Gas analysis device and gas analysis method

Abstract

The present invention prevents mixing of atmospheric air into an optical path and reduces the running cost of a purge gas. The present invention comprises: a measurement cell 2 into which a sample gas is introduced; a light irradiation unit 3 that irradiates the measurement cell 2 with laser light; a light detection unit 4 that detects the laser light that has passed through the measurement cell 2; an optical chamber 6 that accommodates the light irradiation unit 3 and / or the light detection unit 4; and a zero gas introduction path 7 that introduces a zero gas into the measurement cell 2 and the optical chamber 6. The zero gas is introduced into the measurement cell 2 by means of the zero gas introduction path 7 to perform zero calibration, and the zero gas is introduced into the optical chamber 6 by means of the zero gas introduction path 7 to seal the zero gas in the optical chamber 6.

Description

Gas analyzer and gas analysis method

[0001] The present invention relates to a gas analyzer and a gas analyzer.

[0002] In conventional laser analyzers, an optical path exists outside the measurement cell into which the sample gas is introduced, allowing the laser beam to pass through the gas in that optical path. If air enters this optical path, for example, H2 in the air will be affected. ２ O or CO ２ These components can affect the measurement, leading to measurement errors.

[0003] Therefore, as shown in Patent Document 1, for example, N ２ One proposed design involves continuously supplying purge gases such as [mention specific gases here] to the optical path to prevent interference from the atmosphere.

[0004] However, this necessitates a purge gas cylinder to purge the optical path, which not only increases the system size but also raises running costs due to the constant consumption of purge gas.

[0005] Japanese Patent Application Publication No. 5-288606

[0006] Therefore, the present invention has been made in view of the above problems, and its main objectives are to prevent air from entering the optical path, to miniaturize the system, and to reduce the running costs of the purge gas.

[0007] In other words, the gas analyzer according to the present invention is a gas analyzer that analyzes the concentration of a target component contained in a sample gas, comprising: a measuring cell into which the sample gas is introduced; a light irradiation unit that irradiates the measuring cell with laser light; a light detection unit that detects the laser light that has passed through the measuring cell; an optical chamber that houses the light irradiation unit and / or the light detection unit; and a zero gas introduction path for introducing zero gas, wherein the zero gas is introduced into the measuring cell via the zero gas introduction path for zero calibration, the zero gas is introduced into the optical chamber via the zero gas introduction path to seal the optical chamber with zero gas, and the zero calibration period from the time the zero gas is introduced into the measuring cell until the zero calibration is completed and the zero purging period from the time the zero gas is introduced into the optical chamber until the sealing of the zero gas into the optical chamber is completed overlap at least partially.

[0008] With this type of gas analyzer, since zero gas is introduced and sealed into the optical chamber, a purge gas cylinder for constantly purging the optical chamber is unnecessary. This allows for a smaller system and reduces running costs that would otherwise be incurred by constantly introducing and purging purge gas into the optical chamber. Furthermore, because zero gas is sealed into the optical chamber, measurement errors caused by air contamination in the optical chamber can be reduced. In addition, since the zero calibration period and the zero purging period overlap at least partially, the preparation time before sample gas measurement (time for zero calibration and time for sealing zero gas into the optical chamber) can be shortened.

[0009] It is desirable to introduce the zero gas into the optical chamber and seal the optical chamber with the zero gas before the zero calibration is completed. With this configuration, errors caused by the influx of air into the optical chamber during zero calibration can be reduced, and zero calibration can be performed with high accuracy.

[0010] In terms of specific implementations of the zero gas introduction path, it is desirable that the zero gas introduction path comprises a flow path section for the measuring cell connected to the measuring cell, a first flow rate adjustment section provided in the flow path section for the measuring cell for adjusting the flow rate of the zero gas, a flow path section for the optical chamber connected to the optical chamber, and a second flow rate adjustment section provided in the flow path section for the optical chamber for adjusting the flow rate of the zero gas.

[0011] It is desirable that the flow rate of the zero gas introduced into the measurement cell and the flow rate of the zero gas introduced into the optical chamber are set to be different from each other. With this configuration, a flow rate suitable for zero calibration can be introduced into the measurement cell, and a flow rate suitable for gas replacement in the optical chamber can be introduced into the optical chamber.

