Measuring concentrations of a target gas

Abstract

An electronic device comprises a gas sensor sensitive to a target gas and arranged inside a housing of the electronic device or attached thereto, to detect a concentration of the target gas in an environment of the electronic device. A processing unit is provided and configured to determine a concentration of the target gas outgassed from one or more components of the housing or inside the housing dependent on one or more first measurement results supplied by the gas sensor in response to one or more first measurements, and to determine the environmental target gas concentration dependent on the determined outgassed target gas concentration and dependent on a second measurement result (R.sub.OM) supplied by the gas sensor in response to a second measurement (OM). Outgassing is understood as the release of chemical substances from the one or more components.

Claims

1. Method for determining a concentration of a target gas in an environment of an electronic device by means of a gas sensor sensitive to the target gas and arranged inside a housing of the electronic device or attached thereto, comprising conducting one or more first measurements by the gas sensor resulting in one or more first measurement results, determining a concentration of the target gas outgassed from one or more components of the housing or inside the housing dependent on the one or more first measurement results, wherein outgassing is understood as the release of chemical substances from the one or more components, conducting a second measurement by the gas sensor resulting in a second measurement result, and determining the environmental target gas concentration dependent on the determined outgassed target gas concentration and dependent on the second measurement result.

2. Method according to claim 1, wherein the one or more first measurements are preparatory measurements conducted to determine the outgassed target gas concentration, wherein the second measurement is an operational measurement conducted to determine the environmental target gas concentration, and wherein the first and/or second measurement results depend on both the environmental target gas concentration and the outgassed target gas concentration.

3. Method according to claim 1, comprising conducting the more first measurements at different temperatures of the electronic device, resulting in the first measurement results being temperature dependent.

4. Method according to claim 3, comprising determining outgassed target gas concentrations for different temperatures dependent on the temperature dependent first measurement results.

5. Method according to claim 4, comprising measuring a temperature in combination with each of the first measurements at a location of the gas sensor, and storing each outgassed target gas concentration as determined in combination with the corresponding temperature as measured.

6. Method according to claim 3, comprising determining a characteristic of outgassed target gas concentration over temperature from the temperature dependent first measurement results and the different temperatures by interpolation or by extrapolation.

7. Method according to claim 6, comprising determining the characteristic from weighting the temperature dependent first measurement results.

8. Method according to claim 7, comprising determining a slope of the characteristic from a difference between two of the first measurement results divided by a difference between the different temperatures associated with the two first measurement results, determining an offset of the characteristic subject to the determined slope and subject to at least one of the two first measurement results and the different temperatures associated with the two first measurement results, wherein the characteristic is determined subject to the determined slope and subject to the determined offset.

9. Method according to claim 3, comprising measuring a temperature in combination with the second measurement at a location of the gas sensor, and determining the environmental target gas concentration for the subject temperature dependent on the outgassed target gas concentration as determined for the measured temperature and dependent on the second measurement result, wherein the outgassed target gas concentration for the subject temperature is determined from the characteristic by entering the temperature measured and one of calculating, looking up or determining the outgassed target gas concentration for this temperature.

10. Method according to claim 1, comprising starting the first measurements in response to a trigger indicating varying temperatures to be expected and in response to a change in the measured temperature at a location of the gas sensor.

11. Method according to claim 10, comprising starting the first measurements in response to detecting a recharge process of a battery of the electronic device.

12. Method according to claim 1, according to claim 10, comprising conducting the first measurements during a period in time in which the environmental target gas concentration is expected to be constant, starting the first measurements at a predetermined point in time, wherein the predetermined point in time is defined as a specific time of day, at night, per one of days, multiple of days, weeks, multiple of weeks, months, or multiple of months.

13. Method according to claim 1, comprising repeating the step of conducting the one or more first measurements by the gas sensor and resulting in one or more updated first measurement results, determining an updated concentration of the target gas outgassed from the one or more components of the housing or inside the housing dependent on the one or more updated first measurement results, and subsequent to the determination of the updated outgassed target gas concentration determining the concentration of the target gas in the environment of the electronic device dependent on the updated determined outgassed target gas concentration and dependent on the second measurement result.

