33
VI
Diving with more than one gas mixture
VI UWATEC
®
Smart dive computers
Preparation for a dive with several gas mixtures
Before the dive, all transmitters in use must be paired with TEC, the fraction of oxygen must be entered for
each tank and the depth for changing the gas mixture must be set for tanks 2 and D.
Setting the gas mixture and the depth for changing the gas mixture
During dives with more than one gas mixture the bottom mix
(tank 1) contains the lowest fraction of oxygen, while the deco
mix (tank D) contains the highest fraction. The additional travel
mix (tank 2) for dives with 3 gas mixtures holds a fraction of
oxygen that is between that of tank 1 and tank D. TEC will only
accept settings corresponding with this order. Note however
that you can also set 2 or even 3 tanks to the same gas mixture.
TEC will only accept gas mixture switching depths (MOD) as
input where the maximum partial pressure of oxygen (ppO
2
), as
pre-set manually (-> 18 point 6) or by means of SmartTRAK, is
not exceeded.
For gas mixtures having an oxygen percentage of 80% or greater the ppO
2
is
fixed at 1.6bar and cannot be altered in any way.
Procedure:
1.
Enter the setting for the fraction of oxygen and the MOD for tank 1 (bot-
tom mix) according to the instructions on page 18 (points 1-7).
2.
Enter the setting for the fraction of oxygen for tank D (deco mix) accor-
ding to the instructions on page 18 (points 1-5).
3.
By bridging B and + or B and – enter the desired depth at which you will
change to tank D during the ascent phase. Confirm your settings with B and E.
The depth you have selected is the Maximum Operating Depth
(MOD) for this gas mixture and the indicated ppO
2
becomes the
maximum tolerable partial pressure of oxygen (ppO
2 max
). During
the ascent an audible attention message will indicate that you
have reached the depth which requires the change of your gas
mixture. This applies to tanks D and 2 (see points below).
4.
For dives with three gas mixtures enter the setting for the fraction of
oxygen for tank 2 (travel mix) according to the instructions on page 18
(points 1-5).
Note that tank symbol 2 can only be selected after tank symbol
D has been assigned to a gas mixture.
5.
Now enter the maximum depth for the use of tank 2 by bridging B and
+ or B and -. Confirm your settings with B and E.
The information given under point 3. does apply here also.
Without confirmation with B and E the display will disappear
after 3 minutes and your entries will not be accepted.
The time to reset the O
2
% mix to air can be set with SmartTRAK between 1 hour
and 48 hours or to "no reset" (default).
After the reset, the oxygen fraction of tank 1 is set to 21%, tanks 2 and D are
switched off (– – %O
2
).
VI
English
100%
O
2
fraction
Range of O
2
fraction
3 gas mixtures
21%
D
2 gas mixtures
D
WARNING
%
Depth for ppO
2max
change of
gas
mixture,
MOD
+ –
