gas detector

Abstract

To improve detection sensitivity of gas targeted for detection in a gas detector.SOLUTION: A gas detector is provided that comprises: a first gas chamber having a main gas chamber upon which light passing through gas targeted for detection is incident, and a sub-gas chamber communicating with the main gas chamber, in which the light is not incident upon the sub-gas chamber, and having accommodation gas including the same gas as the gas targeted for detection encapsulated; a second gas chamber upon which the light passing through the main gas chamber is incident, and having the accommodation gas encapsulated; a gas sensor outputting a signal corresponding to pressure of the accommodation gas. The main gas chamber may have a first transmission window the light transmits, and the sub-gas chamber may not have the transmission window the light transmits. The second gas chamber may have a second transmission window the light transmits.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gas detector. [Background technology]

[0002] Patent Document 1 states that "In an infrared gas analyzer, when an interfering gas is contained in the sample gas, the influence of interference sensitivity appears, and measurement errors may occur" (Prior Art). Patent Document 2 states that "after passing through the measurement gas in the adjacent chambers, infrared rays produce pressure increases of different heights determined by absorption" (prior art). Patent Document 3 describes a "detector for an infrared gas analyzer that extracts the difference or ratio of the infrared absorption strength between a first detection reservoir and a second detection reservoir" (detailed description of the invention). Patent Document 4 states that "interference components are removed when detecting multiple components" (abstract). [Prior art document] [Patent documents] [Patent Document 1] Patent No. 2572058 [Patent Document 2] Patent No. 1822312 [Patent Document 3] Patent No. 1223655 [Patent Document 4] Japanese Patent Application Laid-Open No. 2004-061207 Summary of the Invention [Problem to be solved by the invention]

[0003] It is desirable for a gas detector to be able to stably detect a target gas even when the gas detector is subjected to external vibrations. [Means for solving the problem]

[0004] A first aspect of the present invention provides a gas detector having a main gas chamber into which light that has passed through a gas to be detected is incident and an auxiliary gas chamber that is in communication with the main gas chamber and into which light is not incident, the gas detector also comprising: a first gas chamber filled with a storage gas containing the same type of gas as the gas to be detected; a second gas chamber filled with the storage gas and into which light that has passed through the main gas chamber is incident; and a gas sensor that outputs a signal corresponding to the pressure of the storage gas.

[0005] The main gas chamber may have a first transparent window through which light passes, the auxiliary gas chamber may not have a transparent window through which light passes, and the second gas chamber may have a second transparent window through which light passes.

[0006] The gas detector may further include a light adjusting unit that adjusts the amount of light. The second gas chamber may have a front chamber into which the light that has passed through the main gas chamber is incident, and a rear chamber into which the light that has passed through the front chamber is incident. The light adjusting unit may be disposed between the front chamber and the rear chamber in the optical path of the light.

[0007] The direction from the main gas chamber to the auxiliary gas chamber and the direction from the first gas chamber to the second gas chamber may be different.

[0008] The auxiliary gas chamber may be disposed at a position that does not overlap with the second gas chamber when viewed in the optical path direction of the light.

[0009] In the direction of the light path, the auxiliary gas chamber may be longer than the main gas chamber.

[0010] When viewed from a direction intersecting the optical path direction of the light, at least a portion of the auxiliary gas chamber may be disposed at a position overlapping at least a portion of the second gas chamber.

[0011] In the optical path direction of the light, the optical path length of the second gas chamber may be greater than 1.0 times and less than or equal to 3.0 times the optical path length of the main gas chamber.

[0012] The volume of the first gas chamber may be 0.8 to 1.5 times the volume of the second gas chamber.

[0013] The volume of the auxiliary gas chamber may be 1.0 to 1.2 times the volume of the main gas chamber.

