Shearwater Teric wish list

[Mike1967]

They are, to get the GTR without a computer would be really tough.

My point was that you saying we don't need a certain feature because it can be worked out anyway can be said about computers in general.

 

[Cleavitt]

My point was that you saying we don't need a certain feature because it can be worked out anyway can be said about computers in general.

You might have a point except he was specifically pointing out that most of the "tank size" features being requested either already exist or don't require knowing the tank size.

SAC rate: This is already a feature of the Teric and SAC rate does not account for tank size. SAC rate is in PSI/BAR per minute.

Gas Time Remaining (GTR): This is also a feature of the Teric and it also does not require tank size info. It is calculated based on total_pressure / PSI_per_minute = minutes_remaining. That calculation doesn't change if your tank is a Spare Air or a submarine ballast tank.

RMV: This does require tank size in order to convert from units of pressure to units of volume. However, it's not really any more useful during a dive than SAC. Other people have asked for this, but Shearwater has stated that they don't really see the value (because SAC/GTR serve the same purpose during a dive) and they have concerns about people getting bad info because they forget to change tank sizes. Personally, I wouldn't mind having it as an option, but I have gotten used to using SAC rate and I know that a SAC rate of ~15psi/minute is an RMV of ~0.45 cuft per minute on my tanks (HP100s).

 

[Ben_3]

Maybe add some smart watch features top side for those who have it on all the time..

 

[Michael Jastrzebski]

My point was that you saying we don't need a certain feature because it can be worked out anyway can be said about computers in general.

I was saying .. we don't need features which are useless for the task at hand.
If your objective is to know RMV (because you happen to like this number for whatever reason) then you do need to know the tank size.
And all this is clearly explained in Teric's manual, it is an excellent manual, I suggest spending some quality time with it.

 

[Mike1967]

Personally, I wouldn't mind having it as an option,

So we agree.

If your objective is to know RMV (because you happen to like this number for whatever reason) then you do need to know the tank size.

I do know my tank sizes.

 

[sharkguy05]

Actually tank volume is not necessary to estimate how many minutes of gas supply you got left and this is primarily what divers care about.

Well your GTR is only valid if you know the operating pressure of your tank also. Most tech divers care very much about the amount of gas you have. It leaves for quick math to have a more accurate GTR since the volume of air you have left is critical to how long you can spend at a certain depth. Simply put if we are both breathing at 50psi a minute and your using a HP 80 and I have a LP 80 or even a lp 105 I am consuming a higher volume of air than you hence I will not be able to stay down as long or at that particular depth. Also while at depth I dont care what my sac rate is, I want to know how much of my tank am I sucking through at that depth. sure i can run rough numbers underwater and figure it out but don't we buy the computers to give us a tool to glance at quickly to confirm our plan

 

[scubadada]

Well your GTR is only valid if you know the operating pressure of your tank also. Most tech divers care very much about the amount of gas you have. It leaves for quick math to have a more accurate GTR since the volume of air you have left is critical to how long you can spend at a certain depth. Simply put if we are both breathing at 50psi a minute and your using a HP 80 and I have a LP 80 or even a lp 105 I am consuming a higher volume of air than you hence I will not be able to stay down as long or at that particular depth. Also while at depth I dont care what my sac rate is, I want to know how much of my tank am I sucking through at that depth. sure i can run rough numbers underwater and figure it out but don't we buy the computers to give us a tool to glance at quickly to confirm our plan

No, neither operating pressure nor tank volume are needed for calculating GTR. It is simply pressure drop over time, heading toward the reserve pressure you have designated. The Shearwater version assumes direct ascent to the surface, other version include stops, safety or deco.

 

[Michael Jastrzebski]

Some folks should recall some laws of the physics of gases, like Boyle's law - perhaps then some of this GTR stuff would sink in.
An alternative is to actually read the Teric's manual.
Otherwise those spouts of ignorance about GTR calculations will never cease.

 

[Jay]

Some folks should recall some laws of the physics of gases, like Boyle's law - perhaps then some of this GTR stuff would sink in.
An alternative is to actually read the Teric's manual.
Otherwise those spouts of ignorance about GTR calculations will never cease.

I don't follow who you're aiming your post at; ScubaDada's already corrected SharkGuy ... ?

Many people get GTR and SAC muddled and what inputs are relevant. I think it becomes easier when describing them correctly either using litres/min or bar/min (RMV and SAC respectively) then the rest (inputs, calcs) become somewhat obvious.

 

[tursiops]

litres/min or bar/min (RMV and SAC respectively)

I agree with this terminology, but many do not.
They use SAC to mean EITHER volume/min or pressure/minute. Most confusing!