Gas detection device and gas detection process with automatic noise compensation

1 . A gas detection device for monitoring a spatial area for a predetermined target gas, the gas detection device comprising:

a sensor unit comprising: a sensor having a detection variable affected by a concentration of the target gas in the area to be monitored; and a detection variable sensor configured to measure an indicator for the detection variable and by using measurement results for the detection variable, to generate a measurement value series which series describes a time course of the detection variable;

an influencing variable estimator configured to compensate by calculation both an influence of a slower influencing variable on the detection variable and an influence of a faster influencing variable on the detection variable, wherein the compensation is performed based on the measurement value series, and to thereby determine an influence-corrected detection variable, wherein the slower influencing variable and the faster influencing variable occur independently of the target gas; and

an evaluation unit configured, depending on at least one value of the influence-corrected detection variable, to decide whether the target gas is present in the spatial area, and/or to determine the concentration of the target gas in the spatial area,

wherein the gas detection device is configured to generate an alarm if the target gas is present or if the target gas concentration is above a predetermined concentration threshold and wherein an output unit is configured to output this alarm in a form that can be perceived by a human;

wherein a narrower change tolerance band is predefined for a possible change per time unit of the detection variable due to the influence of the slower influencing variable on the detection variable such that the change per time unit of the influence is within the narrower change tolerance band,

wherein a wider change tolerance band is predefined for a possible change per time unit of the detection variable due to the influence of the faster influencing variable on the detection variable such that the change per time unit of the influence is within the wider change tolerance band,

wherein the narrower change tolerance band is contained in but does not coincide with the wider change tolerance band,

wherein a narrower value range is predefined for a possible variation of the detection variable due to the influence of the faster influencing variable on the detection variable such that the influence of the faster influencing variable is within the narrower value range,

wherein the influencing variable estimator is configured to compensate for the influence of the slower influencing variable on the detection variable using the measurement value series to determine an estimated time course of the influence of the slower influencing variable such that the change per time unit of the estimated time course of the influence of slower influencing variable lies within the narrower change tolerance band, and to subtract the estimated time course of the slower influencing variable from the detection variable or from the detection variable corrected for the influence of the faster influencing variable, and

wherein the influencing variable estimator is configured to compensate for the influence of the faster influencing variable on the detection variable using the measurement value series to determine an estimated time course of the influence of the faster influencing variable such that each value of the estimated time course lies in the narrower value range and a temporal change per time unit of the estimated time course of the influence of faster influencing variable lies in the wider change tolerance band, and to subtract the estimated time course of the influence of the faster influencing variable from the detection variable or from the detection variable corrected for the influence of the slower influencing variable.

2 . A gas detection device according to claim 1 , wherein:

each measured value of the measurement value series comprises a value of the detection variable at a sampling time;

the evaluation unit is configured to decide for at least one sampling time of the measurement value series, whether or not the target gas is present in the spatial area to be monitored at the sampling time;

the evaluation unit is configured to use for the decision the value of the influence-corrected detection variable at said sampling time, and

the influencing variable estimator is configured to use the measured value of the measurement value series for that sampling time to estimate the time course of the influence of the slower influencing variable and to estimate the time course of the influence of the faster influencing variable only if it has been decided that no target gas is present at the sampling time.

3 . A gas detection process for monitoring a spatial area for a predetermined target gas, the process comprising the steps of:

providing a gas detection device which comprises: a sensor unit comprising a sensor having a detection variable that is affected by a concentration of the target gas in the spatial area; and a detection variable sensor configured to measure an indicator for the detection variable;

providing a state in which a gas sample flows from the spatial area into an interior of the gas detection device;

with the detection variable sensor, repeatedly measuring an indicator for the detection variable, the detection variable being affected by the concentration of the target gas in the gas sample;

generating a measurement value series which describes the temporal course of the detection variable, the generation is performed using the results of the measurements of the detection variable;

