6.2. Diving in NITROX mode (DIVEnitrox)
NITROX mode (DIVEnitrox) is the second dive mode available in Suunto Cobra2 and is
used when using oxygen- enriched gas mixtures.
6.2.1. Before diving in NITROX mode
If set to the NITROX mode, the correct oxygen percentage of the gas in your cylinder must
always be entered into the computer to ensure correct nitrogen and oxygen calculations.
The dive computer adjusts its mathematical nitrogen and oxygen calculation models
accordingly. The dive computer will not accept fractional percentage values of oxygen
concentration. Do not round up fractional percentages. For example, 31.8% oxygen should
be entered as 31%. Rounding up will cause nitrogen percentages to be understated and
will affect decompression calculations. If you want to adjust the computer to provide more
conservative calculations, use the personal adjustment feature to affect decompression
calculations, or reduce the PO
2
setting to affect oxygen exposure according to the entered
O
2
% and PO
2
values. Calculations based on nitrox use result in longer no-decompression
times and shallower maximum depths than diving with air.
As a safety precaution, the oxygen calculations in the computer are made with an oxygen
percentage of 1% + set O
2
% .
When the dive computer is set in NITROX mode, the Dive Planning mode calculates using
the O
2
% and PO
2
values that are currently in the computer.
To set the nitrox mixes, refer to
Section 5.8.3. Setting the nitrox values
.
Default nitrox settings
In NITROX mode, the Suunto Cobra2 allows you to set 1 or 2 nitrox mixes containing 21-
99% oxygen.
In the NITROX mode, the default setting for MIX1 is standard air (21% O
2
). It remains in
this setting until the O
2
% is adjusted to any other percentage of oxygen (22% - 99%). The
default setting for maximum oxygen partial pressure is 1.4 bar, however you are able to
set it in the range of 0.5 - 1.6 bar.
MIX2 is set to OFF by default. To set MIX2 , refer to
Section 6.2.4. Gas change and multiple
breathing gas mixes
. Oxygen percentages and maximum oxygen partial pressures for
MIX2 are stored permanently.
6.2.2. Oxygen displays
When NITROX mode is activated, the display will show the information in the figure below.
In NITROX mode, the maximum operational depth is calculated based on set O
2
% and
PO
2
values.
NITROX DIVE MODE ACTIVATION.
MAXIMUM OPERATIONAL DEPTH BASED ON
SET O
2
% (21%) AND PO
2
(1.4 BAR) IS 56.7 M.
If set to NITROX mode, the Suunto Cobra2 will additionally show on the alternative display:
•
the oxygen percentage, labeled O
2
%
•
the set oxygen partial pressure limit, labeled PO
2
•
the current oxygen toxicity exposure, labeled OLF
•
maximum depth
•
current time
•
water temperature
•
dive time
•
tank pressure
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