AT520532A4 - Apparatus for measuring a measuring component contained in a raw gas stream - Google Patents

Abstract

Apparatus and method for measuring a measurement component contained in a raw gas stream (r), in particular for particle measurement. The device has a raw gas path (1), which runs from a crude gas inlet (2) to a mixing unit (3), a measuring gas path (13) which is conveyed from the mixing unit (3) via a measuring cell (4), a measuring gas mass flow meter (5 ) and a sample gas pump (6), and a dilution path (7) extending from a diluent gas inlet (8) via a diluent gas mass flow meter (9) and a flow controller (10) to the mixing unit (3). The crude gas stream (r) and a diluent gas stream (v) are mixed in the mixing unit (3) to a sample gas stream (m), which flows through the measuring cell (4). The device has a computer unit (11) which has a correction function for a cross sensitivity of the diluent gas mass flow meter (9) and / or a cross sensitivity of the sample gas mass flow meter (5) to at least one component of the measured value determined by the measuring cell (4) Diluent gas stream (v) and / or the raw gas stream (r) applies.

Description

Summary

Device and method for measuring a measurement component contained in a raw gas stream (r), in particular for particle measurement. The device has a raw gas path (1) that runs from a raw gas inlet (2) to a mixing unit (3), a measuring gas path (13) that runs from the mixing unit (3) via a measuring cell (4), a measuring gas mass flow meter (5) and a sample gas pump (6) runs, and a dilution path (7), which runs from a dilution gas inlet (8) via a dilution gas mass flow meter (9) and a flow controller (10) to the mixing unit (3). The raw gas stream (r) and a dilution gas stream (v) are mixed in the mixing unit (3) to form a sample gas stream (m) which flows through the measuring cell (4). The device has a computing unit (11) which, based on the measured value determined by the measuring cell (4), has a correction function for a cross sensitivity of the dilution gas mass flow meter (9) and / or a cross sensitivity of the measurement gas mass flow meter (5) to at least one component of the dilution gas flow (v) and / or the raw gas stream (r) applies.

Fig. ^{1/17 15-}

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Process for regulating the sample gas flow in a measuring cell

The invention relates to a device for measuring a measuring component contained in a raw gas stream, in particular for particle measurement, the device comprising a raw gas path that runs from a raw gas inlet to a mixing unit, a measuring gas path that runs from the mixing unit via a measuring cell, a measuring gas mass flow meter and a measuring gas pump , and has a dilution path that runs from a dilution gas inlet via a dilution gas mass flow meter and a flow controller to the mixing unit, the raw gas stream and a dilution gas flow in the mixing unit being mixable to form a measurement gas flow with which the measuring cell can be flowed through. Furthermore, the invention relates to a method for calibrating such a device and a method for determining a measured value of a measurement component contained in a raw gas stream with this device.

Methods and devices for photoacoustic spectroscopy (PAS) are used very successfully in many areas of gas and particle measurement technology. With the help of a modulated laser, density and pressure fluctuations in the gas to be examined (aerosol) are generated in a resonant cell. These are then picked up as a sound wave by a microphone and converted into electrical signals, which signals can then be evaluated to determine particle or gas concentrations (i.e. the measured variable). Corresponding systems are available, for example, for determining the mass concentration of soot particles in an exhaust gas.

In order to achieve reliable results, the measurement gas (i.e. the gas that is photoacoustically excited in the measurement cell) must generally be conditioned with regard to pressure / temperature / humidity and particle concentration. This can be done practically by mixing the gas to be measured (raw gas) with a dilution gas (usually air) and thereby diluting it to a measurement gas. On the basis of the known mixing ratios, the measurement result obtained from the measurement gas is then used to calculate the desired measurement result of the raw gas (for example the mass concentration of soot particles in an exhaust gas) on the basis of the known dilution rate.