14. Method according to claim 1, comprising determining the environmental target gas concentration Iamb according to: $c_{amb}={\left(\frac{R_{OM}}{R_B}\right)}^{\frac{1}{n}}*c_B-c_B$ wherein: c.sub.B is the outgassed target gas concentration; R.sub.OM is the second measurement result; R.sub.B is the measurement result corresponding to the outgassed target gas concentration c.sub.B; n is the sensitivity of the gas sensor.

15. Method according to claim 1, wherein the target gas includes a volatile organic compound.

16. Computer program element, comprising computer program code for performing the following steps when executed on a processing unit: receiving one or more first measurement results taken by a gas sensor sensitive to a target gas and arranged in or at an electronic device, determining a concentration of the target gas outgassed from one or more components of the housing or inside the housing dependent on the one or more first measurement results, wherein outgassing is understood as the release of chemical substances from the one or more components, receiving a second measurement result taken by the gas sensor, and determining a concentration of the target gas in an environment of the electronic device dependent on the determined outgassed target gas concentration and dependent on the second measurement result.

17. Electronic device, comprising a gas sensor sensitive to a target gas and arranged inside a housing of the electronic device or attached thereto to detect a concentration of the target gas in an environment of the electronic device, and a processing unit configured to determine a concentration of the target gas outgassed from one or more components of the housing or inside the housing dependent on one or more first measurement results supplied by the gas sensor in response to one or more first measurements, wherein outgassing is understood as the release of chemical substances from the one or more components, and determine the environmental target gas concentration dependent on the determined outgassed target gas concentration and dependent on a second measurement result supplied by the gas sensor in response to a second measurement.

18. Electronic device according to claim 17, comprising a temperature sensor configured to measure a temperature at a location of the gas sensor.

19. Electronic device according to claim 18, wherein the housing comprises a cavity, wherein the gas sensor is arranged in or at the cavity, and wherein the temperature sensor is configured to measure a temperature inside the cavity.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The embodiments defined above and further aspects, features and advantages of the present invention can also be derived from the examples of embodiments to be described hereinafter and are explained with reference to the drawings. In the drawings the figures illustrate in

(2) FIG. 1 a schematic electronic device according to an embodiment of the present invention,

(3) FIG. 2 a diagram showing various charts thereby illustrating a method according to an embodiment of the present invention,

(4) FIG. 3 sample concentration characteristics used for introducing a method according to an embodiment of the present invention, and

(5) FIG. 4 a flow chart representing a method for operating a portable electronic device according to an embodiment of the present invention.

MODES FOR CARRYING OUT THE INVENTION

(6) Same or similar elements are referred to by the same reference numerals across all Figures.

(7) FIG. 1 illustrates an electronic device 1 according to an embodiment of the present invention. The electronic device 1 is only schematically illustrated, does not scale, and may be embodied in many different ways. The electronic device 1 comprises a housing 3 and a cavity 31 in the housing 3. A gas sensor 2 is arranged inside the cavity 31, in particular in view of mechanical protection. A temperature sensor 5 is arranged in the cavity 31, e.g. next to the gas sensor 2.

(8) A processing unit 4 is comprised in the electronic device 1 and receives measurement results in form of signals from the gas sensor 2 and the temperature sensor 5. On the other hand, the processing unit 4 may control the gas sensor 2, and possibly the temperature sensor 5, e.g. by triggering a measurement of the gas sensor 2, in one embodiment including activating a heater of the gas sensor 2 prior to taking a measurement, in particular in case the gas sensor 2 is a metal oxide based chemoresistive gas sensor 2.

(9) The electronic device 1 may include a battery 6, such as a rechargeable battery, for powering the functions of the electronic device 1, and specifically for powering the processing unit 4 and the gas sensor 2. As is indicated in FIG. 1, the battery 6 may be thermally coupled to the housing 3, and in particular to the cavity 31. In particular, upon recharging the battery 6 heat may be generated that heats up components of the housing 3, such as components building the cavity 31.

