Energy-optimized measurement method for determining co2 concentration in air atmosphere

Abstract

The invention relates to a measuring method, which permits the energy-optimized determination of the carbon dioxide concentration in the air atmosphere by means of a mobile and energy-sufficient CO2 measuring device (4). For this purpose, the CO2 measuring instrument (4) has, in addition to the CO2 sensor (2), which is designed as an optical sensor, an environmental sensor (3), which is designed as a semiconductor sensor chip (7), by means of which environmental parameters of the air atmosphere (6) can be continuously monitored. In this case, the operation of the CO2 sensor (2) is started by a measuring controller (8) of the CO2 measuring device (4) for measuring a corresponding CO2 concentration in the air atmosphere (6) only if the environmental sensor (3) has detected a significant change in the measured environmental parameter in the air atmosphere (6). By means of this scheme, the CO2 concentration in the air atmosphere (6) by means of the CO2 measuring device (4) can be determined and recorded in an energy-saving manner over a long period of time and with sufficient accuracy (see Figure 3).

Description

Technical Field

[0001] The invention relates to an energy-optimized measurement method for determining the carbon dioxide (CO2) concentration in an air atmosphere. In the method, the CO2 concentration is determined with the aid of a CO2 sensor. The CO2 sensor can preferably be designed in the form of a photoacoustic sensor. The CO2 sensor can measure carbon dioxide, CO2, specifically, i.e., in particular, isolated from other gases of the air atmosphere.

[0002] The invention also relates to a sensor system for measuring the CO2 concentration in air. The sensor system comprises a CO2 sensor designed specifically to determine the concentration of carbon dioxide (CO2) in an air atmosphere.

[0003] Finally, the invention relates to a mobile and energy-autonomous CO2 measuring instrument. The measuring instrument can preferably be designed as a handheld measuring instrument and / or data logger. The CO2 measuring instrument has an electrical storage battery that enables the desired energy-autonomous operation. Background Art

[0004] In order to evaluate the indoor air quality (IAQ), in addition to temperature, air humidity, VOC concentration and particle count, the CO2 content in the air is also detected. The CO2 concentration in the air is an important parameter in order to evaluate the degree of air consumption or the health feeling of the people present and to take corresponding measures, such as for ventilation, if necessary. Conventionally used optical measurement methods are expensive and have a high energy requirement that does not allow practical battery operation.

[0005] For example, to measure the CO2 concentration in the air atmosphere, non-dispersive infrared sensors (NDIR sensors) have been frequently used so far. This is a spectroscopic gas sensor that uses infrared wavelengths to analyze a gas sample. Here, the concentration of the gas being sought is typically measured photoelectrically by the degree of absorption of a specific wavelength in the infrared spectrum. To this end, the light of an infrared source transmits the gas sample in a sample chamber, then transmits an optical IR filter and then impinges on an IR sensor that provides a measurement signal. This concept has been proven and is reliable, but the disadvantage is that sensors of this type show a relatively high current consumption in continuous operation. Therefore, NDIR sensors are generally not suitable for mobile, energy-autonomous use. Summary of the invention

[0006] Based on this background, the present invention aims to provide a CO2 sensor which is operated in a mobile measuring instrument, preferably a handheld measuring instrument, in battery operation, ie, autonomously by a voltage supply. The CO2 sensor should be designed to be energy-saving.

[0007] In order to achieve this object, according to the invention, claim 1 is characterized by a method for determining the CO2 concentration in an air atmosphere. In particular, according to the invention, in order to achieve this object, it is proposed in the measuring method as described at the outset that the CO2 sensor is operated in a discontinuous measuring mode, that environmental events are also continuously monitored (i.e., in particular detected) by means of a separate environmental sensor, in particular at regular time intervals, and that a corresponding measurement of the CO2 concentration is performed using the CO2 sensor only when the environmental sensor detects such an environmental event.

[0008] In other words, according to the invention, it is provided that the operation of the CO2 sensor is interrupted by a pause, the length and / or the timing of the pause being determined based on the measurement results obtained with the environmental sensor. In this case, the CO2 sensor and the environmental sensor can be part of a sensor system according to the invention, as described in more detail below.

[0009] The environmental sensor provided in addition to the CO2 sensor may preferably be based on a semiconductor sensor chip and / or be designed as a metal oxide semiconductor sensor, since this allows environmental events to be monitored relatively energy-efficiently and cost-effectively with sufficient frequency.

