AT526200A1 - Device for measuring an indoor air quality indicator - Google Patents

Abstract

A device for the innovative determination of an air quality indicator is described. According to one exemplary embodiment, the device has a computing unit (50) and sensors (51, 52, 53) for measuring temperature, air humidity and CO2 concentration, which are coupled to the computing unit (50). The computing unit (50) is designed to calculate a (single, meaningful) air quality indicator based on measured values for temperature, humidity and CO2 concentration.

Description

DEVICE FOR MEASURING AN INDOOR AIR QUALITY INDICATOR

TECHNICAL FIELD

[0001] The present description relates to the field of indoor air quality measurement.

clear.

BACKGROUND

[0002] On average, people spend more than 90 percent of their lives indoors, and consequently the quality of the indoor air not only has objective effects on people's well-being and health, but it also depends on the subjective comfort felt by a person in a room the (objectively measurable) indoor air quality. Interior spaces are not only private living spaces, but also offices.

classrooms, schools, hospitals, sports facilities, etc.

[0003] Guide values for indoor air must meet different requirements than limit values for outdoor air. A variety of different sources of pollutants are possible in individual indoor spaces and the different pollutants that may be of importance indoors are correspondingly numerous, while a small set of indicator pollutants is generally sufficient to assess the quality of the outside air. Limit values for a workplace refer to a temporary exposure of healthy people, while indoor guidelines also include vulnerable people who may be indoors (practically) all day.

stay in the room, have to keep an eye on it.

Known devices are able to measure various environmental parameters such as humidity (relative air humidity), temperature, oxygen concentration, carbon dioxide concentration, air pressure or even particles such as volatile organic compounds (VOC) indoors. The publication

EP 3404633 A1 describes a device in which various sensors are used for measurement

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of the environmental parameters mentioned are integrated into one device together with a smoke detector. This device is not only used for the (early) detection of fires, but also

also monitoring the air quality in a room.

[0005] However, the devices that are commercially available today are difficult to handle for interested consumers. In order to get an idea of the air quality in an interior, the user has to read out a variety of measured values and compare them with reference values. Even if the comparison with reference values can in principle be automated, this does not change the fundamental problem that the user has to keep an eye on a large number of parameters. The inventor has set himself the task of improving known concepts and devices for determining indoor air quality and developing a device for the consumer electronics market that provides the user with...

gives the opportunity to record the quality of the indoor air practically “at a glance”.

SUMMARY

[0006] The above-mentioned object is achieved by the device according to claim 1 or the method according to claim 11. Various embodiments and further

developments are the subject of the dependent claims.

A device for determining an air quality indicator is described below. According to one exemplary embodiment, the device comprises a computing unit and sensors for measuring temperature, humidity and CO2 concentration, which are coupled to the computing unit. The computing unit is designed to create a (single, exclusive) based on measured values for temperature, humidity and CO2 concentration.

to calculate a meaningful) air quality indicator.

Furthermore, a method for determining an air quality indicator is described. According to one embodiment, the method includes determining a first parameter that depends on measured CO2 concentrations and mapping the first parameter to a standardized first air quality value. The method further includes determining a second parameter, which depends on measured value pairs of temperature and humidity, and mapping the second parameter to a standardized second air quality value. The two standardized air quality values become one

a single measure that serves as an air quality indicator.

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BRIEF DESCRIPTION OF THE DRAWINGS

The exemplary embodiments described here can be better understood with reference to the following drawings and descriptions. The components shown in the drawings are not necessarily to scale; Instead, emphasis was placed on illustrating the principles underlying the exemplary embodiments. In addition, the same reference numerals denote in the drawings

corresponding parts.

[0010] Figure 1 shows, as an example, a table for classifying measured CO2 concentrations.

centers.

[0011] Figure 2 shows a diagram for visualizing a comfortable room climate

to Leusden and Freymark.

[0012] Figure 3 illustrates an example of a method for determining air quality.

indicator.

[0013] Figures 4 and 5 illustrate examples of the determination of a parameter dependent on temperature and humidity, which is included in the calculation of the air quality indicator.

flows.

