My new Uemis SDA

[Rainer]

Sorry but that's just retarded. The developers need to offer a real fix, not a silly workaround via metric entries. Have the computer take in working pressure and capacity at working pressure. It's really that simple. No need for lame kludges.

When you enter the tank size as the imperial unit, I was told the computer uses a baseline of 3000PSI, which can, theoretically cause some slight differences in the SAC rate. Now, before the screaming starts, let me explain: As Laura has pointed out and as I have said before, we both did several dives with all kinds of different tanks and setups and starting pressure and everything...the difference in the SAC rate was always so minor that at least I do not know if it was because of the calculation or due physical conditions of the dive itself. For 99% of all dives, those differences are not a factor. Do not forget that the computer can only calculate based on the information the user puts in. So if you are diving an 80 Cuft alu tank, the true capacity at the rated pressure is 77Cuft, if you dive a 80 Worthington, it is actually 81,3 Cuft. For Worthington 119 it is actually 123,4Cuft, so you have to specific all the way if you want to get the most accurate SAC.
IF the Sac rate is really that important for your dive planning, it is recommended to enter the nominal tank capacity as a metric measurement and switch to imperial settings afterwards. For calculating the SAC rate, the unit always converts to metric, since this is way more accurate. Only the end result is then converted back (if desired) in Cuft.

Michael

 

[CompuDude]

Sorry but that's just retarded. The developers need to offer a real fix, not a silly workaround via metric entries. Have the computer take in working pressure and capacity at working pressure. It's really that simple. No need for lame kludges.

Agreed. That's how every single desktop software I've seen does it.

It's not complicated math, and should be well within the computer's capabilities, if they take the time to set it up right.

The whole world does NOT dive exclusively 3000 psi aluminum cylinders.

 

[Marc Bryan]

I am sure a resolution from uemis is forthcoming. It really would be a fairly simple fix.

 

[disbelief]

A "3000psi cylinder" doesn't actually mean much to me in a diving context (as opposed to a filling context). I only know what a cylinder of a specific internal volume filled with a specific gas to a specific pressure means.

Working pressure is a redundant construct in this context.

I'm lucky enough only to have to concern myself with actual mass of gas (actual volume, pressure, temperature); but I do sympathize with those for whom the habit of naming cylinders by the product of their volume and an arbitrary number (wp) has become popular... as this thread shows, it can be confusing.

The Uemis guys have 3 choices to handle this habit:
1. add an extra input field (wp), so that internal volume can be derived
2. insist that internal volume is entered directly (as in the metric formulation)
3. make a conservative assumption on wp to permit an automagic volume derivation

Actually, I think they've gone for a reasonable option - anyone who needs to really care about rmv would likely want the precision that can only come from understanding the Uemis assumptions (although perhaps they could make these assumptions a bit more explicit).

Agreed. That's how every single desktop software I've seen does it.

It's not complicated math, and should be well within the computer's capabilities, if they take the time to set it up right.

The whole world does NOT dive exclusively 3000 psi aluminum cylinders.

 

[Michael Gerhartz]

Ladies and Gentlemen,
I see that this really seems to be a concern for some of you and I will talk to Ernst about that once I am back home. At the moment I'm visiting our dealers in Quebec and Ontario and won't be back before end of next week. I will provide them with the information on hand and call him once I am back home with some more time on my hands. Updates will follow.

Michael

 

[CompuDude]

A "3000psi cylinder" doesn't actually mean much to me in a diving context (as opposed to a filling context). I only know what a cylinder of a specific internal volume filled with a specific gas to a specific pressure means.

Working pressure is a redundant construct in this context.

I'm lucky enough only to have to concern myself with actual mass of gas (actual volume, pressure, temperature); but I do sympathize with those for whom the habit of naming cylinders by the product of their volume and an arbitrary number (wp) has become popular... as this thread shows, it can be confusing.

The Uemis guys have 3 choices to handle this habit:
1. add an extra input field (wp), so that internal volume can be derived
2. insist that internal volume is entered directly (as in the metric formulation)
3. make a conservative assumption on wp to permit an automagic volume derivation

Actually, I think they've gone for a reasonable option - anyone who needs to really care about rmv would likely want the precision that can only come from understanding the Uemis assumptions (although perhaps they could make these assumptions a bit more explicit).

Apparently you don't dive in the United States, using US-standard cylinders. Or the Caribbean. Fill how you like, it doesn't change the fact that standard Aluminum cylinders, the most common used throughout the world, are rated for 3000 psi fills under our US laws and regulations. Steel is a different proposition.

And call it a habit if you like, but your habitual nickname for the tanks you dive (whatever that may be) doesn't have anything to do with the way tanks are marketed this country.

The current "solution" will never fly in this country if they have any interest in significantly increasing their marketshare here. I'm glad to see it's being brought to the attention of the people who can implement changes... although I'm surprised it came to this. I would think the people who worked on the Galileo Sol would be well aware of any such issues, since Uwatec has never exhibited this sort of issue.

