Hand-held unit for simultaneous detection of methane and ethane based on NIR-absorption spectroscopy

Study of a new evanescent wave optical fibre sensor for methane detection based on cryptophane molecules

“…One paper reports on the development of a hand-held and low-power sensor, based on direct absorption spectroscopy for leak detection (methane), natural gas identification and lower-explosion-limit (LEL) measurements (methane and ethane). The achievable detection limit is lower than 5 ppm [7].…”

Optical gas sensing: a review

“…It is common to use a spectral fitting technique (typically the Marquardt -Levenburg algorithm [183] ) to determine the gas concentration from a line trace. Spectral fitting allows several gas lines to be separated from a single trace, and has for example been used to detect methane and ethane levels in natural gas, with a limit of detection for methane at the ppm level using a 20cm pathlength [184] .…”

“…A PC based TDLS system has been implemented with four lock-in amplifier channels, with performance claimed to be equal to that of a standard system based around discrete lock-in amplifiers [203] . Various groups have developed board-level systems with 2f WMS and line scanning, laser control, 2f demodulation and curve fitting for standalone sensors, including oxygen sensors [187,204] , and methane / ethane [184] . Using arbitrary waveform programming, an optimal modulation signal has been devised for WMS that maximises the time spent sampling the most important elements of the spectrum in the curve fit, to give a twofold improvement in SNR [205] .…”

Methane sensing at room temperature using photothermal cantilever deflection spectroscopy

“…However, the detection of methane at room temperature using sorption-based techniques is a challenge due to the inert properties of non-polar methane, which has little tendency to lose or gain electrons at room temperature [4], causing detection approaches based on chemoselective interfaces to be less effective when used for relatively inert molecules such as methane. Optical detection systems [5][6][7][8][9] for methane detection have attracted attention due to their several advantages; such as the ability to operate in an oxygen free environment, ability to detect a small amount of gas by choosing an appropriate wavelength, as well as the intrinsic safety of the detection system [5]. Stewart et al [7] have reported the design of a multi-point fiber optic methane sensor using a distributed feedback laser (DFB) source with a branched fiber network and microoptic cells, Cong et al [8] have demonstrated using an InGaAsP distributed feedback laser for developing a methane detection system, and Massie et al [6] have designed a sensor based on near-IR LEDs operating around the overtone absorption lines of methane at 1660 nm.…”