For this purpose, the dilution gas can be provided, for example, in a conditioning unit (separate or integrated into the device) and can be admixed to the raw gas in a controlled manner in a mixing unit upstream of the measuring cell. For control purposes, the sample stream drawn through the measuring cell can be measured, the dilution gas being admixed in accordance with the preset dilution rate. The gas flows can be measured and controlled, for example, using known mass flow meters and control valves.

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To ensure an accurate dilution rate, it is necessary to calibrate both mass flow meters to each other. This is done by “connecting” the mass flow meters in series while the same calibration gas flows through them. Deviations in the display values (i.e. measurement signals measured directly by the mass flow meters) can thus be easily recognized and corrected, whereby this method can be referred to as a “relative calibration”.

In order that this relative calibration ensures correct results even if the composition of the diluent gas changes after the calibration (for example because the proportion of a component of the diluent gas has changed), the state of the art for the sample gas mass flow meter and the diluent gas mass flow meter are as possible similar mass flow meters are used. For example, it is known to use a calorimetric or thermal sensor both for the sample gas mass flow meter and for the diluent gas mass flow meter.

Changes to the components have an essentially identical effect on both sensors, so that the relative calibration continues to ensure the correct result even if the gas composition changes (provided the proportion of the relevant component in the diluent gas and the measurement gas changes essentially in the same way).

On the other hand, there is a problem if a component to which a mass flow meter has a cross sensitivity is introduced via the raw gas during the measurement and therefore does not flow through the diluent gas mass flow meter, but very well flows through the sample gas mass flow meter. When selecting the sensors, you are also restricted to an identical design of the sample gas mass flow meter and diluent gas mass flow meter, since mass flow meters that use different measurement methods generally also have different cross-sensitivities.

In connection with the present disclosure, “sensitivity” of the measuring cell or the mass flow meter and generally any sensors is a sensitivity of the sensor to a component or environmental condition that is not the measured variable. Examples of such cross-sensitivities include the sensitivity to component concentrations contained in the measurement gas, in particular moisture (ie water vapor or water droplets), CO ₂ , nitrogen and nitrogen oxides. These cross-sensitivities can affect both the measuring cell (in particular photoacoustic measuring cells) and mass flow meters.

Therefore, in principle, the problem is that the differences between the calibration gas used for the calibration and the gas compositions arising during the measurement to unexpected (and often unnoticed constant) measurement errors ^{3/17 2}

AV-3953 AT which can be difficult to use in practice, especially if the

Change environmental conditions during a measurement run.

It is an object of the present invention to improve the methods and devices used for gas measurement technology and, in particular, to achieve greater accuracy over broader areas of application or environmental conditions.

These and other objects are achieved according to the invention by a device of the type mentioned at the outset, which has a computing unit with which, based on the measured value determined by the measuring cell, a correction function for a cross-sensitivity of the diluent gas mass flow meter and / or a cross-sensitivity of the measuring gas mass flow meter to at least one component of the Dilution gas stream and / or the raw gas stream is applicable. This has the particular advantage that measurement errors due to cross-sensitivities, which affect the diluent gas mass flow meter and the sample gas mass flow meter differently, can be compensated for.

The measuring cell of the device according to the invention can advantageously have a photoacoustic cell. Photoacoustic measuring cells also have cross-sensitivities to components of the measuring gas, which can be taken into account in the overall system. In addition, it is possible to use the cross-sensitivities of the photoacoustic measuring cell when calibrating with a test gas by measuring a component of the test gas which is known with regard to its properties and its concentration. The measuring cell can thus be used as a measuring probe for the component.

By using the correction function, it is also advantageously possible to use a diluent gas mass flow meter and a measurement gas mass flow meter in the device, which work according to a different measurement method. This enables specific advantages of different measurement methods to be used.

