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TX Scubachick (Austin)
07-30-2007, 20:50
anyone know if there is a way to turn off the "time" left on the air you are breathing. I got very annoyed w/my computer ... because it told me ...after a 55minute dive, we were still at 87ft... that I only had three minutes of air left, but my pressure read 610psi! PLENTY of air to get back safely to the boat... do the saftey stop and all... we were heading to one of the side lines that dangle at 30ft ... and during that swim (nothing strenuous) it told me I was out of air... and started going nuts on me...beeping and the up arrow showed up...but the pressure still read just below 600 psi. I was back on the boat, with 480psi of air... and I was just annoyed with my comptuer ... it was an incorrect estimate... I know IT was eering on 'safety' ...
any tips about this guys??
thanks...

I used to have the Uwatec Alladin Pro Ultra (just got the Smart come, did 14 dives w/it so far) ... and I think I like my Alladin better... but that one lacked some basic features like even the water temperature and stuff...

thanks...

CompuDude
08-03-2007, 12:46
anyone know if there is a way to turn off the "time" left on the air you are breathing. I got very annoyed w/my computer ... because it told me ...after a 55minute dive, we were still at 87ft... that I only had three minutes of air left, but my pressure read 610psi! PLENTY of air to get back safely to the boat... do the saftey stop and all... we were heading to one of the side lines that dangle at 30ft ... and during that swim (nothing strenuous) it told me I was out of air... and started going nuts on me...beeping and the up arrow showed up...but the pressure still read just below 600 psi. I was back on the boat, with 480psi of air... and I was just annoyed with my comptuer ... it was an incorrect estimate... I know IT was eering on 'safety' ...
any tips about this guys??
thanks...

I used to have the Uwatec Alladin Pro Ultra (just got the Smart come, did 14 dives w/it so far) ... and I think I like my Alladin better... but that one lacked some basic features like even the water temperature and stuff...

thanks...
The Smart series computers have some customizable settings if you connect them to a computer. I'm not certain about the specifics of the SmartCom, but my SmartTec allows me to set a reserve amount. The default is 500 PSI.

The way the RBT (remaining bottom time) function works is it calculates how long your air will last at the current rate of consumption. It calculates in how much you'll need for a safety stop and to end up at the surface with the reserve amount in your tank (again, 500 psi is probably default reserve).

If you are at 50' and the RBT reads 0 minutes, that means if you immediately ascend at the appropriate rate, do a safety stop for 3 min at 15' (this may also be customizable), you should then hit the surface with exactly 500 psi, assuming your breathing rate does not change.

If you want to take your tank lower than 500 psi on a regular basis (not necessarily a good idea, although I've done it depending on conditions, and it's your life not mine), you'll want to adjust the amount held in reserve so the computer doesn't beep at you so much.

Important note re RBT function: This should always be taken with a huge grain of salt, and not used in place of proper dive planning. There are a number of assumptions the computer uses is coming up with that number, and if any of them is wrong (or changes) that number can be completely wrong. The RBT number can be both misleading and dangerous to a diver who not thinking, and letting the computer do all the work for them.

Imagine being at 75' and taking your computer down towards the limit. The RBT says 5 minutes left, but you start a leisurely trip back towards the surface anyway. Suddenly, your buddy runs out of air. With two of you breathing, hard, while stressed out due to the emergency, that 5 minutes of "remaining time" air is going to be used up a LOT faster than 5 minutes.

Similarly, if you need to swim back to the shore or boat through a current, your breathing rate is going to climb considerably. The computer has no way of knowing this, so it's assumption that your current breathing rate will continue is all wrong, and thus the number of remaining minutes is way off as well.

Air integrated computers are great. I very much like mine. But it's really important to be aware of their limitations... they do what they do very well, but if you don't know what they're doing and why, and aren't thihnking on your own about things that can happen outside the computer's planning ability, you can get yourself into trouble with one very quickly.