WO2018091673A1

WO2018091673A1 - Battery-powered sensor device and operating method

Info

Publication number: WO2018091673A1
Application number: PCT/EP2017/079646
Authority: WO
Inventors: Declan Patrick Kelly; Xiao-ming ZHOU; Jingwei Tan; Vincent LOU; Weishun BAO; Weizhong Chen
Original assignee: Koninklijke Philips NV
Current assignee: Koninklijke Philips NV
Priority date: 2016-11-21
Filing date: 2017-11-17
Publication date: 2018-05-24
Anticipated expiration: 2019-05-21
Also published as: CN210639486U

Abstract

Disclosed is a battery-powered sensor device (10) comprising a sensor (11) for sensing an analyte of interest coupled to a processor (13) adapted to periodically process sensor signals obtained with the sensor and an accelerometer (15) coupled to the processor for providing an accelerometer signal indicating a degree of movement of the sensor device, wherein the processor is arranged to set a processing frequency of said sensor signals in accordance with said degree of movement. A method (100) of operating such a battery- powered sensor device (10) is also disclosed.

Description

BATTERY-POWERED SENSOR DEVICE AND OPERATING METHOD

FIELD OF THE INVENTION

The present invention relates to a battery-powered sensor device comprising a sensor coupled to a processor adapted to periodically process sensor signals obtained with the sensor.

The present invention further relates to a method of operating such a battery- powered sensor device.

BACKGROUND OF THE INVENTION

Battery-powered sensor devices are becoming increasingly popular, for example as part of a portable device, e.g. a smart phone, smart watch, or the like, or as standalone sensor devices. The may be many reasons why people want to use such battery- powered sensor devices. One such reason is to monitor air quality, for example when exercising, e.g. running, cycling, and so on. In the developed world, and in particular in urban areas, air pollution such as particulate matter (PM) pollution, e.g. pollution caused by vehicle emissions, are an increasing health concern such that there is an increasing interest in obtaining and monitoring information pertaining to pollution levels.

A challenge associated with such a battery-powered sensor devices is to ensure that the battery lifetime is sufficient to provide a user with the desired sensing functionality over a full period of time in which the user wishes to obtain such sensing information, e.g. during exercising. This is particularly challenging in wearable battery-powered sensor devices, which need to have a small form factor such that the devices can be worn in a comfortable manner. This compromises the space available for the battery in such wearable devices.

US 2016/0025628 Al discloses a mobile device which senses particulate matter. The mobile device includes a housing having an air flow path through which air flows when the mobile device is shaken; an inertia sensor that detects acceleration of the mobile device; a light-scattering type sensor that irradiates the air flow path with light and detects particulate matter in air flowing through the air flow path; and a controller that includes a counter for counting the particulate matter detected by the light-scattering type sensor, and a flow rate calculator for detecting an air flow rate of the air flow path based on a detection signal of the inertia sensor. In this manner, an air flow generating component can be avoided, which may improve the battery life. However, such a mobile device still suffers from limited battery life during use of the sensing functionality. Hence, there exists a need for providing a battery-powered sensor device in which the battery life, i.e. its operational time on a single charge, can be extended.

US 2015/0250385 Al discloses a device for continuous physiological monitoring. The device may include a wearable strap that automatically and continually determines a heart rate of a user and provides continuous heart rate data. The sampling rate of the heart rate data may be a function of the level of activity of the wearer of the wearable strap as determined with one or more accelerometers in order to obtain an accurate estimate of the heart rate.

SUMMARY OF THE INVENTION

The present invention seeks to provide a battery-powered sensor device having such an extended battery life.

The present invention further seeks to provide a method of operating such a battery-powered sensor device.

According to an aspect, there is provided a battery-powered sensor device comprising a sensor for sensing an analyte of interest coupled to a processor adapted to periodically process sensor signals obtained with the sensor and an accelerometer coupled to the processor for providing an accelerometer signal indicating a degree of movement of the sensor device, wherein the processor is arranged to set a processing frequency of said sensor signals in accordance with said degree of movement.

