Design Criteria
The electronics and computer systems have been designed
around six main criteria:
1. Safety/Reliability
2. Redundancy
3. Maintenance / Serviceability
4. Modularity
5. Upgradeability
6. Reprogram-ability and PC interface
1. Safety/Reliability
For obvious reasons, the reliability of the system underwater
in providing a breathable gas and user feedback are of paramount
importance. Although the diver would routinely carry backup
and have bailout contingency plans, the system wherever
possible should provide a breathable gas in as extreme an
environment as is feasible.
The external electronic cables have a double
sheath. Cables can be cut or punctured without risk of flooding
or disabling the main control system. Should any of the
front facing displays fail, the in-board control system
will maintain the life support functions, but obviously,
functionality will be reduced. If a severed cable results
in loss of PO2 monitoring or other readings, then this will
be alarmed for on the remaining active displays.
A more complete analysis of the safety
considerations is described in Appendix 1 and Appendix 2
of the Operations Manual, which contains an extract of the
Technical documents used in the CE approval documentation
submission. Appendix 1 focuses particularly on overall safety
design. Appendix 2 focuses on software/programmable systems.
2. Redundancy
In case of main system failure, the redundancy in providing
independent backup information allows the trained diver
to manually control the system and get out of the water
safely.
3. Maintenance / Serviceability
Battery, oxygen partial pressure cell and system status
are provided to the diver, so that these can be changed
when the levels fall below design limits. In particular,
the maintenance is simple, and reduces pre/post service/maintenance
times.
4. Modularity
The electronics systems are designed to allow diving with
all or only parts of the available systems connected. For
example the unit can be supplied with or without the following
items:
• Head Up
Display (HUD)
• High Pressure (HP) sensors
• 4th PO2 sensor and additional VR3 decompression
computer
• In-water communications link
• Rear facing average PO2 display and mimic HUD
• Off-board gas supply plug-ins
On top of this, different diving styles can also be accommodated.
For example only the HUD can be used for diving, with the
Primary display or PC link only used for initial system
setup. This style has been adopted for some military or
other minimal clutter diving missions.
5. Upgradeability
This allows different software options to be activated by
PIN number. Thus units can be easily field upgraded should
this be required. For example, use of different diluent
gasses such as tri-mix helium gasses can be activated as
an upgrade from Nitrox only systems.
6. Reprogram-ability and PC interface
The software can be fully reprogrammed using a PC to download
the new versions. This can be done in the field, or back
at the factory. This provides for new features as well as
decompression algorithm or other diving style rules to be
adapted throughout the life of the product. It also provides
a base on which specific customised functionality can be
achieved for different clients with specific diving procedures
and styles. See section Re-programming system. The Ouroboros
can also connect to the PC to download dive data and revise
settings within the rebreather. See Download Dives section.
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