DAC -> SAC?

[Swedinsidemount]

If you have the average depth for a dive, total time, pressure used and tank size then you can calculate your SAC. Simply work out how many cf of gas you used in total then divide by the average pressure (depth/33 +1) and divide again by total time. Now you have your SAC. In my opinion this is the best way to calculate SAC because it includes the descents and ascents and is more accurate for planning dives. As for whatever dac is I have no idea

According to your calculations, my SAC would be an astonishing .47 cf/min while diving in mild current, it just seems really low to me, when i started diving it was around 0.7- 0.8, thanks for the input....

 

[tursiops]

Tank capacity, pressure, air used, average depth, BT... heres a random example:
(80 cubic foot x 2000 psi)/3000 psi = 53.3 cubic feet of air used
53.3 cubic feet / 20 minutes = 2.6 cubic feet/minute at 66 feet depth
2.6 cubic feet/min / 3x atmospheric density at 66ft = 0.89 cubic feet/min SAC rate

This calculation is perfect for SAC.
What is this "DAC" you speak of?

 

[rick00001967]

i am a bit foggy this morning so i am assuming i am missing something here in this thread.

 

[Swedinsidemount]

This calculation is perfect for SAC.
What is this "DAC" you speak of?

In my mind, it would be your DIVE Air Consumption that could be calculated on the spot. Say you plan to dive down to a 60ft reef, but once you get there it is really cold and there is a strong current, so you move to a shallower part of the reef, how long can you stay there now with your air left? It would be like a deco algorithm.....<TG>

 

[tursiops]

In my mind, it would be your DIVE Air Consumption that could be calculated on the spot. Say you plan to dive down to a 60ft reef, but once you get there it is really cold and there is a strong current, so you move to a shallower part of the reef, how long can you stay there now with your air left? It would be like a deco algorithm.....<TG>

Have you looked at the "Gas Time Remaining" display some computers have?
For example:

 

[Swedinsidemount]

Have you looked at the "Gas Time Remaining" display some computers have?
For example:
View attachment 660744

That's neat! Never heard of that before, wonder why it doesn't become more mainstream.....

 

[Raphus]

That's neat! Never heard of that before, wonder why it doesn't become more mainstream.....

That's more or less what you meant, right?

Check out min gas calculation.
It's not that hard to calculate, but very useful in my opinion.

 

[scubadada]

@Capt. T. Goetz

SAC is psi/min/atm. If you multiply that by the tank factor cu ft/psi, you get your RMV in cu ft/min/atm. SAC is cylinder dependent, RMV is not. When I download my Oceanic computer, it gives me both SAC and RMV, the cylinder is available from a drop down menu. My Shearwater computer gives me just SAC, I have to calculate the RMV by multiplying by the tank factor. Here is an example from the Oceanic log:

My Oceanic computers have given me air time remaining (ATR) since 2002. This is the gas time remaining to make a normal ascent with a safety stop or deco stop(s) and be left with your designated reserve pressure. My Shearwater computer gives me gas time remaining (GTR), defined in @tursiops post, above https://www.scubaboard.com/community/threads/dac-sac.608257/reply?quote=9380806 This does not include a safety stop. GTR is turned off if you go into deco.

 

[Swedinsidemount]

@Capt. T. Goetz

SAC is psi/min/atm. If you multiply that by the tank factor cu ft/psi, you get your RMV in cu ft/min/atm. SAC is cylinder dependent, RMV is not. When I download my Oceanic computer, it gives me both SAC and RMV, the cylinder is available from a drop down menu. My Shearwater computer gives me just SAC, I have to calculate the RMV by multiplying by the tank factor. Here is an example from the Oceanic log:
View attachment 660762 View attachment 660763

My Oceanic computers have given me air time remaining (ATR) since 2002. This is the gas time remaining to make a normal ascent with a safety stop or deco stop(s) and be left with your designated reserve pressure. My Shearwater computer gives me gas time remaining (GTR), defined in @tursiops post, above https://www.scubaboard.com/community/threads/dac-sac.608257/reply?quote=9380806 This does not include a safety stop. GTR is turned off if you go into deco.

Which Shearwater com do you have.... thanks for the example <TG>

 

[tursiops]

@Capt. T. Goetz I have not looked in detail, but it is my impressions that ALL dive computers that are air-integrated (by hose or wireless) have a version of the "air/gas time remaining" information available for display during the dive. I believe, in most cases, it is based on how many psi/minute you have used over the last few (2?) minutes, and extrapolating that to the remaining gas pressure in the tank. (Details will vary from computer to computer.)
It is only a valid estimate if you maintain the same depth and the same workload.