The present invention is based on the insight that typically a correlation exists between a degree of movement of the battery-powered sensor device and the desire of its user for accurate sensing. For example, when the user is asleep or at rest, the user is likely to have less interest in regular updates of sensor data provided with the sensor, whereas when the user is active, e.g. exercising, more frequently updated sensor data is desirable. Also, in a scenario where the user is moving, the user is more likely to be moving between different environments having different concentrations of an (airborne) analyte of interest, e.g. air pollutants, which justifies a higher measurement frequency with the sensor in order to accurately capture such changes. Consequently, by including an accelerometer in the sensor device and setting a processing frequency of the sensor signals in accordance with the movement information provided by the accelerometer, battery power may be preserved during periods of relatively little movement of the sensor device. As such periods typically are prolonged periods, the battery lifetime may be significantly extended. In addition, as the measurement frequency is increased during measurement periods of relevance, the accuracy of the determination of an analyte of interest may improve during such periods.

In an embodiment, the processor is arranged to scale the processing frequency of said sensor signals in accordance with the degree of movement. Hence, with increasing movement an increasing processing frequency, e.g. sample frequency, of the sensor signals may be deployed.

In another embodiment, the battery-powered sensor device further comprises a look-up table comprising table entries associated with movement ranges of the sensor device, each movement range being associated with a particular processing frequency, wherein the processor is adapted to identify a table entry in the lookup table associated with a movement range including the degree of movement; and set the particular processing frequency associated with the identified movement range as the processing frequency of said sensor signals. For example, each of the table entries may be associated with a particular type of activity, e.g. resting, walking, jogging, running, cycling, etcetera, with each activity being defined by a particular movement range of the sensor device as detected with the

accelerometer.

The table entries of the look-up table may be configurable. This has the advantage that a user of the battery-powered sensor device may update the look-up table, e.g. in order to improve the accuracy of the activity detection with the accelerometer.

Alternatively or additionally, the sensor device may be adapted to extract movement ranges based on a learning phase of the device in which the processor monitors data collected with the accelerometer and evaluates the collected data to extract typical movement patterns from the data that may be used to populate the table entries.

The battery-powered sensor device may further comprise a further sensor coupled to the processor adapted to periodically process further sensor signals obtained with the further sensor, wherein the processor is further adapted to set the processing frequency of said sensor signals in response to a processing result of at least one of said further sensor signals. For example, a change in an environmental condition such as C02 level or temperature level as determined with the further sensor may be indicative of a change in the concentrations of a pollutant to be monitored with the sensor, which change may be of interest to the user of the battery-powered sensor device. Such a change for instance may signal a change of location, e.g. a user moving from an indoor location to an outdoor location or the other way around, which is likely to be associated with a change in an analyte of interest such as an air pollution level. Consequently, such a further sensor signal may advantageously trigger a change in the processing frequency of the sensor signals in order to monitor likely changes in the concentration of the pollutant of interest.

The processor may be arranged to set a further processing frequency of said further sensor signals in response to the degree of movement to further extend the battery life of the sensor device.

In an embodiment, the battery-powered sensor device further comprises a user interface coupled to the processor, wherein the processor is further adapted to set the processing frequency of said sensor signals in response to a user input received from the user interface. For example, a user may indicate whether he or she is interested in obtaining data from the sensor, which may be used to overrule or augment the accelerometer data used to control the processor, thereby providing a battery-powered sensor device with extended operational flexibility.

In a particularly advantageous embodiment, the sensor for sensing an analyte of interest is arranged to sense a pollutant and the processor is arranged to derive a pollutant level from a sensor signal provided by the sensor, the sensor device further comprising a communication module coupled to the processor, wherein the processor is arranged to determine if the communication module has access to an external source for providing an external indication of said pollutant level and, if such access is available, obtain said external indication of said pollutant level and disable the sensor. In this embodiment, an external indication of the pollutant level may be used instead of a pollutant level as determined from at least one sensor signal provided by the sensor, e.g. if the external indication is of sufficient reliability. This has the advantage that the battery life of the sensor device can be further extended by temporarily disabling the sensor device of such reliable external pollutant information is available.