using the measurement value series, compensating by calculation both an influence of a slower influencing variable and an influence of a faster influencing variable on the detection variable, to determine an influence-corrected detection variable, wherein the slower influencing variable and the faster influencing variable occur independently of the target gas;

deciding, depending on at least one value of the influence-corrected detection variable, whether the target gas is present in the spatial area, and/or determining the concentration of the target gas in the spatial area,

wherein an alarm is generated if the target gas is present or if the target gas concentration is above a predetermined concentration threshold and wherein an output unit outputs this alarm in a form that can be perceived by a human;

wherein the step of compensating the influence of the slower influencing variable on the detection variable comprises the steps of:

predefining a narrower change tolerance band for a possible change per time unit of the detection variable due to the influence of the slower influencing variable on the detection variable; and

determining an estimated time course of the influence of the slower influencing variable on the detection variable based on the measurement value series such that the temporal change per time unit of the estimated time course of the influence of the slower influencing variable lies in the narrower change tolerance band, and

subtracting the estimated time course of the slower influencing variable from the detection variable or from the detection variable corrected for the influence of the faster influencing variable, and

wherein the step of compensating for the influence of the faster influencing variable on the detection variable comprises the steps of:

predefining a wider change tolerance band for a possible change per time unit of the detection variable due to the influence of the faster influencing variable on the detection variable, wherein the narrower change tolerance band does not coincide with the wider change tolerance band and the narrower change tolerance band is contained in the wider change tolerance band;

predefining a narrower value range as the value range for a possible variation of the detection variable due to the influence of the faster influencing variable on the detection variable;

determining an estimated time course of the influence of the faster influencing variable on the detection variable based on the measurement value series such that each value of the estimated time course lies in the narrower value range, and the temporal change per time unit of the estimated time course of the influence of the faster influencing variable lies in the wider change tolerance band; and

subtracting the estimated time course of the influence of the faster influencing variable from the detection variable or from the detection variable corrected for the influence of the slower influencing variable.

4 . A process according to claim 3 , wherein:

each measured value of the measurement value series comprises a value of the detection variable referring to a respective sampling time;

the process further comprises for at least one sampling time of the measurement value series:

deciding based on the value of the influence-corrected detection variable at that sampling time whether or not the target gas is present in the area to be monitored at that sampling time; and

estimating the time course of the influence of the slower influencing variable and estimating the time course of the influence of the faster influencing variable based on the measured value of the measurement value series for the sampling time only if it was decided that no target gas is present at the sampling time.

5 . A process according to claim 3 , wherein if it has been decided that the target gas is present at the sampling time, a value determined by interpolation or extrapolation is used as the value of the respective estimated time course at the sampling time.

6 . A process according to claim 3 , wherein

first the estimated time course of the influence of the slower influencing variable is subtracted from the detection variable and subsequently the estimated time course of the influence of the faster influencing variable is subtracted from the detection variable corrected for the influence of the slower influencing variable, whereby the step of subtracting the time course of the influence of the slower influencing variable from the detection variable provides a measurement value series compensated for the influence of the slower influencing variable, and the step of determining the estimated time course of the influence of the faster influencing variable on the detection variable is carried out using the measurement value series compensated for the influence of the slower influencing variable; or

first the estimated time course of the influence of the faster influencing variable is subtracted from the detection variable and subsequently the estimated time course of the slower influencing variable is subtracted from the detection variable corrected for the influence of the faster influencing variable, whereby the step of subtracting the influence of the faster influencing variable from the detection variable provides a measurement value series compensated for the influence of the faster influencing variable, and the step of determining the estimated time course of the influence of the slower influencing variable on the detection variable is carried out using the measurement value series compensated for the influence of the faster influencing variable.

7 . A process according to claim 3 , wherein in a first phase, using the measurement value series, both the estimated time course of the influence of the slower influencing variable and the estimated time course of the influence of faster influencing variable are determined, and in a subsequent second phase, both the estimated time course of the slower influencing variable and the estimated time course of the faster influencing variable are subtracted from the detection variable.

