primary controller

VR3 Dive Computers	VRx Dive computers	Sentinel	VR Technology Home
Ouroboros Rebreathers by VR Technology
\| \| \| \| \| \| \| \| \| \|

Ouroboros Primary & Secondary displays

Above; controller travel case
Right; Both displays clearly seen here prior to dive. The primary of the left and the secondary on the right.

To find out more about the alarms built into the Ouroboros rebreather follow this link.

Above; Primary controller handset

Ouroboros Electronics and Computer systems

The electronics and computer systems have been designed with particular criteria in mind, which are explained below. Some of these are relatively obvious and have been implemented based on considerable experience refining existing of in-house and third party equipment.

This has produced the appropriate balance between:
• Sophistication
• Ease of use
• Automation / Manual override
• High level /Low level status presentation
• Alarm condition presentation (see alarms follow this link)
• Reliability

This ensures the diver is not over burdened with too much information or controls, while providing detailed status information, if required, to perform more complex maintenance or emergency procedures.

Above; Secondary po2 passive display read more

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 feedback in the systems operation are of paramount importance. Although the diver would routinely carry backup and have bailout contingency plans, the system wherever possible will 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 or external readings, then this will be alarmed for on the 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 and other operation specific 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 or heliox 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 algorithms) or other diving style rules to be upgraded 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 the section on the 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 in the manual (download section).

Software and Electronics key functional points
1. Key design issues:
a. Chance of free flow oxygen limited by electronics design.
b. Units will turn on and maintain breathable gas in as many automatic modes as possible to keep operation as simple and intuitive as possible

2. System will turn on:
a. when wet
b. when at depth greater than 1.5m at 1000mBar atmospheric – 1.6Bar absolute pressure. Therefore the turn on depth will vary with altitude for this mode of operation.
c. when activated with a Primary display switch

3. System will turn off:
a. When manual turn off selected from front dry screen
b. After 50 minutes after dive if dry, and not diving and in dry front screen
c. After 50 minutes if set point has been turned on, but still dry
d. After 5 minutes if set point not on, and dry

4. Setpoint will turn on:
a. Automatically when dive mode activated
b. When manually selected from front dive screen

5. Setpoint of 0.4 will be maintained if dive setpoint is not activated. This means that the unit will keep the gas in the breathing loop breathable when the unit is on, and the O2 cylinder is turned on.

6. Unit will go into dive mode:
a. At depth greater than 1.5m when rebreather is on
b. When manual chamber dry dive selected
c. When rebreather is off - depth greater than 1.6m at 1000mBar atmospheric –will turn the unit on, and put the rebreather into dive mode. Note that this will abort Pre-dive checks screens – this is not advised, but is included as a safety feature to ensure rebreather is on in as many user error fault scenarios as possible. See section on Pre-dive set-up for the correct turn on procedure. Therefore the turn on depth will vary with altitude for this mode of operation.

7. The Ouroboros will warn on the primary display, and mimic on the heads up and rear facing displays.
See Table of Alarms(follow this link).

Passive secondary display

Backup (secondary) system
This system is separate to the microprocessor system and provides a breathing loop Partial pressure of oxygen display in case of failure of main system, and as confidence in main system operation.

This display is designed with a completely different component set to the main electronics. It also has no software. Therefore, the possibility of it failing under the same conditions as the main electronics is much reduced. Three separate Digital Voltmeter LCD displays are used in-conjunction with variable resistors as a potential divider used for calibration purposes.

Due to the temperature variation and life span of the cells, calibration has to be carried out periodically. In the secondary back up display there are individual variable resistors that can be accessed via a removable waterproof pressure cap.

On top of this there are two switches, which allow:
• The unit to be turned on for approx 10 seconds
• Provide a bypass of the calibration circuit, to check on the raw milli-volt reading from the Oxygen cells. This allows a check on the health of the cells, based on a specified acceptable range for a given oxygen level from the manufacturers.

Downloads >>>>