Preferably, the communication module is arranged to connect to an external source for providing said external indication over a data communication network. For example, the communication module may be adapted to access an Internet service providing such pollutant information in order to assess whether the sensor may be temporarily disabled.

The battery-powered sensor device may further comprise a data storage device coupled to the processor, wherein the processor is arranged to store sensor data derived from the sensor signals in the data storage device for evaluation of said sensor data. This facilitates evaluation of the sensor data at any suitable point in time, e.g. the evaluation of pollutant levels to which a user was exposed during an exercise regime following its completion.

The battery-powered sensor device may be a wearable sensor device, as wearable sensor devices are particularly to benefit from enhanced battery life due to the limited capacity of the relatively small batteries in such wearable devices and are particularly likely to be exposed to a range of movements depending on the type of activity in which its wearer is engaged.

The sensor for sensing an analyte of interest may be an air pollutant sensor such as an aerosol sensor or a particulate matter sensor, e.g. a PM 10 sensor, a PM 5 sensor, a PM 2.5 sensor, a UFP (ultrafine particle) sensor or the like. Such sensors are particularly attractive as they can monitor air pollution, which pollution information may be particularly of interest to users engaged in physical activity.

In an embodiment, the battery-powered sensor device further comprises an air flow channel housing the sensor, wherein the processor is further adapted to calculate an air pollutant concentration from the sensor signal and the accelerometer signal. In particular, in such an arrangement the accelerometer data can provide an accurate estimate of the airflow speed through the air flow channel, such that the volume of air displaced through the airflow channel during the sensor signal acquisition period and the associated air pollutant concentration can be accurately estimated.

According to another aspect, there is provided a method of operating a battery- powered sensor device comprising a sensor for sensing an analyte of interest coupled to a processor adapted to periodically process sensor signals obtained with the sensor and an accelerometer coupled to the processor, the method comprising, with said processor, receiving an accelerometer signal from the accelerometer indicating a degree of movement of the sensor device; determining the degree of movement of the sensor device from the received accelerometer signal; and setting a processing frequency of said sensor signals in accordance with the determined degree of movement. Because this method of operating the battery-powered sensor device intensifies the operation during intensified activity of its user, i.e. scales down operation during periods of inactivity, the battery life of the sensor device is prolonged, thereby reducing the risk of the battery running out of charge during a period of intensified activity of its user.

In an embodiment, the battery-powered sensor device further comprises a communication module coupled to the processor, the method further comprising, with said processor, checking if an external source for providing an external indication of said pollutant level is available; and in case of such availability, receiving an external indication of said pollutant level from the communication module and disabling the sensor. Such an external indication may be used to further enhance the battery life of the battery-powered sensor device as it enables the device to be operated in a low-power mode, e.g. by disabling the sensor, if a reliable external determination of the pollutant level of interest can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described in more detail and by way of non- limiting examples with reference to the accompanying drawings, wherein:

FIG. 1 schematically depicts a battery-powered sensor device according to an embodiment;

FIG. 2 schematically depicts a battery-powered sensor device according to another embodiment;

FIG. 3 is a flowchart of a method of operating a battery-powered sensor device according to an embodiment;

FIG. 4 schematically depicts a battery-powered sensor device according to still another embodiment;

FIG. 5 schematically depicts a battery-powered sensor device according to yet another embodiment;

FIG. 6 is a flowchart of a method of operating a battery-powered sensor device according to another embodiment; and

FIG. 7 is a graph exemplifying an operating principle of a battery-powered sensor device according to embodiments of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

