are made using high levels of PO
2
. The current Mission Clock, CNS, and
OTU can be seen via the Analyst
®
PC interface or the current CNS and
OTU values can be viewed on the Alternate Screen while in the Surface
Interval, Dive Mode, Decompression Mode or Post Dive Interval. The
current CNS and OTU values can also be viewed via the Touch Contact
Programming mode by selecting the InFormation option. The recovery
portion of the OTU algorithm is a linear reduction of OTU over time. The
Mission OTU clock is reset to 0:00 when the OTU Dose reaches zero.
The user via the Analyst
®
can set the OTU Toxicity alarm to any level
between 40% and 80% of the maximum allowable limit. As shipped from
the factory, this is set to 50%. Should the OTU Dose reach 50% of the
maximum allowable, the “WARNING” legend will illuminate and the audible
alarm will sound and on the Alternate Screen the displayed OTU value will
be flashing along with the “WARNING” legend.
Symptoms of Pulmonary Oxygen Toxicity include burning in the throat and
chest, coughing, and shortness of breath. Discontinue diving and consult
a Physician should any of these, or other, symptoms appear.
Figure 39 shows a CNS exposure over the alarm set point (50%), in the
situation were both the CNS and the OTU exposure was over their set
points both values would flash.
EMC-16 – USING TWO GAS NITROX
OVERVIEW:
The EMC-16 is capable of being used for two different Nitrox
mixtures on the same dive. The first gas or Normal Blend is
programmable from 21% to 50% Oxygen in 0.1% increments while the
Deco Blend can be programmed from 21% to 99.9% Oxygen again in
0.1% increments. Both Blends are set at the factory to 21% Oxygen and
use this in its decompression algorithm. PRIOR to diving an Enriched Air
Nitrox gas blend, the unit must be programmed accordingly. This can be
done via the Touch Contacts or via the Analyst
®
PC Interface.
GAS BLEND SWITCHING:
While most other Nitrox dive computers limit
the diver to the use of a single gas blend or percentage of oxygen, the
EMC-16 allows the diver to use two different gas blends during a dive.
These two gas blends are commonly referred to as the Normal or Bottom
Gas Blend and the Decompression Gas Blend. Commonly, the Bottom
Gas Blend is used from initial entry into the water and for most of the time
spent during the dive. The Normal Gas Blend is restricted to a maximum
of 50% oxygen. The Decompression Gas Blend (Deco Blend) is used only
for decompression purposes and can go to 99.9% oxygen content.
Typically, the Deco Blend is in a cylinder that is suspended at some
relatively shallow depth beneath the surface.
Since the depth of the Deco Blend switch is known ahead of time, and the
expected duration of the dive is also known, these two factors can be used
to automatically switch the computer to the Deco Blend or back to the
Normal Blend should the diver descend again. This is accomplished prior
to starting a dive by specifying both the Normal Gas Blend Oxygen
percentage and the Deco Gas Blend Oxygen percentage. The depth of
the Deco switch is also specified. Depending on surface swells, a few feet
may be added to this depth to ensure that when the diver is shallower than
the depth the Deco Blend will actually be in use. If the diver subsequently
descends below this depth, the Bottom (Normal) Blend is again assumed
to be in use. The other important factor that must be specified is the
Bottom Time that must elapse before Blend Switching is enabled. The
purpose of this factor is to ensure that the switch to the Deco Blend does
not occur prematurely should the diver ascend early and not require use of
the Deco Blend, the setting of this factor must be carefully considered.
The Deco Blend switch is enabled when the diver descends below the
switch depth and satisfies the time requirements and then ascends to the
programmed switch depth. If the diver does not exceed the programmed
switch depth the unit will not switch to the Deco Blend. All of these factors
can be set by either the touch contact programming or via the Analyst
®
PC
interface. If switching to the Deco Blend is NOT desired, it may be
disabled via the Analyst
®
. Setting both Blends to the same percentage of
Oxygen is the same as disabling the Deco Blend.
TOUCH CONTACT PROGRAMMING SCREENS:
The following are all of
the screens that the EMC-16 is capable of presenting in the Touch
Programming Mode. Refer to the particular configuration for appropriate
screens.
8
