DE202019101137U1 - Simultaneous measurement of SO2 concentration, NO2 concentration and NO concentration in a gas mixture - Google Patents

Abstract

Device (1, 23) for simultaneously measuring an SO ₂ concentration, an NO ₂ concentration and an NO concentration in a gas mixture, comprising at least one measuring arrangement (2) with at least one measuring chamber (3) receiving a part of the gas mixture, wherein the measuring arrangement (2) for measuring the SO ₂ concentration and the NO ₂ concentration in the part of the gas mixture containing in the measuring chamber (3) is set up, characterized by at least one further measuring arrangement (9, 24) with at least one another part of the gas mixture receiving further measuring chamber (10), wherein the further measuring arrangement (9, 24) is arranged for measuring the NO concentration in the further measuring chamber (10) containing further part of the gas mixture.

Description

Technical area

The invention relates to a device for simultaneously measuring an SO ₂ concentration, an NO ₂ concentration and an NO concentration in a gas mixture, comprising at least one measuring arrangement with at least one measuring chamber receiving a part of the gas mixture, wherein the measuring arrangement for measuring the SO ₂ Concentration and the NO ₂ concentration is set up in the part of the gas mixture contained in the measuring chamber.

State of the art

Combustion gases or flue gases are generated during combustion processes in plants and machines, which as a rule are not allowed to enter the environment of a plant or machine untreated due to legal requirements. To be able to check whether the pollutant emissions of such a plant or machine meet the legal requirements, the combustion gases can be analyzed continuously or at predetermined intervals in order to determine the proportion of a particular pollutant in the combustion exhaust gases. For measuring a pollutant, such as sulfur dioxide (SO ₂ ), nitrogen dioxide (NO ₂ ) and nitrogen monoxide (NO), various measurement techniques or measuring instruments are used.

In addition, automatic analyzers for elemental analysis, in particular for the determination of a carbon and sulfur content in a sample, are known, which usually operate according to a combustion process. The sample to be examined is brought to an ignition temperature by heating, for example using an inductive heating method. In a gas stream, such as pure oxygen, the constituents carbon and sulfur then burn to carbon dioxide and sulfur dioxide. In a downstream gas sensor, these substances can be detected.

The reaction products carbon dioxide and sulfur dioxide show a temporal concentration course, which increases with the beginning of the combustion and drops again after a maximum. The entire combustion process usually takes about 60 seconds. This peak profile of the concentration can be integrated in a downstream electronics, wherein the integral of the gas concentrations is proportional to the carbon dioxide or sulfur dioxide concentration in the sample. In order to obtain the most accurate and reproducible result, the response speed of the gas sensor must be as small as possible, so that delays are largely prevented. In general, the non-dispersive infrared absorption (NDIR) method has become established for the required gas sensor technology.

Such an NDIR gas sensor is for example made of EP 0 794 423 A1 known. The radiation emitted by an infrared radiation source in this case passes through a measuring cuvette in which a gas mixture is located, and impinges on the opposite end of the cuvette on an infrared-sensitive gas sensor. The attenuation of the electromagnetic radiation by the gas mixture enclosed in the cuvette is, according to Lambert-Beer's law, a measure of the concentration of a gas component to be measured. The time behavior of the photometric gas sensor depends essentially on the rinsing time of the cuvette and the time behavior of a signal technically connected to the gas sensor transmitter.

The sensitivity of a gas sensor is determined, among other sizes, by the cuvette length. An extension of the cuvette causes due to the higher amount of trapped gas between the radiation source and radiation sensor increased sensitivity of the gas sensor. However, the absorption coefficient of sulfur dioxide in the IR range is very small. In order to be able to detect low sulfur dioxide concentrations (<1 ppm) in the sample gas, therefore, long measuring cells with a large chamber volume are required. For this reason, in the EP 0 794 423 A1 proposed a cuvette of variable length to adapt the detector to altered concentrations.

A change in the cuvette length before a measurement, however, is hardly practical when used in automatic analyzers, since, for example, the sulfur content of the sample is usually unknown before the measurement. In addition, it has been shown that in particular the time behavior of a gas sensor when used in automatic analyzers limits the length of the cuvette. However, gas sensors are only suitable for a relatively small measuring range with a defined cuvette length. Therefore, in automatic analyzers often more detectors are used with different Küvettenlängen for the required measuring ranges, which on the one hand increases the design effort and on the other hand adversely affects the response time by the extended rinsing time of multiple cuvettes. In addition, an extension of the cuvette due to the attenuation of the infrared radiation by incomplete reflection on the cuvette walls anyway tight limits are set. For this reason, longer cuvettes for NDIR gas sensors are often provided with an expensive gold layer for improved IR reflection.

wobei I die konzentrationsabhängige Strahlungsintensität am jeweiligen Messdetektor, I₀ die Strahlungsintensität an einem Referenzdetektor, α der Absorptionskoeffizient des Gasgemischs, c die Konzentration der jeweiligen Gaskomponente und L die Länge der Messkammer bzw. Messküvette sind. In automatic analyzers, depending on the application, for example, samples with very high and very low sulfur dioxide concentrations occur. At high concentrations, these can produce 0.2% to 10% by volume sulfur dioxide in the gas mixture, while small concentrations require detection of less than 1 ppm sulfur dioxide in the gas mixture. Conventionally, several independent gas sensors are required because the dynamic range of a conventional gas sensor is not sufficient for both ranges. The reason for this behavior lies in the so-called Lambert-Beer's law $$I\left(c\right)=I_0\cdot e^{-\alpha cL}.$$

where I is the concentration-dependent radiation intensity at the respective measuring detector, I _{0 is} the radiation intensity at a reference detector, α is the absorption coefficient of the gas mixture, c is the concentration of the respective gas component and L is the length of the measuring chamber or measuring cuvette.

With increasing concentration c the respective gas component, the radiation intensity I (c) initially changes very much and then comes, with increasing concentration, in the saturation. In this saturation range, accurate measurements are no longer possible. Therefore, gas sensors with a short measuring cuvette are conventionally used for high concentrations, while measuring cuvettes as long as possible are used for the measurement of small concentrations of the gas component.

Conventional gas sensors usually have insufficient time response for use in automated analyzers because they are not adapted to such rapid changes in concentration. It has been found that a measurement frequency of> 5 Hz, better> 10 Hz, is required, which on the one hand requires a special adaptation of the evaluation electronics and on the other hand limits an extension of the cuvette and thus an improvement of the detection limit.

