iMixer
Defaults
From the iPhone/iPad main
screen, select “Settings” and
find iMixer in the list of
installed apps.
Cost calculations are performed
using either a “Shop” set of
values or a “Retail” set of
values. The cost of a fill is
calculated by multiplying O2,
Helium, and Top Off Mix costs by
the number of cubic feet of each
gas used plus the blending fee.
Calculations can be in either
imperial or metric units. If the
Imperial calculation
switch is set to “off”, all
calculations are done in metric
units. Costs must be specified
in the default units. If
Imperial is “on”, O2,
Helium, and Top Off Mix costs
are per cubic feet; otherwise
they are by cubic liter.
When the Real Gas switch
is set to "on", van der Waals
equation is used to calculate
blending plans. When set
to "off", ideal gas calculations
are used. The Real gas
temperature default is the
temperature of the cylinder
during filling. Volume is
the internal volume of the
cylinder. This value can
be obtained either from the
cylinder manufacturer or closely
approximating it using a
formula. A cylinder with
radius r units and height h
units has a volume of V cubic
units given by
v= πr^{2}h. A standard Aluminum 80
has an internal volume of 0.3929
FT^{3} (11.13L^{3}).
The van der Waals equation is
not terribly sensitive to these
parameters so an approximation
is generally good enough.
Fill O2 First
determines the default order gas
is added during the mixing
process. If Fill O2 First
is set to “on” the default
mixing procedure is to add
Oxygen first, then Helium, then
the Top Off Mix. When set to
“off”, Helium is added first
followed by Oxygen and then the
Top Off Mix.
The Doubles Switch
determines if cost calculations
are done for either singles or
doubles. When set to “on”,
calculations are for doubles by
default.
When the Retail Switch is
set to “on”, iMixer uses the
retail values cost set to
determine fill cost. When set to
“off”, the shop cost value set
is used.
The
value Max PO2 is the
partial pressure of Oxygen used
in the maximum operating depth
calculation.
Bank gas and Top off gas can
be any mix (Air, Nitrox, or
Trimix). The default is to top
of with air.
Cylinder Specifications refer to
the characteristics of the tanks
you are filling. In this
example, the default cylinder is
a standard Aluminum 80
containing 80 FT^{3} of
gas with a working pressure of
3000 PSI. This volume refers to
the quantity of gas in the
cylinder when filled to it’s
working pressure; and not the
volume used for real gas
calculations (which is the
internal volume of the cylinder
when empty). If default
calculations are in metric
units, the default volume and
working pressure should be in
metric units as well. In this
example, the cylinder would be
206 BAR and the working pressure
set to 2265 liters.
In order to make your default
cylinder a high pressure
steel 120, you can set these
values to 3500 and 120
respectively. These values
control the calculation of the
volume of gas used in a fill
which directly impacts price.
The Default Starting Mix
is what is in your tank when you
start blending. Default
Target Mix is what you want
to end up with.
All defaults can be overridden
in the iMixer app with the
exception of the Shop and Retail
Cost Set values.
