SAC Tutorial please

[dcdev]

Hello O Knowledgeable Ones (this is the Internet ya know )

I could not find any info on how to properly use the SAC calculation in Oceanlog. The VT3 manual and OceanLog help file don't say much on the subject.
I've seen mentions here and there in some of the threads, but nothing specific. So how does one use Oceanlog to determine one's SAC rate?
Is it as simple as entering 3000 in the Working Pressure for AL80s (or 3500 for HP Steel, etc)?

Thanks

 

[vondo]

Hello O Knowledgeable Ones (this is the Internet ya know )

I could not find any info on how to properly use the SAC calculation in Oceanlog. The VT3 manual and OceanLog help file don't say much on the subject.
I've seen mentions here and there in some of the threads, but nothing specific. So how does one use Oceanlog to determine one's SAC rate?
Is it as simple as entering 3000 in the Working Pressure for AL80s (or 3500 for HP Steel, etc)?

Thanks

In "Imperial" units, if you give Ocean log the working pressure, starting pressure, ending pressure, and capacity of the tank, it will calculate your SAC in cf/min (by using the average depth in the calculation).

In metric units, it doesn't need the working pressure because of the way tank capacities are expressed.

Lots of information elsewhere in this board on how to actually do this (rather simple) calculation.

 

[ocpaul]

OK - what do you need to do the SAC calculation?

1. The duration of the dive - Oceanlog knows this value

2. Average depth - Oceanlog calculates this value..used to have a problem with that calculation, but seems to be doing it OK now.

3. The amount of gas you used during the dive - to calculate this Oceanlog needs to know the starting and ending pressure, and the volume of the tank at a specified pressure. If you have an AI computer the start and end pressure will come in with the rest of the date. If you do not have an AI computer you would have to manually enter start and end pressure. Working pressure is the nominal tank pressure at which the volume of gas in the tank is known - you will need to enter both of the values.

Note: A typical AL80 is actually 77.4 cubic feet at 3000 psi.

Having said all that, I also believe that the latest update (2.1.8) is NOT doing the SAC calculation correctly.

It does appear to be calculating AC (air consumption) in cubic ft / minute (based on system of units I am using) but is not taking the average depth into account to properly compute SAC.

For awhile the calculations were being done correctly, but something seems to have slipped in the latest update.

 

[Darth_Rahl]

I'm a total noob to scuba, I had my first in the water class (read: pool) this weekend, and now I'm fooling around with my dive computer (Oceanic Pro Plus 2)

how do I figure out what my ending pressure was? So I can figure out what my sac rate was?

 

[SparticleBrane]

how do I figure out what my ending pressure was?

Look at your gauge at the end of the dive.

 

[diddler]

Could be wrong, but I believe the only way to get that info from the Pro Plus 2 is to download your dives to your desktop/laptop computer. You'll find all manner of data in there that you can't access just clicking through the buttons on the dive computer.

Ryan