admikar
Contributor
That might be possible. On the other hand it might be possible to find GF that mimic Suunto RGBM. Of course no one is in the know, since no one (well, almost) know how Suunto RGMB works.
Shearwater Perdix AI
- Thread starter Pullmyfinger
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That might be possible. On the other hand it might be possible to find GF that mimic Suunto RGBM. Of course no one is in the know, since no one (well, almost) know how Suunto RGMB works.
Some of us know from experience that Suunto RGBM seems to give additional weight to the very fact that multiple dives have occurred over multiple days (or 24-hour windows?--I'm not sure). In other words, over consecutive days of repetitive diving, it seems to deviate from something resembling the straightforward half-time compartment model. Maybe I'm not stating it technically correctly, but the point is that Buhlmann gives you credit for surface intervals in a predictable way--it doesn't take into account anything except the surface interval--while Suunto RGBM seems to become less predictable with increasing consecutive days of diving. I'm hesitant to call anything "not possible," but I think I agree with Craig in post #692 above that adjusting the GF can't mimic that behavior.
From the Zoop manual, here's Suunto's cryptic explanation of factors the algorithm (somehow) takes into account:
Suunto RGBM addresses a number of diving circumstances outside the range of just dissolved gas models by:
• Monitoring continuous multiday diving
• Computing closely spaced repetitive diving
• Reacting to a dive deeper than the previous dive
• Adapting for rapid ascents which produce high micro-bubble (silent-bubble)
build-up
• Incorporating consistency with real physical laws for gas kinetics.
We can't be sure what it does with whatever information it gains from "monitoring continuous multiday diving," but the implication is that it increases subsequent no-deco times analogously to the way "closely spaced repetitive diving" does. If Suunto lists these two factors separately, it seems reasonable to believe the algorithm treats them differently. And possibly differently than it treats surface intervals that are not "closely spaced."
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admikar
Contributor
@Lorenzoid , sorry, I forgot to say that my first comment was a little tongue in cheek intended.
I know what both you and Craig are saying, since I was diving RGBM algorithm, at least Mares interpretation of it.
I know what both you and Craig are saying, since I was diving RGBM algorithm, at least Mares interpretation of it.
Nevertheless, fundamentally GF is just a linear adjustment to the M-line. The bubble voodoo is not, it a formula that does not necessarily reduce to a straight line. So no, there is no GF setting such that it will mimic Suunto RGBM. There may only be a setting that will mimic it on a specific section of a specific dive.
Not sure if this has been mentioned already, but just FYI, Shearwater has new firmware out. v53
https://www.shearwater.com/wp-content/uploads/2018/02/Release-Notes-Translations-V53.pdf
It has updates for the AI functionality. You can now view the Log on the Perdix and see the T1 and T2 start and end pressures. And, it purports to also show your SAC there, too. But, my dives just show n/a or something for my SAC.
However, I suspect that my SAC doesn't show in the Log because I have 2 transmitters enabled, even when I dive with a single tank. I expect that if I checked a dive where I only had 1 transmitter enabled, it would probably show the SAC.
I realize that showing SAC for 2 transmitters would be difficult. How do you show a single SAC if the 2 tanks are different sizes? What do you use for the divisor (the time component of psi per minute) if the tank in question was only used for a portion of the dive? This is just another reason why I think they should implement an OC Sidemount mode. Then, the computer would assume T1 & T2 are on the same size tanks and the Perdix could calculate SAC and GTR.
It also seems like it should be a simple fix to make it where, if you have T1 and T2 enabled, but the computer only ever receives a signal from one transmitter during the whole dive, it would treat the data the same as if you only had that one computer enabled. Thus, it could report SAC correctly in the Log.
https://www.shearwater.com/wp-content/uploads/2018/02/Release-Notes-Translations-V53.pdf
It has updates for the AI functionality. You can now view the Log on the Perdix and see the T1 and T2 start and end pressures. And, it purports to also show your SAC there, too. But, my dives just show n/a or something for my SAC.
However, I suspect that my SAC doesn't show in the Log because I have 2 transmitters enabled, even when I dive with a single tank. I expect that if I checked a dive where I only had 1 transmitter enabled, it would probably show the SAC.
I realize that showing SAC for 2 transmitters would be difficult. How do you show a single SAC if the 2 tanks are different sizes? What do you use for the divisor (the time component of psi per minute) if the tank in question was only used for a portion of the dive? This is just another reason why I think they should implement an OC Sidemount mode. Then, the computer would assume T1 & T2 are on the same size tanks and the Perdix could calculate SAC and GTR.
It also seems like it should be a simple fix to make it where, if you have T1 and T2 enabled, but the computer only ever receives a signal from one transmitter during the whole dive, it would treat the data the same as if you only had that one computer enabled. Thus, it could report SAC correctly in the Log.