[0012] The zero gas introduction path introduces the zero gas into the optical chamber before the zero calibration is completed, and it is desirable that the flow rate of the zero gas introduced into the optical chamber is set to a flow rate that replaces the gas in the optical chamber before the zero calibration is completed.

[0013] As a specific embodiment for introducing zero gas into an optical chamber and sealing the zero gas, it is desirable that the optical chamber has an introduction port to which the zero gas introduction path is connected and to which the zero gas is introduced, and an outlet port to which the gas inside the optical chamber is discharged to the outside, and that the zero gas is introduced through the zero gas introduction path with a first on-off valve provided on the introduction port side and a second on-off valve provided on the outlet port side open, and that the zero gas is sealed into the optical chamber by closing the first on-off valve and the second on-off valve.

[0014] In order to miniaturize the gas analyzer, it is desirable that the zero gas introduction path is connected to a single zero gas cylinder, and that the zero gas is introduced from this single zero gas cylinder into the measurement cell and the optical chamber.

[0015] To analyze multiple components in a sample gas, it is desirable that the light irradiation unit has multiple laser light sources and multiple optical elements for introducing light from these multiple laser light sources into the measurement cell. In this configuration, since the multiple laser light sources and multiple optical elements are housed in an optical chamber, the optical path through which the multiple laser beams pass can be purged with zero gas. Furthermore, in a configuration with multiple laser light sources (for example, a multi-component analyzer), the optical path becomes longer, and there is a risk that the influence of air contamination in the optical path will become greater. However, in the present invention, since the optical path is purged with zero gas, this influence can be reduced.

[0016] The measurement cell is preferably equipped with a short optical path and a long optical path that is longer than the short optical path. In this configuration, when gas analysis is performed using the short optical path of the measurement cell, the absorption effect of the laser light in the optical path within the optical chamber becomes relatively large. However, since the optical chamber is purged with zero gas, measurement errors can be reduced even when gas analysis is performed using the short optical path.

[0017] The advantage of miniaturization becomes even more pronounced, especially if the gas analyzer is portable.

[0018] Conventionally, when a gas analyzer is mounted on a vehicle, a purge gas cylinder is required to purge the optical chamber of the gas analyzer. Since purge gas is constantly consumed during driving tests that last several hours, a high-pressure gas cylinder must be mounted. During driving tests, there are space constraints inside the vehicle, and the weight of the test equipment is regulated by law, so it is necessary to avoid unnecessarily increasing the weight. In addition, high-pressure gas is required for each test, which leads to increased running costs. The gas analyzer of the present invention, if mounted on a vehicle and used to analyze exhaust gas emitted from the vehicle, eliminates the need to mount a purge gas cylinder (high-pressure gas cylinder) on the vehicle, making it easier to conduct driving tests that comply with regulations, and also suppresses the increase in running costs.

[0019] It is desirable that the components to be measured are the same as those contained in the atmosphere. With this configuration, the effect of purging the optical chamber with zero gas can be made even more pronounced.

[0020] Furthermore, the gas analyzer according to the present invention is a gas analyzer for analyzing the concentration of a target component contained in a sample gas, comprising: a measuring cell into which the sample gas is introduced; a light irradiation unit for irradiating the measuring cell with laser light; a light detection unit for detecting the laser light that has passed through the measuring cell; an optical chamber housing the light irradiation unit and / or the light detection unit; and a zero gas introduction path for introducing zero gas for zero calibration, wherein the zero gas is introduced into the measuring cell via the zero gas introduction path for zero calibration, and the zero gas is introduced into the optical chamber via the zero gas introduction path to seal the optical chamber with the zero gas.

[0021] Furthermore, the gas analysis method according to the present invention is a gas analysis method using a gas analyzer comprising a measuring cell into which a sample gas is introduced, a light irradiation unit that irradiates the measuring cell with laser light, a light detection unit that detects the laser light that has passed through the measuring cell, an optical chamber that houses the light irradiation unit and / or the light detection unit, and a zero gas introduction path for introducing zero gas for zero calibration, wherein the zero gas is introduced into the measuring cell via the zero gas introduction path for zero calibration, the zero gas is introduced into the optical chamber via the zero gas introduction path to seal the optical chamber with the zero gas, after the zero calibration and sealing of the optical chamber with the zero gas are completed, the sample gas is introduced into the measuring cell for sample gas measurement, and the zero calibration period from the time the zero gas is introduced into the measuring cell until the zero calibration is completed and the zero purging period from the time the zero gas is introduced into the optical chamber until the sealing of the optical chamber with the zero gas is completed overlap at least partially.

