Method and apparatus for testing gases, particularly breath alcohol
AssigneeIntoximeters, Inc.
InventorGlenn C. Forrester
Life of this patent
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Abstract
A method and apparatus for measuring the concentration of breath alcohol or other reactants is provided in which a breath sample is introduced to a fuel cell, wherein the number of electrons from the fuel cell resulting from oxidation of the alcohol in the breath rises to a peak and thereafter falls to a substantially steady minimum base to form a curve. The present method is based on the discovery that this curve, regardless of reactant concentration or age of fuel cell, is a log-normal distribution curve.
Claims13
In the method of measuring the concentration of a reactant in a gaseous sample in which the sample is introduced to a fuel cell, the reactant is reacted at the fuel cell, and an electrical output from the fuel cell resulting from reaction of the reactant is measured, the output rising to a peak and thereafter falling to a substantially steady minimum base to form a curve, the improvement comprising fitting the electrical output to a log-normal curve, said method including a step of determining said peak of said curve, a step of determining a point on said curve between said peak and said minimum, and a step of calculating the entire area under the curve from the identification of said peak and said point.
An apparatus for measuring a reactant in a gaseous sample by reacting the reactant in a fuel cell which produces an electrical signal, said signal rising in response to the presence of said reactant in contact with said fuel cell and falling again to a base level to establish a signal-time curve, the apparatus further comprising means for determining a peak of said curve, means for determining a second point on the curve, and means for extrapolating the area under the curve as a log-normal curve based on said peak and said second point.
Dependencies are inferred from the claim text.