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A1 USER MANUAL
4.8.3
Diving with PDIS
When the calculated PDI stop is deeper
than 8m/25ft, the A1 shows it on the display
and continues to do so until you reach the
displayed depth during an ascent. The
displayed value changes during the dive as
the A1 tracks the uptake of nitrogen in the
16 compartments and updates the PDIS
depth accordingly to reflect the optimum at
all times.
During a no-stop dive, as soon as you
reach that depth during an ascent, a
2-minute countdown will appear.
You can have one of these 3 situations:
• You have spent 2 minutes within
3m/10ft above the indicated depth. The
countdown timer disappears and you
have successfully completed the PDIS.
• You have descended more than
0.5m/2ft below the PDIS. The
countdown timer disappears and will
reappear again, starting at 2 minutes,
the next time you ascend to the PDIS
depth.
• You have ascended more than 3m/10ft
above the PDIS. The PDIS value and
countdown timer disappears and PDIS
has not been performed.
F
NOTE: The A1 issues no warnings
relating to a missed PDI stop. When
diving with MB levels, PDIS follows
the same rules as described above.
MB levels, however, introduce stops
earlier and deeper than the L0 base
algorithm. As such, the PDIS display
may be delayed and, for certain dives,
it may not be displayed at all. This,
for example, would be the case for a
shallow dive with air (21% oxygen) and
a MB level L5.
4.9 Altitude diving
4.9.1
Altitude warning after a dive
Climbing to altitude is similar to starting an
ascent from a dive: you expose your body
to a lower partial pressure of nitrogen and
you start off-gassing. After a dive, given the
higher nitrogen loading in your body, even
reaching an otherwise negligible altitude
can potentially cause decompression
sickness. Consequently, the A1 constantly
monitors the ambient pressure and uses it
to evaluate your nitrogen loading and off-
gassing. If the A1 notices a drop in ambient
pressure not compatible with your current
nitrogen loading, it will activate a warning
(altitude symbol starts blinking) to alert you
of a potentially dangerous situation.
The A1 counts down remaining saturation
and indicates this on the Surface screen
with the no-fly time until the available
saturation is no longer dangerous during
a flight or when crossing over a mountain
pass.
The allowable altitude (beyond which the
A1 has computed to be incompatible with
your current nitrogen saturation levels)
is displayed above the no-fly time. Refer
to chapter
2.3 Reading the altitude,
barometric and temperature values
for
more information.
Summary of Contents for Aladin A1
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