OSTC2 V2.96 Gas consuption

[Erik69]

Dear All,

I tried the V2.9, and I couldn't have the gas consuption in CCR mode.

As far as I understood, the ostc displays the gas consuption I would have in open circuit.
The display was always ----

My parameters are
2nd Deco plan
fTTS/Delay :0
Calc.Gas (B/O):Yes
Bottom Gas 20
Deco Gas 17
Tank sizes : all 5 tank set to 11l
Tank press Budget : all 5 set to 200bar

Is tehre another parameter to set in oder to activate the Open Circuit ?Consuption.

Thanks

Eric

OSTC 2 #10039
v 2.96

[Ralph]

Hi Eric,

have you driven the OTSC into deco? The Gas-Needs calculation starts not before you are in deco because it needs deco stops to do the calculation...
Your parameter settings looks ok!

BR
Ralph

[Erik69]

Hi Ralph
Thank you for your answer

No I had no deco
So I dont understand this function

I thought it is a calculation of gas that would be use in open circuit (for cave diving)

If I understand correctly it is a calculation of gas that you need to surface??

Eric

[Erik69]

To continue

I thought it is the CF59 on OSTC 2N & 2C

Eric

[Ralph]

CF59 is discontinued in the moment. This new function is supposed to warn you - while still at the bottom segment - when you are going to becoming short of Deco / Bailout gas later in the dive...

-R.

[heinrichsweikamp]

Erik69 Wrote:
-------------------------------------------------------
> To continue
>
> I thought it is the CF59 on OSTC 2N & 2C
>

Hi Eric,

No, in the hwOS series of computers it's currently different. It's the gas amount required to surface including all stops and all active gases. It's not the "Cave Bailout" as in the OSTC 2N/2C/Mk.2. Maybe something to add for the future...

regards,
Matthias

[heinrichsweikamp]

Hi,

There may indeed be a small issue in the latest beta. With Future TTS>0 I also get a strange behaviour of the "Gas needs" view in OC mode. We'll have a look into this

Regards,
Matthias

[Erik69]

Thank you for your answers

Matthias, It would be a very good Idea to have the CF59 Cave diving function, because :

That's the reason why I bought an OSTC, but I received the brand new one ..

And it's a function that no other dive computer have..


Thanks

Eric

[Ralph]

Hi Eric,

the CF59 tried to calculate how much gas you have used, assuming the SAC rate you configured before the dive matches your actual SAC rate during dive. Any extra consumption it can't be aware of, nor any losses due to leaks, free-flow, etc. The new gas-needs calculation computes how much gas you will need to end your dive following all deco stops, agin given your SAC rate matches. I think the later one is the much more useful function. The old CF59 function can easily be archived by having a look on the finimeter (SPG), and this magic piece of equipment will also figure in your true SAC rate... Future hwos tech firmware for the new TR computers will even go one step further ahead by tracking your actual SAC during the dive. Sure - as the OSTCs do not contain a crystal ball - they will not be able the guess your deco SAC from your working SAC. So it's wise not to put all dive planning and control on the shoulders of your fellow OSTC...

BR
Ralph

[Erik69]

Thank you Ralph for these clear explanations.

the fact is, in cave dving, the CF59 value tells me if I still have enough gas to come back at the entrance, of course without integrating the deco stops.
In this case, you'll have to do the same travel back, sometimes deep, and long time

It it something important when you have 3 or 4 S80 on BO, it increase the security.


As you said the OSTC (or any computer) does not include a crystal ball, but having THE information or informations you need helps to have a safe dive.


Eric

[Ralph]

Hello Eric,

sorry, i missed the cave diving part of your request in my last answer. As i'm not direct part of HeinrichsWeikamp but "only" an open source community programmer who did the gas-needs code and some of the new CCR mode stuff, can you give me a summary of the former CF59 function or a formula what you would like to be computed by the OSTC? I don't know what Matthias' plans are on a second life for CF59, but i'm currently rocking my brain for some nice functionalities for the new TR computer (the one with the pressure transmitters) and maybe there will be a synergy...

best regards,
Ralph

[Erik69]

Hello,
no problem for me, your information was very interesting.

I did not use the CF59 function, but the friends that use it explained me.

