The cloud lidar, with the character of high precision and good stability, is an effective way to detect the cloud height. Pulse diode laser (PLD), as an essential part of the lidar system, needs the triggering pulse. In this paper, the emitting part of the lidar is studied,including the simulation of the backscatter SNR, the choose of the PLD and the design of trigging circuit to drive the 905nm PLD with the consideration of the optical system. A circuit for trigging the laser pulse with adjustable power and pulse width is contrived. Then the software Systemview is used to emulate the design and finally the making of PCB is finished. The results show whatever the parameters of the pulse, namely trigging pulse width, the rising edge, dithering , all these can be qualified to be in use in the practice and enjoys the merits of the low cost and convenience. The emitting module operates well.
KEYWORDS: Absorption, Methane, Signal to noise ratio, Sensors, Signal detection, Gas lasers, Hydrogen, Interference (communication), Adaptive optics, Environmental sensing
The leakage of methane and sulfureted hydrogen in the tunnel may threaten the environment, safety
and lead to damage and casualties. In this paper, a system based on the distribution feedback laser is
introduced to detect the leakage natural gas in the tunnel. The system can be used in the tunnel with the
length over 2km. In the system, two approaches, namely the direct absorption and wavelength
modulation is both adopted to acquire the concentration of methane and sulfureted hydrogen. The
results show that the remote sensing can reach up to two kilometers with the detectability of methane
2ppm and sulfureted hydrogen 20ppm respectively. This system is carried out in the Puguang Gas filed
for the first time and satisfactory results are obtained, making up the gap in such field as detecting
natural gas in domestic market.
Hydrogen Sulfide, with the character of erosion and strong toxicity, is a kind of associated
gas of nature gas. How to measure and monitor the hydrogen sulfide concentration becomes an
important issue to be solved in nature gas transfer-process. Online measurement for the hydrogen
sulfide concentration before the desulphurization remains very difficult in Bonan gas gathering station
of SINOPEC Shengli Oil Field (SOF).TDL(Tunable Diode Laser) can relative easily select the
absorption line of the detecting gas without the interference from other gas thus make the rapid and
accurate hydrogen sulfide measurement a possible. In this paper, a hydrogen sulfide measurement
system is designed and then be carried out in Bonan gas gathering station of (SOF) .The implemented
experiments showed the system effectively solved some problems such as overfall, temperature and
pressure. After comparing the hydrogen sulfide online detection sensor of the TDLAS industry with the
long hydrogen sulfide detection tube, the linear fitted relationship with the correlation coefficient of
99.96% between them was attained. In order to meet the requests of industrial field anti-explosion, the
open-path optical coupling technology was performed in china for the first time. All the results
demonstrate that the system will be put into use and enjoy a high application in the near future.
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