DataTrak Software

[mweitz]

The Data Trak software from Uwatec will calculate your SAC rate based on your tank size and your air consumption. The thing that is puzzling though is that it is missing an important piece of information, and that is the rated pressure of your tank.

I assume that their calculation is based on a standard service pressure, like 3000 PSI. Does anyone know?

Thanks,

Mark

 

[FIXXERVI6]

Doesn't matter what the rated pressure is, you put the volume in and it gows by how fast the pressure drops.

If you had a 1000 cubic foot tank and your suckin in down in leaps and bounds of 20 psi a breath your sac is through the roof, if you have a 10 cubic foot tank and your breathing it off at 10 psi per breath your not breathing as heavy, make sense?

 

[mweitz]

Well, not really. I'm not necessarily talking about using the air integration, though I think it holds true for that as well.

If you manually enter the parameters (don't use the AI) you are just entering the tank size and the PSI used on the dives. Lets say I have two 80 CF tanks, a steel and an AL. The steel is HP, so its service pressure is 3442 and the Al is 3000 (at 77 CF or so). I use 1000 PSI. From the HP tank that is a total of 23.5 CF. In the AL it is 25.5 CF. Not a huge difference, but a difference nonetheless... and it would give me a different SAC rate for the tanks. The SUUNTO software does ask for the rated pressure...

Mark

 

[O2BBubbleFree]

The Data Trak software from Uwatec will calculate your SAC rate based on your tank size and your air consumption. The thing that is puzzling though is that it is missing an important piece of information, and that is the rated pressure of your tank.

I assume that their calculation is based on a standard service pressure, like 3000 PSI. Does anyone know?

Thanks,

Mark

I'm confused. Seems to me the missing pieces are time and depth. 'Rated pressure' isn't relevant.

Surface Air Consumption rate is calculated from starting pressure, ending pressure, volume, time, and depth. Right?

If it is asking for ending pressure and assuming a starting pressure, then I agree that's strange.

If it's asking for 'air consumption,' my guess is that you are supposed to subtract your ending pressure from your starting pressure and enter the result.

 

[O2BBubbleFree]

Well, not really. I'm not necessarily talking about using the air integration, though I think it holds true for that as well.

If you manually enter the parameters (don't use the AI) you are just entering the tank size and the PSI used on the dives. Lets say I have two 80 CF tanks, a steel and an AL. The steel is HP, so its service pressure is 3442 and the Al is 3000 (at 77 CF or so). I use 1000 PSI. From the HP tank that is a total of 23.5 CF. In the AL it is 25.5 CF. Not a huge difference, but a difference nonetheless... and it would give me a different SAC rate for the tanks. The SUUNTO software does ask for the rated pressure...

Mark

As you said, a AL 80 (let's say a Luxfer) at 3000 psi is actually about 77 cu ft. And I guess you know that a PST E7-80 at 3442 psi is actually 80 cu ft.

http://www.huronscuba.com/equipment/scubaCylinderSpecification.html

So when it asked for tank size did you input actual (77 and 80), or did you use 80 for both?

To expand my previous, SAC rate is calculated using starting pressure, ending pressure, time, depth, and 'actual' tank volume.

Does that make sense?

p.s. My guess is that the Suunto software asks for rated pressure to guesstimate an 'actual' tank size, while the DataTrack software is expecting you to input actual size.

 

[mweitz]

Sorry, I left out some information. The computer itself knows your depth and dive time by your profile so if you don't use the AI it averages your SAC for you. It gives you the result in CF per minute.

Service pressure is important because 2000 PSI is a different amount of gas for different tanks. If I use 2000 PSI out of an AL 80, it is a different amount of gas I've breathed than 2000 PSI out of an HP 80 and even different from an LP 80

AL 80, 2000 PSI = approx 51 CF
HP 80, 2000 PSI = approx 46 CF
LP 80, 2000 PSI = approx 60 CF

So, if I input 2000 PSI and 80CF, the application can't actually know how much air I used.

Make sense?

Mark

 

[O2BBubbleFree]

By golly, I don’t know.

To get SAC/SCR/RMV (pick your acronym) in cu ft / min:

(Starting Pressure – Ending Pressure) / Rated Pressure * Rated Volume / Minutes = Cubic Feet per Minute.

Right?

Or you could go:

(Starting Pressure – Ending Pressure) / Starting Pressure * Actual Volume / Minutes = Cubic Feet per Minute.

Where Actual Volume is the volume you started with, but I can’t figure out how you could calculate that without knowing the Rated Volume....

So, you are right. Seems like they are making an assumption somewhere.

 

[mweitz]

Yeah, when you calculate your SAC, at some point you convert the used PSI to CFM. It would be fine if they gave me PSI used per minute, then I could convert it myself. If I knew what tank they use in their calculation, I could probably fudge on the tank size I enter to get an accurate result.

I'll call Uwatec Customer Service today. The crappy thing is that a lot of people use them and probably don't realize that their SAC isn't accurate .. I would be that it is based on a Luxfer 80 at 3000 PSI ... or a 12L Steel tank ...

Wish me luck trying to explain THIS to them

Mark

 

[Kim]

p.s. My guess is that the Suunto software asks for rated pressure to guesstimate an 'actual' tank size, while the DataTrack software is expecting you to input actual size.

The Suunto software asks for rated pressure and actual pressure - as well as tank size.

 

[Corigan]

I had always used the AI in the software. Since I get overfills on a few steel tanks of mine this has always been a concern of mine. What I do is calculate how much cf of gas is really in the tank and then use that as the size of tank. Of course since I use the AI on the computer it knows my starting and ending pressure, depth, time, etc. You are correct though, it doesn't include service pressure. I assume it is probably this calculation by 3dent:

(Starting Pressure – Ending Pressure) / Starting Pressure * Actual Volume / Minutes = Cubic Feet per Minute.

Of course if you are going to calculate what the actual tank size is (Actual Volume) after it being pumped up, etc, then you might as well just complete the equation since you are already doing math work. Just my two cents, when I want my SAC rate I usually calculate by hand. I have noticed that it is pretty close though with the datatrak software.

Matt