Ultra Low Power CH4 Monitoring with Wireless Sensors

We propose a novel method to reveal and measure natural gas presence in air, using commercial off the self MOX gas sensors in wireless sensor networks. This technique reduces the power consumed by the catalytic sensors of a factor 10x, by performing an analysis on a reduced sampled period and thus extending the autonomy of battery powered system. The information about the gas concentration is derived from the sensor transient response through a discrete cosine transform (DCT) analysis. This permits to immediately discriminate between clean air and hazardous situations. The characterization of the sensing device has been conducted using a range of humidity conditions to demonstrate the effectiveness of the proposed approach. Two different duty cycle rates are characterized and simulated to demonstrate that it is possible to achieve up to 75 weeks of autonomy using commercial wireless sensor nodes, each powered by two AA batteries.