O2 Analyzer without decimal

[Dan G]

Changing 31.1% to 32% for the sake of MOD may calculate a more conservative MOD, but won't it also calculate a less conservative NDL? The computer thinks you have 32% N2 and therefore calculates NDL based on that rather than 31% N2. Given the choice, I'd rather my computer calculate my NDL for me rather than my MOD. I can build in my own conservatism by using 111' as my MOD rather than 116' if I want to.

Mathematically, 30.5-31.4 rounds to 31 and 31.5-32.4 rounds to 32.

 

[beldridg]

I generally round down for NDL (and program that into my primary computer) and round up for MOD (and put it in a backup computer if you have it or just remember and label the tank). But honestly, if you are cutting it that close, then....

- brett

 

[BoltSnap]

Changing 31.1% to 32% for the sake of MOD may calculate a more conservative MOD, but won't it also calculate a less conservative NDL? The computer thinks you have 32% N2 and therefore calculates NDL based on that rather than 31% N2. Given the choice, I'd rather my computer calculate my NDL for me rather than my MOD. I can build in my own conservatism by using 111' as my MOD rather than 116' if I want to.

Mathematically, 30.5-31.4 rounds to 31 and 31.5-32.4 rounds to 32.

You can make your dive computer more conservative for NDL much more easily so you put in the next higher whole number O2% in the DC and go to the next conservatism factor for NDL and should be all set. I vaguely remember that Suunto dive computers do this automatically; they calculate MOD and other O2% factors based on the next whole number O2% and the lower O2% number for NDL.

 

[Capt Jim Wyatt]

I would run a few comparisons to analyzers that do have a decimal place and draw my own conclusions.

 

[boulderjohn]

When you use the word "conservative" with O2%, remember that rounding one way is more conservative in terms of NDL and rounding the other way is more conservative for MOD.

 

[Dan G]

When you use the word "conservative" with O2%, remember that rounding one way is more conservative in terms of NDL and rounding the other way is more conservative for MOD.

Precisely and I would rather my computer calculate a more conservative NDL than MOD.

 

[Capt Jim Wyatt]

Precisely and I would rather my computer calculate a more conservative NDL than MOD.

Interesting.

My choice (If I had to make this choice) would be just the opposite.

 

[BoltSnap]

When you use the word "conservative" with O2%, remember that rounding one way is more conservative in terms of NDL and rounding the other way is more conservative for MOD.

Precisely and I would rather my computer calculate a more conservative NDL than MOD.

Yes, exactly. You put in the higher O2%, a whole number, in the O2% in the computer and you adjust your conservatism factor in your computer for more conservatism and everyone is addressed and happy.

 

[lostsheep]

Yes, exactly. You put in the higher O2%, a whole number, in the O2% in the computer and you adjust your conservatism factor in your computer for more conservatism and everyone is addressed and happy.

No.

Round the FO2 down for NDL calculations and your FO2 up for MOD.

Your NDL is calculated using integration, MOD is fixed. Shirley no one is using their computer to tell them when they are approaching too high of a PO2? MOD should be part of your dive plan and doesn’t change, NDL can vary widely.

All that said, none of our empirical models are so accurate that one sig fig is likely to make the difference between DCS or ox tox.

 

[harvalen]

Yes, exactly. You put in the higher O2%, a whole number, in the O2% in the computer and you adjust your conservatism factor in your computer for more conservatism and everyone is addressed and happy.

Changing the conservative factor can have a huge effect, depending on computer. With the older Suunto models you'll be down roughly GF High 55 on consecutive dives if you use the second most liberal setting and have surface intervals that are less than 2 hours.

Much easier to just use the lower O2% and then not go deeper than the MOD of the higher O2%. You could set maximum depth alarm to the shallower depth if you need a reminder.