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Revision NEW
APECS™ 2.7
12 of 19
Date: 10 July 2008
APECS
™ OPERATIONAL
INSTRUCTIONS (v. 2.7)
the percentage. A
long switch is holding the switch for greater than two seconds. The
MENU
long
switch has the effect here of subtracting ten percent from the current setting,
allowing the user quicker setting of the desired oxygen percentage. We
recommend watching the “heartbeat” character in the lower right corner of the
display screen for the third character change, indicating approximately three
seconds have passed, before releasing the switch to decrement by ten percent.
This oxygen percentage is only used during the
CALIBRATE
mode to provide
proper parameters for the determination of the mathematical formula later used
in displaying the setpoint of each oxygen sensor during operation (i.e. sensor
millivolt output vs. PO2 display calculations). It is highly recommended that the
diver use an oxygen analyzer to determine the quality of the oxygen in the O2
cylinder used during calibration.
KNOW YOUR OXYGEN QUALITY
!
One question frequently asked is “Will the oxygen percentage affect my PO2
during the dive?” The answer is no. Once breathing from the loop, the partial
pressure of oxygen in the mix you are breathing will be maintained at the
selected set point by the electronics and is appropriately displayed on the
handsets and HUD as that PO2. A low oxygen percentage results in more of the
oxygen gas mix to be used up faster since the other gasses are treated as part of
the diluent gas. The oxygen percentage setting is only used during calibration.
The diver doesn’t need to recalibrate for each oxygen percentage change when
changing oxygen sources.
WARNING! IF THE OXYGEN PERCENTAGE IS SET INCORRECTLY THE
UNIT WILL NOT CALIBRATE CORRECTLY RESULTING IN A POTENTIALLY
LETHAL CONDITION!
The
MAXIMUM OXYGEN
set point submenu has new checks to attempt to
prevent the user from selecting the maximum O2 while the sensors are still
exposed to ambient air. The effect is the
CONFIRM
switch is ignored until the
system reads a millivolt reading on all three sensors exceeding 20 mv. Pushing
the confirm button several times with no action should alert the user to read the
millivolt output readings on that page of the display to determine that the oxygen
level is not high enough for the HiPO2 point. Many users have accidentally hit
the confirm button for the air point calibration too many times and resulted in
having to restart the entire calibration procedure needlessly. ISC recommends
the user become familiar with the millivolt readings of the three oxygen sensors
at various PO2s (in air, calibration gas, and at depth) to familiarize the healthy
outputs of the sensors for later real-time analysis during a dive of the health of a
suspected bad sensor. Becoming familiar with the normal voltage readings of