[0010] The method according to the invention advantageously allows the instantaneous temporal frequency of the measurements carried out with the CO2 sensor to be adjusted as required, i.e. to be designed variably. If the detected environmental events indicate strong changes in measured values, the frequency of the CO2 measurements can be increased; otherwise, the frequency can be reduced in order to save electrical energy that would otherwise be consumed for the operation of the CO2 sensor. The possible operating duration of the CO2 sensor can thus be significantly extended, which offers advantages to the user in the energy-autonomous and mobile design of the measuring system.

[0011] The measuring method according to the invention therefore has the advantage of reducing the energy requirement for reliable and continuous determination of the CO2 concentration. Thus, a CO2 sensor device of this type can be used in a battery-operated measuring instrument, in particular a CO2 data logger. Thus, the measuring instrument can be operated energy-self-sufficiently over a longer period of time, from a few hours to a few days or even a few months.

[0012] According to the invention, this object is also achieved by further advantageous embodiments according to the dependent claims.

[0013] For example, provision can be made for the discontinuous measuring mode to be characterized in that the CO 2 sensor is not in operation or is at least operated in energy-saving mode during the measuring method on average for at least 30% of the time, preferably even for at least 80% of the time.

[0014] However, the discontinuous measuring operation of the CO2 sensor is also characterized in that the CO2 sensor is only operated during the measuring method when at least one environmental parameter undergoes a change. Thus, if the environmental sensor detects such a (significant) change in the environmental parameter to be measured, this detection can trigger the measuring operation of the CO2 sensor.

[0015] Therefore, according to an advantageous design, the detection of an environmental event by means of the environmental sensor can trigger the measurement of the CO 2 concentration by means of the CO 2 sensor.

[0016] The detection of environmental events and / or the change of at least one environmental parameter can be based on multiple parameters; for example, based on a change in the gas composition of the air atmosphere and / or based on a change in the temperature of the air atmosphere and / or based on a change in the humidity of the air atmosphere and / or based on a change in the concentration of volatile organic compounds (VOC) in the air atmosphere. Therefore, all these environmental events can be recognized by the sensor system as "changes in environmental parameters" or detected as "environmental events". Accordingly, the sensor system can then start the operation of the CO2 sensor with the actual measuring method in response to these changes / detections. Otherwise, the CO2 sensor, on the contrary, does not operate or at least operates in a sleep / energy-saving mode in order to save energy thereby.

[0017] The abbreviation VOC (volatile organic compounds) stands for volatile organic compounds. The substance group of VOC includes, for example, hydrocarbons, alcohols and organic acids. VOCs are practically always present in indoor air. Usually, the concentration of individual VOCs in interior spaces is relatively low and there is therefore no need to worry about health effects. Individual VOCs can have different effects; these range from dulling of the sense of smell and irritation of the respiratory tract and eyes, acute effects to long-term effects. This includes effects on the nervous system and allergy-inducing or allergy-enhancing properties. In indoor spaces, the total concentration of VOCs should be below 0.3 mg / m on average if no single standard value is exceeded. 3 For a large number of substances or substance groups from the VOC spectrum, standard values ​​are often predefined, which therefore take precedence over the overall assessment.

[0018] In this respect it should be emphasized that environmental events do not have to be specifically determined. For example, environmental events can be detected non-specifically using environmental sensors. Therefore, in this case it may not be clear which exact event, in particular which type of change in the air atmosphere, is actually detected using the environmental sensor. This is the case, for example, when the environmental sensor responds to changes in multiple parameters (i.e. it can be detected as an environmental event).

[0019] One embodiment of the method provides that the measurement data of the first measurement are interpolated with the CO2 sensor and the measurement data of the second measurement are interpolated with the CO2 sensor (in particular by the sensor system itself) to determine the instantaneous trend of the measured CO2 concentration. Alternatively or in addition to this, the measurement data of the first measurement can also be interpolated with the ambient sensor and the measurement data of the second measurement can be interpolated with the ambient sensor (in particular by the sensor system itself) to determine the instantaneous trend of the measured CO2 concentration. Based on such a trend, the temporal frequency of the CO2 measurements performed with the CO2 sensor can then be adjusted, i.e., for example, increased or decreased.

