7.2
How does PDIS work?
The
mathematical
model in Aladin 2G, called ZH-L8 ADT
MB PMG, tracks your decompression
status by dividing your body into 8 so-
called compartments and mathematically
following the uptake and release of
nitrogen in each with the appropriate laws
of physics. The various compartments
simulate parts of your body such as central
nervous system, muscles, bones, skin and
so on.
The depth of the PDI stop is calculated as
that at which the leading compartment for
the decompression calculation switches
from ongassing to offgassing, and the
diver is advised to perform a 2-minute
stop above the displayed depth (this is the
opposite of a decompression stop, where
you are asked to remain just beneath the
displayed depth). During this intermediate
stop, the body is not taking up any more
nitrogen in the leading compartment, but
rather releasing nitrogen (though under
a very small pressure gradient). This,
SCUBAPRO ALADIN 2G
7. PDIS (Profile Dependent Intermediate Stop)
combined with the relatively high ambient
pressure, inhibits bubble growth.
decompression
It should be noted that the two fastest
compartments, with 5 and 10 minutes
half times respectively, are not considered
for the determination of the PDI stop
depth. This is due to the fact that these
compartments are only "leading" for very
short dives, for which an intermediate stop
is not required at all.
)
NOTE:
The PDI stop is not a mandatory
stop and it is NOT a substitute for the
3-5 minute safety stop at 5m/15ft.
Even when performing a PDI stop, you still
MUST perform a safety stop at 5m/15ft for 3 to
5 minutes. Performing a 3 to 5 minute stop at
5m/15ft at the end of any dive is still the best
thing you can do for yourself!
WARNING
45