Other disadvantages of the known NDIR technique, for example, a large cross-sensitivity by overlapping the sulfur dioxide absorption band in the IR region with other gases. In particular, water vapor is very critical here and leads to incorrect measurements. For this purpose, reagents must be used on the automated analyzer, which serve to absorb the resulting water vapor and consume over time.

NDIR gas sensors use thermal radiators and thermal sensors that are very sensitive to ambient temperature changes. NDIR gas sensors typically use the AC method at a frequency of 1 Hz to 10 Hz to reduce these temperature effects. Due to the low modulation frequency, the temporal behavior of the NDIR gas sensors is severely limited. T90 times, i. the time it takes for a gas sensor to reach 90% of the jump after a temperature jump is less than 0.5 seconds, which is difficult to achieve, resulting in a high level of noise.

For the selective measurement of sulfur dioxide, for example, to prevent a response to carbon dioxide, special and expensive IR filters are required. These filters often do not work sufficiently narrowband, which can lead to a cross-sensitivity, for example to carbon dioxide, which usually has to be eliminated by means of computational algorithms. This results in additional measurement inaccuracies.

The increasingly demanding requirements of the industry, especially in the measurement of smallest sulfur levels in metallic samples, requires a significant reduction in the detection limit and an increase in measurement accuracy, which with the known NDIR technology due to the mentioned physical and technological limits can be reached.

DE 10 2010 023 453 B3 discloses a gas analyzer device for measuring gas concentrations in a gas mixture. The gas analyzer device comprises a measuring cuvette for receiving the gas mixture and an optoelectronic measuring arrangement for measuring the concentration of a gas component of the gas mixture. The measuring arrangement is set up to illuminate the measuring chamber with electromagnetic radiation and to detect the electromagnetic radiation emerging from the measuring chamber. Gas concentration measurement can be done using ultraviolet light.

DE 10 2016 108 267 A1 discloses an apparatus for measuring a sulfur dioxide concentration (SO ₂ concentration), a nitrogen dioxide concentration (NO ₂ concentration) and a nitrogen monoxide concentration (NO concentration) in a mixed gas comprising a measuring arrangement having a single gas mixture receiving measuring chamber, the measuring arrangement for measuring the said concentrations in the gas mixture contained in the measuring chamber is set up.

Disclosure of the invention

An object of the invention is to provide a device for simultaneously measuring a SO ₂ - To provide concentration, a NO ₂ concentration and an NO concentration in a gas mixture with lower cross sensitivities.

This task is solved by the independent protection claim. Advantageous embodiments are given in the dependent claims, the following description and the figures, these embodiments, taken alone or in various combinations of at least two of these embodiments together may constitute a further developing or advantageous aspect of the invention.

An apparatus according to the invention for simultaneously measuring an SO ₂ concentration, an NO ₂ concentration and an NO concentration in a gas mixture has at least one measuring arrangement with at least one measuring chamber receiving part of the gas mixture, the measuring arrangement for measuring the SO ₂ concentration and the NO ₂ concentration in the part of the gas mixture contained in the measuring chamber is established. Furthermore, the device according to the invention has at least one further measuring arrangement with at least one further measuring chamber receiving a further part of the gas mixture, wherein the further measuring arrangement for measuring the NO concentration is set up in the further part of the gas mixture contained in the further measuring chamber.

With the device according to the invention, the measurement of the SO ₂ concentration and the NO ₂ concentration are carried out simultaneously with the (first) optoelectronic measuring arrangement and the measurement of the NO concentration with the separate further (second) optoelectronic measuring arrangement. As a result, the measurement of the SO ₂ concentration, the NO ₂ concentration and the NO concentration with the device according to the invention is less sensitive to cross sensitivities between the individual measuring channels (SO ₂ measuring channel, NO ₂ -Masskanal, NO measuring channel) with each other, thereby With the device according to the invention a more accurate measurement of the SO ₂ concentration, the NO ₂ concentration and the NO concentration in the gas mixture, in particular in the ppm range, can be done.

For simultaneous measurement of the concentrations with the two measuring arrangements, a part of the gas mixture to be analyzed is introduced into each measuring chamber, so that the compositions of the parts of the gas mixture to be analyzed in the two measuring chambers are identical. The gas mixture may be, for example, an exhaust gas of a combustion

The (first) measuring arrangement can be designed as a photometer or have such. The measuring chamber of this measuring arrangement can be designed as a gas cuvette or measuring cuvette, which can be transilluminated with electromagnetic radiation in the longitudinal direction by means of at least one radiation source of the measuring arrangement. The measuring chamber may have a fixed length with respect to a main direction of the electromagnetic radiation passing through it. Alternatively, the length of the measuring chamber can be variable.

The further (second) measuring arrangement can be designed as a photometer or have such a photometer. The further measuring chamber of this measuring arrangement can be designed as a gas cuvette or measuring cuvette, which can be transilluminated with electromagnetic radiation in the longitudinal direction by means of at least one radiation source of the measuring arrangement. The further measuring chamber may have a fixed length with respect to a main direction of the electromagnetic radiation passing through it. Alternatively, the length of the further measuring chamber can be variable.

The device according to the invention can be used, for example, for the analysis of a combustion exhaust gas of a plant or machine or in pollutant emission measurement technology or in an automatic analyzer described above.

According to an advantageous embodiment, the device has at least one gas supply device connected to the measuring chambers, which is set up to simultaneously supply the measuring chambers with the gas mixture. In order to be able to carry out the simultaneous determination of the SO ₂ concentration, the NO ₂ concentration and the NO concentration not only at static gas component concentration values in the gas mixture but also at dynamic gas component concentration values, the gas component concentrations in both optical measuring chambers should be identical at all times , For this purpose, the measuring chambers should be operated in parallel by means of the gas supply device and the gas flows are kept equal by both measuring chambers, which can be ensured by the simultaneous supply of the measuring chambers with the gas mixture. The gas supply device may have at least one gas supply line communicating with both measuring chambers and at least one gas discharge line communicating with the two measuring chambers. Closing valves may be arranged on these lines, which can be closed after flushing the measuring chambers with the gas mixture in order to have static gas component concentration values in the measuring chambers to be able to measure and measure. Alternatively, the closing valves may be opened or absent so that the gas mixture continuously and uniformly flows through the measuring chambers during the simultaneous measurement of the SO ₂ concentration, the NO ₂ concentration and the NO concentration, so that dynamic gas component concentration values are present and measured can.

According to a further advantageous embodiment, a chamber volume of the measuring chamber corresponds to a chamber volume of the further measuring chamber. This also makes possible a simple, simultaneous determination of the SO ₂ concentration, the NO ₂ concentration and the NO concentration not only for static gas component concentration values but also for dynamic gas component concentration values, since the same measurement conditions are present in the measuring chambers, so that no calculation compensation is required different volumes of the measuring chambers must be made.