[0020] In this case, a preferred embodiment provides that the CO2 sensor is used to perform remeasurements at predetermined time intervals according to the determined trend, or is not used to perform remeasurements (depending on the course of the trend), in particular in order to save energy if necessary. In this case, the trend can be determined at regular intervals by remeasurements with the CO2 sensor, and the trend can thus be updated (in particular continuously) by evaluating the corresponding measurement results. It is also preferred that the CO2 sensor is not operated between the measurements of the CO2 concentration or is at least operated in an energy-saving mode.

[0021] In order to achieve this task, a sensor system as described at the beginning is also proposed. The sensor system can preferably be designed to perform the measurement method according to the invention as explained above. Such a sensor system according to the invention can be characterized in that the sensor system includes a preferably non-optical environmental sensor. For example, the environmental sensor can be based on a semiconductor sensor chip. In addition, the sensor system can include a measurement regulator, which can be designed in particular in the form of a microcontroller. The measurement regulator is designed to implement the measurement method according to the invention as described above or according to any one of the claims for this method. In other words, the measurement regulator can therefore control and / or read the CO2 sensor and the environmental sensor accordingly in order to perform the individual method steps.

[0022] As an alternative or in addition to these features, however, the sensor system according to the invention may also be characterized in that the sensor system comprises a non-optical surroundings sensor; as already mentioned, the surroundings sensor may preferably be based on a semiconductor sensor chip and / or be designed as a metal oxide semiconductor sensor. Furthermore, it may be characterized in that, in contrast, the CO2 sensor is designed as an optical sensor. In this case, the design as a photoacoustic sensor and / or as an NDIR sensor is preferred, since this allows a particularly precise and efficient (spatially and energetically) detection of the CO2 concentration.

[0023] Finally, it can also be provided that (particularly optical) CO2 sensors are designed for discontinuous measurement operation, so as to save energy compared with continuous operation. In such discontinuous measurement operation, the CO2 sensor can for example regularly and automatically not operate or at least operate in energy-saving mode.

[0024] In addition, it can be provided that the CO2 sensor is designed to detect the measured value only according to the measured value of the environmental sensor. In this case, the CO2 sensor therefore does not perform any measurement independently of the environmental sensor, but only performs measurement based on the measurement result provided by the environmental sensor.

[0025] In actual measuring operation, the environmental sensor can, for example, have an electrical energy consumption that is at least 25% lower, preferably at least 50% lower, than that of the CO2 sensor in measuring operation. Thus, in such a design, it is possible to benefit from energy-saving operation of the environmental sensor and still achieve a sufficiently precise time resolution of the current CO2 concentration. Measuring operation can be understood here as the difference from standby operation when the energy consumption is reduced and no measurement is performed in standby mode, or from the difference from placing the sensor in a stationary state without any energy consumption at all.

[0026] Preferably, the environmental sensor of the sensor system can include at least one metal oxide (MOX) semiconductor gas sensor element; this can preferably be designed in the form of a gas-sensitive metal oxide semiconductor layer. The environmental sensor can therefore be designed in particular as a metal oxide (MOX) semiconductor sensor.

[0027] Here, the function of the MOX gas sensor is based on the change of the conductivity of its gas-sensitive MOX semiconductor gas sensor element (which can be designed as a gas-sensitive thin layer in particular) due to the action of the gas. Since a variety of gases can cause such a change in principle, the measurement is necessarily not specific to each gas causing the change.

[0028] According to a particularly preferred design, the environmental sensor can detect at least two, or preferably even at least three, of the following gases in a non-specific manner: carbon monoxide (CO), hydrogen (H2), nitrogen monoxide (NO), nitrogen dioxide (NO2), ozone (O3), ammonia (NH3), sulfur dioxide (SO2), methane (CH4), propane (C3H8), alcohols (CXHYOH) (i.e., for example, ethanol (C2H5OH)) or other volatile organic compounds (VOCs), which have been described above. Non-specific detection also means that the environmental sensor can detect the presence of multiple of the above gases, but cannot force a distinction between the individual gases (two gases can trigger similar measurement results of the environmental sensor).

[0029] In order to improve the accuracy of the measurement results and thus also the energy-optimized operation of the sensor system, it can be provided in particular that the CO2 sensor has an integrated air humidity sensor and an integrated temperature sensor. More precisely, it can be achieved that the measurement result of the CO2 concentration provided by the CO2 sensor is temperature- and humidity-compensated.

