178
NOTE: The result of the computation is the oxygen compo-
sition is approximated to the nearest whole number.
NOTE: The computation of CNS toxicity shown by the rela-
ting graph, takes into account both mixtures used during the
dive. By using highly nitrox mixtures during the decompres-
sion, the toxicity level may be reached during the final phase
of the dive. In this case, the alarm will sound after the seventh
pixel has lit up; the diver must quickly change over to the bot-
tom mixture and the computer must be consequently reset.
DANGER: Do not use nitrox mixtures during diving acti-
vities without proper training by certified training agencies.
Related topics:
• 3.1. - AIR DIVE.
• 3.2. - NITROX MIXTURES DIVE.
• 3.3.1. - PO2 partial pressure setting..
• 3.3.2. - Oxygen fraction FO2 setting.
• 3.3.5. - PO2 alarms.
• 4.1.2. - Logbook.
3.3.5. - PO2 alarm.
Archimedes II computer is able to constantly monitor
another basic parameter relating to oxygen, and that is O2
partial pressure value (PO2). Oxygen toxicity may be caused
both by an excessive accumulation (CNS toxicity, seen in the
previous chapter) and by exceeding the maximum PO2,
which is exceeding the maximum depth allowed by the mix-
ture used. As already seen, the PO2 limit value is set by the
diver in a range between 1.0 bar and 1.6 bar. Archimedes II
considers the 1.6 bar value as the partial pressure maximum
allowable limit and, according to the used mixture, automati-
cally signals the maximum depth which may be reached.
Remember that even by using air, you may reach the oxygen
toxicity limit. Such limit varies according to the set PO2.
Archimedes II is manufactured with a preset value of 1.4 bar,
whose corresponding maximum depth is 1834 ft. in air. It is
possible to set the computer on other PO2 values, up to a
maximum of 1.6 bar. Archimedes II is equipped with two
kinds of PO2 alarms:
1 By reaching the limit depth relating to the set PO2 (from
1.0 bar to 1.6 bar), a sound alarm will start lasting 15
seconds while the display will be flashing, showing the
( ) icon and the reached PO2 limit value, at the top on
the left (picture 16).
2 A second alarm will start by achieving the depth equiva-
lent to PO2 of 1.6 bar and will last 15 seconds. The display
will be flashing and will stop only when the diver will reach
a depth lower than the limit one.
Both alarms will be entered in the Logbook.
Related topics:
• 3.1. - AIR DIVE.
• 3.2. - NITROX MIXTURES DIVE.
• 3.3.1. - PO2 partial pressure setting.
• 4.1.2. - Logbook.
3.4. - Curve dive.
3.4.1. – Ascent rate.
Archimedes II Cressi-sub computer’s algorithm considers
different ascent rates according to the depth. The speed is
Manuale ARCHIMEDE II 2008:Manuale 6 26-06-2008 8:26 Pagina 178
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