| abstract |
The gas monitor of the present invention is capable of simultaneously determining the concentrations of two members of a family of oxygen-containing gases present in an air sample. The monitor utilizes a four electrode potentiostat (58, 70, 12, 14) including two indicating electrodes (58, 70) mounting in a single electrochemical cell (8) and immersed in an aqueous electrolyte (10). The air sample containing the two family members is initially passed to the first indicating electrode (58), where electroreduction of the first family member produces a first electrical current directly proportional to the concentration of the first family member in the sample. Thereafter, the gas sample is passed through an oxidizing means (4) interconnected between the two indicating electrodes (58, 70), where all of the second family member is converted into the first family member. Electroreduction of the first family member at the second indicating electrode (70) is then carried out to produce a second electrical current, which second current is electronically processed in analog measurement circuitry (74) to provide an indirect determination of the amount of the second family member present in the sample. |