[0030] The CO2 sensor of the sensor system can be designed as a photoacoustic sensor and / or an NIR sensor, in particular as an NDIR sensor (NIR stands for "near infrared", i.e., near infrared wavelength range). In other words, the CO2 sensor can therefore have an NIR light source that provides a measuring wavelength in the near infrared wavelength range (780 to 3000 nm).

[0031] Photoacoustic sensors are to be understood here in particular as sensors based on the measuring principle of photoacoustic spectroscopy (PAS). PAS is one of the most sensitive measuring methods for detecting gases and is based on the so-called photoacoustic effect. Here, energy is supplied to the gas sample in rapid sequence by light flashes. The resulting constant changes between heating and cooling in the gas sample (due to absorption of the light flashes) lead to alternating thermal expansion and contraction. These vibrations in the gas sample can be detected as sound waves under suitable circumstances, wherein a certain gas generates a characteristic frequency of the sound waves. This allows a very specific measurement of CO2.

[0032] NDIR sensors can be understood here in particular as non-dispersive infrared sensors. Such sensors can be understood as spectral measurement systems. NDIR sensors are often used for gas analysis. Such NDIR sensors can include, for example, an infrared radiator, a sample chamber, an optical wavelength filter and one or more infrared detectors.

[0033] Finally, the invention also proposes a mobile and energy-autonomous CO2 measuring instrument, which, as already mentioned at the beginning, can be designed as a handheld measuring instrument and / or a data logger (i.e. a device that can store measurement data over a longer period of time including the respective measurement time). The measuring instrument with an electric storage battery described at the beginning enables energy-autonomous operation and is characterized in that it comprises a sensor system according to the invention as described above or a sensor system according to the invention according to any one of the claims for the sensor system. In other words, the CO2 measuring instrument, i.e. in particular the measuring controller of the CO2 measuring instrument, can be designed to carry out, more precisely preferably continuously carry out, the measuring method according to the invention according to any one of the method claims.

[0034] In particular, when the CO2 measuring instrument is designed as a data logger, it can be suggested that the CO2 measuring instrument has an internal memory and is designed to store the measurement data detected by the CO2 sensor in the memory. Alternatively or in addition, the measuring instrument can also output such measurement data via a data interface. Here, the data interface of the measuring instrument can be designed to be wireless in particular. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will now be described in detail with reference to various exemplary embodiments, but the present invention is not limited to these exemplary embodiments. Other configurations of the present invention can be obtained from the following description of a preferred exemplary embodiment in conjunction with the general description, the claims and the drawings.

[0036] In the following description of various preferred embodiments of the invention, elements which correspond in their function are provided with identical reference numerals even in the case of different designs or shapes.

[0037] In the attached picture:

[0038] Figure 1 A schematic illustration showing an energy-saving solution for determining CO2 concentration according to the invention,

[0039] Figure 2 A detailed view over time of a typical measurement profile using the measuring method according to the invention is shown,

[0040] Figure 3 A second detailed view over time shows a typical measurement profile using the measuring method according to the invention,

[0041] Figure 4 A third detailed view over time shows a typical measurement profile using the measuring method according to the invention,

[0042] Figure 5 A schematic illustration of a measuring instrument according to the invention is shown. DETAILED DESCRIPTION

[0043] Figure 5 A mobile and energy-autonomous CO2 measuring instrument 4 designed according to the invention in the form of a handheld measuring instrument 5 is schematically illustrated. The CO2 measuring instrument 4 has an electrical storage battery 10, which provides electrical energy for the energy-autonomous operation of the measuring instrument 4. The measuring instrument 4 can thus be used mobile, i.e. independently of a stationary voltage supply, as a data logger 9, which stores the measured values ​​of the CO2 concentration determined by means of the CO2 sensor 2 of the measuring instrument 4 in an internal memory 14 of the measuring instrument 4. After the measurement has been carried out, the measured values ​​can be called up from the internal memory 14 via a data interface 15, including the corresponding measurement time.

[0044] The measuring device 4 includes not only a CO2 sensor 2 in the form of a photoacoustic sensor 11, which can specifically measure carbon dioxide, i.e. CO2, in an air atmosphere 6 surrounding the measuring device 4, separated from other gases present in the air atmosphere 6, but also an environmental sensor 3. The additional environmental sensor 3 is based on a semiconductor sensor chip 7 and is designed as a metal oxide semiconductor sensor 12. The composition of the air atmosphere 6 can be monitored by the environmental sensor 3, that is, detected in a sensory manner.