6 illustrates tables for exemplary illustration of the normalization of the measured/calculated parameters in order to determine the normalized partial air quality values,

which are combined to form the air quality indicator you are looking for.

[0015] Figure 7 shows an example of a simplified block diagram of the air quality measurement

device.

[0016] Figure 8 illustrates an example of the device described here with a plug-in

Additional module.

DETAILED DESCRIPTION

[0017] The exemplary embodiments described here relate to a concept for determining

measurement of indoor air quality and processing by measuring various

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Environmental parameters, in particular temperature, humidity and carbon dioxide content and the processing of the measured environmental parameters into a single measure representing the air quality in the interior (air quality indicator), which enables a user to record the measurement result based on several individual parameters “at a glance”. The indicator can also be used to take certain measures

To control improvement of indoor air.

In the following, individual environmental parameters and their relevance for air quality will first be discussed. The carbon dioxide (CO2) concentration is an indicator of the impairment of indoor air quality caused by humans themselves. At a concentration of 0.1% based on volume (corresponds to 1000 ppm), around 20 percent of people find the quality of the indoor air to be unsatisfactory. As CO2 concentrations continue to rise, the percentage increases. The stated number of 1000 ppm is also known as the Pettenkofer number (named after the chemist and hygienist Max von Pettenkofer) and has also found its way into government regulations regarding air quality in workplaces. Increased CO2 concentrations arise when a room is used at high intensity and is insufficiently ventilated and has a significantly negative effect on the ability to concentrate and perform. With increasing concentration of CO2

The risk of suffering from sick building syndrome symptoms also increases.

[0019] There are no clear limits for those CO2 concentrations that impair subjective well-being and psychological and physical performance. However, studies have shown that as CO2 concentrations rise from around 800 ppm, the air quality people perceive continuously worsens. 5000 ppm is the limit above which a room should not be used for more than one hour per day. In a guideline issued by the Austrian Ministry of Agriculture, Forestry, Environment and Water Management (currently Climate Protection Ministry, BMK), classes of CO2 pollution are formed and recommendations based on them are made. The classes and the associated CO2 concentrations are shown in Fig. 1. The CO2 concentrations given are average values over a

a specific observation period of, for example, one hour.

Other relevant parameters are the air humidity and the temperature of the interior. When it comes to temperature, for example, there are government regulations in place.

access to workplaces. For example, when carrying out activities, the

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Indoor temperature in the range of 19 to 25°C. lay. There are also standards relating to indoor temperature such as EN ISO 7730. The EN ISO 7730 standard combines the parameters indoor air/radiation temperature, air velocity and relative indoor air humidity (PMV = predicted mean vote, PPD =) in the PMV/PPD index measurement predicted percentage of dissatisfied).

[0021] Regarding relative humidity, there are official limit values only for air-conditioned workplaces. In these cases, the relative humidity must be between 40% and 70%, unless there are production-related reasons to the contrary. The relative humidity is an important parameter because, among other things, the possibility of mold formation depends on it. The EN ISO 13788 standard sets five humidity levels for rooms.

different classes.

[0022] The subjectively perceived comfort of the room climate by people was examined by P. Leusden and F. Freymark in 1951, with Leusden and Freymark describing the room comfort as a location (measuring point) in a two-dimensional parameter space (with the dimensions of relative humidity and temperature). was presented. A supplement

game is shown in Fig. 2.

2, the room climate is represented by a pair (tuple) of measured values for temperature and humidity. Each tuple can be represented by a point in a 2D graph. If this point is in the inner, smaller area (shown shaded in Fig. 2 and labeled 10), then the room is classified as “comfortable”. If the point is outside the inner area but still within the outer, larger area (labeled 20 in Fig. 2), then the room is classified as acceptable (“still comfortable”). If the point is outside the outer, larger area, then the room is classified as “uncomfortable”, with (measuring) points below as “uncomfortably dry” and points above as “uncomfortably damp”, points on the left as “uncomfortable

cool” and points on the right can be described as “uncomfortably warm”.

[0024] The diagram from Fig. 2 essentially allows a yes/no decision (comfortable/uncomfortable), but not the quantification of comfort on a kind of “comfort scale”. Furthermore, only two environmental parameters are taken into account, namely temperature and humidity. In practice, however, there are other environmental parameters

relevant, especially the carbon dioxide concentration.

