Shearwater Research Inc.
Revision 1.1.0
44
Shearwater Petrel
External PPO2 Monitoring
The next menu item is used to turn external PPO2 monitoring on and
off� By default, external monitoring is turned off and reads “Int�” for
Internal fixed setpoint mode. This setting can be changed to “Ext.” to
enable external PPO2 monitoring from oxygen sensors�
Now the PPO2 of the three sensors is displayed� A valid calibration
must have been previously performed (see the Calibration section)�
This system is plugged into three sensors and using the PPO2
input from the sensors as the system average PPO2 used for
decompression calculations and CNS tracking�
A voting algorithm is used to decide which of the three sensors are
likely to be correct� If a sensor matches either of the other two sensors
within ±20%, it passes voting� The system average PPO2 is the
average of all sensors that have passed voting�
For example, here sensor 3 has failed voting� The PPO2 is displayed
in
yellow
to show that it has failed voting� The system average PPO2 is
the average PPO2 of sensor 1 and 2�
If all sensors fail voting, then the display will alternate
VOTING FAILED
with the PPO2 measurements (which will all be
yellow
to indicate that
voting has failed)� When voting has failed, the lowest PPO2 reading will
be used for deco calculations (i�e� the most conservative value)�
Switching to Open Circuit bailout with External PPO2 Monitoring
If you bailout to OC mode, the external PPO2 will continue to display
on the main screen� However, the system PPO2 used for deco
calculations will change to OC mode (i�e� PPO2 is the fraction of O2
multiplied by the current depth’s pressure)�
The external PPO2 continues to display because the diver may need to
return to the loop, and will need to know the PPO2 status of the loop,
even though the sensor input is not being used as the system PPO2�
DEPTH TIME STOP TIME
.96 .97 .97
O2/HE NDL TTS
CC 21/OO O O
O
DEPTH TIME STOP TIME
.96 .97
1.26
DilPO2 CNS AvgPO2
.21 O .97
O
DEPTH TIME STOP TIME
.48 .97
1.26
Switch CC > OC
O
DEPTH TIME STOP TIME
.48 .97
1.26
CNS AvgPO2
O .21
O
DEPTH TIME STOP TIME
.48 .97
1.26
O2/HE NDL TTS
OC
21/OO O O
O
DEPTH TIME STOP TIME
DEPTH TIME STOP TIME
Change
Change
Save
Save
O
O
PPO2 Mode Int.
PPO2 Mode Ext.
.96 .97 .97
.7
Summary of Contents for Petrel EXT
Page 1: ...Standalone EXT Models...