Question Determining SAC Rate

[Pavao]

Not making that distinction at all.

No, and I apologize for not being as clear.
I quoted your post as it makes a distinction from SAC and RMV, but I was commenting about it in more general sense, see examples of threads posted discussing definitions of SAC vs RMV.

And we have seen here on the board and elsewhere where people talk about SAC being psi/min at the surface and RMV being volume/min at depth.

Sometime somewhere someone has/is making it seem important that we have a measurement distinction/definition of a surface consumption and consumption at depth. To make matters worse, there's this psi/min vs volume/min.

PSI/BAR needs to be used at some point in these calculations, because that's how we measure the contents of our cylinders, but because it is cylinder size dependent, we convert it to volume, which is a more convenient straight forward way of planning our dives.

Having this psi/min way of measuring consumption at any ATA just adds unnecessarily confusion.

 

[scubadada]

This artificial swimming at depth for 10 minutes is absolute ********. Calculate your RMV for full dives under a variety of circumstances.

 

[Edward3c]

Flowstate Divers actually made a very good video on this:

I really like their videos, short and sweet without the 15 minute intro. I can't figure out if the fact the narration sounds like the Diary of a Sad Cat guy (Ze Frank) makes it better or worse though.

What a convoluted, and long winded set of calculations. Provided you know your average depth gas consumption can easily be calculated after a series of dives. For me it’s 16Lt/min in U.K. waters and 11Lt/min in the tropics.

 

[Cthippo]

This artificial swimming at depth for 10 minutes is absolute ********. Calculate your RMV for full dives under a variety of circumstances.

The problem s that "Average depth" is a hard thing to measure, functionally impossible if your computer doesn't have that feature. I suppose you could try and dive as close to a square profile and swim in circles on the bottom at a known depth, but that still doesn't account for ascent, descent, safety stop, etc. 10 mins at known depth has fewer variables.

 

[DiveLikeAMuppet]

This artificial swimming at depth for 10 minutes is absolute ********. Calculate your RMV for full dives under a variety of circumstances.

It's good enough to give you a starting point. Depending on what you do, your RMV could be wildly different on different dives. You might also be using breathing from different cylinders on the same dive

 

[tursiops]

This artificial swimming at depth for 10 minutes is absolute ********. Calculate your RMV for full dives under a variety of circumstances.

This is easy to say today, when computers will tell you average depth. Not many years ago you really did need to stay at a constant depth for X minutes.

 

[Pavao]

If someone asks me what my consumption is, whether the person uses SAC or RMV, I'll have to assume they're asking about surface consumption, otherwise they'd have to specify the depth of which they want to know my consumption.
And if on their definition of what either SAC or RMV is they use pressure/min, then they'll have to specify what cylinder they're asking.

Otherwise it'd be an incomplete question to which I can never answer.

I hope this illustrates better how stupid I think the discussion is about using pressure/min.

 

[tursiops]

If someone asks me what my consumption is, whether the person uses SAC or RMV, I'll have to assume they're asking about surface consumption, otherwise they'd have to specify the depth of which they want to know my consumption.
And if on their definition of what either SAC or RMV is they use pressure/min, then they'll have to specify what cylinder they're asking.

Otherwise it'd be an incomplete question to which I can never answer.

I hope this illustrates better how stupid I think the discussion is about using pressure/min.

Maybe you should take into account that many (most?) divers are using AL80s all the time, everywhere they go around the world....psi/min or bars/min is perfectly acceptable. I'm sorry you find pressure/min som confusing. And it is A:LWAYS surface consumption...no matter the names or units.

 

[scubadada]

The problem s that "Average depth" is a hard thing to measure, functionally impossible if your computer doesn't have that feature. I suppose you could try and dive as close to a square profile and swim in circles on the bottom at a known depth, but that still doesn't account for ascent, descent, safety stop, etc. 10 mins at known depth has fewer variables.

Nearly all modern computers have average depth either on the on board log or the download. Even my old Oceanic VT3 has average depth and calculates both SAC and RMV. The computer was released about 2006, I have had it since 2010.

 

[tursiops]

Nearly all modern computers have average depth either on the on board log or the download. Even my old Oceanic VT3 has average depth and calculates both SAC and RMV. The computer was released about 2006, I have had it since 2010.
View attachment 822523

LOL. You and I are obsessive...we actually download our computers!
Only (as far as I know) only rather recent computers display it on the computer.