(10) The gas sensor 2 and, if available, the temperature sensor 5, may be arranged on and electrically connected to a carrier such as a printed circuit board (PCB), which may also contribute to forming the cavity 31. Additionally there may be more carriers such as further PCBs. The processing unit 4 may be arranged on the same carrier, or on a different carrier. Other components of the housing 3 contributing to the cavity 31 may include one or more of: plastic parts of the housing, rubber parts e.g. for sealing purposes, adhesives. There may also be further electrical components inside the housing 3 and/or the PCB may be coated. The gas sensor 2 preferably is embodied as integrated gas sensor chip containing a semiconductor substrate, for example. In one embodiment, the processing unit 4 is integrated into the gas sensor chip. The temperature sensor 5 may be integrated into the same chip. In a different embodiment, the gas sensor 2, the temperature sensor 5 and the processing unit 4 may be embodied as discrete elements assembled e.g. on a common PCB.

(11) The gas sensor 2 is arranged to measure a concentration c.sub.amb of a target gas in the environment, which may include one or more VOCs in one embodiment. As is illustrated in FIG. 1, the environmental target gas concentration c.sub.amb can be found in the environment of the electronic device 1. The environmental target gas concentration c.sub.amb diffuses into the cavity 31 and finally can be detected there by means of the gas sensor 2. However, components of the electronic device 1, such as the PCB, plastic parts of the housing, rubber and/or adhesive material may also outgas VOCs, i.e. the target gas to be detected by the gas sensor 2. Accordingly, a portion of the target gas inside the cavity 31 may not originate from the environment but from the electronic device itself.

(12) Accordingly, what is actually measured by the gas sensor 2 is an accumulation of the environment originating target gas concentration c.sub.amb and of the device originating target gas concentration c.sub.B. Whenever the gas sensor takes a measurement, the supplied measurement result typically is composed of two different concentration portions originating from the two different sources, i.e. the environment and the device.

(13) FIG. 2 shows a diagram of sample target gas concentrations over time supporting an understanding of the method according to an embodiment of the present invention.

(14) The target gas concentration originating from the electronic device itself, also named the outgassed target gas concentration, is denoted as c.sub.B. The target gas concentration of the environment is denoted as c.sub.amb. In FIG. 2, the device originating target gas concentration c.sub.B is assumed to be a constant c.sub.B0 over time t except for two peaks, one in the interval 0<t<t.sub.1, the other one in the interval t.sub.1<t<t.sub.2. The constant c.sub.B0 is also referred to as baseline concentration c.sub.B0 or background concentration c.sub.B0. It is assumed that the rise in the device originating target gas concentration c.sub.B from constant c.sub.B0 is caused by a rise in temperature of/in the electronic device. For example, it may be assumed that components of the device 1 defining a cavity are heated and cause a rise in the target gas released from these components. It is assumed, that at time t=t.sub.01 the temperature T e.g. of the subject components that outgas into the cavity 31 ramps up, e.g. starting from room temperature T.sub.0, and falls back to room temperature T.sub.r at time t=t.sub.04 as is indicated in the temperature T over time t chart in FIG. 2. This causes the device originating target gas concentration c.sub.B to rise from constant c.sub.B0 to a maximum at t=t.sub.04 in view of the inertness of the system, and a subsequent fall down to constant c.sub.B0 again.

(15) The target gas concentration of the environment c.sub.amb is assumed to be constant c.sub.amb0 over time t in interval 0<t<t.sub.1, and rises asymptotically in the interval t.sub.1<t<t.sub.2. Accordingly, a scenario is shown in which during the first interval 0<t<t.sub.1 the electronic device is maintained in an environment with a constant target gas concentration c.sub.amb0 while in the second interval t.sub.1<t<t.sub.2 either the location of the electronic device remains as is but the target gas concentration in the same environment rises, or the electronic device changes location and is brought into a new environment with a different target gas concentration c.sub.amb1. The upper graph shown in FIG. 2 represents the accumulated target gas concentration c.sub.amb+c.sub.B that is measured by the gas sensor, e.g. the gas sensor 2 of FIG. 1. Accordingly, given that the gas sensor supplies measurement results R, it is assumed that the measurement results R are proportional to the sum of the two target gas concentrations:
R˜(c.sub.amb+c.sub.B)  (I)

