Which dive computers provide average depth in their logs?

[Lorenzoid]

In addition to calculating SAC, I believe average depth is also used by some divers who ascend to 50% of their average depth at a certain ascent rate, such as 30 fpm, and then slower, such as 10 fpm, for the rest of their ascent.

 

[stuartv]

(Stolen from another post)
SAC must be calculated in order to figure out RMV. SAC is tank dependent and is measure in PSI/Minute. This is actually valuable to know while underwater since your SPG measures in PSI. It's good to know for instance that your usual rate is 15 psi/minutes.

RMV is measured in cu ft/minute and is useful for planning gas requirements before the dive as in .5 cu ft/minute at the surface which then needs to be corrected for depth (ata's).

The part in bold is incorrect. I have calculated my RMV numerous times and I don't think I have ever calculated my SAC.

To calculate RMV, all you need to know is the total volume of gas you used, the average depth, and the total dive time.

For example, if you use an AL80 that starts at 3000psi and ends with 500psi, then you used 2500 psi. 2500/3000 tells you what percentage of the tank you used (5/6 = ~83%). An AL80 holds 77 cu-ft of air. You used 83% of that, which is 64 cu-ft of air. Factor that by your average depth and divide by your dive time and you'll have your RMV without ever calculating your SAC.

 

[stuartv]

I'm thinking of getting another dive computer. My old Suunto provides average depth as well as maximum depth in the dive log. I find this very helpful. It helps me keep track of my dive profile. I know what I planned to do, I keep an awareness of depth during the dive, then the average depth on the log helps to confirm this. If I need to, I double check with the dynamic log.

I am surprised that some modern dive computers do not provide this information in their logs. So which dive computers do?

ps. If you use Subsurface (free dive log software that supports MANY different computers), it tell you your average depth and, if you enter your start and end pressures, your RMV (which it calls SAC).

 

[dmaziuk]

Actually, it'll tell you the average as half of max depth, but if you trace the profile plot, the info pop-up will give "mean depth to here". Same with RMV, though without AI it depends on how accurate the start and end pressures that you typed in later are.

 

[stuartv]

Actually, it'll tell you the average as half of max depth

That's interesting. I'm looking at my last pool session in Subsurface right now. It says max depth 12 ft and Avg depth 10 ft. The preceding dives all also have Max of 12 ft but the avg varies from 9 to 11, depending on the dive.

My last dive before the pool session shows as Max 59 and Avg 39.

 

[dmaziuk]

Oh kaay... I guess I'm just lucky: the one I looked at when I posted just happened to have "avg" at half the "max". Looking at more dives, you're right: the average on the info tab is the same number that's on the right end of the "average" line on the plot. So it's the "mean depth to here" at the end of the dive. I sit corrected.

 

[scubadada]

Actually, it'll tell you the average as half of max depth, but if you trace the profile plot, the info pop-up will give "mean depth to here". Same with RMV, though without AI it depends on how accurate the start and end pressures that you typed in later are.

I'm sorry, the average depth is not half the max depth, it is the weighted average based on the amount of time you spent at all depths during the dive. The RMV is based on this average depth.

Edit: Typing during your last post, you stand corrected

 

[gfaith]

Being a long time user of Subsurface I check the average (mean) depth on every dive, and as @stuartv explained it is calculated by the program. Pretty simple really every 30 seconds or less (depends on the computer) a data line is built and present depth is in the data. At the end of the dive samples are counted and divided into the sum of all depths, and yes, the dive profile has the mean to here on all points.

As, I have quite a few Suunto computers (I know very conservative) I also have downloaded manuals for most if not all of them. The Zoop, Vyper, Novo-Zoop and Novo-Vyper all have a screen in the logbooks with average depth for each dive. Strangely, the older Vyper-Air has an electronic compass but the average depth is not displayed.