How Does Pdis Work; Diving With Pdis - Uwatec LUNA 2.0 AI User Manual

PDIS Profile 1
PDIS Profile 1
10m 10m
20m
20m
30m
30m
40m
40m

3 .15 .2 How does PDIS work?

The mathematical decompression model in the LUNA 2.0 AI, called ZH-L16 ADT MB PMG, tracks your
decompression status by dividing your body into 16 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 the 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 on-gassing to off-gassing, 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, combined with the relatively high
ambient pressure, inhibits bubble growth. It should be noted that the 4 fastest compartments, up to 10-minute
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.
F NOTE: The PDI stop is not a mandatory stop, and it is NOT a substitute for the 3- to 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 remains the best thing you can do for yourself.

3 .15 .3 Diving with PDIS

When the calculated PDI stop is deeper than 8m/25ft, the LUNA 2.0 AI 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 LUNA
2.0 AI tracks the uptake of nitrogen in the 16 compartments and updates the PDIS depth accordingly to reflect the
optimum at all times.
LUNA 2.0 AI USER MANUAL
8 min 16min
8 min 16min
PDIS Profile 2
PDIS Profile 2
Deep Stop
Deep Stop
Dive Profile 2
Dive Profile 2
Dive Profile 1 Dive Profile 1
24 min 32 min
24 min 32 min
DIVE TIME
DIVE TIME
WARNING
40 min 48 min
40 min 48 min
SAFETY STOP
SAFETY STOP
PDI STOP PDI STOP
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