33
English
ALADIN H USER MANUAL
In recent times, so called “deep” stops have
been introduced in some dive computers and
tables, defined as half the distance from the
dive’s maximum depth and the surface (or
the lowest decompression stop). Spending 2
or 15 minutes at 30m/100ft would result in
the same deep stop at 15m/50ft.
With PDIS, as the name suggests, the
Aladin H interprets your dive profile and
suggests an intermediate stop that is
a function of your nitrogen uptake so
far. The PDI stop will therefore change
through the course of the dive to reflect
the continuously changing situation in
your body. Along the same lines, PDIS
will account for the accumulated nitrogen
from previous dives; hence, PDIS is also
repetitive-dive dependent. Conventional
deep stops completely ignore these facts.
The following figure quantifies the extent
of PDIS and illustrates its dependence on
cumulative nitrogen uptake for 2 sample
dive profiles. This figure also demonstrates
the conceptual difference between PDIS
and the rather rudimentary “deep” stops.
Specifically, the figure compares 2 dive
profiles to a maximum depth of 40m/132ft
that are otherwise very different. Profile
1 stays at 40m/132ft for 7 minutes, then
ascends to 30m/100ft for 3 minutes,
followed by 12 minutes at 20m/65ft. Profile 2
stays less than 2 minutes at 40m/132ft, then
ascends to 21m/69ft and stays there for 33
minutes. Both dive profiles are no-stop dives
to the limit of entering decompression.
The solid line represents the PDIS depth as
displayed on the computer screen during
the course of the dive for profile 1, the
broken line represents the PDIS depth as
displayed on the computer screen during
the course of profile 2. One can see that the
displayed PDIS depth increases as more
nitrogen is accumulated in the body, but
does so very differently in the 2 dives due
to the different exposure in the 2 profiles.
The PDI stop is carried out at 25 minutes
for profile 1 and at 37 minutes for profile 2,
followed by the safety stop at 5m/15ft.
The line made up of small solid dots, on the
other hand, represents the depth that would
be displayed by a computer following the
conventional deep stop method, and it would
be the same for the 2 dive profiles. Deep
stops completely ignore any facts about the
dives themselves aside from max depth.
DEP
TH
DIVE TIME
40m
30m
20m
10m
8min
16min
24min
32min
40min
48min
PDIS Profile 1
PDIS Profile 2
SAFETY STOP
PDI STOP
Dive Profile 1
Dive Profile 2
Deep Stop
40m
30m
20m
10m
8min
16min
24min
32min
40min
48min
DIVE TIME
DEPTH
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