(16) Within the first interval 0<t<t.sub.1, first measurements PM are taken by the gas sensor, and in particular five first measurements PM are taken at times t.sub.01 . . . t.sub.04, t.sub.05 indicated by the dashed lines. These first measurements are also referred to as preparatory measurements given that their aim is to determine the target gas concentration c.sub.B originating from the device and not the environmental target gas concentration c.sub.amb that is determined in the subsequent operational measurement. For this reason, it is preferred to choose an interval in time for the first measurements PM in which the environmental target gas concentration c.sub.amb remains or is expected to be more or less constant, i.e. c.sub.amb0 in the present example. In such scenario, device components exposed to heat and outgassing into the cavity cause the device originating target gas concentration c.sub.B to rise, and fall again after a drop in temperature, i.e. after a deactivation of the heat source.

(17) Preferably, the first measurements PM are triggered by an indicator for a change or an expected change in temperature, and in particular for a rise of the relevant temperature T. For this reason, a temperature sensor such as the temperature sensor 5 of the electronic device 1 of FIG. 1 may measure the temperature T of the cavity 31. In case the temperature T rises, and preferably if such temperature rise exceeds a threshold, the first one of the first measurements PM is executed and finally provides a first measurement result R at t=t.sub.01
R(t=t.sub.01;T=T.sub.0)˜c.sub.amb0+c.sub.B0.

(18) In the same way further first measurements PM are conducted at subsequent times t.sub.02, t.sub.03, t.sub.04, t.sub.05, and the corresponding measurement results R(t,T) are recorded.

(19) FIG. 3 illustrates a characteristic c(T) of the target gas concentration c over temperature T to be determined and quantified e.g. under the conditions for interval 0<t<t.sub.1 of FIG. 2. In particular, two first measurements are taken at two different temperatures T.sub.1 and T.sub.2, the results of which two first measurements are R.sub.1 at temperature T.sub.1, and R.sub.2 at temperature T.sub.2, having in mind that during the first measurements the environmental target gas concentration c.sub.amb=c.sub.amb0 is constant. Another assumption is that there is a temperature T.sub.0, at which the device originating target gas concentration c.sub.B is or approximately is zero. For facilitating illustration, it is assumed that this temperature T.sub.0=0° C. Further, more realistically, the characteristic c(T) may follow a logarithmic function rather than a linear relation such that the characteristics and the corresponding equations rather include logarithmic or exponential functions. However, for the sake of illustration, the present linear function between c and T is assumed.

(20) From the two measurement results R.sub.1 and R.sub.2 and the corresponding temperatures T.sub.1 and T.sub.2, a slope ΔR of the characteristic c(T) can be determined by:
ΔR=(R.sub.2−R.sub.1)/(T.sub.2−T.sub.1)  (II)

(21) On the other hand, the assumed present characteristic c(T) can be described by:
c(T)=c.sub.amb0+ΔR*T  (III)

(22) such that in a next step the environmental target gas concentration c.sub.amb0 present during the first measurements can be derived from (I) by means of:
c.sub.amb0=c(T)−ΔR*T  (IV)
and specifically by:
c.sub.amb0=c(T.sub.1)−ΔR*T.sub.1

(23) wherein c(T.sub.1)=R.sub.1

(24) such that finally the characteristic c over temperature T is described by:
c(T)=(R1−ΔR*T1)+ΔR*T  (V)

(25) By means of equation (V), the device originating target gas concentration c.sub.B can be calculated by:
c.sub.B(T)=c(T)−c.sub.amb0=c(T)−(R1−ΔR*T1)  (VI)

(26) Hence, for any concentration R˜c measured during an operational measurement, in combination with knowing or measuring the corresponding temperature T, the corresponding device originating target gas concentration c.sub.B can be determined by equation (VI).

