Portable Remote Methane Detector A novel gas leak detector enables us to find gas leaks remotely by a hand-scanning laser.

OBJECTIVE The portable remote methane detector using a tunable diode laser was developed for gas leak detection.@An operator can search for gas leaks within a radius of several meters by hand scanning with a laser.

Figure1 The appearance of the detector

PRINCIPLE Remote sensing is accomplished using infrared absorption spectroscopy with a 1.65ƒÊm InGaAsP DFB laser for backscattered light from topographical targets(walls,ceilings,pipes,etc.) The wavelength of the light source is fixed on the 2ƒË3-band R(3) absorotion line of methane(1.6537ƒÊm). High sensitivity is achieved by second-harmonic detection using wavelength modulation spectroscopy.

Figure2 The second-harmonic detection	Figure3 The definition of ppmEm

PERFORMANCE The experimental detection limit(signal-to-noise ratio‚P) obtained in the laboratory was 3ppmEm with the time constant of 0.1sec. In most actual cases, the detector can distinguish 100-ppmEm methane at a distance of 1 to 10 meters. Experimental result shows that an operator can find a city gas leak of 10 cc/min at the distance of 5 meters.

Figure4 The experimental setup	Figure5 The experimental result

PRSPECTS The detector will be commercialized in Japan by March 2001. International export will start in due course.

For More Information: Takaya Iseki Technical Research Institute Tokyo Gas Co., Ltd. 16-25, Shibaura 1-Chome, Minato-ku, Tokyo 105-0023, Japan Tel:+81-3-5484-4811 Fax:+81-3-3453-2674 E-mail:iseki@tokyo-gas.co.jp

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