You enter the tanks size and pressure of the BO
You enter the value of consuption

Those 2 informations are already implemented.

Once you start diving, the computer is calculating the gas quantity you would use in open circuit.
When you reach the given BO quantity, you get an information.
At that point I know that if I have an issue with my rebreather, I can not reach the exit safely.

I think in the 2.96 version, there are almost all information, it's even simplier that calculating the deco gas.


This functionnality used to be on the old 2s, and I'm sure a lot of cave diver would by the OSTC just for this function.
I even thought myself to change the OSTC2 for a 2C

Eric

[heinrichsweikamp]

Hi,

It basically calculates the OC way back in a cave, Based on the average depth and the SAC rate:

[pre]
;---- Retrieve divetime in seconds (since last reset)
movff average_divesecs+0,xA+0
movff average_divesecs+1,xA+1

;---- Multiply by SAC, and divide by 60 (SAC is in liters per minutes)
GETCUSTOM8 d'56' ; Get bottom SAC
movwf xB+0
clrf xB+1
call mult16x16 ; xC:4=xA:2*xB:2

movlw LOW(.60)
movwf xB+0
movlw HIGH(.60)
movwf xB+1
call div32x16 ; xC:4 / xB:2 = xC+3:xC+2 with xC+1:xC+0 as remainder

;---- Multiply by average pressure [absolute, in mbar]
movff xC+0,xA+0 ; Get result (in xC+0, noy xC+2 !) into xA
movff xC+1,xA+1

movf avr_rel_pressure+0,W ; Add surface pressure to get absolute pressure
addwf last_surfpressure_30min+0,W
movwf xB+0
movf avr_rel_pressure+1,W
addwfc last_surfpressure_30min+1,W
movwf xB+1 ; --> Into xB

call mult16x16 ; xC:4=xA:2*xB:2

movlw LOW(.1000) ; Pressure was in milibar, so divide by 1000.
movwf xB+0
movlw HIGH(.1000)
movwf xB+1
call div32x16 ; xC:4 / xB:2 = xC+3:xC+2 with xC+1:xC+0 as remainder

;---- Go RED when limit is exceeded
movff xC+0,sub_a+0
movff xC+1,sub_a+1
GETCUSTOM15 d'59' ; Get Cave bailout alarm threshold
movff lo, sub_b+0
movff hi, sub_b+1
call sub16 ; Computes prediction - limit
btfss neg_flag ; Negativ ?
call DISP_warnings_color ; NO: go RED.

;---- Then display...
movff xC+0,lo
movff xC+1,hi

bcf leftbind
output_16
call word_processor
WIN_FONT FT_SMALL
return
[/pre]

In the hwOS we now have different SAC rates for Deco and non-deco gases and could possibly add this function again. Including the deco stops and gas changes! But that's a potential feature after the next stable...

Regards,
Matthias

[sailor]

Just my 2 cents, I like that CF59 Cave Warning feature a lot in my MK2 and presently I'm not willing to update to a HWOS computer without that fuction.

[Ralph]

OK, as i'm also a CCR diver and intro-cave holder, you got me!

One last question: your faithful MK2 doesn't know if you are already on the way out again and will continue clocking up your bailout exit needs although your bailout gas need will a) decrease due to the way out becoming shorter, but b) increase in case the way out is such deep that your deco is still increasing. How do you (want to) handle that? Or are just fine with the OSTC throwing a warning while you are on the way out, because there was no warning before you turned the dive?

Anyhow: Keep your new 2 and give us a little bit of time!

-R.

[sailor]

I'm fine with just the warning.

[Erik69]

Hi,

Me too, I know I'm on my way back.
I prefer having a simple information on the computer

And.. thanks for the support

Eric

[Ralph]

Hi to both of you,

have almost completed my ideas on how to compute the way-back gas needs, will start coding soon. The new implementation will be ways better than the old one...

Ralph

[Erik69]

Dear all

Has this function been implemented in the V2.99?


Thanks

Eric

[Ralph]

Hi Eric,

honestly - a lot of the coding had been done, but then works have been interrupted in favour of working on the OSTC TR functions. So it's not in 2.99 at the moment. But thanks for remainding!

BR
Ralph

[Erik69]

Thank you ralph,

Hope it will be in the 2.99.2


Eric