10
inside the battery means the battery is ok,
one segment means the battery is low but
the watch functions as dive computer, one
segment blinking means the battery is too low
for use as dive computer).
• 3. DIVING WITH SMART
3.1. A FEW WORDS ABOUT NITROX
Nitrox is the term used to describe breathing
gases made of oxygen-nitrogen mixes with
an oxygen percentage higher than 21% (air).
Because Nitrox contains less nitrogen than
air, there is less nitrogen loading on the
diver’s body at the same depth as compared to
breathing air.
However, the increase in oxygen concentration
in Nitrox implies an increase in oxygen partial
pressure in the breathing mix at the same
depth. At higher than atmospheric partial
pressures, oxygen can have toxic effects on the
human body. These can be lumped into two
categories:
- Sudden effects due to oxygen partial
pressure over 1.4bar. These are not related
to the length of the exposure to high partial
pressure oxygen, and can vary in terms of the
exact level of partial pressure they happen
at. It is commonly accepted that partial
pressures up to 1.4bar are tolerable, and
several training agencies advocate maximum
oxygen partial pressures up to 1.6bar.
- Long exposure effects to oxygen partial
pressures over 0.5bar due to repeated and/
or long dives. These can affect the central
nervous system, cause damage to lungs or
to other vital organs.
Smart keeps you safe with respect to these two
effects in the following ways (as long as it is
set to either air or nitrox):
• Against sudden effects: Smart has an MOD
alarm set for a user-defined ppO
2
max. As
you enter the oxygen concentration for the
dive, Smart shows you the corresponding
MOD for the defined ppO
2
max. The default
value of ppO
2
max from the factory is 1.4bar.
This can be adjusted to your preference
between 1.2 and 1.6bar. Please refer to
section 2.1 for more information on how to
change this setting. If Smart is set to air, the
ppO
2
max is set to 1.4bar by default.
• Against long exposure effects: Smart
“tracks” the exposure by means of the
CNS% (Central Nervous System). At levels
of 100% and higher there is risk of long
exposure effects, and consequently Smart
will activate an alarm when this level of
CNS% is reached. Smart also warns you
when the CNS level reaches 75%. Note that
the CNS% is independent of the value of
ppO
2
max set by the user.
3.2. ALARMS
Smart can alert you of potentially dangerous
situations. There are five different alarms:
- Ascent rate alarm;
- Exceeding a safe ppO
2
/MOD;
- CNS =75%;
- Missed decompression stop;
- Low battery during the dive
WARNING
When in bottom timer mode, all warnings
and all alarms are OFF aside for the low
battery alarm.
NOTE
- Alarms are both visual and audible, as
described in detail below.
- Ascent rate alarm has priority over
other alarms if they are triggered
simultaneously.
3.2.1. ASCENT RATE
As soon as depth decreases Smart activates
the ascent rate control algorithm and displays
the calculated value. This is shown to the very
left in the middle row of the display.
WARNING
A rapid ascent increases the risk of
decompression sickness.
If Smart determines an ascent rate of 10m/min/
30ft/min or higher, the fast ascent alarm is
triggered: an audible alarm goes off, and
appears on the display. This persists until the
ascent rate is reduced to 10m/min / 30ft/min
or less.
If the ascent rate exceeds 12m/min / 40ft/min
at a depth below 12m / 40ft,
appears and
the speed value blinks. If a speed in excess of
12m/min / 40ft/min is maintained for two
thirds or more of the depth at which the alarm
was first triggered, Smart considers it a dive
violation and the display will show the steady
symbol.
In this case, if the diver attempts a repetitive
dive after surfacing, Smart will only function as
a depth gauge and timer (bottom timer mode),
and will display
on the screen
throughout the dive.
3.2.2. MOD/ppO
2
WARNING
- The MOD should not be exceeded.
Disregarding the alarm can lead to
serious injury or death.
- Exceeding a ppO
2
of 1.6bar can lead to
sudden convulsions resulting in serious
injury or death.
When the diver reaches a depth at which the
ppO
2
of the inspired gas exceeds the maximum
limit entered in the corresponding setting (from
1.2 to 1.6bar), an audible alarm goes off, the
current depth starts to blink and the value of the
MOD is shown to the right of the current depth.
The alarm persists until the diver has
ascended enough for the ppO
2
to return within
the set limit.
WARNING
When the
MOD
alarm is triggered, ascend
immediately until the alarm stops. Failure to
do so could result in serious injury or death
.
3.2.3. CNS = 75%
WARNING
When the CNS reaches 100% there is
danger of oxygen toxicity. Start procedure
to terminate the dive.
Oxygen toxicity exposure is tracked on Smart
by means of the CNS% based on currently
accepted recommendations for exposure limits.
This toxicity is expressed as a percentage
value which ranges from 0% to 100%. When
the value reaches 75%, an alarm goes off and
CNS value blinks on the screen. Additionally
the CNS becomes the default item in the lower
right corner: if you call up other information
such as the temperature or the time of day,
after 8 seconds the CNS appears again. Ascend
to shallower depth to decrease oxygen loading
and consider terminating the dive.
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