Suunto Cobra an Nitrox MOD calculation wrong?

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MLWheeler

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Messages
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Location
Columbia S.C.
# of dives
50 - 99
I have been making a MOD chart for my logbook and I noticed that my computer seems to be calculating the Nitrox MOD incorrectly. For instance, the computer says the MOD for 32% at 1.4 ATA is 107ft., but if I use the formula, I come up with 111ft. The computer shows 36% at 1.4, a MOD of 91ft. but the formula shows a MOD for this mix as 95ft. I know this is a conservitive computer, but I would think that this would come into play when calculating the NDL, not the MOD for Nitrox. Can anyone possably let me know what is going on here? It's not so far off as to be unsafe, but it this makes me wonder if any other calculations might be off too.
 
I have been making a MOD chart for my logbook and I noticed that my computer seems to be calculating the Nitrox MOD incorrectly. For instance, the computer says the MOD for 32% at 1.4 ATA is 107ft., but if I use the formula, I come up with 111ft. The computer shows 36% at 1.4, a MOD of 91ft. but the formula shows a MOD for this mix as 95ft. I know this is a conservitive computer, but I would think that this would come into play when calculating the NDL, not the MOD for Nitrox. Can anyone possably let me know what is going on here? It's not so far off as to be unsafe, but it this makes me wonder if any other calculations might be off too.

I found this on the Suunto site:
How to set up Nitrox mode in the Suunto dive computer?
We recommend to round down the calculation of nitrogen to the nearest fraction; for example 32.5% should be programmed in the Suunto dive computer as 32%. As the oxygen content could be greater than the preset value, the computer calculates the oxygen toxicity using 1 percent higher than the value in the computer.

For example, 32.5 % is now set to 32% for nitrogen, and therefore 33% is used for the oxygen calculation (1.6/0.33=4.8 bar) giving an MOD of 38m.

This is for safety reasons

Using 33% I get 107 feet.
 
My ten year old Cobra does the same thing. At least they are consistent. How old is yours? Bruce
 
Most conservative NDL algorithm and most conservative oxygen exposure program, perfect computer for the conservative diver. In this election year, I was tempted to make further comments, but thought better of the idea.

Good diving, Craig
 
My 10 year old Cobra and my son's new Cobra are the same way. The shop owner told me to always ignore the tenths and round down. If the actual is x.0 then round down 1 whole number to match the charts. Same as the example shown above.
 
I have a suntoo d6 and it does the same
 

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