Re: RFC: PSCR dive plots: Part 2.

2018-03-13 Thread Anton Lundin
On 13 March, 2018 - Robert Helling wrote:

> > 
> > 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...
> 
> You could always interpret „gas switch“ not as „switch of gas in cylinder“ 
> but as „switch of breathing gas“ as that what PSCR divers experience when 
> going from the loop to OC.
> 
> I would say, the main difference is to make „PSCR mode“ not a global thing 
> for a dive but more local in time. Note that this is already the case for 
> „CCR mode“: We have set point that can change over time with 0 indicating OC 
> and „CCR mode“ in a more strict sense (as in the combo box) is simply a dive 
> that has at least at some part non-zero set-point (but we don’t use that to 
> determine the breathing gas at any moment).
> 
> Does that make sense?

Yep.

But, currently we're using gaschange events to represent the switching
of OC gas _AND_ the switching of diluent, and we're using setpoint to
switch between CCR-setpoints and OC, if we're not using pO2 sensors.

Intertwining PSCR mode with all of that just doesn't make sense.


I'd suggest we just convert the whole thing into a mode switch event,
and let that switch between OC, CCR and PSCR, independent of everything
else. That could be implemented as a bailout event between whatever mode
you're in and OC, or a dedicated mode switch event.

Ie CCR + bailout -> OC on you're current diluent, and so on.


//Anton


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Re: RFC: PSCR dive plots: Part 2.

2018-03-13 Thread Anton Lundin
On 13 March, 2018 - Robert Helling wrote:

> 
> 
> Am 13.03.2018 um 12:25 schrieb Anton Lundin :
> 
> >> 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.
> > 
> 
> Sorry, I don‘t get it. What is the problem with pO2 Sensors?

If your pO2 sensors says you have a pO2 of 1.0 in the loop, nothing
cares about what your setpoint is, so setting it to zero doesn't matter,
our calculations will be based on the pO2 sensors.

Just because you're bailed out, nothing magical happens to the
pO2-sensors. You're just breathing a different gas, and currently
subsurface has no way of representing this.


What we need is something which changes our dive mode to OC, and in OC
mode, we shouldn't care about setpoint or pO2 sensors.


//Anton


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Re: RFC: PSCR dive plots: Part 2.

2018-03-13 Thread Willem Ferguson

On 13/03/2018 14:49, Robert Helling wrote:


Am 13.03.2018 um 12:25 schrieb Anton Lundin :


 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.


Sorry, I don‘t get it. What is the problem with pO2 Sensors?


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...

You could always interpret „gas switch“ not as „switch of gas in cylinder“ but 
as „switch of breathing gas“ as that what PSCR divers experience when going 
from the loop to OC.
I would say, the main difference is to make „PSCR mode“ not a global thing for 
a dive but more local in time. Note that this is already the case for „CCR 
mode“: We have set point that can change over time with 0 indicating OC and 
„CCR mode“ in a more strict sense (as in the combo box) is simply a dive that 
has at least at some part non-zero set-point (but we don’t use that to 
determine the breathing gas at any moment).

Does that make sense?

Robert


This would affect the whole current dive equipment model with the 
cylinder structures and their definitions. Think of the CCR case where 
the 1st cylinder is O2 and the remaining one diluent. How would you make 
this a local mode in time within a dive? And gas composition varies all 
the time in order to keep pO2 constant? Which gas would one choose? 
There would be continuous gas switches. As for SCR, remember the way it 
is used at present, it is just a special case of CCR.


But, it's worth entertaining your proposal. Let's see where this 
discussion goes...


Kind regards,
willem









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Re: RFC: PSCR dive plots: Part 2.

2018-03-13 Thread Robert Helling


Am 13.03.2018 um 12:25 schrieb Anton Lundin :

>> 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.
> 

Sorry, I don‘t get it. What is the problem with pO2 Sensors?

> 
> 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...

You could always interpret „gas switch“ not as „switch of gas in cylinder“ but 
as „switch of breathing gas“ as that what PSCR divers experience when going 
from the loop to OC.

I would say, the main difference is to make „PSCR mode“ not a global thing for 
a dive but more local in time. Note that this is already the case for „CCR 
mode“: We have set point that can change over time with 0 indicating OC and 
„CCR mode“ in a more strict sense (as in the combo box) is simply a dive that 
has at least at some part non-zero set-point (but we don’t use that to 
determine the breathing gas at any moment).

Does that make sense?

Robert


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Re: RFC: PSCR dive plots: Part 2.

2018-03-13 Thread Anton Lundin
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
> > >> 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


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Re: RFC: PSCR dive plots: Part 2.

2018-03-13 Thread Willem Ferguson

On 13/03/2018 12:28, Robert Helling wrote:
On 12. Mar 2018, at 15:58, Willem Ferguson 
> 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.


So, in the case of rebreathers, bailout does not automatically mean a 
change of gas or cylinders.


Hopes this makes sense?

Kind regards,
willem



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Re: RFC: PSCR dive plots: Part 2.

2018-03-13 Thread Robert Helling


> On 13. Mar 2018, at 11:28, Robert Helling  wrote:
> 
>> On 12. Mar 2018, at 15:58, Willem Ferguson > > 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)?
> 


Sorry, I am too slow. This is of course PSCR.

I wouldn’t add a byte (not even a bool) to indicate that. Rather do it with 
events (given that most of the dives don’t have any such event and those that 
have have very few). You would need to establish a similar logic as with gas 
switches (or even piggy pack this info into the gasswitch events).

Robert

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Re: RFC: PSCR dive plots: Part 2.

2018-03-13 Thread Robert Helling
Willem,

> On 12. Mar 2018, at 15:58, Willem Ferguson  
> 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
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  Ludwig Maximilians Universitaet Muenchen, Dept. Physik
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