According to a further advantageous embodiment, the measuring arrangement has at least one narrow-band radiation source for generating electromagnetic radiation having a first measurement wavelength which corresponds to a wavelength of a maximum of an absorption band specific for SO ₂ , at least one narrow-band radiation source for generating electromagnetic radiation through the measurement chamber with a second measurement wavelength, which corresponds to a wavelength of a maximum of an absorption band specific for NO ₂ , and at least one sensor unit for detecting electromagnetic radiation emerging from the measurement chamber at the first measurement wavelength and the second measurement wavelength. The use of narrowband radiation sources eliminates the need for additional filter elements to ensure spectral selectivation. Alternatively, the measuring arrangement can have at least one broadband radiation source for generating electromagnetic radiation which has the first measuring wavelength and the second measuring wavelength. The sensor unit of the measuring arrangement can have at least one radiation sensor, with which both measuring wavelengths can be detected, or for each measuring wavelength, a separate radiation sensor. The latter has the advantage that additional filter elements which ensure spectral selectivation are not required. The optical radiation sources of the measuring arrangement are arranged relative to the measuring chamber such that the measuring chamber can be transilluminated with the electromagnetic radiation that can be generated by the radiation sources. The sensor unit of the (first) measuring arrangement is arranged relative to the measuring chamber and the radiation sources such that the electromagnetic radiation emerging from the measuring chamber can be detected with it.

The (first) measuring arrangement can be set up to measure a concentration of at least one further gas component of the gas mixture at a measuring wavelength which is outside a wavelength range assigned to the respective absorption band. As a result, an n-channel operation of the device for measuring n-gas components can be realized. Also compensation of cross sensitivities can be useful by using several measurement wavelengths.

The (first) measuring arrangement can be set up, the concentration of the SO ₂ gas component and / or the NO ₂ gas component either at a maximum measuring wavelength which corresponds to a wavelength of a maximum of an absorption band specific for the respective gas component or at most by a predetermined size slightly deviates from the wavelength of the maximum, or to measure at least one side edge measuring wavelength, which is in a wavelength range associated with a side edge of the absorption band and beyond the predetermined size of the wavelength of the maximum deviates. As a result, different concentrations of the particular gas component to be measured over a larger concentration range at a fixed predetermined length of the measuring chamber can be detected very accurately. In this case, a length of the measuring chamber is understood to be the length of the measuring chamber with respect to the direction of the electromagnetic radiation passing through the measuring chamber. If the concentration of the respective gas component lies in a lower range, the determination of the concentration of the gas component can be carried out using the maximum measuring wavelength. If the concentration of the respective gas component is in a higher range, the determination of the concentration of the gas component can be carried out using the side edge measurement wavelength. Thus, the concentration of the respective gas component in the range of a single gas component specific absorption band can be measured at two different measurement wavelengths and with a fixed length of the measurement chamber.

The fact that the maximum measuring wavelength corresponds to the maximum wavelength of the absorption band specific for the respective gas component or deviates slightly from the maximum wavelength by a predetermined value is intended to mean that the maximum measuring wavelength is either identical to the wavelength of the maximum of the absorption band or from the wavelength of the maximum of the absorption band by a predetermined size, for example by a maximum of +/- 10% or by a maximum of +/- 5% the half-width of the absorption band, slightly different. It is known to the person skilled in the art that such an absorption band is not peak-shaped in the region of its maximum, so that a slight deviation of the maximum measuring wavelength from the wavelength of the maximum of the absorption band in determining the concentration of the gas component in comparison to a determination of this concentration the exact wavelength of the maximum of the absorption band would lead to an only slightly different measurement result. A slight deviation of the maximum measurement wavelength from the wavelength of the maximum of the absorption band should be understood to mean that the maximum measurement wavelength is not in the region of a side edge of the absorption band, which is characterized by a steeper course of the absorption band. A determination of the concentration of the respective gas component would lead to a measurement result in this region of the absorption band which, in particular with respect to the measurement accuracy, differs more clearly from the measurement result when determining the concentration of the gas component at the maximum measurement wavelength.

The fact that the at least one side edge measuring wavelength lies in the wavelength range assigned to one side flank of the absorption band and deviates beyond the predetermined size beyond the maximum wavelength is intended to mean that the side flank measuring wavelength is clearer, that is to say more than the predetermined size, for example more than +/- 5% or more than +/- 10% of the half-width of the absorption band, deviates from the wavelength of the maximum of the absorption band. The measuring arrangement can also be set up to measure, depending on the respective concentration of the respective gas component, either at the maximum measuring wavelength or at one of at least two side-edge measuring wavelengths, each lying in the region of a side edge of the absorption band, wherein the side-edge measuring wavelengths in the range the same side edge or in the wavelength ranges of different side edges of the absorption band can lie.

The fact that the (first) measurement arrangement can be set up to measure the concentration of the respective gas component either at the respective maximum measurement wavelength or at the at least one sidewall measurement wavelength means that the measurement arrangement measures the concentration of the gas component at the measurement wavelength that is dependent the respective concentration of the gas component provides a more accurate value of the concentration of the gas component. This is the maximum measurement wavelength at a lower concentration of the respective gas component, and the side edge measurement wavelength at a higher concentration of the gas component.

According to a further advantageous embodiment, the further measuring arrangement comprises at least one gas discharge lamp for generating the further measuring chamber transilluminating electromagnetic radiation having a third measuring wavelength corresponding to a wavelength of a maximum of NO specific absorption band, and at least one further sensor unit for detecting from the further measuring chamber exiting electromagnetic radiation at the third measuring wavelength. Among other things, the gas discharge lamp generates a selective electromagnetic radiation that is absorbed by NO. The sensor unit of the further (second) measuring arrangement can have at least one radiation sensor, with which the third measuring wavelength can be detected. The gas discharge lamp is arranged relative to the further measuring chamber such that the further measuring chamber can be transilluminated with the electromagnetic radiation that can be generated by the gas discharge lamp. The sensor unit of the further measuring arrangement is arranged relative to the further measuring chamber and the gas discharge lamp such that the electromagnetic radiation emerging from the further measuring chamber can be detected with it.

The (second) measuring arrangement can be set up to measure a concentration of at least one further gas component of the gas mixture at a measuring wavelength which is outside a wavelength range associated with the absorption band of the NO gas component. As a result, an n-channel operation of the device for measuring n-gas components can be realized. Also compensation of cross sensitivities can be useful by using several measurement wavelengths.

