 is located within the outer ring reflective surface 11 and should be small to avoid affecting the optical path of the gas under test. The second low-power infrared light source 5, the third infrared detector 6, the fourth infrared detector 7, the second beam splitting structure 86, the third off-axis parabolic reflective surface 83, and the fourth off-axis parabolic reflective surface 84 are all located within the circular area projected by the inner ring reflective surface 12.

[0067] like Figure 4 As shown, the interfering gas detection optical path includes a second low-power infrared light source 5, a third off-axis parabolic reflector 83, a second spectroscopic structure 86, a third infrared detector 6, an inner ring reflector 12, and a fourth off-axis parabolic reflector 84. The infrared light emitted by the second low-power infrared light source 5 first reaches the third off-axis parabolic reflector 83. After being collimated by the third off-axis parabolic reflector 83, it becomes parallel reflected light and is emitted to the second spectroscopic structure 86. The second spectroscopic structure 86 uses its reflection function to reflect part of the light to the third infrared detector 6, and the remaining light passes through the second spectroscopic structure 86 and is emitted to the inner ring reflector 12. The light is reflected only once by the inner ring reflector 12 and then emitted to the fourth off-axis parabolic reflector 84. The light is reflected by the fourth off-axis parabolic reflector 84 and converges to the fourth infrared detector 7. The second light-splitting structure 86 is arranged on the optical path between the reflection point of the inner ring reflection surface 12 and the third off-axis parabolic reflection surface 83. The optical path length L3 from the second low-power infrared light source 5 to the third infrared detector 6 and the optical path length L4 from the second low-power infrared light source 5 to the fourth infrared detector 7 are not the same, so the equivalent optical path of the interference gas detection optical path is (L4-L3).

[0068] like Figure 2As shown, in this embodiment, the hollow plate comprises an outer plate and an inner plate arranged in a concentric circular configuration. The inner sidewalls of both plates are coated with a reflective film to form an outer ring reflective surface 11 and an inner ring reflective surface 12, respectively. The hollow plate is provided with a larger number of hollow openings 13, each corresponding to the second low-power infrared light source 5, the third infrared detector 6, and the fourth infrared detector 7. Light emitted from the second low-power infrared light source 5 enters the space within the inner ring reflective surface 12 through the corresponding hollow openings. Light reflected from the second beam splitting structure 86 enters the third infrared detector 6 through the corresponding hollow openings. Light reflected from the fourth off-axis parabolic reflective surface 84 enters the fourth infrared detector 7 through the corresponding hollow openings. The optical paths from the second low-power infrared light source 5 to the third off-axis parabolic reflective surface 83, the second beam splitting structure 86 to the third infrared detector 6, and the fourth off-axis parabolic reflective surface 84 to the fourth infrared detector 7 are all perpendicular to the plane of the inner ring reflective surface 12, which contains the reflected light path.

[0069] In this embodiment, the distance between the straight line on the optical path from the first off-axis parabolic reflector 81 to the outer ring reflector 11 and the center point of the outer ring reflector 11 is equal to the square root of two times the radius of the outer ring reflector 11. This allows the rectangular optical path of the outer ring reflector 11 to be a square optical path. Geometry shows that a rectangle within a circle has the largest area when it is a square. This helps ensure ample space within the square optical path for the inner ring reflector 12, preventing the inner panel from obstructing the light from the outer gas detection optical path.

[0070] The low-power gas sensor of this embodiment is suitable for use in gas detection environments where interfering gases are present. The detection band of the infrared detector in the optical path for the gas to be detected is within the absorption band of the gas to be detected, and the detection band of the infrared detector in the optical path for the interfering gas is within the absorption band of the interfering gas. The detection results of the optical paths for the gas to be detected and the interfering gas detection may fall into the following categories:

[0071] Case 1--

[0072] The optical path for detecting the gas to be measured responds only to the gas to be measured. This means that the center wavelength of the first low-power infrared light source and the detection bands of the first and second infrared detectors are within the absorption band of the gas to be measured, but not the absorption band of interfering gases. The optical path for detecting interfering gases responds only to interfering gases. This means that the center wavelength of the second low-power infrared light source and the detection bands of the third and fourth infrared detectors are within the absorption band of interfering gases, but not the absorption band of the gas to be measured. In this case, interfering gases will not affect the concentration results of the gas to be measured.

[0073] Case 2--

[0074] The optical path for detecting the gas to be measured responds to both the gas to be measured and the interfering gas. This means that the center wavelength of the first low-power infrared light source and the detection bands of the first and second infrared detectors are both within the absorption band of the gas to be measured and the interfering gas. The optical path for detecting the interfering gas responds only to the interfering gas. This means that the center wavelength of the second low-power infrared light source and the detection bands of the third and fourth infrared detectors are both within the absorption band of the interfering gas and not the absorption band of the gas to be measured.

