mjj@stda.jhuapl.edu (Marshall Jose) (03/17/90)
The utilities around my neighborhood are aging, and I occasionally catch a whiff of what I'm sure is methyl mercaptan (the tracer used in natural gas distribution). I've brought the local gas company out for a look, but they find nothing. I don't believe them. I remember reading some years ago about how to make a methane detector. It had something to do with a vacuum-tube-like filament, and something magic occurred within it when in the presence of methane & some other gaseous hydrocarbons, something about a change in current. Does anybody out there know how one actually makes this device? Or, has anyone seen a recent construction article for a gas leak detector? Thanks, Marshall Jose WA3VPZ mjj@aplvax.jhuapl.edu || ...mimsy!aplcen!aplvax!mjj
bbesler@vela.acs.oakland.edu (Brent Besler) (03/18/90)
I am pretty sure the leak detectors are ionization type. There is a high
potential across two plates sufficient to ionize hydrocarbon gases, but not
oxygen or nitrogen. A current proportional to the HC conc. is passed through
the sensing element. Similar A/C refrigerant leak detectors exist also.
Soapy water works pretty well at finding leaks. You can buy a leak
detector from a heating and cooling jobber/supply house.
Brent H. Beslerlarry@kitty.UUCP (Larry Lippman) (03/19/90)
In article <386@vela.acs.oakland.edu>, bbesler@vela.acs.oakland.edu (Brent Besler) writes: > I am pretty sure the leak detectors are ionization type. There is a high > potential across two plates sufficient to ionize hydrocarbon gases, but not > oxygen or nitrogen. A current proportional to the HC conc. is passed through > the sensing element. The above is not true. You may be alluding to a Flame Ionization Detector (FID) used on a gas chromatograph. Such a detector employs a hydrogen _flame_ to ionize the gas in addition to a DC potential imposed across the detection electrode (which is connected to an electrometer). The traditional explosive gas detector, the MSA "Explosimeter", uses a differential thermal conductivity detector. Some specific gas detection methods use a catalyst whose temperature increases in the presence of the target gas; for example, some CO detectors employ a catalyst which oxidizes CO to CO2, giving off heat in the process. There are also various solid-state detectors for hydrocarhon gases, some of which employ catalytic coatings applied directly to silicon temperature sensors. <> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp. <> UUCP {boulder|decvax|rutgers|watmath}!acsu.buffalo.edu!kitty!larry <> TEL 716/688-1231 || 716/773-1700 {utzoo|uunet}!/ \uniquex!larry <> FAX 716/741-9635 || 716/773-2488 "Have you hugged your cat today?"
davidh8@pogo.WV.TEK.COM (David Haight) (03/20/90)
The last issue of MACHINE DESIGN (2/22) Pg.35 "Thin Film Gas Detectors" reports on work being done at U of MI. It mentions that a thin film of tungsten, rhodium, palladium or titanium will change resistance with exposure to methane. They have had success in the ppm range and expect ppb. These will be cheap - disposable.