[0022] According to the present invention configured in this way, it is possible to prevent air from entering the optical path and to reduce the running costs of the purge gas.

[0023] This is a schematic diagram showing the usage state of a gas analyzer according to one embodiment of the present invention. This is a schematic diagram showing the configuration of the gas analyzer according to the same embodiment. This is a diagram showing the start and end timings of zero calibration and zero purging in the same embodiment. This is a schematic diagram showing the configuration of a modified gas analyzer. This is a schematic diagram showing the configuration of a modified gas analyzer. This is a schematic diagram showing the configuration of a modified gas analyzer. This is a schematic diagram showing the configuration of a modified measurement cell.

[0024] A gas analyzer according to one embodiment of the present invention will be described below with reference to the drawings. Note that all the following drawings are schematic representations, with some parts omitted or exaggerated for clarity. The same components are denoted by the same reference numerals, and their descriptions are omitted as appropriate.

[0025] <Configuration of Gas Analyzer 100> As shown in Figure 1, the gas analyzer 100 of this embodiment is mounted on a vehicle V and analyzes the target components contained in a sample gas obtained by sampling exhaust gas discharged from the vehicle V. Exhaust gas sampled from a sampling unit SU attached to, for example, the exhaust pipe VH of the vehicle V is introduced into this vehicle-mounted gas analyzer 100. Note that the gas analyzer 100 is not limited to being mounted on a vehicle V, but may also be mounted on a mobile body such as a ship or aircraft and analyze exhaust gas discharged from such mobile body. Furthermore, the gas analyzer 100 may be a portable type that can be carried around, and when such a portable gas analyzer 100 is moved, it will be as effective as when it is mounted on a mobile body. Also, the gas analyzer 100 may be a stationary type installed in a test room. Furthermore, the gas analyzer 100 may, for example, analyze exhaust gas or process gas from large-scale equipment such as chemical plants or factories, or it may analyze exhaust gas or process gas from various process equipment such as semiconductor processes or carburizing processes.

[0026] Further, the gas analyzer 100 measures the concentration of the component to be measured in the sample gas by laser absorption spectroscopy. Also, as the component to be measured contained in the sample gas, the gas analyzer 100 measures, for example, the concentration of CO, CO ２ , N ２ O, NO, NO ２ , NO Ｘ , H ２ O, NH ３ , SO ２ , H ２ , HCHO, CH ４ , C ２ H ２ and other hydrocarbons, or THC and the like.

[0027] Specifically, as shown in FIG. 2, the gas analyzer 100 includes a measurement cell 2 into which the sample gas is introduced, a light irradiation unit 3 that irradiates the measurement cell 2 with laser light, a light detection unit 4 that detects the laser light that has passed through the measurement cell 2, a signal processing unit 5 that acquires and performs arithmetic processing on the output signal from the light detection unit 4, an optical chamber 6 that houses the light irradiation unit 3 and / or the light detection unit 4, and a zero gas introduction path 7 for introducing zero gas for zero calibration. In addition, the gas analyzer 100 has a span gas introduction path (not shown) for introducing span gas for span calibration into the measurement cell 2.

[0028] The measurement cell 2 is a multiple reflection cell and includes a cell body 21 into which the sample gas is introduced, and a pair of reflection mirrors 22 and 23 disposed inside the cell body 21. The cell body 21 is made of a transparent material such as quartz, calcium fluoride, or barium fluoride that has almost no light absorption in the absorption wavelength band of the component to be measured, and has an entrance and an exit for light formed thereon. Further, the cell body 21 is provided with an introduction port P1 for introducing the sample gas and the like, and a discharge port P2 for discharging the sample gas and the like.

