System and method for gas concentration measurement

A method of mitigating the distortion of results from a sensor system for ascertaining the concentration of a preselected target substance, said distortion stemming from the sensor system's departure from a state of calibration, which comprises

• providing a metal oxide semiconductor material which is interactive with a preselected target substance whereby, when said material reaches a certain temperature, there is a rapid formation of oxides of the target substance;
• further providing an element, located in operative association with the metal oxide semiconductor material, which element is capable of giving off heat energy sufficient to cause the metal oxide semiconductor material to reach or exceed said certain temperature;
• and
• enabling a determination of the target substance's concentration through
• (i) interconnection of the element with circuitry for emitting a signal at a predetermined time, which signal initiates the powering of the element to increase its output of heat energy such that the temperature of the metal oxide semiconductor material increases from one below said certain temperature, and for further emitting another signal at a subsequent predetermined time, which other signal initiates the depowering of the element to decrease its output of heat energy such that the metal oxide semiconductor material's temperature is permitted to decrease from one at or above said certain temperature to one below said certain temperature, the duration elapsing while the metal oxide semiconductor material is below said certain temperature being such that if present target substance is adsorbed on said metal oxide semiconductor material in an amount effective to support said rapid oxidation formation, and the duration elapsing while the metal oxide semiconductor material is at or above said certain temperature being such that adequate opportunity is afforded for such rapid oxide formation to occur;
• (ii) interconnection of the metal oxide semiconductor material with circuitry capable of detecting a signal provided during the time the temperature of the metal oxide semiconductor material is below said certain temperature, and for detecting another signal representative of the conductivity of the metal oxide semiconductor material during the time the temperature of said material is at or above said certain temperature;
• and
• (iii) interconnection of said detection circuitry with circuitry capable of performing a differential comparison of said respective detected signals to derive yet another signal representative of the target substance concentration.

A method of mitigating the distortion of results from a sensor system for ascertaining the concentration of a preselected target substance, which distortion stems from the sensor system's departure from a state of calibration, said sensor system including a metal oxide semiconductor material which is interactive with said preselected target substance at or above a certain temperature resulting in rapid formation of one or more oxides of said target substance, whereby a change in conductivity of the material also occurs, which method comprises

• contacting said metal oxide semiconductor material with said preselected target substance;
• at a predetermined time during the contact between the metal oxide semiconductor material and the preselected target substance, heating said material such that its temperature increases from one below said certain temperature to one at or above said certain temperature, the duration elapsing while the material is below said certain temperature being such that if present target substance is adsorbed on said metal oxide semiconductor material in an amount effective to support said rapid oxide formation;
• at a subsequent predetermined time during the contact between the metal oxide semiconductor material and the preselected target substance, permitting the temperature to decrease from one at or above said certain temperature to one below said certain temperature, the duration elapsing while the material is at or above said certain temperature being such that adequate opportunity is afforded for said rapid oxide formation to occur;
• generating a signal representative of the conductivity of the metal oxide semiconductor material while the material is below said certain temperature;
• generating another signal representative of the conductivity of the metal oxide semiconductor material while the material is at or above said certain temperature;
• detecting the conductivity-representative signal generated while the material's temperature is below said certain temperature;
• detecting the conductivity-representative signal generated while the material's temperature is at or above said certain temperature;
• and
• performing a differential comparison of said respective detected signals to derive a further signal representative of the target substance concentration.

A sensor system for ascertaining a concentration of a preselected target substance, said system having a mitigated tendency for yielding results distorted by the departure from a state of calibration, which comprises

• a sensor including a metal oxide semiconductor material, which material is interactive with said preselected target substance at a minimum temperature resulting in rapid formation of one or more oxides of said target substance, whereby a change in conductivity of the material also occurs;
• an element for heating the metal oxide semiconductor material, said element being located such that it is capable of bringing about a modulation of the material's temperature from one at which said rapid formation of oxides does not take place, to one at or above said minimum temperature at which rapid oxide formation does take place;
• circuitry for emitting a signal at a predetermined time, which signal initiates manipulation of said heating element's behavior to modulate said material's temperature from one at which rapid oxide formation does not take place to one at or above said minimum temperature at which rapid oxide formation does take place, such that a precursor mode of sensor operation endures up until the time said material's temperature reaches the minimum one at which rapid oxide formation takes place, and for further emitting another signal at a subsequent predetermined time, which other signal manipulates said heating element's behavior to permit said material's temperature to decrease below the minimum one at which rapid oxide formation takes place, such that a measurement mode of sensor operation endures up until the time said material's temperature decreases below the one at which rapid oxide formation takes place, the material being capable of temperature change sufficiently rapid that the duration elapsing between said predetermined time and said subsequent predetermined time is short enough that the effect of any substantial departure from the sensor system's state of calibration is negated, the duration of said precursor mode being such that if present target substance is adsorbed on said metal oxide semiconductor material in adequate amount to support said rapid oxidation formation at said minimum temperature, and the duration of said measurement mode being sufficient that an adequate opportunity is afforded for said rapid formation of oxides and a corresponding increase in conductivity of the metal oxide semiconductor material to take place;
• circuitry for detecting a signal representative of the conductivity of the metal oxide semiconductor material during the precursor mode of sensor operation, and for detecting another signal representative of the conductivity of said material during the measurement mode of sensor operation;
• and
• circuitry for performing a differential comparison of said respective detected signals to derive a further signal representative of the target substance concentration.