[0075] In this case, in the test gas detection optical path, the relationship between the test gas concentration and the absorbance is f1, and the relationship between the interfering gas concentration and the absorbance is f2; in the interfering gas detection optical path, the relationship between the interfering gas concentration and the absorbance is f3. Therefore, f1, f2, and f3 can be obtained through theoretical calculation or experimental data. Assuming that the gas concentration of test gas A is C1, the gas concentration of interfering gas B is C2, the absorbance of the test gas detection optical path is D1, and the absorbance of the interfering gas detection optical path is D2, D1 and D2 can be calculated by the ratio of the current detected light intensity to the zero-point detection light intensity. Therefore, the following relationship can be obtained:

[0076] f1(C1)+f2(C2)=D1 (7),

[0077] f3(C2)=D2 (8);

[0078] In equations (7) and (8), f1, f2, f3, D1, and D2 are known. The values ​​of the measured gas concentration C1 and the interfering gas concentration C2 can be calculated by mathematical calculation or the least squares method. To facilitate understanding, an example of a linear relationship is given. If the absorption rates of the measured gas and the interfering gas are low, and the optical path lengths of the measured gas detection optical path and the interfering gas detection optical path are short, the relationship between the concentration and absorption rate of the measured gas and the interfering gas can be considered a linear relationship, then:

[0079] k1×C1+ k2×C2=D1 (71),

[0080] k3×C2=D2 (81);

[0081] In formulas (71) and (81), k1, k2, k3, D1, and D2 are all known, and the values ​​of the measured gas concentration C1 and the interfering gas concentration C2 can be easily calculated through mathematical calculation.

[0082] Case 3--

[0083] The optical path for detecting the gas to be measured responds to both the gas to be measured and the interfering gas. That is, the center wavelength of the light from the first low-power infrared light source and the detection bands of the first and second infrared detectors are both within the absorption band of the gas to be measured and the absorption band of the interfering gas. The optical path for detecting the interfering gas responds to both the gas to be measured and the interfering gas. That is, the center wavelength of the light from the second low-power infrared light source and the detection bands of the third and fourth infrared detectors are both within the absorption band of the gas to be measured and the absorption band of the interfering gas.

[0084] In this case, in the test gas detection optical path, the relationship between the test gas concentration and the absorbance is f1, and the relationship between the interfering gas concentration and the absorbance is f2; in the interfering gas detection optical path, the relationship between the test gas concentration and the absorbance is f3, and the relationship between the interfering gas concentration and the absorbance is f4. Therefore, f1, f2, f3, and f4 can be obtained through theoretical calculations or experimental data. Assuming that the gas concentration of test gas A is C1, the gas concentration of interfering gas B is C2, the absorbance of the test gas detection optical path is D1, and the absorbance of the interfering gas detection optical path is D2, D1 and D2 can be calculated by the ratio of the current detected light intensity to the zero-point detection light intensity. Therefore, the following relationship can be obtained:

[0085] f1(C1)+f2(C2)=D1 (9),

[0086] f3(C1)+f4(C2)=D2 (10);

[0087] In formulas (9) and (10), f1, f2, f3, f4, D1, and D2 are known. The values ​​of the measured gas concentration C1 and the interfering gas concentration C2 can be calculated by mathematical calculation or least squares method. Similarly, taking an example of a linear relationship, we have:

[0088] k1×C1+ k2×C2=D1 (91),

[0089] k3×C1+ k4×C2=D2 (101);

[0090] In formulas (91) and (101), k1, k2, k3, k4, D1, and D2 are all known, and the values ​​of the measured gas concentration C1 and the interfering gas concentration C2 can be easily calculated through mathematical calculation.

[0091] In summary, in Cases 2 and 3, if the interfering gas affects the concentration calculation of the gas to be measured, the concentration of the gas to be measured and the concentration of the interfering gas can be calculated separately by adding an interfering gas detection optical path, thereby eliminating the influence of the interfering gas on the calculation result of the concentration of the gas to be measured.

[0092] In the present utility model, the first light-splitting structure 85 and the second light-splitting structure 86 both have a metal reflective plate, which is provided with a plurality of light-transmitting holes. The ratio of the area of ​​all the light-transmitting holes to the area of ​​the metal reflective plate is the transmittance of the metal reflective plate, that is, the transmittance of the light-splitting structure; the ratio of the area of ​​the metal reflective plate after removing all the light-transmitting holes to the area of ​​the metal reflective plate is the reflectivity of the metal reflective plate, that is, the reflectivity of the light-splitting structure.

[0093] like Figure 1 As shown, the housing comprises an outer protective cover 10 and a bottom shell, protecting the internal gas chamber and the electrical components therein. An air inlet 101 is provided at the top of the outer protective cover 10, allowing ambient air to enter the sensor and then into the gas chamber through vent 87. The bottom shell is provided with several sensor pins for connecting and securing the low-power infrared gas sensor.

[0094] The low-power gas sensor also includes a low-power circuit board 9, which is arranged under the base plate 20, and the pins of several low-power infrared light sources and several infrared detectors in the gas chamber pass through the base plate 20 and are welded to the low-power circuit board 9.