[0014] The above summary of the invention does not list all of the features of the present invention, and subcombinations of these features may also be inventions. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a diagram showing an example of a gas detector 100 according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged view of the gas detection unit 60 in FIG. [Figure 3] 1 is a diagram illustrating the principle of detection of a target gas 90 by a gas detector 100. FIG. [Figure 4] FIG. 2 is a diagram showing a gas detection section 160 of a first comparative example. [Figure 5] FIG. 10 is a diagram showing a gas detection section 260 of a second comparative example. [Figure 6] FIG. 10 is a diagram showing a gas detection section 360 of a third comparative example. [Figure 7] 3 is a view of the gas detection unit 60 shown in FIG. 2 as seen in the optical path direction of the light ray 54. FIG. [Figure 8] 1. FIG. 4 is another enlarged view of the gas detection unit 60 in FIG. [Figure 9] 9 is a view of the gas detection unit 60 shown in FIG. 8 as viewed from the Z-axis direction. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0017] 1 is a diagram showing an example of a gas detector 100 according to an embodiment of the present invention. The gas detector 100 includes a first gas chamber 16, a second gas chamber 46, and a gas sensor 20. The gas detector 100 may include a light source unit 50, an optical chopper 40, and a sample cell 30. In this example, the light source unit 50 includes a light source 52. The light source 52 generates a light beam 54. The light beam 54 may be infrared.

[0018] In this specification, technical matters may be explained using orthogonal coordinate axes of X-axis, Y-axis, and Z-axis. In this specification, the traveling direction of light ray 54 is defined as the X-axis direction. In this specification, a predetermined direction perpendicular to the X-axis direction is defined as the X-axis, and a direction perpendicular to the XY plane is defined as the Z-axis direction. The Z-axis direction may be the direction of gravity, and the XY plane may be a horizontal plane.

[0019] The optical chopper 40 converts the light beam 54 into chopped light. The optical chopper 40 is connected to a power unit 42. In this example, the power unit 42 rotates the optical chopper 40 around the traveling direction of the light beam 54 as the rotation axis, thereby converting the light beam 54 into chopped light.

[0020] The sample cell 30 is a cell through which the target gas 90 of the gas detector 100 passes. The gas detector 100 detects the target gas 90. The target gas 90 may be, for example, CO (carbon monoxide) gas, CO2 (carbon dioxide) gas, or CH4 (methane) gas. The sample cell 30 has an internal space 32. The internal space 32 is a space in which the target gas 90 exists. The sample cell 30 has a gas inlet / outlet 34. In this example, the sample cell 30 has two gas inlets / outlets 34 (gas inlet / outlet 34-1 and gas inlet / outlet 34-2). The target gas 90 enters the internal space 32 from one of the gas inlet / outlet 34-1 and gas inlet / outlet 34-2 and exits the sample cell 30 from the other.

[0021] The sample cell 30 has a light transmission window 36 and a light transmission window 37. The light transmission window 36 is provided on the entrance side of the sample cell 30 for the light beam 54. The light transmission window 37 is provided on the exit side of the sample cell 30 for the light beam 54. The light beam 54, which has been chopped by the optical chopper 40, passes through the light transmission window 36 and then passes through the target gas 90 in the internal space 32. The light beam 54 that has passed through the internal space 32 passes through the light transmission window 37.

[0022] The gas detector 100 of this example includes a gas detection unit 60. The gas detection unit 60 has a first body 62 and a second body 64. In this example, the first gas chamber 16 is provided in the first body 62, and the second gas chamber 46 is provided in the first body 62 and the second body 64. The first body 62 and the second body 64 are formed of a material that is corrosion-resistant to the detection target gas 90. The first body 62 and the second body 64 are formed of, for example, Al (aluminum).

[0023] In this example, the light ray 54 transmitted through the light transmitting window 37 enters the first gas chamber 16. The light ray 54 passing through the first gas chamber 16 enters the second gas chamber 46.

[0024] 2 is an enlarged view of the gas detection unit 60 in FIG. 1. The first gas chamber 16 has a main gas chamber 71 and an auxiliary gas chamber 72. The auxiliary gas chamber 72 is in communication with the main gas chamber 71. In this example, the main gas chamber 71 and the auxiliary gas chamber 72 are connected by a gas flow path 19. Light that has passed through the target gas 90 (see FIG. 1) enters the main gas chamber 71. Light that has passed through the target gas 90 does not enter the auxiliary gas chamber 72.

