Radiation-absorbing gas analyzer and gas analysis method

Abstract

The gas analyzer of the present invention comprises a first gas inlet (28), a second gas inlet (30), a first measuring cuvette (12), and a second measuring cuvette (14). The first measuring cuvette (12) is provided with a first radiation source (16) and a first radiation detector (20), where radiation passes through the cuvette and is received by the detector. The second measuring cuvette (14) similarly comprises a second radiation source (18) and a second radiation detector (22). The two detectors are different; the first detector (20) performs absorption measurements, while the second detector (22) simultaneously receives radiation. The first and second gases are connected to the cuvettes from the first and second gas inlets, respectively, and supplied alternately, while the first measuring gas is analyzed and the second measuring gas is analyzed simultaneously.

Description

Technical Field

[0001] The present invention relates to a gas analyzer for analyzing a gas according to the principle of optical radiation absorption, which is particularly used for sniffing leak detection for gas detection. One of the radiations commonly used here is infrared rays. However, in principle, radiation absorption measurement is also possible with other types of optical radiation or electromagnetic radiation.

Background Art

[0002] In radiation absorption analysis, a measurement cuvette is filled with a measurement gas. A radiation source and a radiation detector are arranged on opposite sides of the cuvette such that the optical radiation emitted by the radiation source passes through the measurement cuvette and the measurement gas contained therein and is received by the gas detector. By using the change in the intensity of one or individually selected absorption lines or absorption bands of the radiation recorded by the radiation detector, conclusions regarding the gas in the cuvette, the composition of the gas, or the amount of the gas can be drawn.

[0003] Also, for example, from European Patent No. 1161675 B1 (Patent Document 1), it is also known that in optical radiation absorption measurement for gas analysis, a second gas inlet is used as a reference gas inlet, and the reference gas is supplied to a further reference cuvette different from the measurement cuvette, and one or more radiation sources transmit infrared rays through the measurement gas in the measurement cuvette and the reference gas in the reference cuvette. A general radiation detector receives the radiation from the measurement cuvette and the radiation from the reference cuvette. The reference cuvette is connected only to the reference gas inlet, and the measurement cuvette is connected only to the measurement gas inlet.

[0004] Conventional radiation detectors can analyze only the radiation from the measurement cuvette or only the radiation from the reference cuvette; therefore, the test gas and reference gas are analyzed alternately. This means that the reference measurement is performed for half the measurement time, and therefore leaks can only be measured for half the measurement time. Consequently, the sniffer probe must remain on the object under test during the reference gas measurement, during which time the test gas cannot be analyzed, thus reducing the measurement rate of the test gas. Because the reference measurement is not performed simultaneously with the actual measurement, interference can occur due to subsurface variations. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] European Patent No. 1161675B1 [Patent Document 2] European Patent No. 1342070B1 [Patent Document 3] European Patent No. 1342070B1 [Overview of the project] [Problems that the invention aims to solve]

[0006] Against this backdrop, the objective of the present invention is to provide faster, improved, and more reliable radiation absorption analysis of test gases and reference gases.

[0007] The gas analyzer according to the present invention comprises a first gas inlet, a second gas inlet, a first measuring cuvette, and a second measuring cuvette. The first measuring cuvette is provided with a first radiation source and a first radiation detector, and radiation emitted from the first radiation source passes through the first measuring cuvette and is received by the first radiation detector, thereby performing a radiation absorption measurement of the gas contained in the first measuring cuvette. Accordingly, the second measuring cuvette is provided with a second radiation source and a second radiation detector, and radiation emitted from the second radiation source passes through the second measuring cuvette and is received by the second radiation detector, thereby performing a radiation absorption measurement of the gas contained in the second measuring cuvette.

[0008] The first gas inlet is the test gas inlet, into which the test gas to be tested is received, while the second gas inlet is the reference gas inlet, into which a reference gas for comparative measurement is received. Alternatively, the test gas can be supplied from the second gas inlet and the reference gas from the first gas inlet. The crucial element here is that only one of the two gas inlets, the test gas or the reference gas, is supplied from each of the two gas inlets, while the other gas inlet supplies the other gas gas.

[0009] In this disclosure, the gas supplied from the first gas inlet is referred to as the first measurement gas, regardless of whether it is a test gas or a reference gas. Similarly, the gas supplied from the second gas inlet is referred to as the second measurement gas, regardless of whether the second measurement gas is a reference gas or a test gas. If the first measurement gas is the test gas under test, then the second measurement gas is the reference gas for comparative measurement, and vice versa. This indicates that either the test gas or the reference gas can be supplied to the first gas inlet, and the other gas can be supplied to the second gas inlet.