[0029] The light irradiation unit 3 irradiates the measurement cell 2 with laser light in the absorption wavelength range of the component to be measured. Specifically, the light irradiation unit 3 has a plurality of laser light sources 31 that emit laser light of different wavelengths, and a plurality of optical elements 32 for introducing the light from these plurality of laser light sources 31 into the measurement cell 2. Note that the light irradiation unit 3 may also have a configuration with a single laser light source 31.

[0030] The multiple laser light sources 31 are semiconductor lasers that emit laser light in the absorption wavelength range for each of the multiple components to be measured. These semiconductor lasers are capable of modulating (changing) their oscillation wavelength by a given current (or voltage).

[0031] Examples of semiconductor lasers include quantum cascade lasers (QCLs) that emit laser light of a specific wavelength in the wavelength range of approximately 4 μm to approximately 20 μm, interband cascade lasers (ICLs) that emit laser light of a specific wavelength in the wavelength range of approximately 3 μm to approximately 5 μm, or near-infrared laser diodes that emit laser light of a specific wavelength in the wavelength range of approximately 1 μm to approximately 3 μm. Other types of lasers may be used as long as the oscillation wavelength is variable, and the oscillation wavelength may be changed by changing the temperature, etc.

[0032] Multiple optical elements 32 are provided corresponding to each laser light source 31 and include multiple reflective mirrors 32a that reflect laser light and multiple bandpass filters 32b that transmit laser light. These multiple optical elements 32 irradiate the laser light emitted from the multiple laser light sources 31 into the measurement cell 2 from the entrance of the measurement cell 2.

[0033] The light detection unit 4 detects the laser light that has passed through the measurement cell 2 and emerged from the measurement cell 2. Specifically, the light detection unit 4 includes a photodetector 41 that detects the laser light emerging from the measurement cell 2, and a reflection mirror 42 that reflects the laser light emerging from the measurement cell 2 toward the photodetector 41. Note that, if necessary, a configuration without the reflection mirror 42 may also be adopted. The photodetector 41 of the present embodiment uses a thermal type such as a relatively inexpensive thermopile, but other types, for example, quantum type photoelectric elements such as HgCdTe, InGaAs, InAsSb, or PbSe with good responsiveness may also be used.

[0034] The signal processing unit 5 acquires the output signal from the photodetector 41 and calculates the concentration of the measurement target component. It includes an analog electric circuit composed of a buffer, an amplifier, etc., a digital electric circuit composed of a CPU, a memory, etc., and an AD converter, a DA converter, etc. that mediate between these analog / digital electric circuits.

[0035] Then, this signal processing unit 5 functions as an arithmetic unit 51 that receives the output signal from the photodetector 41, performs arithmetic processing on its value, and calculates the concentration of the measurement target component by the cooperation of the CPU and its peripheral devices according to a predetermined program stored in a predetermined area of the memory. The arithmetic result by the arithmetic unit 51 can be displayed by a display unit 10 such as a display.

[0036] Also, the signal processing unit 5 has a function as a calibration unit 52 that controls the introduction of zero gas from the zero gas introduction path 7 and / or the introduction of span gas from the span gas introduction path to perform zero calibration and / or span calibration. Note that the signal processing unit 5 may be further configured to function as a light source control unit 53 that controls the output of the laser light source 31.

[0037] The optical chamber 6 constitutes a sealed space that houses the light irradiation unit 3 and / or the light detection unit 4. The optical chamber 6 of the present embodiment houses a plurality of laser light sources 31 and a plurality of optical elements 32 of the light irradiation unit 3, and a photodetector 41 and a reflection mirror 42 of the light detection unit 4. This optical chamber 6 is composed of a housing portion 61 that houses the light irradiation unit 3 and / or the light detection unit 4. Further, the optical chamber 6 has a light passing window 62 formed of a transparent material such as quartz, calcium fluoride, or barium fluoride that has almost no light absorption in the absorption wavelength band of the measurement target component. And the light passing window 62 of the optical chamber 6 is provided in contact with or close to the light incident and exit ports of the measurement cell 2.

[0038] The zero gas introduction path 7 introduces zero gas for zero calibration into the measurement cell 2 and the optical chamber 6. Further, the zero gas introduction path 7 is connected to a single zero gas cylinder ZB, and is configured such that zero gas is introduced from the single zero gas cylinder ZB into the measurement cell 2 and the optical chamber 6.