[0025] The first gas chamber 16 and the second gas chamber 46 are filled with a stored gas 15 of the same type as the detection target gas 90 (see FIG. 1). The stored gas 15 being the same type as the detection target gas 90 means that the stored gas 15 is a gas containing the same substances as the detection target gas 90. When the detection target gas 90 is CO (carbon monoxide) gas, the stored gas 15 is also CO (carbon monoxide) gas. The stored gas 15 being the same type as the detection target gas 90 may also mean that at least a portion of the light absorption wavelength band of the detection target gas 90 overlaps with at least a portion of the light absorption wavelength band of the stored gas 15. The absorption wavelength band may be an infrared band.

[0026] The contained gas 15 may be a gas containing a predetermined concentration of the same kind of gas as the target gas 90 (see FIG. 1). The predetermined concentration refers to a concentration at which the target gas 90 present in the first gas chamber 16 and the second gas chamber 46 can be detected.

[0027] Light that has passed through the main gas chamber 71 enters the second gas chamber 46. The second gas chamber 46 is filled with the contained gas 15. The second gas chamber 46 may have a front chamber 75 and a rear chamber 76. Light that has passed through the main gas chamber 71 enters the front chamber 75. Light that has passed through the front chamber 75 enters the rear chamber 76.

[0028] In this example, the gas detection unit 60 has a first transmission window 11 and a second transmission window 12. The light ray 54 passes through the first transmission window 11 and the second transmission window 12. The gas detection unit 60 may have a plurality of first transmission windows 11 and a plurality of second transmission windows 12. In this example, the gas detection unit 60 has two first transmission windows 11 (first transmission window 11-1 and first transmission window 11-2) and four second transmission windows 12 (second transmission windows 12-1 to 12-4). In this example, the first transmission window 11-2 and the second transmission window 12-1 are common to each other.

[0029] The main gas chamber 71 has a first transmission window 11. The sub-gas chamber 72 does not have a transmission window through which the light ray 54 passes. The second gas chamber 46 has a second transmission window 12. In this example, the main gas chamber 71 is a space surrounded by the first main body 62, the first transmission window 11-1, and the first transmission window 11-2. In this example, the front chamber 75 is a space surrounded by the first main body 62, the second transmission window 12-1, and the second transmission window 12-2. In this example, the rear chamber 76 is a space surrounded by the second main body 64, the second transmission window 12-3, and the second transmission window 12-4.

[0030] The first body 62 may have a lid portion 63. In this example, the sub-gas chamber 72 is sealed by the lid portion 63.

[0031] The gas sensor 20 outputs a signal corresponding to the pressure of the contained gas 15. The contained gas 15 sealed in the first gas chamber 16 is referred to as contained gas 15-1. The contained gas 15 sealed in the second gas chamber 46 is referred to as contained gas 15-2. In this example, the gas sensor 20 outputs a signal corresponding to the difference in pressure between the contained gas 15-1 and the contained gas 15-2.

[0032] A portion of the light in the specific wavelength band of light beam 54 is absorbed by the gas contained in stored gas 15-1, which is the same type as target gas 90 (see FIG. 1). After this portion is absorbed, another portion of the light in the specific wavelength band is absorbed by the gas contained in stored gas 15-2, which is the same type as target gas 90. The volumes of stored gas 15-1 and stored gas 15-2 increase in accordance with the amount of light absorbed. This can cause a difference in pressure between stored gas 15-1 and stored gas 15-2.

[0033] In this example, the main gas chamber 71 and the second gas chamber 46 are connected by a gas flow path 17. In this example, a gas sensor 20 is provided in the gas flow path 17. When a difference occurs between the pressure of the stored gas 15-1 and the pressure of the stored gas 15-2, a flow of the stored gas 15 corresponding to the pressure difference may occur in the gas flow path 17. The gas sensor 20 may detect the flow of the stored gas 15 and output a signal corresponding to the pressure difference of the stored gas 15. In this example, the gas detection unit 60 is a pneumatic mass flow sensor.