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The concept described here is intended to make it possible to use a measuring device to determine a (single) meaningful, objective measure of the air quality in an interior, which enables the user to determine the air quality “at a glance,” so to speak

assess without having to make comparisons with reference values.

According to the examples described here, the measuring device has a modular structure and, in the “minimal configuration,” contains sensors for measuring the relative humidity, temperature and CO2 concentration. The measured values are included in the calculation of the mentioned measure (air quality indicator), as described in more detail below. The capabilities of the measuring device can be supplemented by plugging in an additional module. The additional module can contain one or more sensors for measuring other environmental parameters, such as a sensor for measuring the radon concentration (radon sensor), a sensor for measuring volatile organic compounds (VOC sensor), a fine dust sensor, a sensor for measuring carbon monoxide -Concentration (CO sensor), etc. Different modules may contain different sensors or combinations of sensors. A controller contained in the measuring device (e.g. a microcontroller, a signal processor or the like) detects the presence of an inserted module and adjusts the calculation of the air quality indicator accordingly

sensors present on the module.

The mentioned controller of the measuring device is coupled to the sensors and is able to receive the measured values. The calculation of the mentioned air quality indicator carried out by the controller is shown below using the one shown in Fig. 3

Flowchart explained.

The method visualized in FIG. 3 includes the regular/continuous measurement of the CO2 concentration (see FIG. 3, block 10) and the determination of a first parameter which represents the moving average of the CO2 concentration (see FIG. 3 , Block 11). The method further includes measuring the temperature (see Fig. 3, block 20a) and the relative humidity (see Fig. 3, block 20b), as well as determining a second parameter that depends on the measured value pairs (temperature and relative humidity). (see Fig. 3, block 21). So the second parameter depends on

temperature and humidity. The first and second parameters are both scalars.

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According to an exemplary embodiment, the second parameter represents a relative frequency with which pairs of measured values lie in a predefined two-dimensional range. The pairs of measured values that were measured at regular intervals over a certain observation period (e.g. one hour) are included in the determination of the second parameter. This observation period can be sliding, i.e. the pairs of measured values that were measured in the last hour, for example, are always considered. For example, if a pair of measured values is recorded every second, in the example mentioned, the last (most current) 3600 pairs of measured values can always be used for the determination.

calculation of the second parameter can be used.

4 illustrates an example of the concept described above for determining the second parameter, which is dependent on humidity and temperature and is required for the calculation of the air quality indicator. As mentioned, the second parameter sought is defined as the relative frequency with which pairs of values (humidity and temperature) measured over a certain period of time lie in a defined two-dimensional range. This area can be based on the comfort diagram from Leusden and Freymark. According to the - simplified - example from Fig. 4, out of 20 measuring points, 16 measuring points are within the range 10 and 4 measuring points are outside the range 10, with each pair of values of temperature and humidity defining a measuring point. In

In the example shown, the relative frequency is 16/20 = 0.8 (corresponds to 80%).

Several areas can also be defined, with each area in particular being a subset of the next larger one. In the example of Figure 5, the central region 10 is a subset of the larger region 20. In this case, the second parameter can be defined as a tuple comprising two relative frequencies. A first relative frequency describes the frequency with which the measurement points are in the central area 10, and a second relative frequency describes the frequency with which the measurement points are in the larger area 20. In the example shown in Figure 5, the second parameter is (0.2; 0.9). This means that 20% of the measuring points are in the central area 10 and 90% of the measuring points are in the larger area 20.

[0032] Back to Fig. 3: After the first parameter (moving average of the CO2 concentration over a time window) and the second parameter (relative frequency(s) of measuring points that were measured within a time window) have been calculated,

the two parameters are mapped onto a standardized scale. This scale can be a value

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be between 0 and 1 (or 100). However, mapping to other standardized intervals such as 1 to 5 (school grading system) is also possible. This normalization is represented in FIG. 3 by blocks 12 and 22. The normalized values are shown below

also referred to as (partial) air quality values.