[0010] According to the present invention, the first measurement gas from the first gas inlet and the second measurement gas from the second gas inlet are supplied alternately to each of the two measurement cuvettes. That is, the test gas and the reference gas are supplied alternately according to the assignment of the test gas and the reference gas to the two gas inlets. It is important that while the first measurement gas is supplied to one measurement cuvette, the other measurement gas is supplied to the other measurement cuvette at the same time. This makes it possible to measure the test gas and the reference gas alternately, and to measure the reference gas and the test gas simultaneously, in each of the two cuvettes without changing the gas at each gas inlet. Therefore, both cuvettes measure the first and second measurement gases alternately. Different measurement cuvettes are always supplied with different measurement gases.

[0011] The switching valves and their control systems according to the present invention are configured such that both gas inlets are never connected to the same measuring cuvette. This makes it possible to supply the test gas from one gas inlet to one measuring cuvette while simultaneously supplying the reference gas from the other gas inlet to the other measuring cuvette. Therefore, by switching the switching valves simultaneously, the two measuring cuvettes are alternately supplied with the test gas and the reference gas, and the two measuring cuvettes are always filled with different measuring gases.

[0012] In this disclosure, a radiation source that penetrates a first measurement cuvette is referred to as the first radiation source, and a radiation source that penetrates a second measurement cuvette is referred to as the second radiation source. The first and second radiation sources do not necessarily have to be different radiation sources. Rather, the first and second radiation sources may be the same radiation source, in which case its radiation penetrates both measurement cuvettes. Alternatively, the first and second radiation sources may be different radiation sources.

[0013] In this disclosure, the radiation detector that receives radiation transmitted through the first measurement cuvette is referred to as the first radiation detector, and the radiation detector that receives radiation transmitted through the second measurement cuvette is referred to as the second radiation detector.

[0014] According to the present invention, the first radiation detector and the second radiation detector are different from each other, and the first radiation detector can perform absorption measurements of radiation passing through the first measurement cuvette, while the second radiation detector simultaneously receives radiation passing through the second measurement cuvette. This means that the first measurement gas in one measurement cuvette and the second measurement gas in the other measurement cuvette are analyzed simultaneously. For this purpose, the first gas inlet and the second gas inlet are connected to both the first and second measurement cuvettes, respectively, and the first measurement gas from the first gas inlet flows only into the first measurement cuvette, and the second measurement gas from the second gas inlet flows only into the second measurement cuvette, thereby enabling the measurement of the second measurement gas independently of the first measurement gas, simultaneously with the measurement of the first measurement gas, and without mixing the two gases.

[0015] Therefore, the radiation absorption measurement of the first measurement gas can be performed simultaneously and independently of the radiation absorption measurement of the second measurement gas. For example, the first measurement gas may be the test gas to be analyzed, and the second measurement gas may be a reference gas for comparative measurement. Thus, while the test gas is being analyzed in one measurement cuvette, the reference gas can be analyzed independently and simultaneously in the other measurement cuvette. The reference gas serves as a comparison with the test gas to correct for interference with the test gas signal. For this purpose, differences in the measurement signals recorded by each radiation detector can be observed between the reference gas and the test gas. A procedure for evaluating each measurement signal is described in European Patent No. 1342070B1 (Patent Document 2).

[0016] According to the present invention, a first measuring line including a first gas inlet may be provided to be connected via a first switching valve to a first input line connected to a first measuring cuvette and a second input line connected to a second measuring cuvette. The first switching valve may be used to alternately and selectively connect the first gas inlet to either the first inlet line or the second inlet line.

[0017] Therefore, the second measurement line, including the second gas inlet, may be connected via a second switching valve to the first input line connected to the first measurement cuvette and to the second input line connected to the second measurement cuvette. Thus, the second switching valve may be used to alternately connect the second gas inlet to the first inlet line or the second inlet line.

[0018] In a preferred embodiment, the two switching valves are configured such that a first gas inlet may be connected to a first measuring cuvette but not to a second measuring cuvette, while a second gas inlet is connected to a second measuring cuvette but not to a first measuring cuvette, and / or vice versa. This means that the two switching valves may be configured such that a second gas inlet is connected to a first measuring cuvette but not to a second measuring cuvette, while a first gas inlet is connected to a second measuring cuvette but not to a first measuring cuvette. This can be accomplished, for example, by a well-configured or designed electronic control unit connected to the two switching valves and controlling their switching state.