[0034] In this example, the front chamber 75 and the rear chamber 76 of the second gas chamber 46 are in communication with each other. In this example, the front chamber 75 and the rear chamber 76 are connected by a gas flow path 18. The gas flow path 18 may be provided in the first body 62 and the second body 64.

[0035] The optical path length of the main gas chamber 71 in the optical path direction of the light beam 54 (in this example, the X-axis direction) is defined as optical path length L1, and the optical path length of the second gas chamber 46 is defined as optical path length L2. The optical path length of the front chamber 75 in the optical path direction of the light beam 54 is defined as optical path length L2-1, and the optical path length of the rear chamber 76 is defined as optical path length L2-2. Optical path length L2 is the sum of optical path length L2-1 and optical path length L2-2. Optical path length L2-1 and optical path length L2-2 may be equal to or different from each other.

[0036] The optical path length L2 may be longer than the optical path length L1. The optical path length L2 may be greater than 1.0 times and less than or equal to 3.0 times the optical path length L1. The gas sensor 20 can more easily detect changes in the concentration of the target gas 90 (see FIG. 1) when the optical path length L2 is greater than the optical path length L1 than when the optical path length L2 is equal to or smaller than the optical path length L1. For this reason, it is preferable that the optical path length L2 is greater than the optical path length L1.

[0037] The volume of the first gas chamber 16 is defined as volume V1. The volume of the main gas chamber 71 is defined as volume V1-1. The volume of the auxiliary gas chamber 72 is defined as volume V1-2. Volume V1 is the sum of volumes V1-1 and V1-2. The volume of the second gas chamber 46 is defined as volume V2. The volume of the front chamber 75 is defined as volume V2-1. The volume of the rear chamber 76 is defined as volume V2-2. Volume V2 is the sum of volumes V2-1 and V2-2.

[0038] The volume V1 may be 0.8 to 1.5 times the volume V2. The volume V1 may be equal to the volume V2. The gas detector 100 may be used for combustion gas analysis of a combustion furnace, air pollution monitoring, automobile exhaust gas measurement, etc. For this reason, the gas detector 100 may be installed in a factory or the like. In a factory or the like, the gas detector 100 may vibrate due to vibrations caused by the operation of equipment in the factory or the like. When the gas detector 100 vibrates, the pressures of the contained gas 15-1 and the contained gas 15-2 may each change.

[0039] If volume V1 is less than 0.8 times or more than 1.5 times volume V2, the imbalance between volume V1 and volume V2 will cause the pressure change of contained gas 15-1 and the pressure change of contained gas 15-2 to differ. Therefore, if volume V1 is less than 0.8 times or more than 1.5 times volume V2, gas detector 100 will likely have difficulty detecting the concentration of target gas 90 (see FIG. 1). For this reason, volume V1 is preferably 0.8 to 1.5 times volume V2.

[0040] The gas detector 100 may further include a light adjusting unit 66. In this example, the gas detection unit 60 has the light adjusting unit 66. The light adjusting unit 66 adjusts the amount of light emitted from the light beam 54. The light adjusting unit 66 may be disposed between the front chamber 75 and the rear chamber 76 in the optical path of the light beam 54.

[0041] The detection target gas 90 (see FIG. 1) may contain other gases whose absorption wavelength bands are close to the light absorption wavelength band of the detection target gas 90. When the detection target gas 90 contains such other gases, the detection sensitivity of the detection target gas 90 by the gas sensor 20 may decrease. This decrease in detection sensitivity can be improved by adjusting the ratio between the optical path length L1 and the optical path length L2 or the ratio between the volume V1 and the volume V2.

[0042] The light adjustment unit 66 may be formed of a member that does not transmit the light ray 54. The light adjustment unit 66 may be a plate-shaped member having a flat surface parallel to the YZ plane. The amount of light ray 54 that transmits through the second gas chamber 46 may be adjusted by the light adjustment unit 66. The amount of light ray 54 that transmits through the second gas chamber 46 may be adjusted by moving the plate-shaped light adjustment unit 66 in the Z-axis direction. The apparent volume V2 of the second gas chamber 46 can be adjusted by the light adjustment unit 66 adjusting the amount of light ray 54 that transmits through the second gas chamber 46. This makes it easier for the gas detection unit 60 to detect the target gas 90 (see FIG. 1 ) with the desired detection sensitivity, even if the target gas 90 contains the other gases described above.