According to a further advantageous embodiment, the further measuring arrangement has at least one narrow-band filter unit located in a beam path between the gas discharge lamp and the further measuring chamber, which only transmits electromagnetic radiation in a narrow-band frequency range which has the maximum wavelength of the NO-specific absorption band. In particular interfering radiation components of the electromagnetic radiation emitted by the gas discharge lamp can be filtered out of this electromagnetic radiation with the frequencies of which lie outside the NO absorption band. The filter unit may have at least one narrow-band interference filter.

According to a further advantageous embodiment, the further measuring arrangement at least one first beam splitter irradiated with electromagnetic radiation transmitted by the narrow-band filter unit and at least one first reference sensor unit irradiated with an electromagnetic partial beam emanating from the beam splitter. To detect low NO concentrations it is necessary to obtain a very good signal stability at zero point. Through the use of the first reference sensor unit in front of the measuring chamber and a comparison of the measuring signals of the first reference sensor unit with measuring signals of the sensor unit of the further measuring arrangement, additional information about a soiling state of the interior of the measuring chamber is obtained. These changes in the measuring chamber can lead to an undesirable zero-point drift, which must be prevented. The use of the second reference sensor unit thus provides an improvement in the zero-point stability of the NO concentration measurement.

According to a further advantageous embodiment, the further measuring arrangement has at least one second beam splitter irradiated with electromagnetic radiation emerging from the further measuring chamber, at least one second reference sensor unit irradiated with an electromagnetic beam emerging from the second beam splitter and at least one in a beam path between the second beam splitter and the second Reference sensor unit located on another filter unit, which filters out of the electromagnetic beam part of a narrow-band frequency range having the wavelength of the maximum of the NO specific absorption band. In addition, within the radiation band of the gas discharge lamp are non-selective radiation components, which are absorbed by the NO in the measuring chamber, which disturbs the measurement of the NO concentration. The further filter unit filters out the selective radiation in the region of the NO absorption band from the electromagnetic radiation emerging from the measuring chamber, while the non-selective radiation of this electromagnetic radiation reaches the second reference sensor unit. In contrast, the sensor unit of the further measuring arrangement receives both the selective and the non-selective radiation. From a comparison of the measurement signals of the sensor unit of the further measurement arrangement and the measurement signals of the second reference sensor unit, the disturbance of the NO concentration by the nonselective radiation components can thus be reduced or eliminated.

According to a further advantageous embodiment, at least one radiation source of the measuring arrangement is designed as a UV light-emitting diode, wherein the sensor unit of the measuring arrangement is set up for detecting UV radiation. For example, a radiation source of the measuring arrangement can be designed as a UV light-emitting diode for NO ₂ measurement, which emits electromagnetic radiation at 405 nm, while the other radiation source of the measuring arrangement is designed as a UV light-emitting diode for SO ₂ measurement, the electromagnetic radiation at 285 nm emitted. This allows the device to operate on the basis of non-dispersive UV absorption (NDUV). Sulfur dioxide has a strong absorption band in the UV range at 285 nm, which is not influenced by other gases such as water vapor or carbon dioxide. Thus, in this spectral range, a selective SO ₂ measurement without filters or reagents can be realized. Carbon dioxide has no absorption band in this UV range, which is why the device according to this embodiment is also not suitable for the measurement of carbon dioxide. The UV light emitting diode preferably emits narrow band in the UV spectral range. The usable LED technology for a present purpose is still relatively young. A disadvantage of the conventional UV LEDs is their limited life. In continuous operation at nominal current, the manufacturer's information is about 1000 hours. This is far too little for industrial applications in an automated analyzer. The automatic analyzers must work without interruptions for one to two years in continuous operation. To be able to meet this service life requirement, the UV light-emitting diode is preferably always switched on only when a sample is being driven. Between the test cycles, the UV light-emitting diode preferably remains switched off.

According to a further advantageous embodiment, the device has at least one signaling and control electronics connected to the measurement arrangements, which is set up for evaluating measurement signals generated by the measurement arrangements and / or for controlling and / or regulating the measurement arrangements during a measurement process.

The control and / or regulating electronics can additionally be set up to detect during the measuring process whether or not the concentration of the SO ₂ gas component or of the NO ₂ gas component exceeds a respectively predetermined concentration limit value, and to carry out the concentration measurement at the respective maximum measuring wavelength if the concentration of the respective gas component does not exceed the concentration limit, and to perform the concentration measurement at the side edge wavelength when the concentration of the respective gas component exceeds the concentration threshold. The control and / or regulating electronics can thus be set up to carry out the respective concentration measurement as a function of the respective concentration of the respective gas component either at the maximum measuring wavelength or at the side edge measuring wavelength. For recording, Whether the concentration of the respective gas component exceeds the predetermined concentration limit value or not, the control and / or regulating electronics can control the measuring arrangement such that a preliminary concentration measurement at the maximum measuring wavelength and / or the side edge measuring wavelength is performed. The control and / or regulating electronics can compare the provisional value of the concentration of the respective gas component with the predetermined concentration limit value. If the concentration of the respective gas component does not exceed the concentration limit value, ie if the gas component has a lower concentration, the measuring arrangement is set up to determine an exact value for the concentration of the gas component using only the maximum measuring wavelength. If, however, the concentration of the respective gas component exceeds the concentration limit value, ie if a higher concentration of the gas component is present, the control and / or regulating electronics are set up to determine an exact value for the concentration of the gas component with the exclusive use of the side edge measuring wavelength. For example, a value for the concentration of the respective gas component can be determined at the maximum measuring wavelength and at the same time at the side edge measuring wavelength, wherein the control and / or regulating electronics can be set up to compare at least one of the determined concentration values with the predetermined concentration value and depending on the comparison result, to select a concentration value from the two detected concentration values as the actual concentration value.

In addition, the control and / or regulating electronics can be set up to carry out a reference measurement at the side flank wavelength simultaneously during the respective concentration measurement at the maximum wavelength. Since the side edge wavelength is in the region of an edge of the respective absorption band, the side edge wavelength or the electromagnetic radiation with the side edge wavelength thus undergoes little absorption by the gas mixture and can therefore serve as the reference wavelength for the reference measurement. As the concentration of the respective gas component in the gas mixture continues to increase, the sidewall wavelength may become the measurement wavelength. In this high concentration range, the measurement of the concentration of the respective gas component is performed without reference. However, since the measuring effect is very high, error influences, which would have to be compensated by a reference, are lower in this case. Therefore, the reference measurement at high concentrations of the respective gas component can be dispensed with.

