Info Two New Dive Computers from Scubapro for 23! LUNA 2.0 (with & without Air Integration with GF) with aggressive pricing
- Thread starter BoltSnap
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Exactly. It's a dive COMPUTER. It should compute. Always. If it says "you did something I don't like, so I'm going to stop computing for the next day (or two)", then it is no longer doing its job, and that is, well, not how I want my dive computer to work.
M-values are the inflection point in the graph of "how likely am I to get bent?"* Before you get to the M-value, you are pretty unlikely to get bent. When you pass the M-value, the chances of getting bent starting increasing very rapidly.
Gradient Factors are kinda like alert values that you set. You choose how far you want to be from the M values when your computer starts alerting you that you're getting close.
They are kinda like the alert values you can set for Gas Time Remaining calculations on Air Integrated computers. You might set the computer to alert you when you're going to drop below 500 psi. Or, you might decide to be more conservative and set it to alert you when you're going to drop below 700 psi.
If it alerts you about 700 psi and you decide to stay longer and run yourself down to 500 psi, does that mean you die? No. Is that a reason for your computer to stop doing its job? No.
Same with Gradient Factors. You might set the computer to alert you and keep you from exceeding 70% of the M-value when you surface. But during the dive, you might decide to stay down and allow yourself to hit 80% when you get to the surface. Does that mean you are bent? No. Is that a reason for your computer to stop doing its job? No.
* M values are a guess based on an aggregation of a lot of data from a lot of different individuals. Your personal "inflection point" in that graph is likely to be somewhere roughly near the actual M-values, but not exactly the M-values.
In other words, your personal graph of "how likely am I to get bent?" could inflect upwards at the M-value, or it could inflect upward at 80% of the M-value. Or 120% of the M-value. And, your inflection point changes from dive to dive based on many factors - like hydration level, for one example.
That is why the best practice in choosing Gradient Factors, and also in choosing what Surface GF you allow yourself, is to start conservatively and, over the course of MANY dives, assess yourself and, if you are so inclined as to use more aggressive GFs, increase them gradually, incrementally, over the course of many dives.
If you gradually and continuously increase your GFs and Surface GF incrementally over time, eventually you will get bent. By approaching that gradually and incrementally, when you do get bent, it is likely to be pretty minor. Not guaranteed, but likely. It could happen with a GF Hi of 85, or it could happen with a GF Hi of 99. Or it might not happen until you get to a GF Hi of 120 (if you can find a computer that will allow that value for GF Hi).
You may also gradually, incrementally increase your GFs until you eventually find numbers that work for you just based on not "feeling great" when you are more aggressive. If you do that, you can potentially settle on those numbers that work for you - that allow you to CONSISTENTLY get out feeling good - and stick with those for future diving. All without ever getting bent.
Good luck. May the odds be ever in your favor.
Gradient Factors are kinda like alert values that you set. You choose how far you want to be from the M values when your computer starts alerting you that you're getting close.
They are kinda like the alert values you can set for Gas Time Remaining calculations on Air Integrated computers. You might set the computer to alert you when you're going to drop below 500 psi. Or, you might decide to be more conservative and set it to alert you when you're going to drop below 700 psi.
If it alerts you about 700 psi and you decide to stay longer and run yourself down to 500 psi, does that mean you die? No. Is that a reason for your computer to stop doing its job? No.
Same with Gradient Factors. You might set the computer to alert you and keep you from exceeding 70% of the M-value when you surface. But during the dive, you might decide to stay down and allow yourself to hit 80% when you get to the surface. Does that mean you are bent? No. Is that a reason for your computer to stop doing its job? No.
* M values are a guess based on an aggregation of a lot of data from a lot of different individuals. Your personal "inflection point" in that graph is likely to be somewhere roughly near the actual M-values, but not exactly the M-values.
In other words, your personal graph of "how likely am I to get bent?" could inflect upwards at the M-value, or it could inflect upward at 80% of the M-value. Or 120% of the M-value. And, your inflection point changes from dive to dive based on many factors - like hydration level, for one example.
That is why the best practice in choosing Gradient Factors, and also in choosing what Surface GF you allow yourself, is to start conservatively and, over the course of MANY dives, assess yourself and, if you are so inclined as to use more aggressive GFs, increase them gradually, incrementally, over the course of many dives.
If you gradually and continuously increase your GFs and Surface GF incrementally over time, eventually you will get bent. By approaching that gradually and incrementally, when you do get bent, it is likely to be pretty minor. Not guaranteed, but likely. It could happen with a GF Hi of 85, or it could happen with a GF Hi of 99. Or it might not happen until you get to a GF Hi of 120 (if you can find a computer that will allow that value for GF Hi).
You may also gradually, incrementally increase your GFs until you eventually find numbers that work for you just based on not "feeling great" when you are more aggressive. If you do that, you can potentially settle on those numbers that work for you - that allow you to CONSISTENTLY get out feeling good - and stick with those for future diving. All without ever getting bent.
Good luck. May the odds be ever in your favor.
I was more getting at the issue where the diver entered or selected the wrong gas for whatever reason. The dive computer will adjust the algorithm accordingly (e.g. 30m/100ft with air is ~20 mins NDL, with 32% it's ~30 mins NDL). The dive computer** doesn't know the gas constitution, but it does know time (quartz clock) and pressure (via sensor). Therefore GIGO - garbage in, garbage out.
Scenario: diving Nitrox, used air setting. Silly maybe, but many dive computers won't allow you to change the gas during the dive if it's not configured.
** A CCR dive computer is connected to oxygen sensors, so does know the oxygen component of the gas. But it too doesn't know the helium content!
That's what you think. The feeble old me, OTOH, thinks that my chances of getting bent start increasing very rapidly earlier than that, and for that reason I set my conservatism factor to 85%. It's not an alert for me, it is the the level of risk I find acceptable, and once I pass my GF85 my chances of getting bent have increased too far too rapidly for my liking.
The question is why should a computer vendor choose your interpretation over mine? From empirical observations to date, there appears to be only one answer to that: because their name is Shearwater.
Belzelbub
Contributor
Any dive computer will do. As long as it:
- Doesn't brick nor arbitrarily mess with simple calculations (e.g. MOD + 2%)
- Has a really easy user interface that clearly displays all the information necessary
- Technical mode for more info
- Clearly displays warning and alert conditions (clearly differentiating)
- Implies a colour screen
- Has simple button presses that aren't confusing
- Is reliable
- Ideally not rechargeable -- as the batteries don't last long
- Must be user replaceable and a commonly available battery
- Uses Buhllmann + GF
- Has a CCR mode with fixed PPO2 and bailout mode
- Has a built in compass
- Has decent logging with iPhone/iPad/Mac/PeeCee
- Has simple software updates
Seems that list excludes a whole bunch of expensive tat. Hello Suunto, etc.
Mine lasts a couple of years, and that's a little watch coin battery, are you sure you put them in right?Similar threads