[0039] Specifically, the zero gas introduction path 7 has a flow path portion 71 for the measurement cell connected to the measurement cell 2, a first flow rate adjustment portion 72 provided in the flow path portion 71 for the measurement cell to adjust the flow rate of the zero gas, a flow path portion 73 for the optical chamber connected to the optical chamber 6, and a second flow rate adjustment portion 74 provided in the flow path portion 73 for the optical chamber to adjust the flow rate of the zero gas. Note that the flow path portion 71 for the measurement cell and the flow path portion 73 for the optical chamber branch from a main flow path portion 70 connected to the zero gas cylinder ZB.

[0040] The flow path portion 71 for the measurement cell is connected to the introduction port P1 of the measurement cell 2, and introduces zero gas into the measurement cell 2 through the introduction port P1 for introducing sample gas or the like. Note that the flow path portion 71 for the measurement cell is connected to the introduction port for zero gas when the measurement cell 2 is provided with an introduction port for zero gas.

[0041] The first flow rate adjustment portion 72 provided in the flow path portion 71 for the measurement cell has a pressure adjustment valve 72a for adjusting the pressure of the zero gas supplied to the measurement cell and a flow rate adjuster 72b such as a capillary or an orifice for adjusting or restricting the flow rate of the zero gas supplied to the measurement cell 2.

[0042] The optical chamber flow path 73 is connected to the introduction port P3 of the optical chamber 6, and introduces zero gas into the optical chamber 6 through the introduction port P3. In addition, the optical chamber 6 is provided with an outlet port P4 for releasing the gas inside the optical chamber 6 to the outside.

[0043] The second flow rate adjustment unit 74 provided in the optical chamber flow path section 73 has a flow rate regulator 74a such as a capillary or orifice that adjusts or limits the flow rate of zero gas supplied to the optical chamber 6. The second flow rate adjustment unit 74 may also be configured to have a pressure regulating valve that adjusts the pressure of the zero gas supplied to the optical chamber 6.

[0044] Furthermore, in the zero gas introduction path 7, the flow path section 71 for the measurement cell is provided with a cell-side on-off valve 75 that switches between supplying and stopping zero gas to the measurement cell 2, and the flow path section 73 for the optical chamber is provided with an optical chamber-side on-off valve 76 that switches between supplying and stopping zero gas to the optical chamber 6. These on-off valves 75 and 76 are controlled by the signal processing unit 5.

[0045] The zero gas introduction path 7, configured as described above, introduces zero gas for zero calibration from the zero gas cylinder ZB into the optical chamber 6, thereby sealing the optical chamber 6 with zero gas. Specifically, with the first on-off valve, the optical chamber-side on-off valve 76 located on the introduction port P3 side, and the second on-off valve 77 located on the outlet port P4 side, open, zero gas is introduced through the zero gas introduction path 7, and the first on-off valve 76 and the second on-off valve 77 are closed to seal the optical chamber 6 with zero gas. The timing of closing the second on-off valve 77 may be set earlier than the timing of closing the first on-off valve 76, thereby creating a positive pressure state in the optical chamber 6 and making it difficult for outside air to enter.

[0046] The timing for introducing zero gas into the optical chamber 6 and sealing it could be, for example, (a) while zero gas is being introduced into the measurement cell 2 and zero calibration is being performed, (b) before introducing the sample gas into the measurement cell 2 and performing sample gas measurement after zero calibration, or (c) before introducing zero gas into the measurement cell 2 and performing zero calibration after sample gas measurement.

[0047] In this embodiment, the zero calibration period, from the time zero gas is introduced into the measurement cell 2 until zero calibration is completed, and the zero purging period, from the time zero gas is introduced into the optical chamber 6 until the sealing of the optical chamber 6 with zero gas is completed, overlap at least partially. "Until zero calibration is completed" means until the calibration unit 52 of the signal processing unit 5 completes the zero point adjustment process due to zero calibration, or until the supply of zero gas to the measurement cell 2 is stopped after the zero point adjustment process.

[0048] More specifically, as shown in Figure 3, various patterns like the following are possible.

