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MOD Discrepancy with Cressi/dive calcuations
markingrassia - 6/11/2015 12:26 PM
Category: New Diver Q&A
Replies: 5

I’m not really a new diver, but closer to intermediate.

My question has to do with the discrepancy between my Cressi Leonardo Dive Computer and my own calculations for MOD. Using PPO2 of 1.4 and Nitrox Settings of 32% I come with the same Mod as does the calculators online — 111 ft. Bud my Cressi calculates 106 ft. The Cressi calculations are consistently shallower. I’ve tried every variation of Safety Factors but that only effects the Diving Plan mode.

I am thinking Cressi uses a different calculation or, its algorithms are inherently more conservative.

Any thoughts?


OleCrab - 6/12/2015 6:22 PM
I have the same problem. I just double check my dive tables and watch the time.
BobW - 7/01/2015 8:34 AM
I did a little checking and believe I have your answer. First the MOD for any PO2 value is always the same, it is just a simple formula as opposed to an algorithm which is a little more complex and requires a number of steps. I state that because Cressi will use the same formula as any dive computer and should be consistent. The Leonardo has added a factor for more conservative dives that could be the reason for the difference. It also allows you to set the ATA from 1.2 to 1.6 (1.4 being the default).

Once you have double checked the
% of oxygen setting
Conservation factor
ATA setting

if the problem still exists I would contact Cressi. While the problem described is not a safety concern since it is more conservative, any problem with a dive computer may manifest in other ways which are not as apparent and not benign.

Good luck
markingrassia - 7/01/2015 9:55 AM
Thank you, Bob. I’m pretty familiar with the setting on the Leonardo. The setting are correct it’s just that the computer has imposed its own more conservative values, which I think is BS. They should show the true numbers and let the diver decide what is or is not conservative.