The control and / or regulating electronics can furthermore be set up to detect a radiation intensity of a radiation source of the measuring arrangement designed as a light-emitting diode via the sensor unit of the (first) measuring arrangement or another radiation sensor and to supply the light-emitting diode with an electric current as a function of the detected radiation intensity supply. By means of the sensor unit of the measuring arrangement, a reference signal without absorption attenuation can thus be recorded in addition to the measurement of the respective concentration of the respective gas component and supplied to the control and / or regulating electronics. In the case of using the other radiation sensor, the electromagnetic radiation generated by the light emitting diode can be passed through a beam splitter from which a portion of the electromagnetic radiation is guided to the further radiation sensor. This makes it possible to monitor the radiation intensity of the electromagnetic radiation or the light-emitting diode produced by the light-emitting diode. The monitoring of the radiation intensity by means of the further radiation sensor, which is technically connected to the control and / or regulating electronics, can serve, for example, to detect the aging of the light-emitting diode. At arbitrary, regular intervals, for example once a day, the residual radiation intensity R _{residual of} the light-emitting diode can thus be determined and compared with the last residual radiation intensity value R *. If the difference ΔR = R * - R _{rest is} greater than a predetermined limit value ΔR *, a diode current I _D supplied to the light-emitting diode can be increased so that the radiation intensity then returns to the original value. This measure also ensures that the signal / noise ratio and thus also the detection limit remain constant over the entire operating life of the light emitting diode. To be able to exploit this control process, for example, 20% of the nominal power of the light-emitting diode can be started. The aging of the LED at this stage is greatly reduced by the low electrical power. Only towards the end of the life of the light-emitting diode, when 100% of the rated power is reached, can be expected with a failure of the light emitting diode. About an analysis software can then be generated by the control and / or control electronics, a signal that is pointed to a maintenance or soon required replacement of the light emitting diode. If the UV light-emitting diode is operated in DC operation, the time response of the control and / or regulating electronics is given, for example, only by the low-pass behavior of a preamplifier of the control and / or regulating electronics and averaging in a microcontroller of the control and / or regulating electronics can be less than 100 ms.

To distinguish the individual spectral components, which are generated with the different light-emitting diodes of the (first) measuring arrangement, the control and / or regulating electronics can be set to turn on and off the light-emitting diodes in a time-shifted manner, so that only one of the light-emitting diodes in one predetermined time interval is switched on while the other LED is turned off. This operation can be carried out continuously, since the control and / or regulating electronics specifies the on and off times for the light-emitting diodes and thus the times of signal generation are known. To compensate for electrical offset voltages, a time dark phase can be specified with the control and / or regulating electronics, in which all light-emitting diodes are switched off and thus the offset can be determined and compensated.

• - $Mod\left(S{O}_2\right)=\frac{Ref\left(D_1\right)-Mess\left(D_2\right)}{Ref\left(D_1\right)},$
  
• - $Mod\left(N{O}_2\right)=\frac{Ref\left(D_1\right)-Mess\left(D_2\right)}{Ref\left(D_1\right)}$
  
  und
• - $Mod\left(NO\right)=\frac{Ref\left(D_3\right)-Mess\left(D_4\right)}{Ref\left(D_3\right)}$
  

zu ermitteln, wobei Ref(D₁) ein Referenzmesssignal der Referenzsensoreinheit der Messanordnung, Mess(D₂) ein Messignal der Sensoreinheit der Messanordnung, Ref(D₃) ein Referenzmesssignal der zweiten Referenzsensoreinheit der weiteren Messanordnung und Mess(D₄) ein Messignal der Sensoreinheit der weiteren Messanordnung ist, wobei die Steuer und/oder Regelelektronik zudem eingerichtet ist, aus den Modulationswerten die SO₂-Konzentration, die NO₂-Konzentration und die NO-Konzentration jeweils unter Verwendung eines Polynoms n-ten Grades zu ermitteln. Die Modulationswerte sind also die Basis für die einzelnen Konzentrationsberechnungen. Die Modulationswerte sind vorliegend normierte Rohmesswerte der Sensoreinheiten und Referenzsensoreinheiten. Aus den Modulationswerten lässt sich die jeweilige Konzentration über ein Polynom n-ten Grades berechnen. Dazu kann eine Linearisierungsfunktion c(M) = α · M + b · M² +··· +x · Mⁿ durch experimentelle Werte mit unterschiedlichen Gaskonzentrationen c ermittelt werden, wobei c die jeweilige Konzentration und M die Modulation ist. Um eine möglichst gute Linearisierungsfunktion c(M) zu erhalten, sollten die einzelnen Konzentrationsänderungen so gewählt werden, dass die Modulationsänderungen ΔM über den gesamten Messbereich konstant sind.According to a further advantageous refinement, the measuring arrangement has at least one beam splitter irradiated with electromagnetic radiation emanating from the narrow-band radiation sources and at least one reference sensor unit irradiated with an electromagnetic beam emanating from the beam splitter, the control and / or regulating electronics being set up from the sensor units and the measurement signals generated by the reference sensor units, the modulation values

• - $MOd\left(S{O}_2\right)=\frac{Ref\left(D_1\right)-Mess\left(D_2\right)}{Ref\left(D_1\right)}.$
  
• - $MOd\left(N{O}_2\right)=\frac{Ref\left(D_1\right)-Mess\left(D_2\right)}{Ref\left(D_1\right)}$
  
  and
• - $MOd\left(NO\right)=\frac{Ref\left(D_3\right)-Mess\left(D_4\right)}{Ref\left(D_3\right)}$
  

Ref (D ₁ ) is a reference measuring signal of the reference sensor unit of the measuring arrangement, measuring (D ₂ ) is a measuring signal of the sensor unit of the measuring arrangement, Ref (D ₃ ) is a reference measuring signal of the second reference sensor unit of the further measuring arrangement, and measuring (D ₄ ) is a measuring signal of Sensor unit of the further measuring arrangement is, wherein the control and / or control electronics is also arranged to determine from the modulation values, the SO ₂ concentration, the NO ₂ concentration and the NO concentration in each case using a polynomial n-th degree. The modulation values are therefore the basis for the individual concentration calculations. The modulation values are presently standardized raw measured values of the sensor units and reference sensor units. From the modulation values, the respective concentration can be calculated using an n-th degree polynomial. For this purpose, a linearization function c (M) = α * M + b * M ² + ··· + x * M ⁿ by experimental values with different gas concentrations c where c is the respective concentration and M is the modulation. In order to obtain the best possible linearization function c (M), the individual concentration changes should be chosen such that the modulation changes .DELTA.M are constant over the entire measuring range.