The normalization mentioned makes it possible to combine the individual partial air quality values. For example, a weighted average can be considered to combine the two air quality values (see Fig. 3, block 30). However, a weighted average only provides a meaningful air quality indicator as long as the individual partial air quality values do not signal excessively poor air quality. The combination of the individual air quality values using weighted averaging can result in a very poor (unacceptably poor) partial air quality value (e.g. due to a very high CO2 concentration) still resulting in a relatively good air quality indicator because the other partial air quality value (e.g. due to an optimal combination of humidity and temperature) provides good values. To address this problem, in one embodiment a weighted average is calculated, with the weighting factors depending on the associated partial air quality values. In this case the weighted

Averaging is non-linear, with “bad” individual values being given greater weight.

6 uses tables to illustrate the mapping of the determined parameters (e.g. CO2 concentration and the relative frequencies discussed above) onto an associated standardized scale. The left table in Fig. 6 concerns the first parameter, which depends on the CO2 concentration, and the right table in Fig. 6 concerns the second parameter, which depends on humidity and temperature. In the example shown, the mapping is a step function, so that a specific range of parameters is mapped to a specific standardized value (partial air quality value). The illustrations according to FIG. 6 can also be used as an assignment of the (first and second) parameters

classes are viewed.

According to the example from FIG. 6, a CO2 concentration of 800 ppm or less is mapped to the standardized value 100. A CO2 concentration of more than 800 ppm to a maximum of 1000 ppm is mapped to the standardized value 85. A CO2 concentration of more than 1000 ppm to a maximum of 1400 ppm is mapped to the standardized value 75. A CO2 concentration of more than 1400 ppm to a maximum of 2000

ppm is mapped to the standardized value of 50. A CO2 concentration of more than

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2000 ppm to a maximum of 5000 ppm is mapped to the standardized value 25. A CO2 concentration of more than 5000 ppm leads to a standardized value of zero. The number of levels and the associated range limits are of course just an example

can also be chosen differently.

A similar procedure can be used for the relative frequencies of the position of the temperature/relative humidity measuring points in order to normalize the relative frequencies. The right table of Fig. 6 refers to the diagram in Fig. 5, according to which two areas 10 and 20 are used. Accordingly, a relative frequency of the measuring points in the inner area 10 of 0.9 or more is mapped to a standardized value of 100. The number of measuring points in the larger area 20 is irrelevant in this situation (d.c. = don’t care). If the relative frequency for the inner area 10 is less than 0.9 but greater than or equal to 0.5 and the relative frequency for the larger area 20 is 0.9 or more, then the normalized value is set to 75. If the relative frequency for the inner area 10 is less than 0.5 and the relative frequency for the outer area 20 is at least 0.5, then the normalized value is set to 50. If the relative frequency for the outer area 20 is less than 0.5, or at least 0.3, then the normalized value is set to 25. If the relative frequency for the outer area 20 is less than 0.3, the normalized value is zero. In this case too, the number of levels and the associated range limits are only to be understood as an example. In other exemplary embodiments, only one area 10 and the associated relative frequency can also be considered. The determination of relative frequencies for more than two conditions is also

rich possible.

[0037] An alternative to this is that a second parameter is determined by calculating the average normal distance of all measuring points to the respective area boundaries.

ter or as a result a partial air quality value is calculated.

According to one exemplary embodiment, the two (normalized) air quality values are weighted equally. This means that the weighting factors are each 0.5 (corresponds to 50%). In order to solve the above-mentioned problem that unacceptably bad individual values are compensated for by good other values, the weighting factors can be modified if certain conditions are met. For example, a first partial air quality value of 0 (more than 5000ppm CO>) can result in this value being weighted by a factor of 1 (corresponding to 100%) (and the other value correspondingly by 0),

which causes the resulting air quality indicator to become zero overall. The same applies if the second partial air quality value is 0 (less than 30% of the measuring points are in the outer area 20). In this case, the associated weighting factor can be set to 1, which results in the resulting air quality indicator becoming zero overall. Switching the weighting factor from 0.5 to 1 is just an example of this.

for very poor partial air quality values to be given higher weight.