[0049] Figure 3(a) shows a pattern where the introduction of zero gas into the measurement cell 2 (start of zero calibration) and the introduction of zero gas into the optical chamber 6 (start of zero purging) occur at the same time, and the completion of zero calibration and the completion of sealing the optical chamber 6 with zero gas (end of zero purging) occur at the same time. In other words, Figure 3(a) shows a pattern where the zero calibration period and the zero sealing period overlap over the entire period.

[0050] Figure 3(b) shows a pattern where zero purging starts after zero calibration begins and ends before zero calibration ends. In other words, Figure 3(b) shows a pattern where the entire zero purging period overlaps with the zero calibration period, and the zero calibration period is longer than the zero purging period.

[0051] Figure 3(c) shows a pattern where zero purging begins before zero calibration begins and ends before zero calibration ends. In this case, the length of the zero calibration period and the length of the zero purging period may be the same or different.

[0052] Figure 3(d) shows a pattern where zero purging begins before zero calibration begins and ends after zero calibration ends. In other words, Figure 3(d) shows a pattern where the entire zero calibration period overlaps with the zero purging period, and the zero purging period is longer than the zero calibration period.

[0053] Figure 3(e) shows a pattern where zero purging starts after zero calibration begins and ends after zero calibration ends. In this case, the length of the zero calibration period and the length of the zero purging period may be the same or different.

[0054] Furthermore, the flow rate of the zero gas introduced into the measurement cell 2 and the flow rate of the zero gas introduced into the optical chamber 6 may be set to the same flow rate or to different flow rates. Specifically, the flow rate of the zero gas introduced into the optical chamber 6 is set to a flow rate that replaces the gas in the optical chamber 6 by the time the zero calibration is completed, regardless of whether the zero calibration starts or ends. These flow rate settings are performed in the first flow rate adjustment unit 72 and the second flow rate adjustment unit 74, respectively.

[0055] <Gas Analysis Method> Next, a gas analysis method using the gas analyzer 100 of this embodiment will be described.

[0056] Before or after mounting the gas analyzer 100 onto the vehicle V, the zero gas cylinder ZB is connected to the zero gas introduction path 7. Note that the zero gas cylinder ZB is not mounted on the vehicle V during the driving test.

[0057] Then, zero gas is introduced into the measurement cell 2 from the zero gas introduction channel 7 to perform zero calibration, and zero gas is also introduced into the optical chamber 6 to seal the optical chamber 6 with zero gas. Once zero calibration and zero purging are complete, the zero gas cylinder ZB is removed from the zero gas introduction channel 7.

[0058] Furthermore, when performing span calibration, the span gas cylinder is connected to the span gas introduction channel, and span gas is introduced from the span gas introduction channel to the measurement cell 2 to perform span calibration. Note that the span gas cylinder is not mounted on the vehicle V during the driving test. Once span calibration is complete, the span gas cylinder is removed from the span gas introduction channel.

[0059] Subsequently, vehicle V is driven on the road, and the exhaust gas emitted from vehicle V is sampled and introduced into measurement cell 2, where the concentration of the target component contained in the exhaust gas is measured.

[0060] <Effects of this embodiment> With the gas analyzer 100 of this embodiment configured as described above, since the zero gas for zero calibration is introduced into the optical chamber 6 and sealed, a purge gas cylinder for constantly purging the optical chamber 6 is unnecessary, and running costs that would otherwise be incurred by constantly introducing and purging purge gas into the optical chamber 6 can be reduced. In addition, since the zero gas for zero calibration is sealed into the optical chamber 6, measurement errors caused by the ingress of air into the optical chamber 6 can be reduced. In particular, the measurement target component (for example, CO) has the same components as those contained in the air. ２ , H ２ Measurement errors (such as O) can be reduced. Furthermore, in this embodiment, the light irradiation unit 3 has a configuration having multiple laser light sources 31, which makes the optical path longer, and the effect of introducing zero gas into the optical chamber 6 and sealing the optical chamber 6 with zero gas becomes even more pronounced.

[0061] <Other Embodiments> The present invention is not limited to the embodiments described above.

[0062] For example, although the optical chamber 6 in the above embodiment accommodated both the light irradiation unit 3 and the light detection unit 4, it may accommodate only one of the light irradiation unit 3 or the light detection unit 4. Furthermore, the optical chamber 6 may be divided into a first optical chamber accommodating the light irradiation unit 3 and a second optical chamber accommodating the light detection unit 4.