8 . A process according to claim 3 , wherein:

another value range is predefined, namely for the influence of the slower influencing variable onto the detection variable;

the value range for the faster influencing variable is narrower than the value range for the slower influencing variable and is included in the value range for the slower influencing variable; and

the estimated time course of the influence of the slower influencing variable is determined such that additionally each value of the estimated time course of the influence of the slower influencing variable lies in the value range for the slower influencing variable.

9 . A process according to claim 8 , wherein if a predefined number of values of the estimated time course of the slower influencing variable is equal to an upper threshold or equal to the lower threshold of the value range for the slower influencing variable, a message is generated and output in a form that can be perceived by a human.

10 . A process according to claim 3 , wherein:

the step of determining the influence-corrected detection variable comprises the additional step of compensating by calculation an influence of a third influencing variable on the detection variable based on the measurement value series;

the third influencing variable also occurs independently of the target gas;

the step of compensating the influence of the third influencing variable on the detection variable comprises the steps of:

predefining a third change tolerance band for a possible change per time unit of the detection variable due to the influence of the third influencing variable on the detection variable, wherein the wider change tolerance band is narrower than the third change tolerance band and is included in the third change tolerance band;

predefining a third value range for the influence of the third influencing variable on the detection variable, wherein the third value range is narrower than the value range for the faster influencing variable and is included in the value range for the faster influencing variable;

determining an estimated time course of the influence of the third influencing variable such that each value of the estimated time course of the influence of the third influencing variable lies in the third value range and the change per time unit of the estimated time course lies in the third change tolerance band; and

subtracting the estimated time course of the influence of the third influencing variable from the detection variable or from the detection variable corrected for the slower and/or the faster influencing variable.

11 . A process according to claim 3 , wherein:

the sensor unit has an initial detection variable which is influenced by the concentration of the target gas in the area to be monitored; and

a calibration is performed at least once, comprising the steps of:

establishing a state in which an environment and/or the interior of the gas detection device is free of the target gas;

measuring a value assumed by the initial detection variable for the established gas-free state;

determining a zero point based on the measured value of the initial detection variable; and

using a difference between the initial detection variable and the zero point as the detection variable.

12 . A process according to claim 3 , wherein the evaluation unit is configured to generate an output based on the decision whether the target gas is present in the spatial area, and/or based on the determination of the concentration of the target gas in the spatial area.

13 . A process according to claim 12 , wherein based on the generated output, an output unit issues an alarm in a form that can be perceived by a human and/or indicates a value of the determined target gas concentration in a form that can be perceived by a human.

14 . A gas detection device according to claim 1 , wherein the evaluation unit is configured to generate an output based on the decision whether the target gas is present in the spatial area, and/or based on the determination of the concentration of the target gas in the spatial area.

15 . A gas detection device according to claim 14 , further comprising an output unit comprised by or connected to the gas detection device and operatively connected to the evaluation unit, wherein based on the generated output, the output unit issues an alarm in a form that can be perceived by a human and/or indicates a value of the determined target gas concentration in a form that can be perceived by a human.

16 . A gas detection device according to claim 1 , wherein:

a value range for the influence of the slower influencing variable on the detection variable is predefined;

the value range for the faster influencing variable is narrower than the value range for the slower influencing variable and is included in the value range for the slower influencing variable; and

the estimated time course of the influence of the slower influencing variable is determined such that additionally each value of the estimated time course of the influence of the slower influencing variable lies in the value range for the slower influencing variable.

17 . A gas detection device according to claim 1 , wherein:

the evaluation unit is configured to access an initial detection variable of the sensor unit, which initial detection variable is influenced by the concentration of the target gas in the area to be monitored; and

the evaluation unit is configured in a gas detection device state in which an environment and/or the interior of the gas detection device is free of the target gas, to provide a calibration, comprising:

measuring a value assumed by the initial detection variable for the established gas-free state;

determining a zero point based on the measured value of the initial detection variable; and

using a difference between the initial detection variable and the zero point as the detection variable.