 

[DiverLaura]

i am not sure that you guys are correct with your assumptions.

As i said, i've now dove numerous tanks with the Uemis Zurich, and i have been watching my Consumption Rate. If this assumption (that everything should be so exact) were correct there should have been wild variations when alternated through my stable of tanks that was in excess of the changing workload during the dive.

the Air X i dove a long time ago seemed to do a reasonable job of telling me how much gas/time i had left based on my consumption rate on that dive relative to the current pressure (in psi). I never inputed any tank info there... in reality, if you are looking for how much time you have left on this specific dive, its looking at how many psi per min you are sucking down and basing it on that. not how many theoretical cuft there are in your tank.

for that pretty Consumption Rate number, ya, i hear what you are saying, but for the reason many people are diving an air integrated (show me my pressure, tell me how long i have left before it time to be done) it does what it's supposed to.

 

[disbelief]

Apparently you don't dive in the United States, using US-standard cylinders. Or the Caribbean. Fill how you like, it doesn't change the fact that standard Aluminum cylinders, the most common used throughout the world, are rated for 3000 psi fills under our US laws and regulations. Steel is a different proposition.

And call it a habit if you like, but your habitual nickname for the tanks you dive (whatever that may be) doesn't have anything to do with the way tanks are marketed this country.

The current "solution" will never fly in this country if they have any interest in significantly increasing their marketshare here. I'm glad to see it's being brought to the attention of the people who can implement changes... although I'm surprised it came to this. I would think the people who worked on the Galileo Sol would be well aware of any such issues, since Uwatec has never exhibited this sort of issue.

ROFL!!! You're funny.
Dive your way, brother. I'm happy for ya any which way.

For me, 3000psi Ali 80s are 678 cu inches and 3300psi Ali 80s are 625 cu in. Lessee... I could use 2 numbers, or I could use 1. (But if it's 2, I should make sure one of them is 77.4 and not 80, right?) You, of course, are welcome to use as many as you wish.

And I don't think it's a solution, it's a kludge.

(BTW: my tanks are nicknamed 'Tom', 'Dick' and 'Ernie'. I used to dive 'Mcdonald', but had to stop because of the way things are marketed in this country.)

 

[disbelief]

i am not sure that you guys are correct with your assumptions.

As i said, i've now dove numerous tanks with the Uemis Zurich, and i have been watching my Consumption Rate. If this assumption were correct there should have been wild variations when alternated through my stable of tanks.

I dive it strictly imperial units.

Enter an imperial tank size, then set it to metric... what does it read?
Try a few others both ways. Are the numbers consistent with a 3000psi assumption? I think they are, but I can't say I burned a lot of cycles checking it.

There won't be a wild variation unless you're switching between tanks with wild variations in working pressure (say a Luxfer S106W vs a Catalina S80). Even a Worthington steel will only be around 10-15% out, which probably wouldn't be immediately apparent in SAC rate.

The 3000psi service pressure assumption just acts as a way to convert tank size to internal volume.

 

[DiverLaura]

my tanks vary in pressure from LP steel so 2400psi, standard Al 30's, 40's and 80's, to HP steels 3500psi. Singles and doubles.

So, i guess for me, however they are figuring it (basing it on 3000 or 3200 psi), doesn't make that much of a difference. I have a SAC rate that vary's between .2 and .4 depending on work load. Perhaps that is why I didn't really notice it.

Ya, i agree that you should be able to input your tank size and working pressure, and most likely since everyone here (owners and people who've never used one) is up in arms, it will at some point.

and again, the important number for the recreational diver, stating how long your tank will last "right now" is not based on the number kludging, it's based on PSI being consumed on the dive.

Yes, i am a huge advocate of being able to calculate your SAC rate, and having an idea of how long a tank will last you on a given dive. but if you are doing dives that need that kind of planning, i somehow don't think you need a computer to tell you. I understand that people are wanting the data to be 'correct', and agree with that philosophy, but you can see the important thing (trend, working hard or at rest) even with the current calculations.

I have not used a galilleo. how does it calculate consumption rate?

again, before anyone jumps on me for 'defending a flaw', I said "i'd like to see the ability to input a tanks 'common name' volume and working pressure and have it base its consumption calculations off that" for the US market, and have given my input (and yours) to the next up on the food chain

Now we get to sit back and wait to see what Michael has to say after speaking to the big dog.

Enter an imperial tank size, then set it to metric... what does it read?
Try a few others both ways. Are the numbers consistent with a 3000psi assumption? I think they are, but I can't say I burned a lot of cycles checking it.

There won't be a wild variation unless you're switching between tanks with wild variations in working pressure (say a Luxfer S106W vs a Catalina S80). Even a Worthington steel will only be around 10-15% out, which probably wouldn't be immediately apparent in SAC rate.

The 3000psi service pressure assumption just acts as a way to convert tank size to internal volume.