Shearwater Research Inc.
Revision 1.1.0
26
Shearwater Petrel
These are the gases that will be used to estimate TTS in the event that you switch to open
circuit during a dive� In OC mode, the computer will assume that you will switch gases when
the PPO2 of the next available gas is less than 1�6�
Automatic decisions of when to switch gases for the TTS calculation means that it is very easy
to set up your CC and OC gases� There is no need to enter a depth or a PPO2 to switch gas�
Any gases that are turned on will be used in the decompression calculation�
If a gas is available in the CC gas list, (entered and turned on),it will be used in CC, and it will
be used at an appropriate depth. The same is true for OC. It is always configured correctly if
you are actually carrying the gases you have entered and turned on�
If it is necessary to switch to OC while diving, 4 button pushes will do it� You will be switched
to OC and will be using the gas that has the highest PPO2 less than 1�61� Your OC gas
list is likely very different from your diluent gas list, but you set it up before the dive so it is
immediately available in the case of a bail-out�
Now switch back to closed circuit and start the dive�
We have reached a depth now that will incur decompression soon�
The NDL is 8 minutes, and the TTS is 4 minutes� The TTS is
showing the planned ascent time at 30 fpm�
The computer has automatically switched to the high setpoint� This
can be disabled if automatic setpoint switching isn’t required�
We are now at our maximum depth. Our first stop is at 90 feet.
The diver is ascending to the 90 foot stop� Note the ascent rate
indicator showing a 20 fpm / 6 mpm ascent rate� The Petrel
assumes a 30 fpm ascent rate in calculating the decompression
schedule� Since the diver ascended slower than was predicted,
there is now a 100 foot stop�
DEPTH TIME STOP TIME
O
Switch OC > CC
.98 .98 .98
DEPTH TIME STOP TIME
O
CC 1O/5O O O
.98 .98 .98
O2/HE NDL TTS
DEPTH TIME STOP TIME
126 2
CC 1O/5O 8 4
1.3O 1.29 1.29
O2/HE NDL TTS
DEPTH TIME STOP TIME
257 8 9O 1
CC 1O/5O O 23
1.31 1.29 1.22
O2/HE NDL TTS
DEPTH TIME STOP TIME
98 15
1OO 1
CC 1O/5O O 22
1.3O 1.29 1.29
O2/HE NDL TTS
Summary of Contents for Petrel EXT
Page 1: ...Standalone EXT Models...