The diluent gas mass flow meter can advantageously operate according to a calorimetric measuring method and / or the measuring gas mass flow meter can operate according to a differential pressure-based measuring method. In particular, the measuring gas mass flow meter can be designed as a measuring orifice or measuring orifice block. While thermal mass flow meters (i.e. mass flow meters that use a calorimetric measuring method) are advantageous in the dilution path, orifices in the sample gas path offer the advantage that they can be used for gas flow measurement and at the same time

Flow stabilization can be used. In addition, they are usually less expensive and less susceptible to any reactive exhaust gas components. ^{4/17 3}

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In an advantageous embodiment, at least one measuring probe for the at least one component of the dilution gas flow and / or the raw gas flow can be provided on the dilution path and / or on the raw gas path and / or on the measurement gas path. This allows the correction function to be adapted immediately if the proportion of the component in the sample gas changes during a test run. For example, the CO ₂ content of exhaust gases is subject to strong fluctuations, which, however, only affect the sensors in the sample gas path. These can be determined by a CO ₂ sensor arranged in the sample gas path (and / or in the raw gas path) and compensated for by adapting the correction function. The moisture that enters the dilution path and the sample gas path via the ambient air, for example, also causes significant cross-sensitivities, but these are very different for thermal flow sensors and for orifices. A change in the ambient humidity during a test run can therefore falsify the relative calibration, especially if different measuring methods are used for the diluent gas mass flow meter and the sample gas mass flow meter. By measuring the humidity with a humidity sensor (preferably in the dilution path, but possibly also in the sample gas path and / or in the raw gas path), such changes can be compensated for by adapting the correction function accordingly. Cross-sensitivities to nitrogen and nitrogen oxides can also be corrected in a similar way.

In an advantageous embodiment, at least one measuring probe is therefore selected from the following group: CO ₂ probe, moisture sensor, nitrogen sensor, nitrogen oxide sensor.

Advantageously, the dilution path upstream of the dilution gas mass flow meter can preferably be switched to a zero gas inlet by means of a switching valve, which additionally allows calibration with a clean, dry and known gas.

The method for calibrating the device mentioned at the outset can have the following steps according to the invention: generating a test gas flow which flows through at least the diluent gas mass flow meter and the measurement gas mass flow meter; Determining the proportion of a component in the test gas stream; Determining a measurement deviation between the measurement value of the diluent gas mass flow meter and the measurement value of the measurement gas mass flow meter; and determining a correction function for a cross sensitivity of the diluent gas mass flow meter and / or a cross sensitivity of the measurement gas mass flow meter to at least one component of the test gas flow. The same gas is drawn through the dilution gas mass flow meter and the measurement gas mass flow meter, which enables an accurate relative calibration.

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The proportion of the component can advantageously be determined by means of a measuring probe. This allows special environmental conditions (such as high humidity during tests in tropical areas) to be taken into account for calibration immediately before a test run.

In a further embodiment, the proportion of the component with the measuring cell can be determined on the basis of a known cross sensitivity of the measuring cell to the component. As a result, the measuring cell, which has no function during the relative calibration of the two mass flow meters, can advantageously be used as a sensor for the relevant component.

The component can advantageously be selected from the following group: moisture (H ₂ O), carbon dioxide (CO ₂ ), nitrogen (N), nitrogen oxides (NOx). With these components, cross-sensitivities were determined by the applicant, which may be relevant to the measurement result of the device.

The test gas stream can advantageously be obtained from the ambient air, so that differences between a laboratory situation and use in a real environment can be taken into account.

On the other hand, the test gas flow can also be supplied via a zero gas inlet, so that calibration to "laboratory conditions" is also possible during use.

In a further advantageous embodiment, the proportion of the component in the test gas stream can be regulated. This allows a specific adjustment of the correction function.

The method according to the invention for determining a measured value of a measurement component contained in a raw gas stream with a device according to the invention has the following steps: directing a raw gas stream via the raw gas inlets to the mixing unit; in the mixing unit, mixing the raw gas stream with a diluent gas stream to form a sample gas stream; Directing the sample gas flow over the measuring cell; Determining a measured value of the measuring cell; Determining the proportion of at least one component in the raw gas stream and / or the dilution gas stream and / or the measurement gas stream; Depending on the proportion of the component, determining a correction function for a cross sensitivity of the diluent gas mass flow meter and / or a cross sensitivity of the measurement gas mass flow meter to the at least one component; Apply the correction function to the measured value of the measuring cell to determine the measured value of the measuring component. ^{6/17 5} '

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The present invention is explained in more detail below with reference to FIG. 1, which explains exemplary, schematic and non-limiting advantageous embodiments of the invention. It shows

1 shows a schematic block diagram of a measuring device according to the invention.

