<div dir="auto">Shearwater published their approach for po2 > 1.6. Seems pretty conservative and given their position in the market I suspect it would be pretty agreeable to most people to follow their lead.<div dir="auto"><br></div><div dir="auto"><a href="https://www.shearwater.com/monthly-blog-posts/shearwater-and-the-cns-oxygen-clock/">https://www.shearwater.com/monthly-blog-posts/shearwater-and-the-cns-oxygen-clock/</a><br></div><div dir="auto"><br></div><div dir="auto">Dean</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sat, 10 Aug. 2019, 6:30 pm Willem Ferguson, <<a href="mailto:willemferguson@zoology.up.ac.za">willemferguson@zoology.up.ac.za</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<div class="m_-1740244774540623821moz-cite-prefix">On 2019/08/09 23:23, Robert Helling
wrote:<br>
</div>
<blockquote type="cite">
Willem,
<div><br>
</div>
<div>could you please have a look at the final
computation in <span style="color:rgb(128,128,0)">static</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(128,128,0)">double</span><span style="color:rgb(192,192,192)"> </span><span style="font-weight:600;color:rgb(0,103,124)">calculate_cns_dive</span>(<span style="color:rgb(128,128,0)">const</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(128,128,0)">struct</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(128,0,128)">dive</span><span style="color:rgb(192,192,192)"> </span>*<span style="color:rgb(9,46,100)">dive</span>)</div>
<div>in divelist.c</div>
<div><br>
</div>
<div>It seems to me that the first minus in </div>
<div><br>
</div>
<div>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:#c0c0c0"> </span><span style="color:#092e64">cns</span><span style="color:#c0c0c0"> </span>+=<span style="color:#c0c0c0"> </span>(<span style="color:#808000">double</span>)<span style="color:#092e64">t</span><span style="color:#c0c0c0"> </span>/<span style="color:#c0c0c0"> </span>((<span style="color:#808000">double</span>)cns_table[<span style="color:#092e64">j</span>][<span style="color:#800080">SINGLE_EXP</span>]<span style="color:#c0c0c0"> </span>-<span style="color:#c0c0c0"> </span>((<span style="color:#808000">double</span>)<span style="color:#092e64">po2i</span><span style="color:#c0c0c0"> </span>-<span style="color:#c0c0c0"> </span>(<span style="color:#808000">double</span>)cns_table[<span style="color:#092e64">j</span>][<span style="color:#800080">PO2VAL</span>])<span style="color:#c0c0c0"> </span>*<span style="color:#c0c0c0"> </span>(<span style="color:#808000">double</span>)cns_table[<span style="color:#092e64">j</span>][<span style="color:#800080">SINGLE_SLOPE</span>]<span style="color:#c0c0c0"> </span>/<span style="color:#c0c0c0"> </span><span style="color:#000080">10.0</span>)<span style="color:#c0c0c0"> </span>*<span style="color:#c0c0c0"> </span><span style="color:#000080">100</span>;</pre>
<pre style="margin-top:0px;margin-bottom:0px">
</pre>
<pre style="margin-top:0px;margin-bottom:0px">should be plus (at least according to the formula in the comment above. At least, with this minus, you get negative CNS values for a planned air dive to 80m of depth.</pre>
<pre style="margin-top:0px;margin-bottom:0px">
</pre>
<pre style="margin-top:0px;margin-bottom:0px">Best</pre>
<pre style="margin-top:0px;margin-bottom:0px">Robert</pre>
<div><br>
</div>
</div>
</blockquote>
<p>The reason for the negative value is because the dive plan
involves pO2 values above 1.6bar (EAN38 at 35m=pO2 of 1.7bar). The
NOAA tables do not provide values above pO2 = 1.6.</p>
<p>I am working on a sensible solution because we need a sensible
approach for this use case.<br>
</p>
<p>Kind regards,</p>
<p>willem</p>
<p><br>
</p>
</div>
<br>
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