Shearwater Petrel EXT, Operation Manual, Page: 61 / 65

Shearwater Petrel
Revision 1.1.0 61 Shearwater Research Inc.
Error Displays
The system has several displays that alert an error condition�
Each of the alarms will display the message in yellow until dismissed� The error is dismissed
by pressing SELECT�
This message will appear if the average PPO2 goes above 1�6 for
more than 30 seconds�
This message will appear if the average PPO2 goes below 0�4 (�19
for OC or SC) for more than 30 seconds�
It is not unusual to get this error immediately after submerging
with a manual CCR and a hypoxic mix. The first breath after
submerging floods the loop with low PPO2 gas. The situation is
usually resolved by increasing depth such that when the error is
noticed, the PPO2 is no longer low�
This condition will also cause the “ LOW PPO2 ” display to appear�
Here, the computer does not have two sensors that have confirming
values� There is no way to know the actual PPO2, and the average
PPO2 will be calculated as 0�11 (the lowest value is the most
conservative for decompression calculations)�
This message will appear when your internal battery is low for 30
seconds� The battery needs to be changed� The computer will also
flash the battery symbol red �
DEPTH TIME STOP TIME
1.6O 1.62 1.61
Error Confirm
HIGH PPO2
45
DEPTH TIME STOP TIME
.3O .32 .31
Error Confirm
LOW PPO2
45
DEPTH TIME STOP TIME
.3O .62 .11
Error Confirm
LOW PPO2
45
DEPTH TIME STOP TIME
1.3O 1.32 1.31
Error CONFIRM
LOW BATTERY INT
45
Limitations of Alarms
All alarm systems share common weaknesses�
They can alarm when no error condition exists (false positive)� Or they can fail to alarm
when a real error condition occurs (false negative)�
So by all means respond to these alarms if you see them, but NEVER depend on them�
Your judgement, education, and experience are your best defenses� Have a plan for
failures, build experience slowly, and dive within your experience