• - $Mod*\left(S{O}_2\right)=Mod\left(S{O}_2\right)-Mod\left(N{O}_2\right)$
  
  und
• - $Mod*\left(NO\right)=Mod\left(NO\right)-Mod\left(S{O}_2\right)-Mod\left(N{O}_2\right)$
  

zu ermitteln. Befinden sich verschiedene Gaskomponenten in dem Gasgemisch, so ergeben sich durch spektroskopische Überlappungen Querempfindlichkeiten (CS=Cross Sensitivity), die zu einer messbaren Modulation führen. Eine Verrechnung dieser Querempfindlichkeiten kann nur über die korrigierten Modulationswerte erfolgen, da ansonsten die Konzentrationswerte verfälscht werden würden. Im Nullpunkt würde eine Modulationsänderung ΔM(CS) durch eine Störgaskomponente zu einer geringeren Konzentrationsänderung führen, während im Ausschlag (bei gleicher Modulationsänderung) ein wesentlich höherer Fehler bzw. eine stärkere Konzentrationsänderung von Δc₂ entstehen würde. Daher werden die korrigierten Modulationswerte berechnet, um diesen Messfehler zu vermeiden.According to a further advantageous embodiment, the control and / or control electronics is set up, from the modulation values the corrected modulation values

• - $MOd*\left(S{O}_2\right)=MOd\left(S{O}_2\right)-MOd\left(N{O}_2\right)$
  
  and
• - $MOd*\left(NO\right)=MOd\left(NO\right)-MOd\left(S{O}_2\right)-MOd\left(N{O}_2\right)$
  

to investigate. If different gas components are present in the gas mixture, cross sensitivities (CS = cross sensitivity) result due to spectroscopic overlaps, which lead to a measurable modulation. An offsetting of these cross-sensitivities can only take place via the corrected modulation values, since otherwise the concentration values would be falsified. At zero point would be a modulation change .DELTA.M (CS) lead by an interfering gas component to a lower concentration change, while in the rash (at the same modulation change) a much higher error or a greater concentration change of Δc ₂ would arise. Therefore, the corrected modulation values are calculated to avoid this measurement error.

list of figures

• 1 eine schematische Darstellung eines Ausführungsbeispiels für eine erfindungsgemäße Vorrichtung;
• 2 ein Diagramm zu einem Ausführungsbeispiel für eine Linearisierungsfunktion c(M);
• 3 ein Diagramm zu einem Abschnitt der in 2 gezeigten Linearisierungsfunktion c(M); und
• 4 eine schematische Darstellung eines weiteren Ausführungsbeispiels für eine erfindungsgemäße Vorrichtung.

In the following, the invention will be explained by way of example with reference to the attached figures with reference to preferred exemplary embodiments, wherein the features explained below may represent a further developing or advantageous aspect of the invention, taken alone or in different combinations with one another. Show it:

• 1 a schematic representation of an embodiment of a device according to the invention;
• 2 a diagram of an embodiment for a linearization function c (M);
• 3 a diagram to a section of in 2 shown linearization function c (M); and
• 4 a schematic representation of another embodiment of an inventive device.

Detailed description of the figures

In the figures, the same or functionally identical components are provided with the same reference numerals. A repeated description of such components may be omitted below.

1 shows a schematic representation of an embodiment of a device according to the invention 1 for simultaneously measuring an SO ₂ concentration, an NO ₂ concentration and an NO concentration in a gas mixture.

The device 1 has a measuring arrangement 2 with a part of the gas mixture receiving measuring chamber 3 on. The measuring arrangement 2 is for measuring the SO ₂ concentration and the NO ₂ concentration in the in the measuring chamber 3 containing part of the gas mixture. The measuring chamber 3 is designed as a cuvette.

The measuring arrangement 2 has a narrowband radiation source 4 for generating the measuring chamber 3 Transmitted electromagnetic radiation having a first measurement wavelength corresponding to a wavelength of a maximum of an absorption band specific for SO ₂ , a narrow-band radiation source 5 for generating the measuring chamber 3 fluoroscopic electromagnetic radiation having a second measurement wavelength corresponding to a wavelength of a maximum of a NO ₂ specific absorption band, and a sensor unit 6 for detecting from the measuring chamber 3 exiting electromagnetic radiation at the first measurement wavelength and the second measurement wavelength. Every radiation source 4 or. 5 the measuring arrangement 2 is designed as a UV light-emitting diode, wherein the sensor unit 6 the measuring arrangement 2 is set up to detect UV radiation.

In addition, the measuring arrangement 2 one with the narrowband radiation sources 4 and 5 Outgoing electromagnetic radiation irradiated beam splitter 7 and one with one of the beam splitter 7 outgoing electromagnetic component beam irradiated reference sensor unit 8th on.

The device 1 further includes another measuring arrangement 9 with a further measuring chamber receiving a further part of the gas mixture 10 on. The further measuring arrangement 9 is for measuring the concentration of NO in that in the other measuring chamber 10 containing further part of the gas mixture. The further measuring chamber 10 is designed as a cuvette. One chamber volume of the measuring chamber 3 corresponds to a chamber volume of the other measuring chamber 10 ,

The further measuring arrangement 9 also has a DC powered gas discharge lamp 11 for generating the further measuring chamber 10 transmitted electromagnetic radiation having a third measurement wavelength corresponding to a wavelength of a maximum of a NO specific absorption band. In addition, the further measuring arrangement points 9 another sensor unit 12 for detecting from the other measuring chamber 10 leaking electromagnetic radiation at the third measurement wavelength.

Furthermore, the further measuring arrangement 9 one in a beam path between the gas discharge lamp 11 and the other measuring chamber 10 located, narrow-band filter unit 13 which transmits electromagnetic radiation only in a narrow band frequency range having the wavelength of the maximum of the NO specific absorption band.

In addition, the further measuring arrangement 9 one with out of the other measuring chamber 10 exiting electromagnetic radiation irradiated second beam splitter 14 one with one of the second beam splitter 14 outgoing electromagnetic beam irradiated second reference sensor unit 15 and one in a beam path between the second beam splitter 14 and the second reference sensor unit 15 located further filter unit 16 which filters out from the electromagnetic partial beam a narrow band frequency range which has the wavelength of the maximum of the NO specific absorption band.

The device 1 also has one with the measuring chambers 3 and 10 connected gas supply device 17 on, which for simultaneously supplying the measuring chambers 3 and 10 is set up with the gas mixture. The gas supply device 17 has a communicating with the measuring chambers 3 and 10 connected gas supply line 18 and one communicating with the measuring chambers 3 and 10 connected gas discharge line 19 on.