[0045] Figure 5 The CO2 measuring device 4 also has a measuring controller 8 designed as a microcontroller 13, which controls and reads the CO2 sensor 2 and the environmental sensor 3. The measuring controller 8 thus performs the measuring method according to the invention in cooperation with the two sensors 2, 3, wherein the CO2 sensor is used for the corresponding CO2 measurement only as required, depending on the measurement signal detected by the environmental sensor 3, at different times and in particular at different time intervals.

[0046] If with the help of Figure 1 , for which the environmental sensor 3 is used to continuously (e.g., at always the same time measurement intervals) perform measurements, so that environmental events, i.e., changes in environmental parameters in the air atmosphere 6, can be detected by the environmental sensor 3. Such environmental events can, for example, consist in a significant change in the gas composition of the air atmosphere 6. However, the environmental sensor 3 can also be designed, for example, to detect changes in the temperature of the air atmosphere 6 or changes in the humidity of the air atmosphere 6 or, for example, changes in the concentration of volatile organic gases (VOC) in the air atmosphere 6.

[0047] Due to the MOX technology used for the environmental sensor 3, the latter can carry out a continuous monitoring of the air atmosphere 6 in an extremely energy-saving manner, but has the disadvantage that environmental events can only be detected non-specifically with the environmental sensor 3. It may therefore be unclear which exact event, for example which type of change in the air atmosphere 6, the environmental sensor 3 has actually detected.

[0048] If just Figure 1 Although not illustrated, it is possible to detect in an energy-saving manner whether there are important environmental events or whether the air atmosphere 6 is relatively static using the environmental sensor 3: Figure 1 In region a), for example, only small measured value changes are detected by the surroundings sensor 3 (black dots), whereas in region b), relatively strong measured value changes are detected by the surroundings sensor 3 .

[0049] Figure 1The star symbol in the diagram illustrates the individual measurements performed with the CO2 sensor 2 at different times. As can be seen, the frequency of the measurements with the CO2 sensor 2 in area b) is increased due to relatively strong changes in the air atmosphere 6 detected with the environmental sensor 3. In other words, the CO2 sensor 2 is operated in a discontinuous measurement mode, wherein the individual measurement times are interrupted by pauses of different lengths. Environmental events are detected continuously at regular time intervals with the individual environmental sensors 3.

[0050] In this case, only when the environmental sensor 3 has detected an environmental event, i.e. a significant change in its measurement signal, is a corresponding measurement of the CO2 concentration performed by the CO2 sensor 2. As a result, the CO2 sensor is not operated at all during the measuring method on average for more than 30% of the time, thereby significantly saving electrical energy. This is because the CO2 sensor 2 is only operated during the measuring method when the above-mentioned environmental parameters (which are monitored by the environmental sensor 3) undergo significant changes.

[0051] Thus, between two measurements with the CO2 sensor, the measurement data of the environmental sensor 3 designed as a semiconductor gas sensor can be used to interpolate the CO2 trend. In this case, the energy consumption of the CO2 sensor only plays a secondary role, since the measurement with the CO2 sensor is only automatically carried out when necessary. The advantage of this solution according to the invention is that the energy requirement of the entire measuring method is reduced. However, it can still provide a reliable CO2 determination in a battery-operated sensor system 1, which can be designed, for example, as an IAQ (Indor Air Quality: indoor air quality) recorder.

[0052] This concept according to the invention is particularly advantageous Figure 2 Illustration: With the aid of the MOX measurement signal provided by the environmental sensor 3 and related to the corresponding composition of the air atmosphere 6, it is possible to detect the occurrence of an environmental event at a specified time, i.e., with the aid of a significant change in the MOX signal. Accordingly, the sensor system 1 reacts to this (more precisely, its measurement controller 8, which is designed to implement the measurement method according to the invention), by increasing the frequency of the CO2 measurement performed with the CO2 sensor 2, which Figure 2 As can be seen from the horizontal spacing of the vertical lines in , the vertical lines show the individual measurement times for the CO2 measurement.

[0053] Figure 3 and Figure 4A further example of a typical measurement situation is shown, in which the concept according to the invention offers advantages with regard to energy efficiency: Here, the dashed line represents the CO2 concentration recorded with the reference measuring system. It can also be seen here that the temporal frequency of the CO2 measurement changes as a function of the measurement signal of the environmental sensor 3 designed as a MOX sensor. In other words, the sensor system 1 intelligently selects the measuring time of the corresponding CO2 measurement with the CO2 sensor 2 itself based on the environmental events detected with its environmental sensor 3, so that the temporal curve of the CO2 concentration can be detected with sufficient accuracy and stored as measurement data in the internal memory 14 of the CO2 measuring device 4.