An advantageous embodiment of a device according to the invention for measuring a measurement component contained in a raw gas stream is described below with reference to FIG. 1. For reasons of clarity, only the elements and lines relevant to the description have been shown schematically.

The device can essentially be divided into a raw gas path 1, a measuring gas path 13 and a dilution gas path 7, raw gas path 1 and dilution gas path 7 opening into a mixing unit 3 in which the measuring gas path 13 has its starting point. During the measuring operation, a raw gas stream r, which is supplied via the raw gas path 1, is mixed with a diluent gas stream v, which is supplied via the diluent gas path 7, in the mixing unit 3. The mixture of raw gas stream r and dilution gas stream v is referred to in connection with the present disclosure as the measuring gas stream m, and this flows through the measuring gas path 13.

In the sample gas path 13, the sample gas m flows through a photoacoustic measuring cell 4 and a sample gas mass flow meter 5. A sample gas pump 6 in the sample gas path 13 serves as the main pump which draws the sample gas through the device. The measurement gas path 13 opens into an exhaust gas outlet 16, which usually leads to exhaust gas disposal (not shown in FIG. 1). If necessary, the CO ₂ concentration in the sample gas can be determined using a CO ₂ probe.

The raw gas path 2 conducts a raw gas stream from a raw gas inlet 2 to the mixing unit 3. The raw gas can be, for example, undiluted exhaust gas, for example from an internal combustion engine to be tested, wherein the raw gas stream can optionally be preconditioned in front of the mixing unit 3 in a pressure reducer.

The dilution path 7 starts from a dilution gas inlet 8 and runs via a switching valve 15, a dilution gas mass flow meter 9, a flow controller 10 and also opens into the mixing unit. If appropriate, the ambient air drawn in via the dilution gas inlet 8 can be dried using an airflow dryer (not shown in FIG. 1). Via the switching valve 15, the dilution path can be switched to a zero gas inlet 14, via which dry, clean compressed air can be supplied, for example, for calibration. ^{7/17 6}

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If necessary, the dilution path 7 and / or the sample gas path 13 and / or the

Raw gas path 1 additional sensors may be arranged, a moisture sensor 12b, a nitrogen sensor 12c and a nitrogen oxide sensor 12d being shown by way of example in FIG. 1.

All sensors and controllable components can be connected to a central processing unit 11. On the one hand, the computing unit 11 permits central control of the controllable components, such as the laser of the measuring cell 4, the flow controller 10, the switching valve 15, the measuring gas pump 6 and, if appropriate, all other pumps, valves and switchable elements contained in the device. The measured values of all sensors can also be evaluated and used centrally with the computing unit 11 in accordance with methods that can be influenced by programming and, if necessary, output to other devices via interfaces.

Exemplary methods are described below, which can be carried out with the device shown, wherein in particular the actual measuring method and calibration methods that can be carried out before the measurement are discussed in detail. The person skilled in the art is aware that other methods, such as rinsing, cleaning, maintenance and / or functionality testing methods, can also be carried out on the device as shown in FIG. 1, additional components, valves and lines possibly being used may be necessary, which are not shown here for the sake of clarity.

