<html>
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<div class="moz-cite-prefix">On 04/11/2014 11:10, Robert Helling
wrote:<br>
</div>
<blockquote
cite="mid:FA18D01F-4A31-4E07-B1D0-0E8D1BBDF636@atdotde.de"
type="cite">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<br>
<div>
<div>On 04.11.2014, at 08:45, Willem Ferguson <<a
moz-do-not-send="true"
href="mailto:willemferguson@zoology.up.ac.za">willemferguson@zoology.up.ac.za</a>>
wrote:</div>
<div><br>
</div>
<div>Willem,</div>
<br>
<blockquote type="cite">The calculation of MOD, EAD and the like
that happens in profile.c does not work for CCR because it is
based on the gas mix info associated with individual
cylinders. Function gas_mod in dive.h is a case in point. I
was starting to mess around with these calculations to use
dynamic fo2 values for each point on the dive profile (instead
of fixed cylinder-specific fo2 values), but then I saw that
this function is used in many places, including extensively in
the planner.<br>
</blockquote>
</div>
<div><br>
</div>
<div>I am not sure exactly what would be the meaning of MOD for a
CCR given the dynamic O2 content. The only way I think this
makes sense would be the MOD of the dillutant (since that sets
the minimum fO2 that the CCR can deliver and that determines the
depth).</div>
<div><br>
</div>
</blockquote>
I was thinking that it would be useful that a diver could review a
dive and see at a particular moment, how far he/she was from the
MOD, given the gas composition at that moment in time. Let's the fo2
was 35% at a particular moment and the diver was 30m deep. The diver
should know that this was pretty close to the MOD for that
particular gas combination. This might for instance affect decision
making with respect to setpoints. Of course the dive computer should
provide such facilities for decision making and/or automatic control
during the dive, but for the review of a dive afterwards, this
information might be useful.<br>
<br>
<blockquote
cite="mid:FA18D01F-4A31-4E07-B1D0-0E8D1BBDF636@atdotde.de"
type="cite">
<div>Indeed, gas_mod is used in various places but only the call
in profile.c is about the current gas, in all other cases the
MOD of an explicit cylinder is calculated (essentially to find
the max depth to switch to it). What I would probably do is to
leave everything as it is and only wrap the call in profile.c
with an if(dc.dctype != CCR) { and in the else clause make sure
the dillutant is used.</div>
<div><br>
</div>
<div>I guess the others EAD, END and EADD should be ok the way
they are since they use the info from fill_pressures which takes
CCR-ness into account.</div>
<div><br>
</div>
</blockquote>
<br>
At the moment it gives EAD of 0m throughout the dive and EADD of
current_depth, but I have not looked at that code closely to explain
that. However I note that fhe and fo2 are derived from
cylinder-related data, using get_o2() and get_he().<br>
<br>
<blockquote
cite="mid:FA18D01F-4A31-4E07-B1D0-0E8D1BBDF636@atdotde.de"
type="cite">
<div>What do you think?</div>
<div><br>
</div>
<div>Best</div>
<div>Robert</div>
</blockquote>
<br>
</body>
</html>