A method of mitigating distortion of results from a sensor system for ascertaining a concentration of a preselected target substance, said distortion stemming from the sensor system's departure from a state of calibration, which comprises

• providing a metal oxide semiconductor material, which material is interactive with said preselected target substance at a minimum temperature resulting in rapid formation of one or more oxides of said target substance, whereby a change in conductivity of the material also occurs;
• further providing an element for heating the metal oxide semiconductor material, said element being located such that it is capable of bringing about a modulation of the material's temperature from one at which said rapid oxide formation does not take place, to one at or above said minimum temperature at which rapid oxide formation does take place;
• and
• enabling a determination of the target substance's concentration through
• (i) interconnection of the heating element and circuitry, wherein the circuitry is configured to emit a signal at a predetermined time, which signal initiates manipulation of said heating element's behavior to modulate said material's temperature from one at which rapid oxide formation does not take place to one at or above said minimum temperature at which rapid oxide formation does take place, such that a precursor mode of sensor operation endures up until the time said material's temperature reaches the one at which rapid oxide formation takes place, and for further emitting another signal at a subsequent predetermined time which other signal initiates manipulation of said element's behavior to permit said material's temperature to decrease from one at or above which rapid oxide formation does take place to one at which rapid oxide formation does not take place, such that a measurement mode of sensor operation endures up until the time said material's temperature decreases below the one at which rapid oxide formation takes place, the material being capable of temperature change sufficiently rapid that the duration of time elapsing between said predetermined time and said subsequent predetermined time is short enough that the effect of any substantial departure from the sensor system's state of calibration is negated, the duration of said precursor mode being such that if present target substance is adsorbed on said metal oxide semiconductor material in adequate amount to support said rapid oxidation formation at said minimum temperature, and the duration of said measurement mode being sufficient that an adequate opportunity is afforded for said rapid oxide formation and a corresponding increase in conductivity of the metal oxide semiconductor material to occur;
• (ii) interconnection of said metal oxide semiconductor material and said power source, or an alternative power source, whereby to generate current in, and provide a signal representative of the conductivity of the metal oxide semiconductor material during the precursor mode of sensor operation, and generate a current in, and provide a further signal representative of the conductivity of said material during the measurement mode of sensor operation;
• and
• (iii) interconnection of said material with circuitry capable of detecting the signal provided during the precursor mode of sensor operation, and the further signal provided during the measurement mode of sensor operation;
• and
• (iv) interconnection of said detection circuitry with circuitry capable of performing a differential comparison of said respective detected signals to derive yet another signal representative of the target substance concentration.

A method of mitigating distortion of results from a sensor system for ascertaining a concentration of a preselected target substance, which distortion stems from the sensor system's departure from a state of calibration, said sensor system including a metal oxide semiconductor material which is interactive with said preselected target substance at a minimum temperature resulting in rapid formation of one or more oxides of said target substance, whereby a change in conductivity of the material also occurs, which method comprises

• contacting said metal oxide semiconductor material with said preselected target substance;
• at a predetermined time during the contact between the metal oxide semiconductor material and the preselected target substance, heating said material such that its temperature is modulated from one below the minimum temperature at which rapid oxide formation occurs to one at or above said minimum temperature at which rapid oxide formation occurs for a period sufficient that rapid oxidation of the target substance is effected, such that a precursor mode of sensor operation endures up until the time said material's temperature reaches the one at which rapid oxide formation takes place and, at a subsequent predetermined time during the contact between the metal oxide semiconductor material and the preselected target substance, permitting the temperature of said material to modulate from one at or above said minimum temperature at which rapid oxide formation occurs to one less than the minimum temperature at which rapid oxide formation occurs, such that a measurement mode of sensor operation endures up until the time said material's temperature decreases below the one at which rapid oxide formation takes place, the material being capable of temperature change sufficiently rapid that the duration elapsing between said predetermined time and said subsequent predetermined time is short enough that the effect of any substantial departure from the sensor system's state of calibration is negated, the duration of said precursor mode being such that if present target substance is adsorbed on said metal oxide semiconductor material in adequate amount to support said rapid oxidation formation at said minimum temperature, and the duration of said measurement mode being sufficient that an adequate opportunity is afforded for said rapid oxide formation and a corresponding increase in conductivity of the metal oxide semiconductor material to occur;
• generating a signal representative of the conductivity of the metal oxide semiconductor material during the precursor mode of sensor operation, and another signal representative of the conductivity of the metal oxide semiconductor material during the measurement mode of sensor operation;
• detecting the signal generated during the precursor mode of sensor operation, and the other signal generated during the measurement mode of sensor operation;
• and
• performing a differential comparison of said respective detected signals to derive a further signal representative of the target substance concentration.