In order to carry out a relative calibration before a measurement, the measuring gas mass flow meter 5 and the dilution gas mass flow meter 9 are connected in series and flowed through with an identical gas composition, preferably ambient air (or possibly zero gas). Ambient air is drawn in as test gas stream p via the diluent gas inlet 8 with the sample gas pump, flows through the diluent gas mass flow meter 9, the flow controller 10, the mixing unit 3, the measuring cell 5 and the sample gas mass flow meter 5, and is emitted via the exhaust gas outlet 16. The raw gas inlet 2 is closed. Since both the sample gas mass flow meter 5 and the diluent gas mass flow meter 9 are traversed by the same test gas stream p with the same gas composition (humidity, CO ₂ , NO _x , ...), the measured value of the sample gas mass flow meter 5 can be based on the measured value of the diluent gas -Mass flow meter 9 are calibrated so that the (calibrated) measured values of the two flow meters match.

In addition, during the calibration, the proportion of components in the gas composition can be measured with the measuring probes 12a-12d, in particular a humidity, a CO2 proportion, a nitrogen proportion and / or a nitrogen oxide proportion. During the calibration the following measurement, one or more of the components in ^{8/17 7}

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Dilution gas flow v or the sample gas flow m are continuously determined, and the

Calibration can be corrected on the basis of known or previously determined cross-sensitivities if it is known that cross-sensitivities differ individually

Components.

Alternatively, the relative calibration can also be carried out using a dry, preconditioned zero gas of known composition, which is used as the test gas flow p via the zero gas inlet 14 in the same way as described above.

The relative calibration can be carried out in several steps, for example to carry out the calibration at different flow velocities.

Since the measuring cell 4 is not used during the calibration for the actual measurement of the actual measurement component (the raw gas inlet 2, via which the measurement component is supplied, is closed during the calibration), a portion of a component can be determined instead of the measurement probes 12a 12d, the measuring cell 4 can also be used. The prerequisite is that the measuring cell 4 has a sufficiently high cross sensitivity to this component. In particular, there is sometimes a pronounced cross-sensitivity to water vapor in photoacoustic measuring cells, which can be used to measure the moisture in the test gas stream. The respective cross sensitivity depends on the specific design of the measuring cell 4 and on the excitation frequency, which is usually designed to minimize interfering cross sensitivities. Nevertheless, certain cross-sensitivities cannot be completely avoided, so that it is often possible to measure certain components, which can be used here according to the invention.

After calibration, the actual measurement can then be started. The raw gas with the measuring component to be determined (e.g. soot particles) is fed as raw gas stream r to the mixing unit 3 via the raw gas inlet 2 and the raw gas path 1, mixed with the dilution gas stream v in the mixing unit 3 and then passed as a measuring gas stream m through the measuring cell 4. The measuring cell 4 generates a measuring signal. In the case of a photoacoustic measuring cell 4, the measuring gas is excited by means of laser radiation, and the acoustic signal obtained is recorded by a microphone. This signal (or the value evaluated from this signal) represents the measurement signal.

To get from the measurement signal to the measurement value of the measurement component, the current dilution must first be "calculated out". This is easily possible, since the dilution is constantly regulated to a known dilution via the flow controller 10 on the basis of the measured values of the sample gas mass flow meter 5 and the diluent gas mass flow meter 9. Based on this known dilution, the / 17 ⁸ '

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Measurement signal a (initially uncorrected) measured value determined. However, this uncorrected measured value can be faulty (despite the calibration being carried out), namely if a change in the proportion of one (or more) components has "shifted" the measured value of the mass flow meter relative to one another due to cross-sensitivity, so that the relative calibration previously performed under other conditions no longer true. During the measurement, a faulty relative calibration immediately causes the regulation of the flow controller 10 to be based on an incorrect measurement basis. This in turn affects the dilution rate, which immediately falsifies the measured value that was generated on the basis of this dilution rate.

In practice, this is always relevant, for example, when a portion of a component changes during a measurement compared to the portion during calibration. Investigations carried out by the applicant on a test arrangement have shown, for example, that a change in the ambient air (ie the air with which the calibration is carried out) from 22 ° C. at 30% atmospheric humidity during calibration to 40 ° C. at 75% atmospheric humidity during the measurement an incorrect measurement of the sample gas mass flow meter, designed as an orifice arrangement, of 0.11 l / min compared with the measurement of the calorimetric diluent gas mass flow meter (with a total flow of approx. 6 l / min). Applicants have calculated that in practice (depending on the dilution rate and the total flow) this deviation can lead to a dilution error of up to 33%.

