How-To Guide

CXR-I Dive Comput er
2.2.3. PERSONALIZATION
This menu allows you to define additional
conservatism in a way similar to going from
R0 to R1, R2 or R3 but in a more personal way .
It comprises two submenus, labelled MAIN
and ALTERNATE , each of which has thr ee
submenus, called PHYSIO, DIVE, I TOD A Y . The
values set in each menu are subtracted from
the respective MAIN GF and ALTERNATE GF
value yielding the values used by CXR-I f or
the decompression c al culations.
PHYSIO allows you to define an additional
conservatism based on how you feel about
y ourself and diving overall. Each step from
LOW to MEDIUM to HIGH incr ement all y
reduces both gradient factor values by 10.
There is also a setting called AD V ANCED ,
which increases the gradient factor by 5 so
that a maximum of 90/90 can be achie v ed.
This is only for experienced divers who hav e
accumulated enough experience to know the y
can tolerate such levels of inert gas. We do not
recommend doing this since it increases the
risk of decompression sickness thus CXR-I
requires that you insert a code (1234) to all o w
the setting.
The value set in PHYSIO remains stored until
you manuall y change it. The default value is
OFF.
DIVE allows you to define an additional
conservatism based on how you feel about
the dive conditions. Each step from LOW to
MEDIUM to HIGH incr ement all y reduces both
gradient factor values by 3. If you think ther e
will be much current or the water will be
very cold, pick one of these settings. Sinc e
conditions can actually be different from what
you expected, this parameter can be edit ed
also DURING the dive (via the underwat er
menu). The default value is OFF.
The value set in DIVE resets aut omatic all y t o
OFF at midnight.
I TODAY allows you to define an additional
conservatism based on how you feel about
y ourself today, for instance to account f or
a restless night or not having hydr at ed
sufficiently. Each step from LOW to MEDIUM
to HIGH incr ement all y reduces both gr adient
factor values by 5.
The default value is OFF . Also the value set
in I TODAY resets aut omatic all y to OFF at
midnight.
interval will carry an automatic additional
gradient factor reduction. If you set the v alue
to OFF , the GF values are not modified during
a surface interv al.
The setting can be applied independentl y t o
the MAIN GF and ALTERNATE GF v alues. The
default values are OFF for MAIN GF and OFF
for ALTERNATE GF.
fill pressure of your tanks. This can be set
individually for each tank ( G1 through G5).
This value is used to scale the graphic t ank
representation but also to define the pr es sure
ranges for color coding (described in section
2.3.1). When the units are set to ft/°F/psi,
this value is important because together with
the tank volume it allows CXR-I to c orr ectl y
e v aluat e your gas consumption in cu ft/min.
Default values are 200bar and 3000psi.
The fifth menu, MID TANK WARNING , is the
value at which CXR-I triggers a half t ank
warning. This can be set individually for each
tank ( G1 through G5 ). This value is also used in
the definition of the pressure ranges for c ol or
coding as described below. Default values are
100bar and 1500 psi .
The sixth menu, TANK RESERVE , is the
value at which an alarm is triggered because
you should always be at the surface bef or e
reaching this level. Furthermore, this v alue
is used to calculate the TTR and RGT v alues
(see section 8.5.5 and 9.1). This can be set
individually for each tank ( G1 through G5).
Default values are 50bar and 750psi .
The se v enth and last menu is c alled
AUT OZERO RESET and it allows you to set the
ambient pressure reading on the tank modul e
in the unlikely event of a drift of the zero v alue.
Y ou would perform this operation if you notic ed
a significant difference between the r ead-out
of CXR-I and a calibrated pressure gauge also
connected to the same first s t age.
Due to the potential of introducing an error in
the tank module measurement, please cont act
your Mares Authorized Service Center bef or e
performing this oper ation.
2.2.5. MUL TID A Y
Increasing inert gas load on your tissues o v er
se v er al days of diving has effects that are not
fully understood and are different from per son
to person. Most dive computers available t oday
do not account for this and compute simpl e
inert gas offgassing by diffusion. CXR-I all o ws
you to increase the conservatism aut omatic all y
for each day of diving with less than 24-hour s
of surface interval by reducing both gr adient
factor values by 2 on the second day, an
additional 2 on the third day and an additional
2 on the fourth day up to a maximum of 6.
Default values are OFF for MAIN GF and OFF
for ALTERNATE GF.
2.3. GAS INTEGRATION
This menu contains seven submenus. The fir s t
one allows you to pair the tank modules t o
the CXR-I. Please refer to section 1.8 for the
description of the pairing pr oc es s.
The second menu, GAS SUPPLY ESTIMATE
allows you to choose between two concepts of
available gas supply es timate:
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TTR (time to reserve) is the time, in minut es,
before you will reach the tank reserve at the
current depth and at the current br eathing
r at e;
RGT (remaining gas time) (TO BE
INTRODUCED VIA FREE FIRMWARE
UPGRADE SOON) is the time you can s till
spend at the depth you are at, based on
the current gas consumption, before y ou
must initiate an ascent in order to arrive at
the surface without going below the t ank
reserve. This calculation accounts for all
existing and upcoming decompr es sion
obligations.
2.3.1. COLOR CODING FOR PRES SURE
RANGES
In addition to a numeric value for the t ank
pressure, CXR-I uses color coding f or
an immediate at-a-glance tank pr es sure
visualization. The color is applied to the inside
of the tank pictogram. The pressure r ange
from operating tank pressure to empty t ank
is split into 4 ranges, from BLUE to GREEN to
YELLOW to RED . The ranges are so defined:
BLUE : the upper half between OPERA TING
TANK PRESSURE and MID TANK W ARNING
GREEN : lower half between OPERATING T ANK
PRESSURE and MID TANK WARNING
YELLOW : between MID TANK WARNING and
50bar/750psi.
RED : below 50bar / 750psi
-
When using TTR , you have a clear idea of when
you will reach the tank reserve, but you mus t
use it c ar efull y to gauge when to initiate the
ascent in order to arrive at the surface with
the tank reserve. This is a good method when
you don’t have decompression obligations, but
is less powerful when doing decompr es sion
div es.
The RGT is very useful when doing
decompression dives since it accounts f or
additional decompression incurred during the
RGT itself.
The third menu, TANK VOLUME , allows you t o
set the size of the volume of the t ank,
individually for G1 through G5. This paramet er
is important for a correct e v aluation of y our
gas consumption in l/min or cu ft /min. Def ault
setting is 12l for metric system and 80 cubic
feet in imperial. For the imperial setting it
is paramount that you also set the c orrect
operating tank pressure, since the size of the
tank is referenced to this pr es sur e.
The fourth menu, OPERATING TANK
PRESSURE , is where you define the nominal
2.2.4. REPETITIVE DIVES
The original Bühlmann algorithm as sumes
normal offgassing of inert gas via diffusion
after a dive. This seems to work well f or
most people and indeed most dive comput er s
available today compute repetitive dives lik e
this. There is evidence however that some
people produce bubbles after a dive, or
produce more bubbles than others, and these
bubbles though harmless slow down the
offgassing process. Surface intervals of thr ee
hours or longer are known to dissipate most if
not all bubbles. CXR-I allows you to ac count
for this by applying an additional c onservatism
to repetitive dives, reducing both gr adient
factor values by 8 upon surfacing from a div e
and then increasing it again by 1 every 15
minutes of surface interval. When setting REP
DIVE to ON you will have r ec o v er ed the full
gradient factor values after a two-hour surf ac e
interval. Any dive started before such surf ac e
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