A high-sensitivity combustible gas monitor based on dual metal oxide semiconductor sensors

We used the differential method of a dual metal oxide semiconductor sensor configuration to measure low concentrations, about 10 ppm, of combustible gases such as methane, propane, and hexane. One sensor was a measuring component and the other was a compensating component located downstream of a carbon absorption filter. Nafion tubes, which are water molecule exchangers, were used upstream of the sensors to regulate the moisture level in the gas passing through the tube. The difference of the two sensor signals was a measure of the concentration of combustible gases. This system solution utilized sensor potentials and at the same time resolved sensor problems. We believe that a few ppm of propane can be measured by a carefully matched sensor pair. We also tested the dual sensor monitor to detect methane leaks for landfill or pipeline applications.