The same problem can be relevant in practice, for example if a test drive leads from a tropical environment (calibration with high humidity) to a mountain region (low humidity) or vice versa. Calibration with ambient air at high humidity could also be problematic if the dilution air is then passed over an airflow dryer and dried during the measurement.

To compensate for this problem, the different effects of the changed moisture on the diluent gas mass flow meter and the sample gas mass flow meter are determined, and these effects are mapped in the correction function. During the measurement, the moisture of the dilution air flow is continuously measured with the moisture sensor 12b. As soon as the humidity differs from the value measured during calibration, the relative calibration is adjusted with the correction function and the measuring differences between the diluent gas mass flow meter and the sample gas mass flow meter are compensated.

Corresponding correction functions can be used not only for the humidity, but also for other components of the diluent gas stream v, the / 17

AV-3953 AT requires adjustments upon knowledge of the teachings of this disclosure in the area of

Knowledge of an average specialist.

A correction function can be used not only for components of the dilution air flow v, but generally for components whose proportions only affect one of the mass flow meters. This must be taken into account in particular if the corresponding component is supplied with the raw gas flow r and is therefore present in the measurement gas flow m which flows through the measurement gas mass flow meter 5, but not in the dilution gas flow v which flows through the dilution gas mass flow meter 9. In this case too, an incorrect measurement can occur due to the cross-sensitivity of the measuring gas mass flow meter 5 to the component, which measurement was not compensated for by the relative calibration. In connection with the exhaust gas measurement of internal combustion engines, the CO ₂ portion and the moisture portion in the raw gas stream r are particularly relevant in this context. In particular, CO ₂ in the raw gas to be measured has a noticeable effect on the output value of mass flow meters, both with thermal mass flow meters and with orifice plates.

In order to be able to correct the effects of changes in the CO ₂ concentration in the measurement result, according to the invention the CO ₂ portion in the measurement gas flow m is measured with the CO ₂ sensor. If the CO ₂ content changes, the measured value or the dilution rate is corrected on the basis of previously determined cross-sensitivities.

In a similar way, a correction function for other components in the raw gas stream r, for example a changed humidity, a changed nitrogen content or a changed content of nitrogen oxides, can be implemented, with appropriate additional sensors on the measurement gas path 13 and / or on the dilution gas path 7 and / or on Raw gas path 1 must be provided.

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Reference numerals:

Raw gas path 1

Raw gas inlet 2

Mixing unit 3

Measuring cell 4

Sample gas mass flow meter 5

Sample gas pump 6

Dilution path 7

Diluent gas inlet 8

Diluent gas mass flow meter 9

Flow controller 10

Computing unit 11

Measuring probe 12

Sample gas path 13

Zero gas inlet 14

Switch valve 15

Exhaust outlet 16

Raw gas flow r

Diluent gas stream v

Sample gas flow m

Test gas flow p / 17

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Claims (17)