I used the Shearwater Cloud app on my Android phone to perform the firmware upgrade on my Perdix AI. As with the previous firmware, the first time I tried it, it appeared to be working. Both the phone and the computer displays reflected that it was uploading the firmware to the computer. It was really slow. Eventually, it crapped out and the Perdix showed a message that the update failed. I rebooted my phone and tried again and it worked. It was still slow, but it worked.
I had the same results last time I did this, and that was with a Samsung Galaxy S5 phone. This time was with a Samsung Galaxy Note 8.
I had the same results last time I did this, and that was with a Samsung Galaxy S5 phone. This time was with a Samsung Galaxy Note 8.
Also, the Subsurface-mobile app is working quite well now for uploading my log from the Perdix, via Bluetooth. I do my upload on my phone and then fire up Subsurface on my desktop computer, it automatically syncs with the Subsurface Cloud, and my log opens with all the dives shown that I just uploaded from the Perdix.
Very convenient.
Very convenient.
It only shows SAC for one transmitter just as GTR is only one transmitter.
From "PerdixAI_Operating_Instructions_RevA" page 10
"GTR Mode
Gas Time Remaining (GTR) is the time in minutes that can be spent at the current depth and SAC rate until a direct ascent to the surface at a rate of 33 feet/min (10 m/min) would result in surfacing with the reserve pressure.The SAC rate is averaged over the last two minutes of diving for calculating GTR.
GTR can only be based on one tank.The Surface Air Consumption (SAC) measurements are also based on the tank selected for GTR calculations."
Yes it would be nice if it could log both for both transmitters but only display the tank you're on, especially, after a gas switch. I see a problem here, but I always look for problems. What if you are using the second transmitter to monitor your buddy's tank, or as a backup on your single tank. However, this info would be good in the electronic log.
Cheers -
Edit: Added the information from the manual and deleted frivolous comment. - M²
From "PerdixAI_Operating_Instructions_RevA" page 10
"GTR Mode
Gas Time Remaining (GTR) is the time in minutes that can be spent at the current depth and SAC rate until a direct ascent to the surface at a rate of 33 feet/min (10 m/min) would result in surfacing with the reserve pressure.The SAC rate is averaged over the last two minutes of diving for calculating GTR.
GTR can only be based on one tank.The Surface Air Consumption (SAC) measurements are also based on the tank selected for GTR calculations."
Yes it would be nice if it could log both for both transmitters but only display the tank you're on, especially, after a gas switch. I see a problem here, but I always look for problems. What if you are using the second transmitter to monitor your buddy's tank, or as a backup on your single tank. However, this info would be good in the electronic log.
Cheers -
Edit: Added the information from the manual and deleted frivolous comment. - M²
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With an OC Sidemount mode, it could display the aggregated SAC easily.
If, in the last minute, one tank dropped 10 psi and the other dropped 0.1 psi (presumably, due to the tank internal temp dropping to match water temp), it would report 10.1 psi/min.
If, in the last minute, one tank dropped 5 psi and the other dropped 5 psi (because you switched regs halfway through that minute), it would report 10 psi/min.
That is all slightly simplified, but not much, really. For a sidemount mode, it really could just add the tank pressure deltas and use the sum for determining SAC. And add the total tank pressures to use in calculating GTR.
I have previously posted that I would really like to see a big change where you tell the Perdix which transmitter goes with which gas, so that it could handle things like automatically displaying the SAC for whatever gas you are currently breathing, but that would be a major change in the implementation. It seems like adding an OC Sidemount mode wouldn't be AS big of a change. Though, now that I said it, I guess the question would then be, is OC SM a clone of OC Tec or OC Rec? Personally, I would want a clone of OC Tec, but I guess others might prefer a clone of OC Rec for use with sidemount.
If, in the last minute, one tank dropped 10 psi and the other dropped 0.1 psi (presumably, due to the tank internal temp dropping to match water temp), it would report 10.1 psi/min.
If, in the last minute, one tank dropped 5 psi and the other dropped 5 psi (because you switched regs halfway through that minute), it would report 10 psi/min.
That is all slightly simplified, but not much, really. For a sidemount mode, it really could just add the tank pressure deltas and use the sum for determining SAC. And add the total tank pressures to use in calculating GTR.
I have previously posted that I would really like to see a big change where you tell the Perdix which transmitter goes with which gas, so that it could handle things like automatically displaying the SAC for whatever gas you are currently breathing, but that would be a major change in the implementation. It seems like adding an OC Sidemount mode wouldn't be AS big of a change. Though, now that I said it, I guess the question would then be, is OC SM a clone of OC Tec or OC Rec? Personally, I would want a clone of OC Tec, but I guess others might prefer a clone of OC Rec for use with sidemount.
Mike1967
Contributor
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