[0019] This allows for the selective supply of the first measurement gas to one of the two measurement cuvettes and the exclusive supply of the second measurement gas to the other measurement cuvette. The two measurement gases are supplied to one measurement cell and then alternately to the other measurement cell by synchronously switching two switching valves, allowing both measurement gases to be analyzed sequentially using both measurement cells. For example, in the first switching cycle of the switching valves, the first measurement cuvette performs the analysis of the test gas and the second measurement cuvette performs a reference measurement using a reference gas, while in the subsequent second switching cycle, the first measurement cuvette performs the reference measurement and the second measurement cuvette performs the analysis of the test gas. This switching can be performed continuously as many times as needed.

[0020] Alternatively, the first gas inlet may be connected to both the first switching valve and the second switching valve, i.e., to the first port of the first switching valve and the first port of the second switching valve, and the second gas inlet may also be connected to both switching valves, but may be configured to be connected to different gas inlets of the switching valves. The first measurement cuvette is connected to the third port of the first switching valve, which is different from the two first ports, while the second measurement cuvette is connected to the third port of the second switching valve, which is different from the two first ports of the second switching valve. In this way, the effects described above can also be achieved.

[0021] The first radiation source and the second radiation source may be configured for modulating the radiation transmitted through the first measurement cuvette and the second measurement cuvette, respectively. [[ID=S]]

[0022] As an alternative to radiation modulation using a modulated light source, it is also possible to utilize the gas change as modulation ("gas modulation") by switching the switching valves provided in each of the two measurement cuvettes. This principle is described, for example, in European Patent No. 1342070 B1 (Patent Document 3).

[0023] Preferably, the first measurement cuvette has a first outlet for the measurement gas, the second measurement cuvette has a second outlet for the measurement gas, and the first measurement cuvette outlet and the second measurement cuvette outlet are connected to a vacuum pump that evacuates the measurement cuvette, the two inlet lines, the two measurement lines, and / or the two gas inlets to a vacuum.

[0024] Examples of the switching valve include a three-way gas valve.

[0025] In the gas analysis method based on the principle of optical radiation absorption using the gas analyzer of the above type according to the present invention, the following steps are continuously executed in the following order: a) Supply the first measurement gas received through the first gas inlet to one of the two measurement cuvettes, for example, the first measurement cuvette, while supplying the second measurement gas received through the second gas inlet to the other measurement cuvette, for example, the second measurement cuvette. b) Perform a radiation absorption analysis of the radiation passing through the first measurement cuvette using the first detector and perform a radiation absorption analysis of the radiation passing through the second measurement cuvette using the second detector. c) Supply the first measurement gas received through the first gas inlet to the other, for example, the second measurement cuvette, while supplying the second measurement gas received through the second gas inlet to the one, for example, the first measurement cuvette. d) Repeat step b).

[0026] In the context of the present invention, the "first measurement gas" refers to the gas supplied through the first gas inlet. Depending on the assignment, this can be a test gas or a reference gas. Thus, the "second measurement gas" refers to the gas supplied through the second gas inlet. These are each other's gases. That is, if the first measurement gas is a test gas, the second measurement gas automatically becomes a reference gas, and vice versa.

[0027] Therefore, in the method according to the present invention, first, only the first measurement gas is supplied to one measurement cuvette, and simultaneously, only the other measurement gas is supplied to the other measurement cuvette, so that the first measurement gas in the first measurement cuvette is analyzed, while the other measurement gas is analyzed in the other measurement cuvette. Then, the measurement gases in the two measurement cuvettes are changed by switching the two gas inlets to different measurement cuvettes, respectively. Therefore, it is not necessary to change the assignment of the test gas and reference gas at the two gas inlets. In other words, first, one measurement gas, then the other measurement gas, is analyzed alternately using each measurement cuvette, while first, the other measurement gas, then the first measurement gas, is analyzed simultaneously using the other measurement cuvette. After measurements are taken in each measurement cuvette, each gas is discharged via a vacuum pump.