[0054] In summary, a measuring method is proposed which allows the energy-optimized determination of the carbon dioxide concentration in an air atmosphere using a mobile and energy-self-sufficient CO2 measuring instrument 4. For this purpose, the CO2 measuring instrument 4 has, in addition to a CO2 sensor 2 designed as an optical sensor, an environmental sensor 3 designed as a semiconductor sensor chip 7, by means of which an environmental parameter of the air atmosphere 6 can be continuously monitored. In this case, the operation of the CO2 sensor 2 is started by a measuring controller 8 of the CO2 measuring instrument 4 in order to measure the corresponding CO2 concentration in the air atmosphere 6 only when the environmental sensor 3 has detected a significant change in the measured environmental parameter in the air atmosphere 6. With this concept, the CO2 concentration in the air atmosphere 6 using the CO2 measuring instrument 4 can be determined and recorded in an energy-saving manner over long time intervals and with sufficient accuracy (see Figure 3 ).

[0055] Reference numerals list

[0056] 1 Sensor system

[0057] 2 CO2 sensor

[0058] 3 Environmental Sensors

[0059] 4 Mobile CO2 measuring instrument (energy self-sufficient due to its battery)

[0060] 5 Handheld measuring instruments

[0061] 6 Air atmosphere, such as indoor air

[0062] 7 Semiconductor sensor chip

[0063] 8 (1) Measurement Regulator

[0064] 9 Data logger

[0065] 10 (5) batteries

[0066] 11 Photoacoustic sensor and / or NDIR sensor

[0067] 12 MOX semiconductor sensor

[0068] 13 (1 of) Microcontrollers

[0069] 15 (5 of) internal memory

[0070] 15 (5) data interface

[0071] 16 Operating elements

[0072] 17 Display

[0073] 18 Temperature display

[0074] 19 CO2 Display

Claims

1. Energy-optimized measurement method for determining the CO2 concentration in the air atmosphere (6), --in, determining the CO2 concentration by means of a CO2 sensor (2), preferably in the form of a photoacoustic sensor (11), The CO2 sensor (2) is capable of measuring carbon dioxide, i.e. CO2, specifically, in particular separately from other gases of the air atmosphere (6), and is characterized in that: The CO2 sensor (2) is operated in a discontinuous measurement mode, - in addition, environmental events are continuously monitored, in particular at regular time intervals, by means of separate environmental sensors (3), - Preferably, the environmental sensor is based on a semiconductor sensor chip (7) and / or is designed as a metal oxide semiconductor sensor (12), and - Only when the environmental sensor (3) detects such an environmental event is a corresponding measurement of the CO2 concentration performed using the CO2 sensor (2).

2. The measuring method according to claim 1, wherein: The discontinuous measuring operation is characterized in that - the CO2 sensor (2) is not in operation or is operated in energy-saving mode during the measuring method on average for at least 30% of the time, preferably at least 80% of the time, and / or is characterized in that - The CO2 sensor (2) is operated during the measurement method only when at least one environmental parameter undergoes a change.

3. The measuring method according to claim 1 or 2, ——Wherein, the detection of an environmental event by means of the environmental sensor (3) triggers the measurement of the CO2 concentration by means of the CO2 sensor (2).

4. The measuring method according to any one of the preceding claims, --in, Detection of an environmental event and / or a change in at least one environmental parameter based on a change in the gas composition of the air atmosphere (6), and / or - based on a temperature change of the air atmosphere (6), and / or - based on changes in humidity of the air atmosphere (6), and / or - Based on the concentration change of volatile organic gases (volatile organic compounds = VOC) in the air atmosphere (6).

5. The measuring method according to any one of the preceding claims, - wherein the environmental event is detected in an unspecific manner using the environmental sensor (3), - in particular so that it is not clear which exact event, in particular which type of change in the air atmosphere (6), is actually detected using the environmental sensor (3).

