forum.heinrichsweikamp.com

Hi all,

After a night shift from JeanDo (You should sleep sometimes!) the 1.87beta has been released:
http://www.heinrichsweikamp.com/en/ostc_2n/firmware/

- Gas Setup has been modified carefully
- Runtime simulator got some new features and bugfixes
- ppO2 of the diluent can be shown in CCR modes
- Live EAD and END calculations for OC and CCR
- Bugfixes in the logbook
- and much more...

Nach einer Nachtschicht von JeanDo ist die 1.87beta nun verfügbar:
http://www.heinrichsweikamp.com/de/ostc_2n/firmware/

- Das Gas Setup wurde leicht verändert
- Der interne Runtime Simulator hat einige neue Funktionen und Bugfixes
- ppO2 des Diluent-Gases kann in den CCR Modi angesehen werden
- Echtzeit EAD und END Berechnung für OC und CCR Modi
- Bugfixes im Logbuch
- und vieles mehr...

Cheers,
Matthias

Hallo,

erst einmal vielen Dank für die neuen Funktionen. Leider ist im Simulator ein Bug.

Grundzeit 35min
Tiefe 42m
letzter Stop 6m
GF 30/85

aktive Gase Air oder 21/35
Deko Gas 50

Zeit läuft runter auf Null, max Depth läüuft runter bis 6m und dann hängt sich der Simulator auf und ein Resetmit Magnet muss durchgeführt werden.

Gruß Uwe

Uwe S. Wrote:
-------------------------------------------------------
> Leider ist im Simulator ein Bug.

Das stimmt (leider). Mal sehen wie der da jetzt wieder rein gekommen ist...

> runter bis 6m und dann hängt sich der Simulator
> auf und ein Resetmit Magnet muss durchgeführt
> werden.

Nein, das ist nicht nötig. Es dauert nur sehr lange.

Gruß,
Matthias

Thx a lot

Display Error: If you descent below 100m the Max Display is garbaged, you will only see 3digits then and a half one from the max depth below 100m (most likely because of the comma missing now)

While playing with JdiveLog OSTC Dive Simulation I managed to dive below 150m and the unit just switched back to surface mode. The 2nd try the unit shut down completely somewhere around 147m and kept black. I had to use a magnet to get a back to life. The following screen showed:

[pre]
Unexpected reset from
Divemode! Please help
and report the Debug
Information below!
1 jAsvjp. 36 11
160 24 32 132 193
0 0 32 129 64
[/pre]

On a following simulation I stayed quite a long while at 20m and pressed stop in JdiveLog resulting in showing -51,3m on the MK2 for some time and resetting to surface mode afterwards. I also noted a difference in the depth displayed in JdiveLog and the MK2 quite often, especially if you ascent or descent fast. This will usually corrected after "crossing" the next full meter mark. Maybe this is an other issue in the reported depth differences lately...


I'm also afraid there is a bug in the EAD/END calculation. I'm having a 14/41 with SetPoint 1.3, depth is 60m. The display is:
[pre]
ppO2: 0.93
EAD 28m
END 33m
[/pre]

Assuming Air as 21% O2 and 79% N2, rounding to the nearest full m (should maybe to next full one?) the correct values for CC are:
ppO2: 1,30
EAD: 28 (27,73)
END: 33 (32,83)

Assuming I would dive OC the values should be:
ppO2: 0,98
EAD: 30 (29,87)
END: 31 (31,3)

The values for OC and CC for this specific example are quite similar so lets try an other one. Again 14/41, SP 1.3 but this time 20m. Display is:
[pre]
ppO2: 0.28
EAD 2mm
END 13m
[/pre]

I assume the 2mm as an other display bug (this time while ascenting showing the EAD/END display, corrected to 2m after toggling the display)

The correct CC values should be:
ppO2: 1,30
EAD: 1 (1,26)
END: 12 (11,9)

Assuming I would dive OC the values should be:
ppO2: 0,42
EAD: 7 (7,09)
END: 8 (7,7)

Did you know there is also an EADD (equivalent Air Depth) calculation in use by some tech divers? This could replace the ppO2 which could be displayed by setting the appropriate CF at an other position. I can provide a calculation example if you like...

If you decide to stick with showing the ppO2 then I would suggest to show the Diluent ppO2 instead (in case you have to do a diluent flush).

Thx a lot,
Jan (just coming out of the water finding there is a new firmware avaiable(

@solodiver:

* You should not dive below 130m with the OSTC. The used decompression model is not meant to.

* I corrected the 2mm depth (an obvious missing trailling space missing)

* In CCR mode, this is the dilluent ppO2 which is displayed. This is why it is different from SetPoint (except when you exceed you diluent depth).