[0028] These procedures can be repeated as many times as needed, offering the advantage of reducing offset errors in measurements. The assignment of two measurement gases to two measurement cuvettes can be changed by switching two switching valves accordingly. [Brief explanation of the drawing]

[0029] Hereinafter, exemplary embodiments of the present invention will be described in more detail with reference to the drawings. In the drawings: [Figure 1] This is a schematic diagram of a first exemplary embodiment. [Figure 2] This is a schematic diagram of a second exemplary embodiment. [Modes for carrying out the invention]

[0030] A first measuring cuvette 12 and a second measuring cuvette 14 are shown in both drawings. Both cuvettes 12 and 14 have a cylindrical shape. A first radiation source 16 is located on one end face of the first measuring cuvette 12. Similarly, a second radiation source 18 is located on one end face of the second measuring cuvette 14. A first radiation detector 20 is located on the end of the first measuring cuvette 12 opposite to the first radiation source 16, so that the light radiation emitted by the first radiation source 16, typically in the form of infrared radiation, is transmitted longitudinally through the first measuring cuvette 12 and received at the opposite end by the first radiation detector 20.

[0031] Similarly, the second measuring cuvette 14 is provided with a second radiation source 18 on one end face and a second radiation detector 22 on the end face opposite the second radiation source 18. The second radiation detector 22 receives the radiation emitted by the second radiation source 18 and transmitted longitudinally through the second measuring cuvette 14 in a corresponding manner.

[0032] Alternatively, the first radiation source 16 and the second radiation source 18 may be the same radiation source, and that radiation may pass through both measuring cuvettes 12 and 14, and that radiation may be received by the two radiation detectors 20 and 22, respectively.

[0033] For the sake of simplicity, Figure 2 does not show radiation sources 16 and 18 and radiation detectors 20 and 22, but they are still present.

[0034] In Figure 1, the first measuring cuvette 12 is provided with a first measuring cuvette inlet 24. Similarly, the second measuring cuvette 14 is provided with a second measuring cuvette inlet 26. The first measuring cuvette inlet 24 is connected to the first switching valve 36 by gas conduction, while the second measuring cuvette inlet 26 is connected to the second switching valve 38 by gas conduction. The first switching valve 36 is connected to the first measuring gas line 32, which opens to the first gas inlet 28. The second switching valve 38 is connected to the second measuring gas line 34, which opens to the second gas inlet 30. The two switching valves 36, 38 are also interconnected by a connecting line 41, and each switching valve 36, 38 can connect each of the two gas inlets 28, 30 to either the first or second measuring cuvettes 12, 14.

[0035] Therefore, the first measuring gas line 32 is connected to the first switching valve 36 in the form of a three-way valve, and the second measuring gas line 34 is connected to the second switching valve 38 in the form of a three-way valve. The first measuring gas line 32 is connected to the first port 36a of the first switching valve 36, and the second measuring gas line 34 is connected to the first port 38a of the second switching valve 38. The third port 36c of the first switching valve 36 is connected to the second port 38b of the second switching valve 38 via a connecting line 41 in a gas conduction manner. The connecting line 41 opens into a common second measuring cuvette line 42 connected to the second measuring gas inlet 26.

[0036] The second port 36b of the first switching valve 36 and the third port 38c of the second switching valve 38 are also connected to each other and open to a common first measuring cuvette line 40 connected to the first measuring gas inlet 24.

[0037] The first ports 36a and 38a of the two switching valves 36 and 38 can be selectively connected to the second ports 38b and 36b or the third ports 38c and 36c, respectively. In Figure 1, the first port 36a of the first switching valve 36 is connected to its second port 36b, and the first measuring gas from the first gas inlet 28 flows into the first measuring cuvette 12 through the first measuring cuvette line 40. Similarly, the first port of the second switching valve 38 is connected to its second port, and the second measuring gas from the second gas inlet 30 reaches the second measuring cuvette 14 via the second measuring cuvette line 42. For each of the two valves 36 and 38, the connection from the first ports 36a and 38a of each valve to the third ports 36c and 38c is blocked.

[0038] Therefore, the gas from the first gas inlet 28 cannot enter the second measuring cuvette line 42 and the second measuring cuvette 14, and similarly, the second measuring gas from the second gas inlet 30 cannot enter the first measuring cuvette line 40 and the second measuring cuvette 12. This switching state corresponds to method steps a) and b). Next, the switching state corresponding to method steps c) and d) is established by synchronously switching the two switching valves so that the second measuring gas is supplied to the first measuring cuvette 12 and the first measuring gas is supplied to the second measuring cuvette 14.

