A novel compact intrinsic safety full range Methane microprobe sensor using “trans-world” processing method based on near-infrared spectroscopy

Abstract

Abstract A novel compact intrinsic safety full range methane (CH4) microprobe sensor based on spectroscopy techniques is proposed for leaking detection in explosion risk environment, such as: nature gas industries, petro-chemical enterprise and coal mines. The developed detection method combines the benefits of calibration-free direct absorption spectroscopy (CF-DAS) and the high sensitivity wavelength modulation spectroscopy (WMS). And the “trans-world” method results are switched according to the selected variation point of the detection concentration, thereby ensuring the possibility of high accuracy of full-range detection. The physical dimension of the sensor is minimized into 4.7 cm (length) and 3.5 cm (diameter), that benefit of the highly integrated circuit board and compact optical design. After proportional integral differential (PID) modulation, the temperature fluctuation range of laser can be limited within -0.02 ∼ +0.02 ℃. The relative detection error is -1.5 %∼0.53 % within the full detection range. And the continuous detection analysis indicates that measurement precision of 89 ppm for CH4. Through the signal-to-noise ratio (SNR) analysis, the minimum detection limit can be obtained as 6.48 ppm m (1σ). Meanwhile, the measurement response time of the microprobe is about 8 s. Compared with other reported results, this probe sensor reveals the further improvement of the probe structures, detectable range and column density.