Furthermore, the device 1 a signal with the measuring arrangements 2 and 9 Connected control and / or regulating electronics 20 on to evaluating with the measuring arrangements 2 and 9 generated measuring signals and / or for controlling and / or regulating the measuring arrangements 2 and 9 is set up during a measurement process.

• - $Mod\left(S{O}_2\right)=\frac{Ref\left(D_1\right)-Mess\left(D_2\right)}{Ref\left(D_1\right)},$
  
• - $Mod\left(N{O}_2\right)=\frac{Ref\left(D_1\right)-Mess\left(D_2\right)}{Ref\left(D_1\right)}$
  
  und
• - $Mod\left(NO\right)=\frac{Ref\left(D_3\right)-Mess\left(D_4\right)}{Ref\left(D_3\right)}$
  

zu ermitteln, wobei Ref(D₁ ) ein Referenzmesssignal der Referenzsensoreinheit 8 der Messanordnung 2, Mess(D₂ ) ein Messignal der Sensoreinheit 6 der Messanordnung 2, Ref(D₃ ) ein Referenzmesssignal der zweiten Referenzsensoreinheit 15 derweiteren Messanordnung 9 und Mess(D₄ ) ein Messignal der Sensoreinheit 12 der weiteren Messanordnung 9 ist. Die Steuer und/oder Regelelektronik 20 ist zudem eingerichtet, aus den Modulationswerten die SO₂-Konzentration c₃ , die NO₂-Konzentration c₂ und die NO-Konzentration c₁ jeweils unter Verwendung eines Polynoms n-ten Grades zu ermitteln.The control and / or control electronics 20 is set up, off of the sensor units 6 and 12 and the reference sensor units 8th and 15 generated measurement signals the modulation values

• - $MOd\left(S{O}_2\right)=\frac{Ref\left(D_1\right)-Mess\left(D_2\right)}{Ref\left(D_1\right)}.$
  
• - $MOd\left(N{O}_2\right)=\frac{Ref\left(D_1\right)-Mess\left(D_2\right)}{Ref\left(D_1\right)}$
  
  and
• - $MOd\left(NO\right)=\frac{Ref\left(D_3\right)-Mess\left(D_4\right)}{Ref\left(D_3\right)}$
  

to determine where Ref ( D ₁ ) a reference measurement signal of the reference sensor unit 8th the measuring arrangement 2 , Measuring ( D ₂ ) a measuring signal of the sensor unit 6 the measuring arrangement 2 , Ref ( D ₃ ) a reference measurement signal of the second reference sensor unit 15 the further measuring arrangement 9 and measuring ( D ₄ ) a measuring signal of the sensor unit 12 the further measuring arrangement 9 is. The control and / or control electronics 20 is also set up, from the modulation values, the SO ₂ concentration c ₃ , the NO ₂ concentration c ₂ and the NO concentration c ₁ each using an n-th degree polynomial.

• - $Mod*\left(S{O}_2\right)=Mod\left(S{O}_2\right)-Mod\left(N{O}_2\right)$
  
  und
• - $Mod*\left(NO\right)=Mod\left(NO\right)-Mod\left(S{O}_2\right)-Mod\left(N{O}_2\right)$
  

zu ermitteln.Furthermore, the control and / or control electronics 20 set the modulation values from the modulation values

• - $MOd*\left(S{O}_2\right)=MOd\left(S{O}_2\right)-MOd\left(N{O}_2\right)$
  
  and
• - $MOd*\left(NO\right)=MOd\left(NO\right)-MOd\left(S{O}_2\right)-MOd\left(N{O}_2\right)$
  

to investigate.

In 1 are top left drive currents 21 and 22 for driving the radiation sources 4 and 5 shown by the control unit 20 be generated. The control and / or regulating electronics 20 is thus set up, the radiation sources 4 and 5 time-shifted alternating on and off, so that only one of the radiation sources 4 and 5 is turned on in a given time interval, while the other radiation source 4 or. 5 is off.

2 shows a diagram of an embodiment for a linearization function c (M). It is the concentration c the respective gas component SO ₂ , NO ₂ and NO with respect to the modulation M applied. From the means of control and / or control electronics off 1 or 4 determined modulation values can be the respective concentration of the respective gas component over a polynomial n-th degree calculate. For this purpose, a linearization function c (M) = α * M + b * M ² + ··· + x * M ⁿ by experimental values with different gas concentrations c be determined. In order to obtain the best possible linearization function c (M), the individual concentration changes should be chosen such that the modulation changes .DELTA.M are constant over the entire measuring range.

3 shows a diagram to a section of in 2 shown linearization function c (M). If different gas components are present in the gas mixture, cross sensitivities (CS = cross sensitivity) result due to spectroscopic overlaps, which lead to a measurable modulation. A settlement of these cross-sensitivities can only on the with the control and / or control electronics 1 or 4 determined corrected modulation values take place, since otherwise the concentration values would be falsified. At zero point would be a modulation change .DELTA.M (CS) by an interfering gas component to a concentration change of Δc ₁ lead, while in the rash (with the same modulation change) a much higher error of Δc ₂ would arise. Therefore, the corrected modulation values are calculated to avoid this measurement error.

4 shows a schematic representation of another embodiment of a device according to the invention 23 for simultaneously measuring an SO ₂ concentration, an NO ₂ concentration and an NO concentration in a gas mixture.

The device 23 differs solely from the in 1 shown embodiment, that the further measuring arrangement 24 one with the narrow band filter unit 13 transmitted electromagnetic radiation irradiated first beam splitter 25 and one with one of the beam splitter 25 outgoing electromagnetic partial beam irradiated first reference sensor unit 26 having. Between the first beam splitter 25 and the first reference sensor unit 26 is a filter 27 connected. Incidentally, in order to avoid repetition, the above description also applies 1 directed.