[0095] To summarize, the utility model arranges a first low-power infrared light source, a first infrared detector, a second infrared detector, a first spectroscopic structure, a first off-axis parabolic reflector and a second off-axis parabolic reflector in the gas chamber to detect the gas concentration. The signal intensity of the infrared light emitted by the same low-power infrared light source reaching two infrared detectors with the same filter band is collected, and the signal intensity ratio of the two infrared detectors is measured. Since the ratio is not affected by temperature, the concentration value calculated by inversion using the ratio is consistent with the actual situation, thereby solving the influence of temperature changes on the detection results of the low-power gas sensor and improving the stability of the low-power gas sensor.

[0096] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0097] The above embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the concept of the present invention, and these variations and improvements fall within the scope of protection of the present invention. Therefore, the scope of protection of the present utility model patent shall be determined by the appended claims.

Claims

1. A high-stability, low-power gas sensor, comprising a housing and a gas chamber located inside the housing, characterized in that: The air chamber comprises a bottom plate and an upper reflective plate arranged in parallel, and the upper reflective plate is provided with a plurality of vent holes; The bottom plate is provided with a first low-power infrared light source, a first infrared detector and a second infrared detector, and the upper reflector is further provided with a first light splitting structure, a first off-axis parabolic reflective surface and a second off-axis parabolic reflective surface; The first low-power infrared light source and the first off-axis parabolic reflector, the first infrared detector and the first light splitting structure, the second infrared detector and the second off-axis parabolic reflector are respectively arranged correspondingly; An outer ring reflective surface is provided between the bottom plate and the upper reflective plate, and the first light splitting structure is located on the reflected light path of the outer ring reflective surface.

2. The high-stability, low-power gas sensor according to claim 1, characterized in that: It also includes an air chamber frame for connecting the base plate and the upper reflective plate, the air chamber frame includes a hollow plate and an outer plate arranged at the edge of the hollow plate, the inner side wall of the outer plate is plated with a reflective surface to form the outer ring reflective surface, and the hollow plate is provided with a plurality of hollow openings, which respectively correspond to the first low-power infrared light source, the first infrared detector and the second infrared detector.

3. The high-stability, low-power gas sensor according to claim 2, characterized in that: The upper reflective plate is provided with a limiting boss, the top edge of the peripheral plate is provided with a limiting groove, and the limiting boss is connected to the limiting groove in a limiting manner.

4. The high-stability, low-power gas sensor according to claim 2, characterized in that: The first light splitting structure is arranged at the rear end of the first reflection point, or the rear end of the second reflection point, or the rear end of the third reflection point of the reflection light path of the outer ring reflection surface.

5. The high-stability, low-power gas sensor according to claim 1, characterized in that: The bottom plate is further provided with a second low-power infrared light source, a third infrared detector and a fourth infrared detector, and the upper reflector is further provided with a second light-splitting structure, a third off-axis parabolic reflective surface and a fourth off-axis parabolic reflective surface; the second low-power infrared light source and the third off-axis parabolic reflective surface, the second infrared detector and the second light-splitting structure, the fourth infrared detector and the fourth off-axis parabolic reflective surface are respectively arranged correspondingly; An inner ring reflective surface is provided between the bottom plate and the upper reflective plate, and the second low-power infrared light source, the third infrared detector, the fourth infrared detector, the second light-splitting structure, the third off-axis parabolic reflective surface and the fourth off-axis parabolic reflective surface are all located within the projected circular area of ​​the inner ring reflective surface.

6. The high-stability, low-power gas sensor according to claim 5, characterized in that: It also includes an air chamber frame provided with the outer ring reflective surface, the air chamber frame includes a hollow plate, the hollow plate is provided with an outer plate and an inner plate in a concentric circle structure, and the inner side walls of the outer plate and the inner plate are coated with a reflective film to form the outer ring reflective surface and the inner ring reflective surface respectively.

7. The high-stability, low-power gas sensor according to claim 5, characterized in that: Both the first light-splitting structure and the second light-splitting structure have a metal reflective plate, which is provided with a plurality of light-transmitting holes. The ratio of the area of ​​all the light-transmitting holes to the area of ​​the metal reflective plate is the transmittance of the metal reflective plate, and the ratio of the area of ​​the metal reflective plate after removing all the light-transmitting holes to the area of ​​the metal reflective plate is the reflectivity of the metal reflective plate.

8. The high-stability, low-power gas sensor according to claim 5, characterized in that: The distance between a straight line on which an optical path from the first off-axis parabolic reflective surface to the outer ring reflective surface lies and a center point of the outer ring reflective surface is equal to square root of two of a radius of the outer ring reflective surface.

9. The high-stability, low-power gas sensor according to claim 1, characterized in that: The shell comprises an outer protective cover and a bottom shell. An air inlet is provided on the top of the outer protective cover, and a plurality of sensor pins are passed through the bottom shell.

10. The high-stability, low-power gas sensor according to claim 1, characterized in that: It also includes a low-power circuit board, which is arranged below the base plate, and the pins of several low-power infrared light sources and several infrared detectors in the air chamber pass through the base plate and are welded to the low-power circuit board.

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