(27) The lower graph in FIG. 3 referred to by c.sub.ini shows a characteristic that initially is used in the electronic device prior to the first determination of the (upper graph) characteristic c(T). Such initial characteristic may be measured and recorded in the device e.g. at the manufacturer of the gas sensor or the electronic device. In the present example, the subject one or more gas sensors may be located in a defined environment, e.g. a test/calibration environment where the environmental target gas concentration c.sub.amb=0, or, alternatively is at a defined level known. The one or more electronic devices may be heated to different temperatures T and the measurement results may be processed to the characteristic c.sub.ini(T) and recorded in the gas sensor or in the device. As can be derived from FIG. 3, the slope of the characteristic may change over time. Presently, c(T) has steeper rise than c.sub.ini(T). In another embodiment, subsequent to the determination of c(T), either at fixed intervals or in response to a trigger, the characteristic c(T) may be updated into c.sub.upd(T) by applying the same routines as during the first measurements PM described.

(28) Returning to FIG. 2, once the device originating target gas concentration c.sub.B(T) is determined—e.g. according to equation (VI) or any other equation that matches the subject characteristic—operational measurements OM can be conducted. The only difference of an operational measurement OM from a preparatory measurement PM is that for the operational measurement OM the device originating target gas concentration c.sub.B is to be determined upfront, and that, of course, the measurement conditions now allow for a varying environmental target gas concentration c.sub.amb.

(29) In FIG. 2, in the second interval t.sub.1<t<t.sub.2, two operational measurements OM are conducted at times t.sub.11 and t.sub.12 resulting in two second measurement results R.sub.OM. While at time t.sub.11 the device is not heated and thus c.sub.B is not increased but remains constant at a constant value c.sub.B0 for the subject temperature T, the environmental target gas concentration c.sub.amb rises, e.g. because the subject target gas concentration actually rises in the environment of the electronic device. At time t.sub.12 instead, the rise of the environmental target gas concentration c.sub.amb has stopped at c.sub.amb1, however, the device was heated again such the device originating target gas concentration c.sub.B exceeds c.sub.B0.

(30) Accordingly, and decoupled from any specific embodiment, the environmental target gas concentration c.sub.amb preferably is calculated by:

(31) $\begin{array}{cc}{c}_{\mathrm{amb}}={\left(\frac{R_{OM}}{R_B}\right)}^{\frac{1}{n}}*c_B-c_B& \left(\mathrm{VII}\right)\end{array}$

(32) wherein:

(33) c.sub.B is the device originating target gas concentration for the subject temperature T, may be determined e.g. by equation (VI) with c(T)=R.sub.OM; T may be measured by the temperature sensor;

(34) R.sub.OM is the second measurement result, i.e. the raw data of the gas sensor measured at e.g. at t.sub.11 or t.sub.12;

(35) R.sub.B is also referred to as baseline concentration, i.e. measurement result R corresponding to the device originating target gas concentration c.sub.B at the subject temperature T; n is the sensitivity of the gas sensor.

(36) FIG. 4 illustrates a sample flow chart of a method according to an embodiment of the present invention, e.g. with reference to FIG. 2: In step S20, the gas sensor takes a measurement and returns R.sub.OM as a result. In step S21, the present temperature T(t.sub.11) is measured. In step S22, the device originating target gas concentration c.sub.B is looked up for the specific temperature T(t11). In step S23, the environment originating target gas concentration c.sub.amb is determined according Formula (VII).

(37) In step S24, appropriate measures may be taken in response to the determination of the environmental target gas concentration c.sub.amb, such as issuing a warning in case the environmental target gas concentration c.sub.amb exceeds a threshold, the threshold e.g. representing a toxic concentration level, or displaying the determined environmental target gas concentration c.sub.amb on a display of the electronic device, or transmitting the environmental target gas concentration c.sub.amb to a server or a different device for further processing.

(38) As to the second operational measurement, the gas sensor provides a measured value R.sub.OM at t=t.sub.12, while the same steps S20 to S24 are executed. The only difference is that a different device originating target gas concentration value c.sub.B is determined in view of a different temperature T measured at time t=t.sub.12 compared to the temperature measured at time t=t.sub.11.

(39) While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practised within the scope of the following claims.