On Tue, Oct 28, 2014 at 9:36 AM, Paul Sargent <paul.lions...@icloud.com> wrote: > > On 27 Oct 2014, at 17:56, Rodrigo Severo <rodr...@fabricadeideias.com> wrote: > >>> For example: A one hour dive should be 20bar (60 litres) out of a standard 3 >>> litre cylinder - just calculating 1 litre a minute. That's just way off. I >>> always use about ~50 bar on a ~40 metre dive, so I tend to make sure I've >>> got at least 100 bar when I jump in. >>> >>> (or have a missed a different method of calculating things in the various >>> mails?) >> >> The method of calculation is just that but, as I see things, it would >> happen the other way around: >> >> After this dive Subsurface would show you that your oxygen SAC is 2,5 >> l/min (50 bar of a 3 l cylinder used on an hour dive). So on your next >> planning you should use 2,5 l/min for oxygen and not the usual 1 >> l/min. > > The problem here is that going from a one hour to a two hour dive doesn’t > double my O2 use. I might go from 50 bar to 70 bar (i.e. Same use for the > ascent aspects, another 20 bar for the extra hour). > > To me it sounds to me like we’d need a SAC component (litres/min) and an > ascent component (litres/metre.bar). Diluent would just have a descent > component (litres/metre.bar). In the example above reasonable figure might be: > > - O2 SAC: 1 litre/min > - O2 Ascent: > 30bar * 3l = 90l > 90l / 40 metres = 2.25 litres/metre > 2.25l / 2.5 bar (Avg. Pressure during ascent) = 0.9l / metre.bar
I don't understand way the ascent component has a bar in it (and why you divided the average consumption per meter by the average pressure). Shouldn't the ascent component just be 2.25 litres/metre here? > - Diluent Descent: > 50bar * 3l = 150l > 150l / 40 metres = 3.75l / metre > 3.75l / 2.5 bar (Avg. Pressure during descent) = 1.5l / metre.bar Here again I don't understand why getting a litre/metre*bar. Why not jsut litre/metre? Rodrigo _______________________________________________ subsurface mailing list subsurface@subsurface-divelog.org http://lists.subsurface-divelog.org/cgi-bin/mailman/listinfo/subsurface