[0063] The optical chamber 6 only needs to be configured to house all or part of the optical path from the laser light source 31 of the light irradiation unit 3 to the measurement cell 2, and does not need to house all of the laser light source 31 and / or optical elements 32. Figure 4 shows an example in which the multiple laser light sources 31 of the light irradiation unit 3 are not housed, but multiple optical elements 32 are housed. In this case, the housing section 61 forming the optical chamber 6 has light-passing windows 63 formed corresponding to each laser light source 31. Collimating lenses that make the laser light parallel may be provided in these light-passing windows 63. Furthermore, the optical chamber 6 only needs to be configured to house all or part of the optical path from the measurement cell 2 to the photodetector 41 of the light detection unit 4, and does not need to house all of the photodetector 41 and / or reflective mirrors 42.

[0064] Furthermore, as shown in Figure 5, the optical chamber 6 may also be configured to house a measurement cell 2 in addition to the light irradiation unit 3 and the photodetector 4. With this configuration, the entire optical path from the laser light source 31 of the light irradiation unit 3 to the measurement cell 2, and the entire optical path from the measurement cell 2 to the photodetector 41 of the photodetector 4 of the photodetector unit 4, can be sealed with zero gas.

[0065] In the above embodiment, zero gas was introduced into the measurement cell 2 and the optical chamber 6 using a single zero gas cylinder ZB. However, as shown in Figure 6, it is also possible to introduce zero gas into the measurement cell 2 and the optical chamber 6 from separate zero gas cylinders ZB. In this case, the flow path section 71 for the measurement cell and the flow path section 73 for the optical chamber of the zero gas introduction path 7 can be independent of each other. Furthermore, the zero gas introduced into the optical chamber 6 may be atmospheric air introduced through a filter.

[0066] Furthermore, the measurement cell 2 may have a short optical path and a long optical path that is longer than the short optical path, as shown in Figure 7. For example, the measurement cell 2 may have a configuration that includes a reflective mirror M1 for the short optical path and a reflective mirror M2 for the long optical path, as shown in Figure 7(a), or it may form a short optical path and a long optical path by making the incident angle of the laser beam on a pair of reflective mirrors M3 different, thereby making the number of reflections on the pair of reflective mirrors M3 different, as shown in Figure 7(b). When using the measurement cell 2 in the short optical path, the optical arrangement of the light irradiation unit 3 and the light detection unit 4 is set for the short optical path, and when using the measurement cell 2 in the long optical path, the optical arrangement of the light irradiation unit 3 and the light detection unit 4 is set for the long optical path.

[0067] Furthermore, the measurement cell 2 is not limited to a multiple reflection cell; it may be a single reflection cell or a non-reflective transmission cell.

[0068] Furthermore, various modifications and combinations of the embodiments are permitted, as long as they do not contradict the spirit of the present invention.

[0069] According to the present invention, it is possible to prevent air from entering the optical path and to reduce the running costs of purge gas.

[0070] 100...Gas analyzer 2...Measurement cell 3...Light irradiation unit 31...Laser light source 32...Optical element 4...Photodetector 6...Optical chamber P3...Inlet port P4...Outlet port 7...Zero gas inlet path ZB...Zero gas cylinder 71...Flow path for measurement cell 72...First flow rate adjustment unit 73...Flow path for optical chamber 74...Second flow rate adjustment unit 76...First on / off valve 77...Second on / off valve