[0043] Fig. 3 is a diagram illustrating the detection principle of the target gas 90 (see Fig. 1) by the gas detector 100 (see Fig. 1). Fig. 3 conceptually illustrates a measurement component ΔPS1, an interference component ΔPK1, and a vibration influence component ΔPn1-1 of the pressure of the contained gas 15-1 in the first gas chamber 16, and a measurement component ΔPS2, an interference component ΔPK2, and a vibration influence component ΔPn2-1 of the pressure of the contained gas 15-1 in the second gas chamber 46. In Fig. 3, the measurement component ΔPS of the pressure difference between the pressure of the first gas chamber 16 and the pressure of the second gas chamber 46 is the difference between ΔPS1 and ΔPS2, the interference component ΔPK of the pressure difference is the difference between ΔPK1 and ΔPK2, and the vibration influence component ΔPn of the pressure difference is the difference between ΔPn1-1 and ΔPn1-2.

[0044] The pressure difference between the contained gas 15-1 and the contained gas 15-2 may include a measurement component ΔPS, an interference component ΔPK, and a vibration influence component ΔPn, as shown in FIG. 3. The measurement component ΔPS is a component of the pressure difference caused by the contained gas 15 absorbing light. The interference component ΔPK is a component of the pressure difference between the contained gas 15-1 and the contained gas 15-2 caused by the difference in the optical paths between the first gas chamber 16 and the second gas chamber 46. The vibration influence component ΔPn is a component of the pressure difference between the contained gas 15-1 and the contained gas 15-2 caused by vibration of the gas detector 100.

[0045] 1, the optical path length L2 is longer than the optical path length L1, and the volume V1 is 0.8 to 1.5 times the volume V2. Therefore, the gas detector 100 can easily maintain the magnitude of the measurement component ΔPS while suppressing an increase in both the vibration-affected component ΔPn and the interference component ΔPK. This makes it easier to maintain the detection sensitivity of the gas sensor 20 for the detection target gas 90 (see FIG. 1).

[0046] The volume V1-2 (see FIG. 2) of the auxiliary gas chamber 72 may be 1.0 to 1.2 times the volume V1-1 (see FIG. 2) of the main gas chamber 71. By making the volume V1-2 1.0 to 1.2 times the volume V1-1, the pressure of the contained gas 15-1 in the auxiliary gas chamber 72 on the contained gas 15-1 in the main gas chamber 71 and the pressure of the contained gas 15-1 in the main gas chamber 71 on the contained gas 15-1 in the auxiliary gas chamber 72 are easily balanced. Therefore, when a difference occurs between the pressure of the contained gas 15-1 in the main gas chamber 71 and the pressure of the contained gas 15-1 in the auxiliary gas chamber 72, the contained gas 15-1 can easily move smoothly between the main gas chamber 71 and the auxiliary gas chamber 72.

[0047] The direction from the main gas chamber 71 (see FIG. 2) to the auxiliary gas chamber 72 (see FIG. 2) may be different from the direction from the first gas chamber 16 to the second gas chamber 46. The direction from the main gas chamber 71 to the auxiliary gas chamber 72 may be the direction of movement of the contained gas 15-1 between the main gas chamber 71 and the auxiliary gas chamber 72. The direction from the first gas chamber 16 to the second gas chamber 46 may be a direction that intersects the first gas chamber 16 and the second gas chamber 46, or a direction that is perpendicular to the first gas chamber 16 and the second gas chamber 46, or may be the traveling direction of the light beam 54. In this example, the direction from the main gas chamber 71 to the auxiliary gas chamber 72 is the Z-axis direction, and the direction from the first gas chamber 16 to the second gas chamber 46 is the X-axis direction. Since the direction from the main gas chamber 71 to the auxiliary gas chamber 72 is different from the direction from the first gas chamber 16 to the second gas chamber 46, the light beam 54 is less likely to be incident on the auxiliary gas chamber 72.

