On Thu, Feb 13, 2014 at 16:58:02 +0200, Willem Ferguson wrote: > I am doing a technical qualification with IANTD and they use SAC as > the rate of decrease per minute in the pressure in the gas cylinder > (units=bar/minute). -- [SAC/RMV] Is this something worth worrying > about for the SAC rate given on the dive info panel?
I'd show the actual units where possible, be it psi/minute, litres/minute or something else. With the units visible it's easier to understand what the figures mean, even if your understanding of SAC/RMV would differ from that of mine. Point being, in my opinnion "SAC: 9.7" isn't obvious, but "SAC: 9.7 psi/min" and "SAC: 16 l/min" are. (I hope I didn't get my numbers all wrong.) In a way I prefer RMV because of "minute" and "volume" in it, but I also dislike it because it's not immediately obvious if it means surface consumption or not. On the other hand SAC is clear about this, but it gives no clues about used units. That said, I've learnt to measure my (surface) gas consumption in litres/minute. In Finnish/local scuba jargon we often refer to this with "pintakulutus", which nicely translates to "surface consumption". In fact the first time I heard of RMV (and using pressure per time) was just six months ago. When I was going through IANTD's material I found that having gas consumption in pressure/time caused me lots of unnecessary work. Apart from trivial calculations in which using psi/minute required only a single division, I always ended up calculating everything in volume/time. That was obviously because of my fixation with methods I was familiar with, but IIRC also because that allowed me to avoid using IANTD's comprehensive collection to conversion and gas matching tables. Besides, with proper units, the calculations were actually very simple. ;-) _______________________________________________ subsurface mailing list [email protected] http://lists.hohndel.org/cgi-bin/mailman/listinfo/subsurface
