| CPC G01N 27/4141 (2013.01) [G01N 33/0016 (2013.01); G01N 33/007 (2013.01)] | 21 Claims |
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1. A sensor system for ascertaining the 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 metal oxide semiconductor material which is interactive with said preselective target substance whereby, when said material reaches a certain temperature, there is a rapid formation of oxides of the target substance;
an element, 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;
circuitry for emitting a signal at a predetermined time which 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 to one at or above 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 said rapid oxide formation to occur;
circuitry for detecting a signal representative of the conductivity of the metal oxide semiconductor material during the time the temperature of said 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
circuitry for performing a differential comparison of said respective detected signals to derive a further signal representative of the target substance concentration.
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