As mentioned, the air quality measuring device can have a modular structure, i.e. it can be supplemented by at least one module that contains additional sensors. These can be, for example, parameters such as fine dust concentration (in ug/m”), volatile organic compounds (in ug/m*) and/or the radon concentration (in Bq per m”). These factors are referred to here as secondary factors and can be included in the calculation of the air quality indicator in a similar way to the CO2 concentration. In one example, the additional module contains an optical fine dust sensor, whereby the measured fine dust concentration can be mapped to an interval from 0 to 100, analogous to the CO2 concentration. For example, the values 0.2 (fine dust), 0.4 (CO2) and 0.4 (temperature/humidity) can be used for weighting when averaging, although if the individual values are very poor, the weighting can be modified accordingly. Analogously, other parameters such as radon concentration or VOC concentration can be

go.

Secondary influencing factors (for example radon concentration, VOC concentration or fine dust concentration) can also be taken into account in the form of so-called cut-off thresholds, provided the additional module has corresponding sensors. This means that the respective factors have no influence on the air quality indicator as long as the respective cut-off threshold values are not exceeded. However, if a cut-off threshold value is exceeded (e.g. fine dust concentration is above the threshold value), then the overall air quality indicator is set to zero. Optionally, if a maximum air humidity is exceeded, the overall air quality indicator can be set to zero, because in this case the room climate

promotes mold formation.

[0041] Fig. 7 shows an example of a procedure using a simplified block diagram.

direction for determining an air quality indicator. Accordingly, the device includes one

Main board 5 and a replaceable additional module 6, which can have another board. Main board 5 and additional module 6 can be connected via a connector 4. This means that the device is designed in such a way that the additional module 6 can be plugged into the main board 5. The additional module 6 is optional. If no additional module is used, a housing cover or a dummy module without function can be arranged in its place. Different additional modules can have different functionalities

exhibit.

In the example shown, the main board has a computing unit 50, which can be designed, for example, as a microcontroller or signal processor. A computing unit is understood to mean any entity that can carry out the functions described here. The computing unit can be a combination of processor, memory and software, as well as hard-wired and one-time programmable logic circuits and peripheral electronics. The motherboard can also have a communication interface 55 which is connected to the computing unit/controller 50. In the example shown, the communication interface 55 is an interface for wireless communication such as a Bluetooth or a WLAN (wireless local area network) interface. Sensors 51, 52, 53 are also connected to the computing unit 50 (controller), which measure the primary influencing factors of temperature, air humidity and CO2 concentration.

sen.

The board of the additional module can have an interface 60 for communication with the computing unit 50. The interface 60 can also have a microcontroller, but this does not necessarily have to be the case. Communication with the computing unit 50 can take place, for example, using a known digital bus system such as SPI (Serial Peripheral Interface) or °C (Inter-Integrated Circuit). The interface 60 also enables additional sensors 62, 63 to be coupled to the computing unit 50. The computing unit 50 can be designed to detect which functions or capabilities the additional module has and, depending on the detected functions or capabilities, the algorithm for calculating the Air quality indicator to change, for example by adjusting the weighting factors discussed above, and / or by incorporating an additional parameter (which, for example, is dependent on the sensor signals from sensors 62 or 63) into the resulting air quality indicator. In the example shown, sensor 62 is a VOC sensor and sensor 63 is a radon sensor and the

Algorithm will do this when detecting the presence of the two sensors

modified so that the resulting air quality indicator is set to zero if defined limit values (cut-off threshold values) for the VOC or radon concentration are exceeded.

will be,

[0044] According to a further example, the additional module 6 can also have a further communication interface. For example, the communication interface 55 can be a Bluetooth interface, whereas the communication interface located on the additional module 6 is a WLAN interface. Using the communication interface 55 (or the further communication interface on the additional module), the device can communicate with another device such as a smart phone or a tablet PC on which the calculated air quality indicator is visualized. This also makes it possible to warn the user via push notifications, for example if the air quality falls below an adjustable threshold. Using the communication interface, the device can also be connected to a smart home controller, which then controls certain other devices depending on the air quality indicator determined. For example, if the air quality indicator falls below an adjustable value, the setting of a ventilation or air conditioning system can or can be changed

a window will automatically open.