18 . A gas detection device for monitoring a spatial area for a predetermined target gas, the gas detection device comprising:

a sensor unit comprising: a sensor having a detection variable affected by a concentration of the target gas in the area to be monitored; and a detection variable sensor configured to measure an indicator for the detection variable and to generate a detection variable measurement value series, which detection variable measurement value series describes a time course of the detection variable;

an influencing variable estimator comprising a processor and memory configured to determine an influence-corrected detection variable that at least partially corrects an influence of a slower influencing variable on the detection variable and at least partially corrects an influence of a faster influencing variable on the detection variable, wherein the slower influencing variable and the faster influencing variable occur independently of the target gas, wherein a narrower change tolerance band is predefined and stored in the memory for a possible change per time unit of the detection variable due to the influence of the slower influencing variable on the detection variable, wherein a wider change tolerance band is predefined and stored in the memory for a possible change per time unit of the detection variable due to the influence of the faster influencing variable on the detection variable and wherein the narrower change tolerance band is narrower than the wider change tolerance band and wherein the narrower change tolerance band is contained in the wider change tolerance band and wherein a narrower value range is predefined and stored in the memory for a possible variation of the detection variable due to the influence of the faster influencing variable on the detection variable,

wherein the influencing variable estimator is configured to determine an estimated time course of the influence of the slower influencing variable with a recursive calculation based on the measurement value series such that the change per time unit of the determined estimated time course of the influence of slower influencing variable lies within the narrower variable change tolerance band,

wherein the influencing variable estimator is configured to determine an estimated time course of the influence of the faster influencing variable with a recursive calculation based on the measurement value series such that each value of the determined estimated time course of the influence of the faster influencing variable lies in the narrower value range and the change per time unit of the determined estimated time course of the influence of the faster influencing variable lies in the wider change tolerance band, and

wherein the influencing variable estimator is configured to determine the influence-corrected detection variable by:

subtracting the determined estimated time course of the influence of the slower influencing variable from the detection variable to form a detection variable corrected for the influence of the slower influencing variable and subtracting the determined estimated time course of the influence of the faster influencing variable from the detection variable corrected for the influence of the slower influencing variable; or

subtracting the determined estimated time course of the influence of the faster influencing variable from the detection variable to form a detection variable corrected for the influence of the faster influencing variable and subtracting the determined estimated time course of the influence of the slower influencing variable from the detection variable corrected for the influence of the faster influencing variable; and

an evaluation unit comprising the processor and memory or comprising another processor and memory, the evaluation unit being configured to decide whether the target gas is present in the spatial area, and/or to determine the concentration of the target gas in the spatial area based on at least one value of the influence-corrected detection variable, wherein the gas detection device is configured to generate an alarm if the target gas is present or if the target gas concentration is above a predetermined concentration threshold and wherein an output unit is configured to output this alarm in a form that can be perceived by a human.

19 . A gas detection device according to claim 18 , further comprising an output unit comprised by the gas detection device or connected to the gas detection device and operatively connected to the evaluation unit, wherein based on the generated output that indicates whether the target gas is present in the spatial area, and/or indicates the concentration of the target gas in the spatial area, the output unit issues an alarm in a form that can be perceived by a human and/or indicates a value of the determined target gas concentration in a form that can be perceived by a human.

20 . A gas detection device according to claim 19 , wherein:

a value range for the influence of the slower influencing variable on the detection variable is predefined;

the value range for the faster influencing variable is narrower than the value range for the slower influencing variable and is included in the value range for the slower influencing variable; and

the estimated time course of the influence of the slower influencing variable is determined such that additionally each value of the estimated time course of the influence of the slower influencing variable lies in the value range for the slower influencing variable.