* EAD/END is rounded to the nearest value. I don't see hard reason to round up, as this won't bring more security.

* EAD/END are computed using alveolar partial pressures. Hence it take into account water vapor inside the limbs, and shows finer result than if not.

* EAD is calculated considering N2 only narcotic effects. END considering N2 and O2 equally narcotic effects. I didn't considered He narcotic effects, has is seems a less wide spread formula, at least for the depth range supported. But I don't know of a EADD formula...

Thanks for the report !

PS: Here are the used formulas:
[pre]
ppWater = 0.0627;
ppN2 = N2_ratio * (pres_diluent - ppWater);
ppHe = He_ratio * (pres_diluent - ppWater);
EAD = (ppN2 / 0.7902 + ppWater- pres_surface) * 10.0150;
END = (pres_respiration - ppHe - pres_surface) * 10.0150;
[/pre]

(formula edited for ppWater value, and to correct the bar->meter conversio factor, as in 1.88)

JeanDo Wrote:
-------------------------------------------------------
> * You should not dive below 130m with the OSTC.
> The used decompression model is not meant to.

I know.

> * In CCR mode, this is the dilluent ppO2 which is
> displayed.

But it is wrong IMHO, see my examples. For a 14/41@20m it should be something like 0,42, you display 0,28 (which is for 10m)!?
I appreciate to show the Dil ppO2, maybe it could be renamed to something which makes it more intuitiv to understand? ppo2Dil is tooo long I guess, what about DppO2 or DilO2?

> * EAD/END are computed using alveolar partial
> pressures. Hence it take into account water vapor
> inside the limbs, and shows finer result than if
> not.

?? Sorry, here I need some more description please .


> * EAD is calculated considering N2 only narcotic
> effects. END considering N2 and O2 equally
> narcotic effects. I didn't considered He narcotic
> effects, has is seems a less wide spread formula,
> at least for the depth range supported. But I
> don't know of a EADD formula...

EADD is based on the sum of the density of the single gases compared to air in the same depth. My formula uses theses values:

dO2 1,429 g/l
dHe 0,1786 g/l
dN2 1,251 g/l

A formula for OC looks like this:

pressure*(fO2*dO2+fHe*dHe+fN2*dN2)/dAir with dAir something like 0,21*dO2+0,79*dN2

Adapt to CC as with EAD/END.

> ppN2 = N2_ratio * (pres_diluent -
> ppWater);
> ppHe = He_ratio * (pres_diluent - ppWater);
> EAD = (ppN2 / 0.7902 + ppWVapour - pres_surface)
> * 9.985;
> END = (pres_respiration - ppHe - pres_surface) *
> 9.985;

The formula for ppO2 is then also including ppWater? What is this exactly and how is it calculated? And is 9,985 for adapting to the alveloar pressure?

Should we siwtch this discussion to an seperate thread or discuss it via PM? I can send you excel sheets for EADD calculations or set up a GoogleDoc spreadsheet...

Thx,
Jan

Hi Solodiver,

Here is the computations done by the OSTC, with a 14/41 mix, a SetPoint of 1.30, and a depth of 20m, you have:

Current depth and setpoint:
ppO2 = 1.3
pres_respiration = 3.0

Partial pressures:
ppN2 + ppHe = pres_respiration - ppO2 = 3.0 - 1.3 = 1.7

Everything but oxygen comes from the diluent
pres_diluant = (ppN2 + ppHe) / (fN2 + fHe) = 1.7 / (100% - fO2) = 1.7 / 86% = 1.98

And oxygen from the diluent
ppO2[Diluent] = pres_diluant * fO2 = 1.98 * 14% = 0.277 ~ 0.28

I don't see anything wrong in those formulas, yet. I'm curious on how you would compute this ?

PS: I would like to have the reference for EADD (based on the sum of the density of the single gases compared...). I was not able to google anything...

Hallo Matthias,

habe mich gestern noch weiter mit dem Simulator beschäftigt und folgendes festgestellt.

GF 30/85
Gas1 Air aktiv
Gas2 21/35
Gas3 18/45
Gas4 50 aktiv
Gas5 O2

Bei einem TG von 19min auf 24m schein alles OK. Bei tieferen und längeren TG braucht der Simulator sehr lange. Bei dem Ergebnis kommt immer keine Deko und die Gasverbrauchsrechnung zeigt nur den Verbrauch beim Grundgas Air und nicht beim Dekogas 50 an.

Gruß Uwe

Hello Uwe,

I just fixed a typo in Gas4 handling ! If you avoid using gas 4, it should work. And will be of course in the next 1.88 beta.

Thanks for the report !

