Uwatec Galileo HUD User Manual page 65

10m
20m
30m
40m
How does PDIS work?
The mathematical decompression model
in the HUD, 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 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
GALILEO HUD USER MANUAL
8min 16min
PDIS Profile 1 PDIS Profile 2
Deep Stop
Dive Profile 2
Dive Profile 1
24min 32min 40min
DIVE TIME
PDI STOP
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.
WARNING
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!
Special considerations when diving
with more than one gas mixture (2G)
Switching to a higher oxygen concentration
mix during the dive influences the PDI stop.
This needs to be accounted for, in line with
the predictive nature of multi-gas handling
in ZH-L16 ADT MB PMG.
When diving with more than one gas
mixture, the HUD displays the PDIS depth
according to the following rules:
• If the PDI stop calculated for the bottom
mix (gas 1) is deeper than the switch
depth, then this calculated value is
displayed.
• If the PDI stop calculated for gas 1
is shallower than the switch depth to
gas 2, then the displayed PDI stop is a
48min
SAFETY STOP
65