8 illustrates an example of the device described here with a plug-in additional module in a kind of exploded view. Fig. 8 shows the housing 1, in which the main board 50 and the sensors 50-53 are accommodated (see Fig. 7). The housing 1 is partially open and has a slot into which the additional module 6 with an additional sensor board can be inserted. The additional module 6 includes a housing part that covers the housing when the additional module 6 is plugged in. The insertion direction

8 is shown by an arrow and dashed lines.

Even if no additional sensors are required, a dummy additional module is still necessary, which in this case essentially only consists of the housing part, which forms a cover for the opening in the housing 1. The housing part of the additional module 6 that serves as a housing cover can have openings 65 and 64, which enable air to flow through the housing (towards the sensors arranged therein). The openings 64 and 65 can be covered by grids (not shown in FIG. 8), for example to prevent the penetration of larger dirt particles or insects

to prevent.

The housing 1 has an approximately truncated cone, cylindrical or disk-shaped shape, whereby the device can be mounted on an approximately circular top surface on a wall or a ceiling. The opposite cover surface has the central opening 65. The opening 64 is located on a side surface of the access

sentence module 6.

Claims (12)

PATENT CLAIMS 1. A device that has: a computing unit (50), Sensors (51, 52, 53) for measuring temperature, humidity and CO2 concentration, which are coupled to the computing unit (50), wherein the computing unit (50) is designed to do so based on measured values for Temperature, humidity and CO2 concentration to calculate an air quality indicator. 2. The device according to claim 1, wherein the air quality indicator is a measure within a defined range of values. is rich. 3. The device according to claim 1 or 2, further comprising: an additional module (6) that can be plugged into the device and has at least one further sensor (62, 63) for measuring at least one further environmental parameter, wherein the computing unit (50) is designed to detect the presence of the additional module (6) and, if the additional module (6) is present, to determine the at least one further environmental parameter (62, 63) when calculating the air quality indicator. take into account. 4. The device according to one of claims 1 to 3, wherein the computing unit is further designed to: to calculate a first parameter that depends on the CO2 concentration, to calculate a second parameter that depends on both the temperature and the humidity, to map the first parameter and the second parameter onto a standardized scale in order to obtain a first and second air quality value, respectively, and the first and second air quality values into a single combined measure to combine, which represents the air quality indicator. 5. The device according to claim 4, for the calculation of the first parameter, the computing unit is designed to regularly record and store a measured value of the CO2 concentration and calculate a moving average over a certain number of measurements. 6. The device according to claim 4 or 5, for the calculation of the second parameter, the computing unit is designed to regularly record measuring points, each of which is given by a pair of values of temperature and humidity, and to determine a relative frequency which the measuring points lie in a two-dimensional area. 7. The device according to claim 4 or 5, for the calculation of the second parameter, the computing unit is designed to regularly record measuring points, each of which is given by a pair of values of temperature and humidity, and to calculate the average normal distances of the measuring points to the boundaries of a predefined two-dimensional area, where the second parameter follows from the calculated normal distances. 8. The device according to one of claims 4 to 7, wherein for combining the first and the second air quality values, the computing unit is designed to produce a weighted average of the first and the second air quality values. to calculate the quality value. 9. The apparatus of claim 8, wherein the weighting factors for calculating the weighted average of depend on the air quality values to be weighted. 10. The device according to one of claims 1 to 10 as far as referenced to claim 3, wherein the at least one further environmental parameter is taken into account when calculating the air quality indicator in that the air quality indicator is set to zero when the respective environmental parameter reaches or exceeds an associated limit value. increases. 11. A procedure comprising: determining a first parameter that depends on measured CO2 concentrations; Mapping the first parameter to a standardized first air quality value; Determining a second parameter that depends on measured value pairs of temperature and humidity; Mapping the second parameter onto a standardized second air quality value; and Combining the first normalized air quality value and the second normalized air quality value quality value into a single measure that serves as an air quality indicator. 12. The method according to claim 11, further comprising: detecting the presence of an additional module with at least one further sensor for measuring at least one further environmental parameter, and taking into account measured values of the at least one further environmental parameter when calculating the measure if the additional module is available.