Ostc Sport menu "Config Tanks" and needed pressure

OSTC's running hwOS sport or tech
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gouyen-cassou
Posts: 10
Joined: Thursday 16. January 2020, 09:32

Ostc Sport menu "Config Tanks" and needed pressure

Post by gouyen-cassou »

Hello
I'm new on the forum. Let introduce me.
My name is Jerome From Bordeaux
I'm a French diver N4 E2 Nx. I hope In Juin be E3 2 stars monitor.
And I'm a new user of Ostc Sport

I wonder if someone could give some help with the menu "Config Tanks". I FInd nothing about this in the forum.
Matthias said me this menu was developped by Ralph, if he red this post he wil be welcome here.
I explain what I have undersntand and my Questions:

I think we could set up before dive=> the volume and the initial pressure of the tank less the pressure we want keep at the end of the dive? In other words, the pressure avalable to the dive.
And during the dive, the computer predict the needed in bar to the ascend, and give an advice at the buttom when there is not enough gaz?
I put a sample of a simulation in the attached files : Bloc 15l 210b => in the simulation prof 21m for 1'. No dec time . The computer indicate needed gaz to ascend = 21 bar ?? I don’t understand because in reality we need about 5-6 bars

Many thanks if someone could explain this menu
Attachments
03.jpg
01.jpg
Ralph
Posts: 708
Joined: Saturday 24. June 2017, 11:31

Re: Ostc Sport menu "Config Tanks" and needed pressure

Post by Ralph »

Hi Jerome, this is Ralph!

Your guessing is completely right! Anyhow, there are three more infos you need to have to fully understand trhe function:

1) The SAC rate (l/min breathing rate at 1 bar) needs to be configured. For the part of the ascent before the first stop ("Initial ascent"), the SAC work will be used, at and after the 1st stop the calculations will use SAC deco.

2) The gas needs calculation will always pick the best gas. To decide which gas is the best one, the algorithm only looks at the change depths of the gases. So if you configure a Nx50 with change depth 30 meters, calculations will pick the Nx30 once passing 30m. In other words: it doesn't look at the resulting ppO2. Anyhow, in case you actually would switch to that gas on that depth, the OSTC will prompt you a big warning.

3) Last but not least, when you have set a fTTS time, the calculations will figure in the amount of gas you will consume on the current depth for the fTTS delay time before doing the ascent. The idea behind is to use the fTTS time to have the gas included that is needed between deciding to end the dive (or having an event that will force you to turn the dive) and actually starting the ascent, e.g. to signal to the buddies, send an SMB, etc. This gives the unexpeced extra in your numbers.
gouyen-cassou
Posts: 10
Joined: Thursday 16. January 2020, 09:32

Re: Ostc Sport menu "Config Tanks" and needed pressure

Post by gouyen-cassou »

Hello, RAlph
Big Thank you for your fast reply.
(I dont have the computer with me today, so I will test this an over time.)

Otherwhise, when you say: "when you have set a fTTS time" is it a set up in simulation mode? or in your mind?
I'm not very sure of your meaning of "fTTS time" => My problem is : I have my firmware in french

And in the menu Config Tank or for me in french "config BLocs (see my picture) i am not sure of the meaning of "besoin press. Rem."'
If i translate in english => need pressure ascend
Is it only the securtity reserve we want to keep after the dive ??

Jerome
jb2cool
Posts: 142
Joined: Tuesday 21. January 2014, 21:19

Re: Ostc Sport menu "Config Tanks" and needed pressure

Post by jb2cool »

fTTS is Future Time To Surface

It's a prediction if what your TTS (time to surface) will be in x minutes. I have mine set at 5mins so I may have a current TTS of 3mins (a direct ascent) but a future TTS of 6mins meaning that I'm within 5mins of going into deco. I find this particularly useful when monitoring deco commitment as this can escalate quite quickly.
Ralph
Posts: 708
Joined: Saturday 24. June 2017, 11:31

Re: Ostc Sport menu "Config Tanks" and needed pressure

Post by Ralph »

Again completely right!