[0048] 4 is a diagram showing a gas detection unit 160 of a first comparative example. The gas detection unit 160 has a first gas chamber 116 and a second gas chamber 146. The gas detection unit 160 does not have an auxiliary gas chamber 72. The second gas chamber 146 does not have a rear chamber 76. The gas detection unit 160 differs from the gas detection unit 60 shown in FIG. 2 in these respects.

[0049] The volume of the first gas chamber 116 is defined as volume V1'. Volume V1' is equal to the volume V1-1 of the main gas chamber 71 (see FIG. 2). The volume of the second gas chamber 146 is defined as volume V2'. Volume V1' is smaller than volume V2'.

[0050] The optical path length of the second gas chamber 146 in the optical path direction of the light beam 54 (in this example, the X-axis direction) is defined as optical path length L2-1'. Optical path length L2-1' may be longer than the optical path length L2-1 shown in FIG.

[0051] In the gas detection unit 160, the optical path length L2-1' is longer than the optical path length L1', but the volume V1' is smaller than the volume V2'. Therefore, the gas detection unit 160 can suppress an increase in the interference component ΔPK (see FIG. 3), but it is difficult to suppress an increase in the vibration-affected component ΔPn (see FIG. 3). Therefore, in the gas detection unit 160, it becomes difficult to maintain the detection sensitivity of the gas sensor 20 for the detection target gas 90 (see FIG. 1).

[0052] 5 is a diagram showing a gas detection unit 260 of a second comparative example. The gas detection unit 260 has a first gas chamber 216 and a second gas chamber 246. The gas detection unit 260 does not have an auxiliary gas chamber 72. In this respect, the gas detection unit 260 differs from the gas detection unit 60 shown in FIG. 2. The second gas chamber 246 has a front chamber 275 and a rear chamber 276.

[0053] The volume of the first gas chamber 216 is defined as volume V1". Volume V1" is equal to volume V1-1 of the main gas chamber 71 (see Figure 2). The volume of the second gas chamber 246 is defined as volume V2". The volume of the front chamber 275 is defined as volume V2-1". The volume of the rear chamber 276 is defined as volume V2-2". Volume V2-1" is equal to volume V2-1 of the front chamber 75 (see Figure 2). Volume V2-2" is equal to volume V2-2 of the rear chamber 76 (see Figure 2).

[0054] The optical path length of the first gas chamber 216 in the optical path direction of the light ray 54 (in this example, the X-axis direction) is defined as optical path length L1'', the optical path length of the front chamber 275 as optical path length L2-1'', and the optical path length of the rear chamber 276 as optical path length L2-2''. The optical path lengths L1'', L2-1'', and L2-2'' are assumed to be equal to the optical path lengths L1, L2-1, and L2-2 shown in FIG. 2, respectively.

[0055] The gas detection unit 260 includes a light adjustment unit 66. Therefore, in the gas detection unit 260, the light adjustment unit 66 adjusts the amount of light of the light beam 54 passing through the second gas chamber 246, thereby enabling the gas sensor 20 to maintain its detection sensitivity for the target gas 90. However, since the gas detection unit 260 does not include the sub-gas chamber 72 (see FIG. 2), the volume V1'' is smaller than the volume V2''. Therefore, it is difficult for the gas detection unit 260 to suppress an increase in the vibration-affected component ΔPn (see FIG. 3). Therefore, in the gas detection unit 260, it becomes difficult to maintain the detection sensitivity of the gas sensor 20 for the target gas 90 (see FIG. 1).

[0056] 6 is a diagram showing a gas detection unit 360 of a third comparative example. The gas detection unit 360 has a first gas chamber 316 and a second gas chamber 346. The first gas chamber 316 has a front chamber 372 and a rear chamber 371. The front chamber 372 and the rear chamber 371 are in communication with each other. The front chamber 372 and the rear chamber 371 are connected by a gas flow path 29. The second gas chamber 346 has a front chamber 375 and a rear chamber 376.

