Did anyone ever find the answer to the OP's question? It would seem, to me, that when you have "notified" the computer that you switched from the tank with the transmitter to a tank with no transmitter, the computer would stop displaying any pressure/GTR info. That is the only thing that makes sense. Otherwise, conflicting, irrelevant, and perhaps dangerous information could be displayed (ie, giving the impression of valid gas information based on a tank no longer in use). it would be a highly unsafe way to manage the display and I can't imagine Shearwater would allow gas information to be displayed once the computer "knows" from the gas switch that you are no longer breathing from the tank with the transmitter.
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The Perdix AI does not know which gas tank has the transmitter - you do not tie the transmitter to a specific gas when you set it up - that is left up to the user to manage. So, if you have 2 tanks and only 1 has a transmitter, the Perdix will keep displaying the psi/GTR info from the tank with the transmitter after you switch to the gas that does not have a transmitter on the tank.
No the GTR is a seperate setting you can switch the psi SENSOR FROM A TO B BUT YOU CAN NOT CHANGE The gtr SENSOR SETTING IN THE WATER. So using sensor A for both tank psi and GTR, and you switch the psi display to sensor B GTR reimains on sensor A. That is how you monitor your buddies remaining air in his tank.
AI is display and GTR is for calculation. AI can be changed under water but GTR can not per the manual.
In the age of AI (artificial intelligence) it is possible for the Pedrix to be programmed to deduce which tank (gas) the transmitter is attached to. But Shearwater's implementation of air integration does not appear to include artificial intelligence features, perhaps because the Perdix is based on gas instead of tank. For example, you can define 21% oxygen (air) only once even if you carry two tanks of air.
It allows the monitoring of your buddy's tank, an option in so many multi sonsor DC's.
I have an Aeris t3 elite. It has 3 gasses stored. If I remember,,,, the rules say #1 is on your tank 2&3 IS ON YOUR BUDDIES TANKS. I think that #1 is me #3 is the buddy and #2 can be either got GTR In comparison to the Shearwater It is saying that you can monitor any of 3 tanks but #1) or the GTR selected sensor) is the sensor that drives your GTR calculations.
In regards to having 2 tanks with 21%,,, it is a pecking order thing and not a 21% thing. cant have 2 gasses with the same mix in it. I don't know if you can have air and 21% though. I would think not. I depends on how the duplicate gas check is done. That is easily worked around by making the gasses 21 and 22. Have to remember that if you gas select list has 3 gasses in it,,, it selects which one to use as you ascend from low O2 to high O2. IE 32 to 50 deco to 100 deco. If that is not exactly correct then apply that to your gas planning module. Knowing the gasses the DC plans what depth to switch to what gas and how long to minimize the dive time in deco. I don't have the book so I still have to find out how the multi gasses and GTR is handled in independent doubles. I suspect that you start the dive on your non GTR tank. As far se artificial intleeigence goes you are right the DC only cares about your max PPO2 value and related gasses. Again just a guess but if yo are going to do deco I can not think of a situation that you would be entering it from greater than 40% mix. so a tank with 50% would be determined as deco gass and utilize the max 1.6 PPO2 instead of your rpefered 1.4PPO2 for te dive,,,, for deco depth selection. Hence 50% would change at 70 ft and 100% would be called for at 20 ft.
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admikar
Contributor
I am not really sure this is correct. I think deco calculations are done on your current gas during a dive. Available gases are considered for deco in dive planner. What would happen if you do not change from travel to deco gas?
@Shearwater, care to clarify this, please?
If you enter deco, GTR is disabled, instead you'll get "deco" (page 14 of manual).
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I have done this in the past and so can you. plan a dive in dive planner with travel gas and then a tank of deco 50 then the same with deco 99. . you will see that the difference in deco obligation is based on the gas carried and declared in the available gasses. gasses declaired or available changes the psi's ect on all tanks you are carrying. for grins try a dive plan with say trimix 24/28 and a tank of 50 and 99 with you. With out changing gass you may run out of gas.
I think you are right about deco being calculated on current gas. It makes sense however the planned deco time prescribed would be based on the gasses you have said is available. That is one reason for prompt gas changeover on the computer when you physically change gasses.
Here is a hypothetical you are gong up and have deco 50 and 100. you skip or cut short the 70 foot stop with deco 50 for what ever reason and go to 20 and change to deco100. Its my opinion that the puter will be fine with it and recalculate the deco time at 20 to correct. On the other hand you may have to shut off the deco50 from being available to keep it from squaking. about a missed stop,,,,,,,, as least it doesn't shut down. As far as the reason for skipping or cutting short the 70 stop. It might be done if your buddy finds his deco is empty from a leak ect or a reg failure and you have to share your deco50 or just skip it and take a longer stop at 20' on deco 99. good reason to not use a al30 for a 25 cuft deco obligation.
As mentioned GTR calcs have to stop when in deco cause gtr defined to be calculated on a specific sensor for the entire dive. once yo change regs to the next gass GTR is out the window.
admikar
Contributor
Maybe I should elaborate my previous post. What I said about deco on your current gas, is that Perdix will calculate deco based on available gases, but if you fail to change gas for whatever reason, it will recalculate on your current gas. I had a dive with 32% and 50%. While planing a dive, we decided not to do a switch at 18m, but at 15m instead (as part of buoyancy control for AN/DP). At switch time, my Perdix showed 19 TTS, after switch it dropped down to something like 10 minutes.
I agree, I don't know what it does witht he violation other than it dies not shut down for 24 hours. That is what is nice about shearwater it geves you some credit for knowing what your doing. I don't know just how it decides where the deco stops are. By theory the stop should have been at 70 ft with a 1.6 PPO2 I have never had to deal with a situation like that. I have no clue how to force the deco to 20 with 50% other than setting a deco PPO2 setting to make the calc say 20 ft. Been a long time since I fooled with the settings. Perhaps there is a calc to say what depth and the 1.6 PPO2 sets the max depth the calculation. I did a planning dive with I think 25/28 to 140 for perhaps 30 min and it called for a stop at 70 ft on deco50 and then a 20 ft stop on deco 99. then I ran the same dive on just deco 99 and it said go to 20 and deco longer. the time ended up being the same deco time total on both options, so I did the actual dive on deco 99 and skipped taking the deco 50.
This is a good converstion thanks.
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