FIG. 1 schematically depicts a battery-powered sensor device 10 according to an embodiment of the present invention. The battery-powered sensor device 10 comprises a sensor 1 1 communicatively coupled to a processor 13, which processor 13 is further coupled to accelerometer, i.e. an inertia sensor, 15. The battery-powered sensor device 10 further comprises a battery 17 that powers the various components of the battery-powered sensor device 10. The battery-powered sensor device 10 in preferred embodiments is a portable battery-powered sensor device, such as a smart phone, tablet computer or the like including sensor functionality. Alternatively, such a portable battery-powered sensor device is a dedicated device that may be worn in a pocket or the like of its user or alternatively may be fastened to an exercise device, e.g. a bicycle or the like, of the user using any suitable fastening means, e.g. a clip, a strap or the like. In another preferred embodiment, the battery- powered sensor device is a wearable device, such as a smart watch or the like or a dedicated sensor device. In case of such a wearable battery-powered sensor device 10, the device may comprise any suitable fastening means, e.g. a strap, belt, or the like for securing the device to the body of its wearer.

The sensor 1 1 for sensing an analyte of interest may be any suitable type of sensor, such as a sensor for measuring air pollution. In example embodiments, the sensor 1 1 may be an aerosol sensor, e.g. a particulate matter sensor such as a PM 2.5 sensor, a UFP sensor, a PM 5 sensor, a PM 10 sensor, and so on for detecting particulate matter particles of a particular size. Any suitable embodiment of such a particular matter sensor may be contemplated. For example, the battery-powered sensor device 10 may be configured as schematically depicted in FIG. 2, in which the particulate matter sensor 1 1 is located in an air flow channel 19 through the housing of the battery-powered sensor device 10. The housing may be made of any suitable material, e.g. a plastics material, a metal, a metal alloy or combinations thereof. The air flow channel 19 extends between a first opening and a second opening that are each open to an ambient environment. For example, the first opening may oppose the second opening in case of a linear air flow channel 19.

In an embodiment, the particulate matter sensor 1 1 is an optical particle sensor comprising an optical module (not shown) for emitting light through a sensing area of the air flow channel 19 and a detector (not shown) for detecting light scattered by particles in the air flowing through the sensing area. The optical module for example may be a LED module or a laser module and the detector for example may be a photodetector such as a photodiode or the like. Any suitable optical particle sensor design may be used. As such optical particle sensors are well-known per se, this will not be described in further detail for the sake of brevity only.

In case of the sensor 1 1 being placed in the air flow channel 19, the accelerometer data generated with the accelerometer 15 may be used by the processor 13 to calculate an air flow speed through the air flow channel 19, using a known volume of the air flow channel 19, as for instance has been disclosed in US 2016/0025628 Al . The processor 13 may take any suitable form. For example, the processor may be a single discrete device, e.g. an ASIC, a suitably programmed general purpose processor,

microcontroller or the like, or may be a distributed arrangement comprising a plurality of processing devices cooperating to implement the processor functionality. The processor 13 is typically adapted to process signals obtained with the sensor 1 1 at a defined processing frequency. During each sensor signal processing event, e.g. measurement cycle, the processor 13 may enable the sensor 1 1, e.g. switch the sensor 11 from a dormant state to an active state, to facilitate the generation of a sensor signal with the sensor 1 1, after which the processor 13 may disable the sensor 1 1, e.g. switch the sensor 1 1 from the active state to the dormant state in order to reduce the energy consumption by the sensor 1 1. For example, in case of an optical particle sensor 1 1, during each sensor signal processing event the processor 13 may activate the optical module and detector to trigger a sensing event. Thus obtained sensor readings, e.g. determined concentrations of analytes of interest, e.g. air pollutants such as particulates of a certain size, may be stored by the processor 13 in a data storage device 14 for evaluation at a later stage. Any suitable data storage device 14, e.g. a memory device such as a Flash or EEPROM, a solid state disk, a magnetic disk or the like, may be used for this purpose.