[0057] The volume of the first gas chamber 316 is defined as volume V1'". The volume of the front chamber 372 is defined as volume V1-1'". The volume of the rear chamber 371 is defined as volume V1-2'". Volume V1'" is equal to the sum of volumes V1-1'" and V1-2'". The volume of the second gas chamber 346 is defined as volume V2'". The volume of the front chamber 375 is defined as volume V2-1". The volume of the rear chamber 376 is defined as volume V2-2". Volume V2'" is equal to the sum of volumes V2-1'" and V2-2'". In the gas detection unit 360, volumes V1'" and V2'" are defined as being equal.

[0058] The volume V1-1''' is equal to the volume V1-1 of the auxiliary gas chamber 72 (see FIG. 2). The volume V1-2''' is equal to the volume V1-2 of the main gas chamber 71 (see FIG. 2). The volume V2-1''' is equal to the volume V2-1 of the front chamber 75 (see FIG. 2). The volume V2-2''' is equal to the volume V2-2 of the rear chamber 76 (see FIG. 2).

[0059] The optical path length of the front chamber 372 in the optical path direction of the light ray 54 (in this example, the X-axis direction) is defined as optical path length L1-1''', and the optical path length of the rear chamber 371 is defined as optical path length L1-2'''. The sum of the optical path lengths L1-1''' and L1-2''' is equal to the optical path length L1 shown in Figure 2. The optical path length of the front chamber 375 in the optical path direction of the light ray 54 (in this example, the X-axis direction) is defined as optical path length L2-1''', and the optical path length of the rear chamber 376 is defined as optical path length L2-2'''. The optical path length L2-1''' is equal to the optical path length L2-1 shown in Figure 2. The optical path length L2-2''' is equal to the optical path length L2-2 shown in Figure 2. The sum of the optical path length L1-1''' and the optical path length L1-2''' is equal to the sum of the optical path length L2-1''' and the optical path length L2-2'''.

[0060] In the gas detection unit 360, the volume V1''' and the volume V2''' are equal, but the sum of the optical path lengths L1-1''' and L1-2''' is equal to the sum of the optical path lengths L2-1''' and L2-2'''. Therefore, although the gas detection unit 360 can suppress an increase in the vibration-affected component ΔPn (see FIG. 3), it is difficult to suppress an increase in the interference component ΔPK (see FIG. 3). Therefore, in the gas detection unit 160, it becomes difficult to maintain the detection sensitivity of the gas sensor 20 for the detection target gas 90 (see FIG. 1).

[0061] 2 is viewed in the optical path direction of the light beam 54 (in this example, the X-axis direction). In FIG. 7, the outer edges of the main gas chamber 71 and the second gas chamber 46 are indicated by thick lines, and the outer edge of the auxiliary gas chamber 72 is indicated by a dashed line. In this example, when viewed in the optical path direction of the light beam 54, the outer edges of the main gas chamber 71 and the second gas chamber 46 overlap.

[0062] The auxiliary gas chamber 72 may be disposed at a position that does not overlap with the second gas chamber 46 when viewed in the optical path direction of the light beam 54. This makes it difficult for the light beam 54 to enter the auxiliary gas chamber 72.

[0063] 8 is another enlarged view of the gas detection unit 60 in FIG. 1. The length of the main gas chamber 71 in the optical path direction of the light beam 54 is defined as length Lm1, and the length of the auxiliary gas chamber 72 is defined as length Ls1. The lengths Lm1 and Ls may be set so that the volume V1-2 of the auxiliary gas chamber 72 (see FIG. 2) is 1.0 to 1.2 times the volume V1-1 of the main gas chamber 71 (see FIG. 2). In this example, the length Ls1 is longer than the length Lm1. This makes it easier for the user of the gas detector 100 to design the auxiliary gas chamber 72 in the first body 62.

[0064] Figure 9 is a view of the gas detection unit 60 shown in Figure 8 as viewed from the Z-axis direction. The Z-axis direction may be a direction intersecting the optical path direction of the light beam 54, or may be a direction perpendicular to the optical path direction. In Figure 9, the gas sensor 20, the contained gas 15, the gas flow path 17, the gas flow path 18, and the light adjustment unit 66 shown in Figure 8 are omitted. In Figure 8, the position of the auxiliary gas chamber 72 is indicated by a thin, fine dashed line, the position of the main gas chamber 71 is indicated by a thick, coarse dashed line, and the position of the second gas chamber 46 is indicated by a thick, dashed line.