Claims

A gas analyzer that analyzes the concentration of a target component contained in a sample gas, A measuring cell into which the sample gas is introduced, A light irradiation unit that irradiates the measurement cell with laser light, A photodetector that detects laser light that has passed through the measurement cell, An optical chamber housing the light irradiation unit and / or the light detection unit, Equipped with a zero-gas introduction path for introducing zero gas, The zero gas is introduced into the measuring cell through the zero gas introduction path to perform zero calibration. The zero gas is introduced into the optical chamber through the zero gas introduction path and the zero gas is sealed into the optical chamber. A gas analyzer in which the zero calibration period, from the time the zero gas is introduced into the measuring cell until the zero calibration is completed, and the zero purging period, from the time the zero gas is introduced into the optical chamber until the sealing of the zero gas into the optical chamber is completed, overlap at least partially. 　 The gas analyzer according to claim 1, wherein the zero gas is introduced into the optical chamber and the zero gas is sealed into the optical chamber before the zero calibration is completed. 　 The aforementioned zero-gas introduction path is A flow channel section for the measuring cell connected to the aforementioned measuring cell, A first flow rate adjustment unit is provided in the flow path section for the measuring cell to adjust the flow rate of the zero gas, A flow channel section for the optical chamber connected to the optical chamber, The gas analyzer according to claim 1 or 2, further comprising a second flow rate adjustment unit provided in the optical chamber flow path for adjusting the flow rate of the zero gas. 　 The gas analyzer according to any one of claims 1 to 3, wherein the flow rate of the zero gas introduced into the measuring cell and the flow rate of the zero gas introduced into the optical chamber are set to different flow rates. 　 The zero gas introduction path introduces the zero gas into the optical chamber before the zero calibration is completed. The gas analyzer according to any one of claims 1 to 4, wherein the flow rate of the zero gas introduced into the optical chamber is set to a flow rate that replaces the gas in the optical chamber before the zero calibration is completed. 　 The aforementioned optical chamber is The zero gas introduction path is connected to an introduction port into which the zero gas is introduced, It has an outlet port for releasing the gas inside the optical chamber to the outside, A gas analyzer according to any one of claims 1 to 5, wherein the zero gas is introduced through the zero gas introduction path with the first on-off valve provided on the introduction port side and the second on-off valve provided on the outlet port side open, and the zero gas is sealed into the optical chamber by closing the first on-off valve and the second on-off valve. 　 The gas analyzer according to any one of claims 1 to 6, wherein the zero gas introduction path is connected to a single zero gas cylinder, and the zero gas is introduced from the single zero gas cylinder to the measuring cell and the optical chamber. 　 The gas analyzer according to any one of claims 1 to 7, wherein the light irradiation unit comprises a plurality of laser light sources and a plurality of optical elements for introducing light from the plurality of laser light sources into the measurement cell. 　 The gas analyzer according to any one of claims 1 to 8, wherein the measuring cell has a short optical path and a long optical path that is longer than the short optical path. 　 A portable gas analyzer according to any one of claims 1 to 9. 　 A gas analyzer according to any one of claims 1 to 10, which is mounted on a vehicle and analyzes exhaust gas emitted from the vehicle. 　 The gas analyzer according to any one of claims 1 to 11, wherein the component to be measured is the same component as the component contained in the atmosphere. 　 A gas analyzer that analyzes the concentration of a target component contained in a sample gas, A measuring cell into which the sample gas is introduced, A light irradiation unit that irradiates the measurement cell with laser light, A photodetector that detects laser light that has passed through the measurement cell, An optical chamber housing the light irradiation unit and / or the light detection unit, It is equipped with a zero gas introduction path for introducing zero gas for zero calibration, The zero gas is introduced into the measuring cell through the zero gas introduction path to perform zero calibration. A gas analyzer that introduces the zero gas into the optical chamber through the zero gas introduction path and seals the optical chamber with the zero gas. 　 A gas analysis method using a gas analyzer comprising a measuring cell into which a sample gas is introduced, a light irradiation unit that irradiates the measuring cell with laser light, a light detection unit that detects the laser light that has passed through the measuring cell, an optical chamber that houses the light irradiation unit and / or the light detection unit, and a zero gas introduction path for introducing zero gas for zero calibration, The zero gas is introduced into the measuring cell through the zero gas introduction path to perform zero calibration. The zero gas is introduced into the optical chamber through the zero gas introduction path and the zero gas is sealed into the optical chamber. After the zero calibration and sealing of the optical chamber with zero gas are completed, the sample gas is introduced into the measurement cell and the sample gas measurement is performed. A gas analysis method in which the zero calibration period, from the time the zero gas is introduced into the measuring cell until the zero calibration is completed, and the zero purging period, from the time the zero gas is introduced into the optical chamber until the sealing of the optical chamber with the zero gas is completed, are overlapped by at least a portion.

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