[0039] According to the present invention, absorption analysis of radiation received by two detectors 20 and 22 can be performed simultaneously while the two switching valves 36 and 38 are in their respective switching states. Absorption analysis of radiation received by the first radiation detector 20 is performed independently of the analysis of radiation received by the second radiation detector 22. The first radiation detector 20 and the second radiation detector 22 are connected to a common evaluation unit (not shown), where the recorded measurement signals are evaluated for the absorbed radiation components, and the gas or gas composition in the first measurement cuvette 12 and the second measurement cuvette 14 is determined based on the absorption spectra. Alternatively, the first radiation detector 20 may be connected to a different evaluation unit than the one to which the second radiation detector 22 is connected. According to the present invention, absorption analysis of radiation spectra recorded using the first radiation detector 20 and the second radiation detector 22 can be performed simultaneously and independently of each other.

[0040] By synchronously switching the two switching valves 36 and 38, the first and second measurement gases can be alternately analyzed in each of the two measurement cuvettes 12 and 14. The first measurement gas is a test gas for analyzing the possibility of leak gas, while the second measurement gas may be a reference gas for reference measurement. By switching the two switching valves 36 and 38, test gas measurements can be performed in one (e.g., the first) cuvette, and reference measurements can be performed alternately in the other (e.g., the second) cuvette. Then, reference measurements can be performed in the other (e.g., the second) measurement cuvette, and test gas measurements can be performed in one (e.g., the first) measurement cuvette. This allows for correction of offset errors between the two measurement cuvettes 12 and 14. The first measuring cuvette 12 and the second measuring cuvette 14 are provided with corresponding outlets 48 and 50, respectively, in the region opposite their respective inlets 24 and 26. The outlet 48 of the first measuring cuvette is associated with the first measuring cuvette 12, while the outlet 50 of the second measuring cuvette is associated with the second measuring cuvette 14. The outlets 48 and 50 of the first measuring cuvette are open to a common outlet line 52, which is evacuated by a vacuum pump 54.

[0041] The exemplary embodiment in Figure 2 differs from the exemplary embodiment in Figure 1 in that the first gas inlet 28 is connected to both the first port 36a of the first switching valve 36 and the first port 38a of the second switching valve 38, while the second gas inlet 30 is connected to both the third port 36c of the first switching valve 36 and the third port 38c of the second switching valve 38. The first port 36a is connected to the first gas inlet 28 via the first measuring gas line 32, the first port 38a is connected to the second gas inlet 30 via the second measuring gas line 34, the third port 36c is connected to the second measuring gas line 34, and the first port 38a is connected to the first measuring gas line 34. Furthermore, the second port 36b of the first switching valve 36 is connected only to the first measuring cuvette 12 via the first measuring cuvette line 40, while the second port 38b of the second switching valve 38 is connected only to the second measuring cuvette 14 via the second measuring cuvette line 42.

[0042] In this exemplary embodiment, by synchronously switching the two switching valves 36 and 38, one gas inlet can be alternately and continuously assigned to one switching valve and the other gas inlet to the other switching valve, thereby supplying the first measuring gas and the second measuring gas to each of the two measuring cuvettes 12 and 14 alternately and successively.

[0043] The first gas inlet 28 and the second gas inlet 30 can be positioned on or inside a handheld sniffer probe in a manner known by itself, for example, as described in European Patent No. 1161675B1 (Patent Document 1).

Claims

1. A gas analyzer comprising a first gas inlet (28), a second gas inlet (30), a first measuring cuvette (12), and a second measuring cuvette (14), The first measuring cuvette (12) is provided with a radiation source (16) and a first radiation detector (20), and the radiation emitted by the radiation source (16) passes through the first measuring cuvette (12) and is received by the first radiation detector (20). The second measuring cuvette (14) is provided with a second radiation source (18) and a second radiation detector (22), and the radiation emitted by the second radiation source (18) passes through the second measuring cuvette (14) and is received by the second radiation detector (22). The first radiation detector (20) and the second radiation detector (22) are different from each other, with the first radiation detector (20) capable of performing absorption measurements of radiation passing through the first measurement cuvette (12), while the second radiation detector (22) simultaneously receives radiation passing through the second measurement cuvette (14). The first gas inlet (28) and the second gas inlet (30) are connected to the first measuring cuvette (12) and the second measuring cuvette (14), respectively, and the first measuring gas from the first gas inlet (28) and the second measuring gas from the second gas inlet (30) are alternately supplied to the two measuring cuvettes (12, 14), the first measuring gas is analyzed in one of the two measuring cuvettes (12, 14), and the second measuring gas is analyzed simultaneously in the other of the two measuring cuvettes (12, 14). Gas analyzer.

