GB1105046A - Instruments and methods for measuring the carbon monoxide content of combustion engine exhaust gases - Google Patents

Abstract

1,105,046. Measuring carbon monoxide concentration electrically. WESTF€LISCHE BERGGEWERKSCHAFTSKASSE. Sept. 8, 1966 [Sept. 8, 1965 (2)], No.40195/66. Heading G1N. Carbon monoxide is detected in the presence of hydrogen and hydrocarbons, i.e. in exhaust gases from an I. C. engine, by mixing the exhaust with air in known proportions and catalyzing the exothermic oxidation of both the carbon monoxide and the hydrogen present but not the hydrocarbons, by passing the gases over two platinum resistors 19, 20, Fig. 4, the latter heated to a temperature at which it catalyzes the oxidation of both the carbon monoxide and hydrogen and the former heated to a lower temperature at which it catalyzes the oxidation of the hydrogen only. The two resistors are connected in one branch of a Wheatstone Bridge, Fig. 3 (not shown), which is balanced in the absence of carbon monoxide and hydrogen. In operation, therefore, the out-of-balance reading on the meter (5), gives an indication of the concentration of carbon monoxide present. The different temperatures of the resistors 19, 20 are obtained, using the same heating current, by using different wire strengths and/or coil distance and/or diameter. In the embodiment, exhaust gases are withdrawn from the exhaust by a probe (2, 12), Figs. 1, 2 (not shown), adjustably attached to a vertical rod (1, 11). The gases are cooled as they pass along the probe, the condensed water vapour collecting in a water separator (6). Solid impurities in the gases are removed by a ceramic filter (7) and lead tetraethylene by a further filter (8) of e.g. active carbon. The gases then pass into the measuring device where they are mixed with air in the ratio 1:1 and finally flow over the two heated resistors.