Gas detection device and gas detection process with automatic noise compensation

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.

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.