In accordance with the present invention, the processor 13 is adapted to dynamically adjust the processing frequency of the sensor signals generated with the sensor 1 1 in response to an accelerometer signal provided by the accelerometer 15 indicative of a degree of movement of the battery-powered sensor device 10, such as a movement speed or the like, such that the battery life of the battery 17 may be extended by lowering the processing frequency of the sensor signals from the sensor 1 1 during periods of decreased movement (i.e. user activity) of the battery-powered sensor device 10. This will be explained in further detail with the aid of FIG. 3, which depicts a flowchart of an operating method 100 of the battery-powered sensor device 10. The method 100 starts in 101, for example by switching on the battery-powered sensor device 10, and optionally setting a default value for the processing frequency of the signals from the sensor 1 1, after which the method 100 proceeds to 103 in which the processor 13 receives an accelerometer signal from the accelerometer 15. This accelerometer signal provides an indication of the degree of movement of the battery-powered sensor device 10.

In case of a wearable or portable battery-powered sensor device 10, this degree of movement typically is correlated to a level of activity of its user. For example, when the user is at rest, this will be reflected by the accelerometer 17 detected limited motion of the battery-powered sensor device 10, with increased activity of the user causing the

accelerometer 17 to generate accelerometer signals indicative of the increased motion of the battery-powered sensor device 10. Given that a user of the battery-powered sensor device 10 typically is more interested in the sensor readings of the sensor 1 1 during increased levels of activity, the degree of motion detected with the accelerometer 17 may be used by the processor 13 to adjust the processing frequency of the sensor signals produced, e.g. to be generated, with the sensor 1 1 accordingly. As explained above, this may include enabling and disabling the sensor 1 1 to preserve energy.

To this end, the processor 13 processes the accelerometer signals received from the accelerometer 17 in 105 to determine a degree of movement of the battery-powered sensor device 10 from the received accelerometer signals and sets the processing frequency of the signals produced with the sensor 1 1 in 107 in accordance with the determined degree of movement. In an embodiment, the processor 13 may scale the processing frequency of the signals with the determined degree of movement, e.g. in accordance with a linear relationship (correlation) between the determined degree of movement and the set processing frequency. Alternatively, the processor 13 may access a lookup table (LUT), which for example may be stored in the data storage device 14, which LUT may contain table entries associated with movement ranges of the sensor device 10. Each movement range is associated with a particular processing frequency, such that the processor 13 may be adapted to identify a table entry in the lookup table associated with a movement range including the degree of movement and set the particular processing frequency associated with the identified movement range as the processing frequency of the sensor signals of the sensor 1 1.

Each table entry of the LUT may be associated with a particular activity of the user, e.g. resting, walking, jogging, running, cycling, and so on, with each activity being associated with a typical degree of movement of the battery-powered sensor device 10. The table entries of the LUT may be pre-populated and/or in some embodiments may be configurable. For example, the processor 13 may be adapted to implement a machine learning routine in which the processor 13 collects data from the accelerometer 15 over a defined period of time and stores the data in the data storage device 14 for evaluation of the collected data upon completion of the defined period of time to recognize trends in the accelerometer data, which trends may be translated into respective table entries of the LUT. In another embodiment, the LUT may be programmable by a user, for example to define the respective table entries of the LUT or to amend the pre-populated table entries in accordance with user experience such that the table entries accurately correspond to the respective activity levels of that particular user. To this end, the battery-powered sensor device 10 may comprise a user interface (not shown) such as a touchscreen, one or more buttons or dials, or the like to facilitate programming of the LUT by the user. Alternatively, the battery-powered sensor device 10 may comprise a data communication module such as a Bluetooth module or the like to allow programming of the LUT using the user interface of a further device, e.g. a smart phone, tablet computer or the like.