2. The gas analyzer according to claim 1, characterized in that the first radiation source (16) and the second radiation source (18) are different radiation sources or the same radiation source.

3. The gas analyzer according to claim 1 or 2, characterized in that the first measurement line (32) having the first gas inlet (28) is connected via a first switching valve (36) to a first input line (40) connected to the first measurement cuvette (12) and a second input line (42) connected to the second measurement cuvette (14).

4. The gas analyzer according to any one of claims 1 to 3, characterized in that the second measurement line (34) having the second gas inlet (30) is connected via a second switching valve (38) to a first input line (40) connected to the first measurement cuvette (12) and a second input line (42) connected to the second measurement cuvette (14).

5. The gas analyzer according to claim 1 or 2, characterized in that the first gas inlet (28) is connected to the first port (36a) of the first switching valve (36) and the first port (38a) of the second switching valve (38), while the second gas inlet (30) is connected to the third port (36c) of the first switching valve (36) and the third port (38c) of the second switching valve (38), the second port (36b) of the first switching valve is connected to the first measuring cuvette (12), and the second port (38b) of the second switching valve (38) is connected to the second measuring cuvette (14).

6. The gas analyzer according to any one of claims 3 to 5, characterized in that the two switching valves (36, 38) are configured such that the first gas inlet (28) can be connected to the first measuring cuvette (12) but not to the second measuring cuvette (14), while the second gas inlet (30) can be connected to the second measuring cuvette (14) but not to the first measuring cuvette (12), and vice versa.

7. The gas analyzer according to any one of claims 1 to 6, characterized in that the second radiation detector (22) and the first radiation detector (20) are connected to an evaluation device configured to evaluate the measurement signals transmitted by the first radiation detector (20) and the second radiation detector (22) in accordance with the principle of radiation absorption analysis.

8. The gas analyzer according to any one of claims 1 to 7, characterized in that the first radiation source (16) and the second radiation source (18) are configured for gas modulation of radiation transmitted through the first measuring cuvette (12) and the second measuring cuvette (14), respectively.

9. The gas analyzer according to any one of claims 1 to 8, characterized in that the first measuring cuvette (12) has a first measuring cuvette outlet (48) for measuring gas, the second measuring cuvette (14) has a second measuring cuvette outlet (50) for measuring gas, and the first measuring cuvette outlet (48) and the second measuring cuvette outlet (50) are connected to a vacuum pump (54).

10. A gas analysis method according to the principle of light emission absorption using a gas analyzer described in any one of claims 1 to 9, wherein the order is as follows: a) A step of supplying the first measuring gas received by the first gas inlet (28) to one of the two measuring cuvettes (12), while supplying the second measuring gas received by the second gas inlet (30) to the other measuring cuvette (14), b) A step in which radiation absorption analysis is performed on the radiation that passes through the first measurement cuvette (12) using the first detector (20), while radiation absorption analysis is performed on the radiation that passes through the second measurement cuvette (14) using the second detector (22), c) The steps of supplying the first measuring gas received by the first gas inlet (28) to the other measuring cuvette (14), while supplying the second measuring gas received by the second gas inlet (30) to the other measuring cuvette (12), and d) A step that repeats step b), A method characterized by performing each step accordingly.

11. The method according to any one of claims 1 to 10, characterized in that, in step a) and step b), only the first measurement gas from the first gas inlet (28) is analyzed in the one measurement cuvette (12), and the second measurement gas from the second gas inlet (30) is not introduced into the one measurement cuvette (12), while only the second measurement gas from the second gas inlet (30) is analyzed in the other measurement cuvette (14), and the first measurement gas from the first gas inlet (28) is not introduced into the other measurement cuvette (14).

12. The method according to any one of claims 1 to 11, characterized in that, in step c) and d), only the second measurement gas from the second gas inlet (30) is analyzed in the one measurement cuvette (12), and the first measurement gas from the first gas inlet (28) is not introduced into the one measurement cuvette (12), while only the first measurement gas from the first gas inlet (28) is analyzed in the other measurement cuvette (14), and the second measurement gas from the second gas inlet (30) is not introduced into the other measurement cuvette (14).

13. The method according to any one of claims 1 to 12, characterized in that steps a) to d) are repeated at least once.

14. The method according to any one of claims 1 to 13, characterized in that the two switching valves (36, 38) are switched after step a) and before step c), and after step c) and before the repeated step a).

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