LIST OF REFERENCE NUMBERS

1

device

2

measuring arrangement

3

Measuring chamber of 2

4

Radiation source of 2

5

Radiation source of 2

6

Sensor unit of 2

7

Beam splitter of 2

8th

Reference sensor unit of 2

9

further measuring arrangement of 1

10

further measuring chamber of 9

11

Gas discharge lamp of 9

12

Sensor unit of 9

13

Narrow-band filter unit of 9

14

second beam splitter of 9

15

second reference sensor unit of 9

16

further filter unit of 9

17

Gas supply

18

Gas supply line of 17

19

Gas discharge line of 17

20

Control and / or regulating electronics

21

Drive current for 4 . 5

22

Drive current for 4 . 5

23

device

24

further measuring arrangement of 23

25

first beam splitter of 24

26

first reference sensor unit of 24

27

Filter from 24

c

concentration

c ₁

NO concentration

c ₂

NO ₂ concentration

c ₃

SO ₂ concentration

c _x

concentration value

Δc ₁

concentration change

Ac ₂

concentration change

M

modulation

.DELTA.M

modulation change

.DELTA.M (CS)

Modulation change due to cross sensitivities

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0794423 A1 [0005, 0006]
• DE 102010023453 B3 [0015]
• DE 102016108267 A1 [0016]

Claims (12)

Device (1, 23) for simultaneously measuring an SO ₂ concentration, an NO ₂ concentration and an NO concentration in a gas mixture, comprising at least one measuring arrangement (2) with at least one measuring chamber (3) receiving a part of the gas mixture, wherein the measuring arrangement (2) for measuring the SO ₂ concentration and the NO ₂ concentration in the part of the gas mixture containing in the measuring chamber (3) is set up, characterized by at least one further measuring arrangement (9, 24) with at least one another part of the gas mixture receiving further measuring chamber (10), wherein the further measuring arrangement (9, 24) is arranged for measuring the NO concentration in the further measuring chamber (10) containing further part of the gas mixture. Device (1, 23) according to Claim 1 , characterized by at least one gas supply device (17) connected to the measuring chambers (3, 10), which is set up to simultaneously supply the measuring chambers (3, 10) with the gas mixture. Device (1, 23) according to Claim 1 or 2 , characterized in that a chamber volume of the measuring chamber (3) corresponds to a chamber volume of the further measuring chamber (10). Device (1, 23) according to one of Claims 1 to 3 , characterized in that the measuring arrangement (2) at least one narrow-band radiation source (4) for generating the measuring chamber (3) radiated electromagnetic radiation having a first measurement wavelength corresponding to a wavelength of a maximum of an SO ₂ specific absorption band, at least one narrow-band radiation source (5) for generating the electromagnetic radiation radiated through the measuring chamber (3) with a second measuring wavelength which corresponds to a wavelength of a maximum of an absorption band specific for NO ₂ , and at least one sensor unit (6) for detecting electromagnetic emerging from the measuring chamber (3) Radiation at the first measurement wavelength and the second measurement wavelength has. Device (1, 23) according to one of Claims 1 to 4 , characterized in that the further measuring arrangement (9, 24) comprises at least one gas discharge lamp (11) for generating electromagnetic radiation which transilluminates the further measuring chamber (10) and has a third measuring wavelength which corresponds to a wavelength of a maximum of a NO specific absorption band, and at least one further sensor unit (12) for detecting from the further measuring chamber (10) exiting electromagnetic radiation at the third measuring wavelength. Device (1, 23) according to Claim 5 , characterized in that the further measuring arrangement (9, 24) has at least one narrow-band filter unit (13) located in a beam path between the gas discharge lamp (11) and the further measuring chamber (10), which transmits electromagnetic radiation only in a narrow-band frequency range, which has the wavelength of the maximum of the NO specific absorption band. Device (1, 23) according to Claim 6 , characterized in that the further measuring arrangement (9, 24) comprises at least one first beam splitter (25) irradiated with electromagnetic radiation transmitted through the narrow-band filter unit (13) and at least one first reference sensor unit irradiated with an electromagnetic beam emerging from the beam splitter (25) ( 26). Device (1, 23) according to one of Claims 1 to 7 , characterized in that the further measuring arrangement (9, 24) comprises at least one second beam splitter (14) irradiated with electromagnetic radiation emerging from the further measuring chamber (10), at least one second reference sensor unit irradiated with an electromagnetic beam emerging from the second beam splitter (14) (15) and at least one in a beam path between the second beam splitter (14) and the second reference sensor unit (15) located further filter unit (16) which filters out of the electromagnetic beam part of a narrowband frequency range, the wavelength of the maximum of NO specific Has absorption band. Device (1, 23) according to one of Claims 1 to 8th , characterized in that at least one radiation source (4, 5) of the measuring arrangement (2) is designed as a UV light-emitting diode, wherein the sensor unit (6) of the measuring arrangement (2) is adapted to detect UV radiation. Device (1, 23) according to one of Claims 1 to 9 characterized by at least one control and / or regulating electronics (20) which are connected with the measurement arrangements (2, 9, 24) and which are capable of evaluating measuring signals generated by the measuring arrangements (2, 9, 24) and / or for controlling and / or or rules of the measuring arrangements (2, 9, 24) is set up during a measuring process. Device (1, 23) according to Claim 10 , characterized in that the measuring arrangement (2) at least one outgoing from the narrow-band radiation sources (4, 5) comprising electromagnetic radiation irradiated beam splitter (7) and at least one with one of the beam splitter (7) outgoing electromagnetic beam irradiated reference sensor unit (8), wherein the control and / or control electronics (20) is set up, from the sensor units (6, 12) and the reference sensor units (8, 15, 26) generated measurement signals, the modulation values $$MOd\left(S{O}_2\right)=\frac{Ref\left(D_1\right)-Mess\left(D_2\right)}{Ref\left(D_1\right)}.$$

$$MOd\left(N{O}_2\right)=\frac{Ref\left(D_1\right)-Mess\left(D_2\right)}{Ref\left(D_1\right)}$$

and $$MOd\left(NO\right)=\frac{Ref\left(D_3\right)-Mess\left(D_4\right)}{Ref\left(D_3\right)}$$

where Ref (D ₁ ) is a reference measuring signal of the reference sensor unit (8) of the measuring arrangement (2), measuring (D ₂ ) is a measuring signal of the sensor unit (6) of the measuring arrangement (2), Ref (D ₃ ) is a reference measuring signal of the second reference sensor unit (15) of the further measuring arrangement (9, 24) and measuring (D ₄ ) is a measuring signal of the sensor unit (12) of the further measuring arrangement (9, 24), wherein the control and / or regulating electronics (20) is also set up from the Modulation values to determine the SO ₂ concentration, the NO ₂ concentration and the NO concentration each using an n-th degree polynomial. Device (1, 23) according to Claim 11 , characterized in that the control and / or control electronics (20) is arranged, from the modulation values, the corrected modulation values $$MOd*\left(S{O}_2\right)=MOd\left(S{O}_2\right)-MOd\left(N{O}_2\right)$$

and $$MOd*\left(NO\right)=MOd\left(NO\right)-MOd\left(S{O}_2\right)-MOd\left(N{O}_2\right)$$

to investigate.

Images