It is subsequently checked in 109 if the method 100 may be terminated. If not, the method 100 returns to 103, otherwise the method terminates in 1 1 1. As will be understood by the skilled person, the termination of the method 100 may signal the termination of a sensor data acquisition mode of the battery-powered sensor device 10, which may be followed by a data evaluation mode in which the collected sensor data is evaluated, for example to determine air pollution levels in case of a sensor 1 1 detecting air pollutants as previously explained. Such data evaluation may be performed by the processor 13 or alternatively may be performed on a remote device communicatively coupled to the battery- powered sensor device 10, for example by transmitting the acquired sensor data to the remote device, e.g. a smart phone, tablet computer, laptop computer, desktop computer, and so on. As this is well-known per se, this will not be explained in further detail for the sake of brevity only. It should suffice to say that any suitable implementation of such data evaluation may be used in the context of the present invention.

In some embodiments, the processing frequency of the sensor signals generated with the sensor 1 1 of the battery-powered sensor device 10 with the processor 13 by further mechanisms in addition to the aforementioned degree of motion detection based on the accelerometer signals provided by the accelerometer 15. For example, the battery- powered sensor device 10 may comprise or may be responsive to a user interface, e.g. of a remote device communicatively coupled to the battery-powered sensor device 10, through which a user may manually define the desired processing frequency. In this manner, a user for example may increase the processing frequency of the sensor signals when being stationary within a space in which increased levels of an analyte of interest, e.g. an air pollutant, are expected, for example a living space in which food is being prepared or a wood fire is being lit, such that the user may trigger an increased (or decreased) sampling rate of the sensor signals from the sensor 1 1 with the processor 13 in the absence of an associated change in the degree of movement of the battery-powered sensor device 10.

FIG. 4 schematically depicts a battery-powered sensor device 10 according to another embodiment in which a further sensor 12 communicatively coupled to the processor 13 is present. Such a further sensor 12 may be any suitable type of sensor, such as for example a temperature sensor, a C02 sensor, or the like. As with the sensor 1 1, the processing frequency of the further sensor signals generated with the further sensor 12 by the processor 13 may be dynamically adjusted in accordance with the degree of motion derived from the accelerometer signals from the accelerometer 15 as explained above. Such adjustment of the processing frequency of the further sensor signals may involve disabling and enabling the further sensor 12 as previously explained. Where the sensor 1 1 and the further sensor 12 are both operated in accordance with a dynamically adjustable processing frequency, the respective processing frequencies may be the same or may be different.

In an embodiment, the processor 13 is adapted to set the processing frequency of the sensor signals of the sensor 1 1 in response to a processing result of at least one of the further sensor signals from the further sensor 12. For example, a sudden change in a property such as temperature or concentration of a further analyte of interest monitored with the further sensor 12 may indicate an increased likelihood of an associated change in the property monitored with the sensor 1 1, e.g. an increased likelihood of a change in an air pollution level such as a particulate matter level, which may trigger the processor 13 to adjust, e.g. increase or decrease, the processing frequency of the sensor signals of the sensor 1 1 in the absence of an associated change in the degree of movement of the battery-powered sensor device 10.

FIG. 5 schematically depicts a battery-powered sensor device 10 according to another embodiment in which the battery-powered sensor device 10 further comprises a data communication module 16 coupled to the processor 13. In this embodiment, the sensor 1 1 is an air pollutant sensor such as a particulate matter sensor. The data communication module 16 in preferred embodiments is a wireless data communication module 16 such as a wireless radio, a Wi-Fi module, a Bluetooth module, a NFC module, or the like. The processor 13 may be adapted to operate the data communication module 16 in order to access an external source of air pollution data, either by connecting directly to the external source over a data communication network such as the Internet or by indirectly connecting to the external source over such a data communication network, e.g. through a relay device such as a smart phone, tablet computer, router or the like.

This method of operation will be explained in more detail with the aid of FIG.

6, which depicts a flowchart of the method 100 in accordance with the present embodiment. As explained before, the method 100 may start in 101 by enabling the battery-powered sensor device 10 as previously explained. Next, the method 100 proceeds to 201 in which the processor 13 may, through the data communication module 16, check if a reliable external source of air pollution data is available, e.g. within communication range of the battery- powered sensor device 10. Such an external source for example may be an Internet service for providing air pollution information for a particular region, e.g. a cloud-based service or the like.