[Google translate ]
Hallo Uwe,

Ich habe einen Tippfehler in Gas4 Handling behoben! Wenn Sie mit Gas 4 zu vermeiden, sollte es funktionieren. Und wird natürlich in den nächsten 1,88 beta werden.

Vielen Dank für den Bericht!

JeanDo Wrote:
-------------------------------------------------------
> And oxygen from the diluent
> ppO2 = pres_diluant * fO2 = 1.98 * 14% = 0.277 ~
> 0.28

JD, this is - how to say - uncommon . What should be the meaning of this? Sure, from a mathematical view you are right: this is the part of the loop ppO2 which is contributed by the diluent O2 content (in the begining) and not added from the O2 supply. The only interesing thing is the real ppo2 (1,3 which is displayed by the MK2 anyway so there is no real sense for this) or the ppO2 if I would flush my loop with diluent (0,42 - importatnt to know for cell checking f.i.).

> PS: I would like to have the reference for EADD
> (based on the sum of the density of the single
> gases compared...). I was not able to google
> anything...

This is an article at RBW:
http://www.rebreatherworld.com/dive-med ... -eadd.html

More:
http://www.yorkshire-divers.com/forums/ ... rmula.html
http://www.mindspring.com/~divegeek/density.htm
http://www.deepdiving.net/rants/norcotic.html

Solodiver Wrote:
> This is an article at RBW:
> ...
> More:
> ...

Jan, _you_ want this feature but others should extract a useable formula from the texts in the linked articles? And you still wonder why nobody takes note of your "whishlist"?

jeando posted the used EAD formula:
EAD = (ppN2 / 0.7902 + ppWater- pres_surface) * 9.985;

Now you can post EEAD:
EEAD =

Danke für's mitdenken,
Jostein

Thanks for the new beta. I haven't had time to really check it out yet but the Simulator dive planner and CNS% display looks good.

Just a note on some of the suggestions above. I bought an OSTC MK2 because I thought the display was very nice, the interface very easy to understand and the menu system easy to navigate.

I use the OSTC MK2 as a backup to my Vision CCR computer for the purpose of sanity checking and emergency bailout if I lose my primary electronics. For me it has to be very simple and intuitive to understand in very stressful circumstances.

Anyone involved in computer software / IT business will have seen products deteriorate from "feature bloat" i.e. too many unnecessary features & information overload.

I'd urge you to keep it simple and useful. Just because it is possible to include a feature does not mean it should be there. Some things better belong to PC based simulators / smartphone apps.

Keep it simple and it will be a winner!

JoStein Wrote:
-------------------------------------------------------
> Jan, _you_ want this feature but others should
> extract a useable formula from the texts in the
> linked articles?

Not exactly, I posted the my formula already some days ago and JD asked for some proof.

Danke fürs vollständige Lesen,
der Jan

JeanDo Wrote:
-------------------------------------------------------
> EAD = (ppN2 / 0.7902 + ppWater- pres_surface) *
> 9.985;
> END = (pres_respiration - ppHe - pres_surface) *
> 9.985;

JeanDo, thinking about this alveloar pressure (which is considered by *9.985) I'm still not sure about this. Is it common to take it into account? Shouldn't you also consider this for the base (air - if one does a dive with air then there is also this reduced alveloar pressure)?
May I asked again what exactly you define by ppWater?

Thx,
Jan

Solodiver Wrote:
-------------------------------------------------------
> JeanDo Wrote:
> --------------------------------------------------
> -----
> > EAD = (ppN2 / 0.7902 + ppWater- pres_surface)
> *
> > 9.985;
> > END = (pres_respiration - ppHe - pres_surface)
> *
> > 9.985;
>
> JeanDo, thinking about this alveloar pressure
> (which is considered by *9.985) I'm still not sure
> about this. Is it common to take it into account?
> Shouldn't you also consider this for the base (air
> - if one does a dive with air then there is also
> this reduced alveloar pressure)?
> May I asked again what exactly you define by
> ppWater?
>
> Thx,
> Jan

Yes, its very common. All of workman's papers have it and that is back 60 years plus ago. Go to the Rubicon foundation you'll find them all.

Alveolar pressure is indeed at the basis of Workmann model, the ancestor of Bühmann's model. It account for the difference between the gas in your tank, and what is indeed in the alveoli participating the the exchanges. Mainly water vapor, but maybe also a bit of CO2. It is a constant 0.0627 bar, at whatever depth you are (so NOT proportional to the ambient pressure).

The 0.09985 is the conversion factor from meter to bar. Or 10.0150 from bar to meters (I fixed that in 1.88). This is for fresh water (1 Kg/l) of course...

Cheers,