KEYWORDS: Detection and tracking algorithms, Signal detection, Absorption spectrum, Sensors, Environmental sensing, Environmental monitoring, Temperature metrology, Calibration, Gas sensors, Signal processing
With the rapid development of industry, the content of greenhouse gases such as CH4 in the atmosphere is increasing, which has a certain impact on human production and life. Therefore, high-precision gas detection has been a research hotspot in the field of gas sensing, but the temperature and pressure changes in the environment will affect the line shape of the gas absorption spectra, resulting in errors in gas concentration monitoring. This paper presents a temperature-pressure compensation algorithm. Firstly, the temperature and pressure compensation coefficients under different ambient temperatures and pressures are obtained by simulation. Then, the temperature and pressure of the ambient gas are monitored, and the detection signal is compensated in real time. Finally, the monitored gas concentration is calculated according to the linear relationship between the detection signal amplitude and the gas concentration. The experimental results show that the detection accuracy of the gas detection system is significantly improved after using the compensation algorithm to compensate for the signal amplitude. Taking the measurement of 2 ppm CH4 concentration as an example, the maximum error of CH4 concentration obtained after using the temperature-pressure compensation algorithm is 5%, while the maximum error of CH4 concentration obtained without using the temperature-pressure compensation algorithm is 9.5%. The system was also utilized for long-term stability monitoring of 2 ppm CH4, and the concentration fluctuation of the system was only 0.04 ppm. According to theoretical and experimental proofs, the monitoring stability of the TDLAS gas sensing system can be effectively improved and the monitoring error can be reduced by this temperature-pressure compensation algorithm.
A methane leakage monitoring system based on light-induced thermoelastic spectroscopy (LITES) is proposed in this manuscript. We use our methane leakage monitoring system for methane detection at the wavelength of 1650.961 nm. This system has a minimum detection limit of 62.8 ppm·m and a good linear response (R-square = 0.997). We also simulated methane leakage, and the results show that our system has the ability to monitor methane leakage.
Quartz enhanced photoacoustic spectroscopy (QEPAS) is a high performance trace gas detection technique that plays an important role in food safety, pollution monitoring and breath analysis applications. It is well known that the sensitivity of QEPAS gas detection system is proportional to excitation laser power and thus the performance of QEPAS-based sensors can benefit from the high output power levels achieved as a result of technology developments by the high power laser. This paper mainly introduces three kinds of QEPAS gas sensor based on fiber-ring laser.
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