For example, the processor 13 may contain a list of recognized reliable external sources for providing a pollution information for a particular region and may check if any of these sources are within communication range. Alternatively, the processor 13 may receive a user instruction to check if a particular external source for such air pollution data is within communication range, e.g. through a user interface of the battery-powered sensor device 10 or a user interface of a remote device communicatively coupled to the battery- powered sensor device 10. And if they are in communication range, can provide air pollution data for the space in which the battery-powered sensor device 10 is present.

The processor 13 checks in 203 if such reliable external indication of the air pollution levels in the relevant space, e.g. a particular region such as a particular part of a town or city, is available. If no such external indication is available, the method 100 may proceed to 103 as previously explained in which the processing frequency of the sensor signals from the sensor 1 1 is set in accordance with the accelerometer signals received from the accelerometer 15. This will not be explained again for the sake of brevity only. On the other end, if it is decided in 203 that a reliable external indication of the air pollutant levels can be obtained, the method 100 proceeds to 205 in which the reliable external indication of the air pollutant levels is obtained from the external source, e.g. a network- connected service for providing such external indications, which means that as long as such external indications are available, at least the sensor 1 1 may be placed in a sleep mode, thereby reducing energy consumption by the battery-powered sensor device 10 and extending battery life. As will be immediately understood by the skilled person, further components of the battery-powered sensor device 10, e.g. the accelerometer 15, may also be placed in a sleep mode at the same time to further prolong battery life. Moreover, where the sensor device 10 can rely on such external indications, e.g. generated with professional measurement devices in a relative vicinity to the sensor device 10, the accuracy of the sensor device 10 may be further improved.

As before, it is checked in 109 if the method 100 may terminate in 1 1 1. If not, the method 100 reverts back to 201 in which it is checked again if a reliable external source of air pollutant levels is available, such that the dormant components of the battery-powered sensor device 10, e.g. the sensor 1 1 and the accelerometer 15, may be woken up in case of the loss of availability of such a reliable external source.

FIG. 7 is a graph of a particulate matter concentration (Y-axis) over time (X- axis) as developed in a kitchen at which at the point in time a meal has been prepared and cooked, as demonstrated by the increase in particulate matter concentration. Under the X- axis, the equidistant top row of arrows indicate a static processing frequency of sensor signals of a typical prior art battery-powered sensor device, with each arrow indicating a sampling event. The bottom row of arrows indicate a dynamic processing frequency of sensor signals achieved with the battery-powered sensor device 10 according to embodiments of the present invention worn by the person preparing the meal.

Upon the person starting to prepare the meal, the accelerometer 15 detected an increased motion of the battery-powered sensor device 10, which was translated into an increased processing frequency of the sensor signals from the sensor 1 1 as demonstrated by the closer spacing of the arrows in the bottom row. Consequently, the data points 1 in which sudden changes in the particulate matter concentration within the monitored space occurred associated with the increased activity of the person preparing the meal were all captured with the battery-powered sensor device 10 but missed by the prior art battery-powered sensor device operating at a static processing frequency of the sensor signals, thereby demonstrating that the battery-powered sensor device 10 can achieve improved coverage of pollution events triggered by user activity in addition to achieving improved battery life of the battery 17. Specifically, it was found that compared to prior art battery-powered sensor devices operating in accordance with a static processing frequency of the sensor signals of the sensor 1 1, battery life of the battery 17 of the battery-powered sensor device 10 could be increased by up to 50%, and further increases in battery life may be expected based on the degree of activity of the user of the battery-powered sensor device 10.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several distinct elements. In the device claim enumerating several means, several of these means can be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

CLAIMS:

1. A battery-powered sensor device (10) comprising a sensor (1 1) for sensing an analyte of interest coupled to a processor (13) adapted to periodically process sensor signals obtained with the sensor and an accelerometer (15) coupled to the processor for providing an accelerometer signal indicating a degree of movement of the sensor device, wherein the processor is arranged to set a processing frequency of said sensor signals in accordance with said degree of movement.

