On 10 January, 2017 - Robert Helling wrote: > Hi, > > > On 10.01.2017, at 14:01, Anton Lundin <[email protected]> wrote: > > > > I don't have a solution to your libdivecomputer issues, but other > > goodies. > > > > I saw the issue you created and got a idea, and found a probable > > explanation for the issue. > > > > It looks to be the pressure / volume calculations work done by Linus who > > "broke" the sac-tests. The sac-tests are planned for a ideal gas, but > > now when we do better sac calculations, we're off by a bunch. > > > > The proper fix would probably to fix pressure-track-code to use real > > volumes and not ideal gases, and also fix the sac-test.xml pressures to > > match with reality. > > > you were spot on. When I make gas compressibility factor always return 1.0, I > get back the 20l/min SAC. > > Which worries me a bit: I am surprised that the effect of using real gas > compressibility vs ideal gas law makes such a difference. 18.5 vs 20 is an 8% > difference in SAC rate!
Even if its 8%, more or less, we should change so the populate_pressure_information() works with volumes instead of pressures. That would get the calculations to match up, and get rid of the ugly sac-rising weirdness we currently are seeing. I have had "debug this sac-rising weirdness" on my todo-list for quite some time, but I never got around to actually look at it. Its great that we now know what the source of this weirdness is. //Anton -- Anton Lundin +46702-161604 _______________________________________________ subsurface mailing list [email protected] http://lists.subsurface-divelog.org/cgi-bin/mailman/listinfo/subsurface
