Cochran Nemesis IIa NITROX, User Manual

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10
Enriched Air Nitrox, Three-Blend Capability
Your NEMESIS™ IIa NITROX has the unique ability to provide the diver with the ability
to select a single bottom mix and TWO decompression mixes. Using the included
Field Programmer, you can set the oxygen percentage for the three different mixes
within the following ranges:
Mix 1: 21.0% to 50.0% in 0.1% increments
Mix 2: 21.0% to 99.9% in 0.1% increments
Mix 3: 21.0% to 99.9% in 0.1% increments
In order to obtain the full benefit of this unique feature, you must designate Mix 1 as
your bottom mix, Mix 2 as your first (deeper) decompression mix and Mix 3 as your final
(shallower) decompression mix. The TU must be attached to the cylinder contain-
ing Mix 1. Here is how the automatic switching occurs:
1. With the TU attached to Mix 1, it continually "senses" a drop in cylinder pressure until
you are prepared to switch to your first decompression mix (Mix 2).
2. Once you have made the switch to Mix 2, the TU no longer senses a drop of cylinder
pressure from your Mix 1 cylinder and automatically changes its algorithm to Mix 2.
3. For Mix 3, you will be required to not only have programmed the oxygen percentage
for this mix, but also the:
a) bottom time you will be beyond at which you will begin breathing from Mix 3
b) the maximum depth at which you will begin breathing from Mix 3
when switching to this final decompression gas. The time and depth do not have to be
exact. They are simply used as a benchmark with the necessity of both being met in
order to allow the algorithm switching to Mix 3. We find that most divers participating
in this type of extreme diving usually have a bottom time of greater than 20 minutes
before beginning to decompress on a second decompression gas. Therefore, they
leave the bottom time factor set for 20 minutes. The depths at which a switch to Mix 3
is allowed in the algorithm is limited to a maximum of 30 feet.
NOTE: As you will discover in the Subsurface Mode section of this manual, your
NEMESIS™ IIa NITROX displays your breathing rate (BP) on the alternate display of
the WU. If the BP is displaying 0, Mix 2 is being calculated in the algorithm. Mix 3 is
indicated by displaying a BP of 99. Should you switch back to your bottom mix (Mix
1), your TU will sense a drop in cylinder pressure and the Mix 1 algorithm will be
calculated. This switching between Mix 1, 2, and 3 is continuous based upon the
BP and current depth. Mix 1 BP is displayed between 1 and 98.
The following describes the various factors that determine which mix is being calcu-
lated in the algorithm:
Mix 1: TU senses drop in cylinder pressure with BP between 1 and 98 displayed.
Mix 2: TU does not sense a drop in cylinder pressure, BP displays 0; bottom time and
depth factors for Mix 3 are not met.
Mix 3: TU does not sense a drop in cylinder pressure, BP displays 99, bottom time and
depth factors for Mix 3 are met.
NOTE: For Mix 3, even though no drop in cylinder pressure is detected, BP will
display 99 as a means of informing the diver that the Mix 3 algorithm is being