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If your going to to reinvent the wheel than maybe you need to figure in the leek rate of Helium through scuba valves. Alex >Granted, there is no great mystery to partial pressure blending, which is >what nearly everyone is doing to mix either nitrox or Tri-Mix. > >But I am not trying to build a partial pressure blending equation. >I am trying to build one that takes into account the compressibility of each >of the gases as well as the temp rise in the cylinder. If you can show me a >program that already does this, Please send me in that direction. So far I >have not been able to find such a beast. > >The gas companies can give you a very precise fill based upon standardized >tables they have developed over the years. They know their cylinders, and >they know exactly what to add to give you your desired blend. > >Dive shops can either fill by partial pressure, and check for O2 as a >partial verification of final contents or fill by molecular weight if they >have the proper scales to do so (and I have only seen 1 shop that does that.) > >If we are able to come up with some decent examples of what people are >doing, then we should be able to tune this little program to offer a third >option, the first that will take into account what is happening inside of >the cylinder during the fill. > >Molecular weight is probably the best route, as it is independant of temp >and compressibility. >but the scales are not cheap, and commonly not made to stand up to cylinders >being place upon them. >Though I did find a manufacturer that offer a scale with 0-120 lb range, and >accuracy of 1.0 grams who claims it is fully industrial and should stand up >to having steel cylinders "dropped" on it on a regular basis, and all this >for the low price of $1,250.00 > > > >Christopher M. Parrett, President, Abysmal Diving Inc. >Makers of ABYSS, Advanced Dive Planning Software. >6595 Odell Place, Suite G. Boulder CO, 80301 >Ph, 303-530-7248, Fx, 303-530-2808 >ftp://abysmal.com/users/abysmal http://www.emi.net/gulfstream/abyss/abyss.html > >-- >Send mail for the `techdiver' mailing list to `techdiver@terra.net'. >Send subscription/archive requests to `techdiver-request@terra.net'. >
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