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The CO2 transitions near 2.6 μm are analized systematically to find the best line pairs for measurement of gas temperature and CO2 concentration in a elevated temperature environment. A line pair of CO2 at 3727.94 cm-1 and 3728.41 cm-1 is selected based on some selection criterions. The selected line pair is useful for development of CO2 concentration and temperature TDL sensors.
The accidents of methane explosion affect the coal mine safety in production and the lives of workers seriously. Monitoring the methane concentrations safely with real-time and accurately protection is very important. In this paper, detecting methane concentrations by the infrared methane sensing system based on infrared spectra absorption method. In view of the shortcomings used for mine sensor Currently,...
The detection sensitivity of methane trace-gas concentration using optical fiber gas sensor based on tunable diode laser absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy (WMS) is very high, the absorption line is detected using a laser diode wavelength-sweep technique, and Fourier series is used to analysis WMS signal. The ratio of the second harmonic peak and the first harmonic...
Tunable diode laser absorption spectroscopy (TDLAS) is a widely used technique in measuring the concentration of trace gas due to its high sensitivity, high selectivity, and fast time response. The fluctuations of temperature in the gas cell can cause the characteristics of the absorption spectra to change in the TDLAS methane sensing system. The three absorption lines in the R(3) transitions of 2v...
We demonstrate that employing integrated absorption of multiple lines or summation of the absolute values of the wavelength modulation spectroscopy signals, sensitivities of ppb can be achieved for the detection of trace gases.
This paper describes an optical fiber sensor for the monitoring of ammonia gas. An open path optical technique is used to analyze the absorption lines of ammonia within the ultra violet region. Experimental results describing the operation of the sensor are presented and are compared with theory. A comparison between a commercial sensor has been carried out and cross sensitivity testing with regard...
We report on the realization of an optoacoustic sensor based on mid-infrared quantum-cascade lasers (QCLs) for the detection of nitric oxide (NO) and formaldehyde (CH2O). A resonant photoacoustic cell equipped with 4 electret microphones was excited in its first longitudinal mode by the modulated laser light. A detection limit of 150 parts in 109 (ppbv) for NO and CH2O was found, using distributed...
This paper describes an optical fibre sensor for the monitoring of ammonia gas. An open path optical technique is used to analyze the absorption lines of ammonia within the ultra violet region. A cross sensitivity study mainly regarding water vapor and the advantage of using ultra violet light have been discussed. Experimental results describing the operation of the sensor are presented and are compared...
A novel integrated sensor system for indoor air quality (IAQ) measurement based on infrared absorption principle is developed; the system is designed to monitor and evaluate the indoor air quality according to Malaysian IAQ standard. It can measure the concentration of three gases; carbon dioxide (CO2), carbon monoxide (CO) and formaldehyde (CH2O) to the 1 part per million (ppm) level. The system...
Emission control and reduction of harmful gases produced by combustion engines is a very important task. There is need for a high resolution online detection of harmful gases. This work presents a novel optical sensor system based on newly developed LEDs working in the ultraviolet and visible wavelength range. The developed potentially low cost LED based system is able to individual detect NO2 and...
In this paper, high performance of distributed feedback quantum cascade lasers operation at 7.7 ??m and 8.4 ??m have been investigated. With a broad gain spectrum, the DFB QCLs employing different grating periods exhibit a wavelength span of 0.17 ??m at room temperature and total wavelength coverage of 0.33 ??m at various heatsink temperatures. For the 8.4 ??m DFB-QCLs with a high side mode suppression...
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