Based on direct absorption spectroscopy (DAS), a portable methane (CH4) detection device was implemented. The device mainly includes a dual-channel non-dispersive infrared sensor (integrated with an infrared light source, light path and pyroelectric detector), a driving circuit of the sensor, an ARM11 embedded WinCE system, and a LabVIEW-based data-processing platform. Experiments were carried out with prepared CH4 samples to investigate the sensing performance. The relative detection error is less than 9.14% within the measuring range of 0—7×10-2. For a CH4 sample with concentration of 0 (i.e., pure nitrogen), the measured concentration fluctuation range is −1.2×10-5—+2×10-5. An Allan deviation analysis on the gas sample with concentration of 0 indicates that the 1σ limit of detection (LoD) of the device is 4.8×10-6 with an average time of 1 s. Experiments were performed on three CH4 samples with different concentrations to test the response time, which is validated to be less than 20 s. Due to the small size of the ARM11 embedded system and the powerful data processing capability of the LabVIEW platform, the proposed portable and miniaturized CH4 sensor shows a good application prospect in mining operations and some other industrial fields.
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