On 13 March, 2018 - Willem Ferguson wrote: > On 13/03/2018 12:28, Robert Helling wrote: > >On 12. Mar 2018, at 15:58, Willem Ferguson > ><willemfergu...@zoology.up.ac.za > ><mailto:willemfergu...@zoology.up.ac.za>> wrote: > >> > >>b) Adapting the gas partial pressure graphs to reflect what the > >>diver breathes during bailout. When rendering the dive by > >>creating a plot_info structure for each sample, the easiest > >>mechanism of incorporating bailout would be to use the > >>Shearwater approach: have a byte indicating Loop or Bailout and > >>perform the appropriate calculation for gas partial pressures. > >>Alternatively, it may be possible to reference the linked list > >>of existing events, find the next bailout event and plot the pO2 > >>depending on the type of bailout event (i.e. Bailout or > >>OC->Loop). But this would incur significantly more computational > >>overhead since this lookup will be needed for each plot_info on > >>the dive profile. > > > >how is a bailout different than a gas change event (except > >semantics of “emergency”). Why don’t you insert a gaschange to OC > >(i.e. with set point 0)? > > > >Best > >Robert > > > A bailout can be an event where one changes from the loop to open > circuit, but using the same cylinder. > > For instance a CCR diver can use the bailout valve to switch from > recycling gas to using the same diluent cylinder but using it in an > OC way. > > For PSCR, a diver can do the last part of the dive using EAN50, but > recycling the EAN50. However, the last 10-15 m is usually done on OC > (no emergency implied, just because the pO2 drop across the injector > valve becomes very large at shallow depths). So, this PSCR diver > switched to OC without switching cylinders.
Eh. There's no drop across a injector. The drop in po2 is due to the diver metabolising the o2, and a fraction is evicted and replaced. > So, in the case of rebreathers, bailout does not automatically mean > a change of gas or cylinders. > > Hopes this makes sense? From subsurface point of view, it really doesn't matter if we represent a bailout as a gasswitch event or not. The problem with the gasswitch and setpoint change, is that it doesn't work for dives with po2 sensors or the SCR steady state approximation. A setpoint change to 0 is sort of a clever hack which just works for planed/setpoint-only CCR dives, and not for CCR dives with po2-sensors, or SCR dives. I'd suggest we clean that up into some bailout sematics which works for both SCR and CCR code, with or without o2 sensors. If we implement that as a divemode switching event, a gaschange event with some special flags, i don't really have a opinion until i see a real suggestion. Nothing says we can't have a gaschange event which switches to the same gas as we're currently using... //Anton -- Anton Lundin +46702-161604 _______________________________________________ subsurface mailing list firstname.lastname@example.org http://lists.subsurface-divelog.org/cgi-bin/mailman/listinfo/subsurface