[0065] When viewed from a direction intersecting the optical path direction of the light beam 54, at least a portion of the auxiliary gas chamber 72 may be disposed at a position overlapping at least a portion of the second gas chamber 46. In this example, when viewed from the Z-axis direction, a portion of the auxiliary gas chamber 72 is disposed at a position overlapping with a portion of the front chamber 75 of the second gas chamber 46. This makes it easier for the user of the gas detector 100 to design the auxiliary gas chamber 72 in the first body 62.

[0066] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[0067] It should be noted that the execution order of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before," "prior to," etc., and that the processes can be performed in any order unless the output of a previous process is used in a subsequent process. Even if the operational flow in the claims, specifications, and drawings is described using "first," "next," etc. for convenience, this does not mean that the processes must be performed in this order. [Explanation of symbols]

[0068] 11...First transmission window, 12...Second transmission window, 15...Accommodated gas, 16...First gas chamber, 17...Gas flow path, 18...Gas flow path, 19...Gas flow path, 20...Gas sensor, 29...Gas flow path, 30...Sample cell, 32...Inner space, 34...Gas inlet / outlet, 36...Light beam transmission window, 37...Light beam transmission window, 40...Light chopper, 42...Power unit, 46...Second gas chamber, 50...Light source unit, 52...Light source, 54...Light beam, 60...Gas detection unit, 62...First main body, 63...Cover unit, 64... Second main body, 66, light adjustment unit, 71, main gas chamber, 72, auxiliary gas chamber, 75, front chamber, 76, rear chamber, 90, detection target gas, 100, gas detector, 116, first gas chamber, 146, second gas chamber, 160, gas detection unit, 216, first gas chamber, 246, second gas chamber, 260, gas detection unit, 275, front chamber, 276, rear chamber, 316, first gas chamber, 346, second gas chamber, 360, gas detection unit, 371, rear chamber, 372, front chamber, 375, front chamber, 376, rear chamber

Claims

1. A gas detector comprising a first body and a second body, a first gas chamber having a main gas chamber into which light that has passed through a gas to be detected is incident and an auxiliary gas chamber that is in communication with the main gas chamber and into which the light is not incident, the first gas chamber containing a gas containing the same type of gas as the gas to be detected; a second gas chamber into which the light having passed through the main gas chamber is incident and into which the storage gas is sealed; a gas sensor that outputs a signal corresponding to the pressure of the stored gas; Equipped with the main gas chamber has a first transmission window through which the light passes; the auxiliary gas chamber does not have a transmission window through which the light passes, the second gas chamber has a second transmission window through which the light passes; a light adjusting unit that adjusts the amount of light; the second gas chamber has a front chamber into which the light that has passed through the main gas chamber is incident, and a rear chamber into which the light that has passed through the front chamber is incident, the light adjusting unit is disposed between the front chamber and the rear chamber in the optical path of the light, the main gas chamber, the auxiliary gas chamber, and the front chamber are provided in the first body, and the rear chamber is provided in the second body, The gas detector, wherein the auxiliary gas chamber is disposed at a position not overlapping with the second gas chamber when viewed in the optical path direction of the light.

2. 2. The gas detector according to claim 1, wherein a direction from the main gas chamber to the auxiliary gas chamber is different from a direction from the first gas chamber to the second gas chamber.

3. 3. The gas detector according to claim 1, wherein the auxiliary gas chamber is longer than the main gas chamber in the optical path direction of the light.

4. 4. The gas detector according to claim 1, wherein the optical path length of the second gas chamber in the optical path direction of the light is greater than 1.0 times and not more than 3.0 times the optical path length of the main gas chamber.

5. 5. The gas detector according to claim 1, wherein the volume of the first gas chamber is 0.8 to 1.5 times the volume of the second gas chamber.

6. 6. The gas detector according to claim 1, wherein the volume of the auxiliary gas chamber is 1.0 to 1.2 times the volume of the main gas chamber.

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