2. The battery-powered sensor device (10) of claim 1 , wherein the processor (13) is arranged to scale the processing frequency of said sensor signals in accordance with the degree of movement.

3. The battery-powered sensor device (10) of claim 1 or 2, further comprising a look-up table comprising table entries associated with movement ranges of the sensor device, each movement range being associated with a particular processing frequency, wherein the processor (13) is adapted to:

identify a table entry in the lookup table associated with a movement range including the degree of movement; and

set the particular processing frequency associated with the identified movement range as the processing frequency of said sensor signals.

4. The battery-powered sensor device (10) of claim 3, wherein the table entries are configurable.

5. The battery-powered sensor device (10) of any of the preceding claims, further comprising a further sensor (12) coupled to the processor (13) adapted to periodically process further sensor signals obtained with the further sensor, wherein the processor is further adapted to set the processing frequency of said sensor signals in response to a processing result of at least one of said further sensor signals.

6. The battery-powered sensor device (10) of claim 5, wherein the processor (13) is arranged to set a further processing frequency of said further sensor signals in response to the degree of movement.

7. The battery-powered sensor device (10) of any of the preceding claims, further comprising a user interface coupled to the processor, wherein the processor (13) is further adapted to set the processing frequency of said sensor signals in response to a user input received from the user interface.

8. The battery-powered sensor device (10) of any of the preceding claims, wherein the sensor (1 1) for sensing an analyte of interest is arranged to sense a pollutant and the processor (13) is arranged to derive a pollutant level from a sensor signal provided by the sensor, the sensor device further comprising a communication module (16) coupled to the processor, wherein the processor is arranged to:

determine if the communication module has access to an external source for providing an external indication of said pollutant level and, if such access is available, obtain said external indication of said pollutant level and disable the sensor.

9. The battery-powered sensor device (10) of claim 8, wherein the

communication module (16) is arranged to connect to the external source for providing said external indication over a data communication network.

10. The battery-powered sensor device (10) of any of the preceding claims, further comprising a data storage device (14) coupled to the processor (13), wherein the processor is arranged to store sensor data derived from the sensor signals in the data storage device for evaluation of said sensor data.

1 1. The battery-powered sensor device (10) of any of the preceding claims, wherein the sensor device is a wearable sensor device.

12. The battery-powered sensor device (10) of any of the preceding claims, wherein the sensor (1 1) for sensing an analyte of interest is an air pollutant sensor such as an aerosol sensor or a particulate matter sensor.

13. The battery-powered sensor device (10) of claim 12, further comprising an air flow channel (19) housing the sensor (1 1), wherein the processor (13) is further adapted to calculate an air pollutant concentration from the sensor signal and the accelerometer signal.

14. A method (100) of operating a battery-powered sensor device (10) comprising a sensor (1 1) for sensing an analyte of interest coupled to a processor (13) adapted to periodically process sensor signals obtained with the sensor and an accelerometer (15) coupled to the processor, the method comprising, with said processor:

receiving (103) an accelerometer signal from the accelerometer indicating a degree of movement of the sensor device;

determining (105) the degree of movement of the sensor device from the received accelerometer signal; and

setting (107) a processing frequency of said sensor signals in accordance with the determined degree of movement.

15. The method (100) of claim 14, wherein the sensor (1 1) for sensing an analyte of interest is a pollutant sensor for determining a pollutant level and the battery-powered sensor device (10) further comprises a communication module (16) coupled to the processor (13), the method further comprising, with said processor:

checking if an external source for providing an external indication of said pollutant level is available; and in case of such availability:

receiving (201) an external indication of said pollutant level from the communication module; and

disabling (205) the sensor.