The tank pressure you set in the menu, along with the tank size in liters, tells the OSTC how much gas is available. When a computed need reaches 70% of the available amount, a yellow attention message is generated. Upon reaching 100%, a red warning comes on. So it is clever to set the OSTC to a little less pressure than there actually is, so that the red warning does not come right on the edge of tank depleption but a little bit earlier. All given your SAC is also set accurately. For deco tanks, you can set the fill pressure (minus a small delta, as said), for the back gas set your planned turn pressure (minus the delta, again). Example: planned turn press: 120 bar -> set OSTC to 100 bar, so will get the first attention when the ascent is computed to take 70 bar and the warning on 100 bar, leaving you with a final reserve of 20 bar.

cheers,
Ralph
gouyen-cassou
Posts: 10
Joined: Thursday 16. January 2020, 09:32

Re: Ostc Sport menu "Config Tanks" and needed pressure

Post by gouyen-cassou »

Thank you both of you :D

Ok now for Ftts .

I think i will change my firmware in English. It' Strange for me in french (I usually dives with english language computers...)

Now I understand, I see the link between Ftts and the "amount of gas you will consume on the current depth for the fTTS delay time before doing the ascent".

But if I could give my little point of vue:
without a tank Pressure transmitter , for me it will be nice and easier to just have in real time the indication of the need in bar for the current time to surface (TTS) (intended the sac and bloc volume of course). I always plane my recreative dives like that. Max TTS with a security reserve of gaz; like TTS 15' with an amount of 100bars. And before the dive I use a factor multiplier to calculate my need of gaz. Example at 40m with a 15l tank. 3b*min-tts. if dive under 40m 4b*min-tts.
It will be very interesting to have the possibility to see this calculation in real time and easely manage ourselves to start the ascend when we are close to this value of pressure + the security reserve.
Sample: TTs 15' Pressure Needed 45b (tank 15l sac 20l/min) . => In my mind, i want to exit with a reserve of 50b so i have to leave the buttum at 95b (45+50).

Thank you for your help
Jerome
gouyen-cassou
Posts: 10
Joined: Thursday 16. January 2020, 09:32

Re: Ostc Sport menu "Config Tanks" and needed pressure

Post by gouyen-cassou »

Hello,
I did many simulations yesterday evening.
I 'm ok now. I think I have all undrestood. Sory I have a little brain ;)
The fonction give the pressure needed to the TTS included the Ftts and the gap of buttum time :D
I have set up the ftts to 3' so it give me a security reserve to check my end of buttum time and begin my ascend

I think I will set up very large "need pressure ascend" in the tank menue to avoid the big warning. I prefair not be disturbed by this advice, and just during the dive manualy compare my instantaneous pressure (gauge) and the calcul of gaz to ascend. The computer will replace me only to calculate my by out gaz

Thanks again guys . It's perfect
Ralph
Posts: 708
Joined: Saturday 24. June 2017, 11:31

Re: Ostc Sport menu "Config Tanks" and needed pressure

Post by Ralph »

Thanks for that info!

It's always nice to hear when diver's needs have been propperly assessed and put into OSTC functionality :-)
gouyen-cassou
Posts: 10
Joined: Thursday 16. January 2020, 09:32

Re: Ostc Sport menu "Config Tanks" and needed pressure

Post by gouyen-cassou »

YOu're Welcome Ralph

a last think, you writed in the menue a function to "appair a ransmitter". Do you think in the future it will exist a bluetooth pressure transmitter?

Jérôme
Ralph
Posts: 708
Joined: Saturday 24. June 2017, 11:31

Re: Ostc Sport menu "Config Tanks" and needed pressure

Post by Ralph »

Hi Jerome,

Bluetooth is a radio standard using radio waves, and radio waves have a very very limited reach under water. Essentially, water shorts the electro-magnetic waves. So all pressure transmitters use some kind of magnetic waves only, which also has it's own range of problems, e.g. steel tanks close to the transmitter interact with the magnetic field, absorbing energy from it.

BR
Ralph
gouyen-cassou
Posts: 10
Joined: Thursday 16. January 2020, 09:32

Re: Ostc Sport menu "Config Tanks" and needed pressure

Post by gouyen-cassou »

Ok Ralf.
I agree with you bluetooth, is not efficient underwater . I saw only short waves antenas in transmitters.....
I was just curius to know why you wrote this in the firmware....

:D
Ralph
Posts: 708
Joined: Saturday 24. June 2017, 11:31

Re: Ostc Sport menu "Config Tanks" and needed pressure

Post by Ralph »

...because there is an OSTC TR model that supports pairing with pressure transmitters.
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