claims 1. Device for measuring a measuring component contained in a raw gas stream (r), in particular for particle measurement, the device comprising a raw gas path (1) that runs from a raw gas inlet (2) to a mixing unit (3), a measuring gas path (13) that from the mixing unit (3) via a measuring cell (4), a measuring gas mass flow meter (5) and a measuring gas pump (6), and a dilution path (7) leading from a dilution gas inlet (8) via a dilution gas mass flow meter (9) and a flow controller (10) runs to the mixing unit (3), wherein the raw gas stream (r) and a dilution gas stream (v) in the mixing unit (3) can be mixed to form a measuring gas stream (m) with which measuring gas stream (m) the measuring cell (4) can be flowed through, characterized in that the device has a computing unit (11) with which, based on a measured value determined by the measuring cell (4), a correction function for a cross-sensitivity of the diluent gas mass flow ussmessers (9) and / or a cross-sensitivity of the measuring gas mass flow meter (5) to at least one component of the dilution gas flow (v) and / or the raw gas flow (r) is applicable. 2. Device according to claim 1, characterized in that the measuring cell (4) has a photoacoustic cell. 3. Device according to claim 1 or 2, characterized in that the diluent gas mass flow meter (9) and the measuring gas mass flow meter (5) operate according to a different measuring method. 4. Device according to one of claims 1 to 3, characterized in that the diluent gas mass flow meter (9) operates according to a calorimetric measuring method and / or that the measuring gas mass flow meter (5) operates according to a differential pressure-based measuring method, the measuring gas mass flow meter ( 5) is designed in particular as an orifice plate or an orifice plate block. 5. Device according to one of claims 1 to 4, characterized in that on the dilution path (7) and / or on the raw gas path (1) and / or on the measurement gas path (13) at least one measuring probe (12) for the at least one component of the dilution gas flow ( v) and / or the raw gas stream (r) is provided. 6. The device according to claim 5, characterized in that at least one measuring probe (12) is selected from the following group: CO ₂ probe (12a), moisture sensor (12b), nitrogen sensor (12c), nitrogen oxide sensor (12d). 13/17 AV-3953 AT 7. Device according to one of claims 1 to 6, characterized in that the dilution path (7) upstream of the dilution gas mass flow meter (9) is preferably switchable to a zero gas inlet (14) by means of a switching valve (15). 8. A method for calibrating a device according to one of claims 1 to 7, characterized in that the method comprises the following steps: Generating a test gas flow (p) which flows through at least the dilution gas mass flow meter (9) and the measurement gas mass flow meter (5), - determining the proportion of a component in the test gas stream (p), - Determining a measurement deviation between the measured value of the diluent gas mass flow meter (9) and the measured value of the sample gas mass flow meter (5), and - Determining a correction function for a cross sensitivity of the dilution gas mass flow meter (9) and / or a cross sensitivity of the measurement gas mass flow meter (5) to at least one component of the test gas flow (p). 9. The method according to claim 8, characterized in that the proportion of the component is determined by means of a measuring probe (12). 10. The method according to claim 8, characterized in that the proportion of the component with the measuring cell (4) is determined on the basis of a known cross sensitivity of the measuring cell (4) to the component. 11. The method according to any one of claims 8 to 10, characterized in that the component is selected from the following group: moisture (H ₂ O), carbon dioxide (CO ₂ ), nitrogen (N), nitrogen oxides (NOx). 12. The method according to any one of claims 8 to 11, characterized in that the test gas stream (p) is obtained from the ambient air. 13. The method according to any one of claims 8 to 11, characterized in that the test gas stream (p) is fed via a zero gas inlet (14). 14. The method according to any one of claims 8 to 13, characterized in that the proportion of the component in the test gas stream (p) is regulated. 15. A method for determining a measured value of a measurement component contained in a raw gas stream with a device according to one of claims 1 to 7, the method being characterized by the following steps: Passing a raw gas stream (r) via the raw gas inlets (2) to the mixing unit (3), 14/17 AV-3953 AT - in the mixing unit (3) mixing the raw gas stream (r) with a dilution gas stream (v) to a measuring gas stream (m), - guiding the sample gas flow (m) over the measuring cell (4), - determining a measurement signal from the measuring cell (4), Determining the proportion of at least one component in the raw gas stream (3) and / or the dilution gas stream (v) and / or the measuring gas stream (m), - determining a correction function for a cross sensitivity of the dilution gas mass flow meter (9) and / or a cross sensitivity of the measurement gas mass flow meter (5) to the at least one component, - Apply the correction function to the measuring signal of the measuring cell (4) to determine the measured value of the measuring component. , -14- 15/17 AVL List GmbH 1.1 16/17 AVL List GmbH 1.1 17/17 LAST DRAWINGS