6. The measuring method according to any one of the preceding claims, --in, interpolating the measurement data of the first measurement using the CO2 sensor (2) and interpolating the measurement data of the second measurement using the CO2 sensor (2) to determine the instantaneous trend of the measured CO2 concentration, ——Preferably, carrying out a new measurement with the CO2 sensor (2) at predetermined time intervals depending on the trend determined, or not carrying out a new measurement, in particular in order to thereby save energy, if necessary, - in particular, the determination of the trend is updated at regular intervals by re-measuring with the CO2 sensor (2) and evaluating the measurement results, - Preferably, the CO2 sensor (2) is not operated or is operated in an energy-saving mode between measurements of CO2 concentration.

7. A sensor system (1) for measuring the CO2 concentration in air, the sensor system comprising: a CO2 sensor (2) which is designed to specifically determine the concentration of carbon dioxide in the air atmosphere (6), It is characterized in that The sensor system (1) comprises a preferably non-optical environment sensor (3) which is based on a semiconductor sensor chip (7), and a measuring controller (8), in particular in the form of a microcontroller (14), and the measuring controller (8) is designed to carry out the measuring method according to any of the preceding claims, - Preferably and for this purpose the CO 2 sensor ( 2 ) and the ambient sensor ( 3 ) are activated and / or read out accordingly.

8. A sensor system (1) for measuring the CO2 concentration in air, in particular a sensor system (1) according to the preceding claim, comprising: a CO2 sensor (2) which is designed to specifically determine the concentration of carbon dioxide, CO2, in the air atmosphere (6), It is characterized in that The sensor system (1) comprises a non-optical environmental sensor (3), - Preferably, the environmental sensor is based on a semiconductor sensor chip (7) and / or is designed as a metal oxide semiconductor sensor (12), The CO2 sensor (2) is designed as an optical sensor, - preferably designed as a photoacoustic sensor (12) and / or an NDIR sensor (11), and - Optical CO2 sensors (2) are designed for discontinuous measurement operation, - Preferably, the CO2 sensor (2) is regularly and automatically deactivated or operated in energy-saving mode, and / or - designed to detect measured values, in particular solely based on measured values ​​of the environmental sensor (3).

9. The sensor system (1) according to any one of claims 7 or 8, wherein: The environmental sensor (3) has an electrical energy consumption during measuring operation that is at least 25% lower, preferably at least 50% lower, than that of the CO2 sensor (2) during measuring operation.

10. The sensor system (1) according to any one of claims 7 to 9, wherein: The environmental sensor (3) comprises at least one metal oxide (MOX) semiconductor gas sensor element (8), preferably in the form of a gas-sensitive metal oxide semiconductor layer and / or is designed as a metal oxide (MOX) semiconductor sensor (12). In particular, the environmental sensor (3) can non-specifically detect at least two, preferably at least three of the following gases: Carbon monoxide (CO), hydrogen (H2), nitric oxide (NO), nitrogen dioxide (NO2), ozone (O3), ammonia (NH3), sulfur dioxide (SO2), methane (CH4), propane (C3H8), alcohols (CXHYOH), such as ethanol (C2H5OH) or other volatile organic compounds (VOCs).

11. The sensor system (1) according to any one of claims 7 to 10, wherein: The CO2 sensor (2) has an integrated air humidity sensor and an integrated temperature sensor, - Preferably, the measurement result of CO2 concentration provided by the CO2 sensor (2) is temperature and humidity compensated.

12. The sensor system (1) according to any one of claims 7 to 10, wherein: The CO2 sensor (2) is designed as a photoacoustic sensor (11) and / or a NIR sensor (11), preferably wherein: The CO2 sensor (2) has a NIR light source.

13. A mobile and energy-autonomous CO2 measuring device (4), preferably designed as a handheld measuring device (5) and / or a data logger (9), --in, The CO2 measuring device (4) has an electrical storage battery (10) which enables energy-self-sufficient operation and is characterized in that The CO2 measuring instrument (4) comprises a sensor system (1) according to any one of claims 7 to 9, and / or The CO 2 measuring device ( 4 ), in particular the measuring controller ( 8 ) of the CO 2 measuring device ( 4 ), is designed to preferably continuously carry out the measuring method according to any one of claims 1 to 6 .

14. CO2 measuring instrument (4) according to the preceding claim, --in, The CO2 measuring instrument (4) is designed as a data recorder (9), - wherein the CO2 measuring device (4) has an internal memory (14) and / or a data interface (15), in particular a wireless one, and - wherein the CO2 measuring device (4) is designed to store the measurement data detected by the CO2 sensor (2) in the memory (14) and / or output it via the data interface (15).

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