Aqualung i300c Average Depth Calculation Issues?

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drk5036

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I think there is a problem in the firmware of the i300c dive computer on how it calculates the average depth for the dives... and the dive log shows the wrong average depth. Here is an example for my last 6 dives:

Code:
#    Start Time   End Time     Date      Pre Dive Surface Interval    Max Depth (m)    Dive Time    Average Depth (m)
6    13:49        14:28        06-Sep    00:22                        8.9              33           0.6
5    12:43        13:27        06-Sep    23:50                        7.4              43           0.9
4    11:51        12:48        05-Sep    00:31                        12.9             57           2.7
3    10:29        11:19        05-Sep    21:52                        21.9             50           5.6
2    11:40        12:32        04-Sep    00:28                        15.9             52           5.5
1    10:26        11:11        04-Sep                                 21.3             44           16.8

The only accurate average depth is for dive #1... all the rest are wrong until the dive numbering is reset again, when the first dive is correct and the rest appear as if the computer includes the surface interval or some other values in the average making the average go down and down, regardless of the actual recorded maximum depth and dive profile.

For the example above, the correct average depth should have been as follows:

Code:
#    Average Depth (m)
6    5.1
5    4.7
4    9.3
3    16.4
2    10.1
1    16.8

Is this a bug in the firmware or I am not understanding something correctly on how the computer should calculate the average depth for each dive?
Given the first dive calculates it correctly, it seems like it could be related to the surface interval.

after the dive finishes, does it immediately go back to predive mode?

Edit: I figured out what the computer is doing. I need to figure out how to post it. One second.
 

drk5036

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There's a problem with the computer, I think you should contact aqualung. Effectively, the computer is dividing the "true" saturation by the total immersion time in the current repetitive dive profile.

Code:
#    time (min)    real avg (m)    Saturation (integral of depth vs. time) (min*m)    cumulative time (min)    wrong average (saturation / cum. Time) (m)
6    33    5.1    168.3    279    0.6
5    43    4.7    202.1    246    0.8
4    57    9.3    530.1    203    2.6
3    50    16.4    820    146    5.6
2    52    10.1    525.2    96    5.5
1    44    16.8    739.2    44    16.8

column 1: dive #
column 2: true dive time
column 3: true average depth
column 4: true saturation (in this case, calculated by true dive time *average depth)
column 5: total cumulative dive time from the start of the repetitive dive profile
column 6: true saturation in the dive divided by the total cumulative time (column 5)

the values that we see in column 6 math the ones you're seeing on your dive computer, so it's pretty clear that this is where the problem is.

For what it's worth, I have the i300 computer. It didn't show average depth which was part of the reason I 'moved on' because I think calculating SAC is very important for dive debriefing. This is a pretty big oversight on the part of aqualung. I'd be interested to see if other i300c owners have the same problem.

edit: not sure how to make the table columns line up on the forum. the excel file I did the math in is attached.
 

Attachments

  • i300c error.xlsx
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Prometheanfire

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my perspective as a i300c owner (eventually getting a perdix but that's not what this is about). I chose the i300c because it could sync bluetooth and show me 'live' readings on a dive (basic stats). I did not chose it for reviewing dive info after a dive, that's why I import via bluetooth into subsurface. That said, it's bluetooth sync sucks, fails 4/5 times...
 

dannysporea

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I figured out what the computer is doing. I need to figure out how to post it. One second.

You are a genius! So at least there is an explanation on how the calculation is done. This leads me to believe it is a firmware bug and not a hardware issue, so it should behave the same for everyone having firmware 1B.
 

wnissen

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There's a problem with the computer, I think you should contact aqualung. Effectively, the computer is dividing the "true" saturation by the total immersion time in the current repetitive dive profile.

Code:
#    time (min)    real avg (m)    Saturation (integral of depth vs. time) (min*m)    cumulative time (min)    wrong average (saturation / cum. Time) (m)
6    33    5.1    168.3    279    0.6
5    43    4.7    202.1    246    0.8
4    57    9.3    530.1    203    2.6
3    50    16.4    820    146    5.6
2    52    10.1    525.2    96    5.5
1    44    16.8    739.2    44    16.8

column 1: dive #
column 2: true dive time
column 3: true average depth
column 4: true saturation (in this case, calculated by true dive time *average depth)
column 5: total cumulative dive time from the start of the repetitive dive profile
column 6: true saturation in the dive divided by the total cumulative time (column 5)

the values that we see in column 6 math the ones you're seeing on your dive computer, so it's pretty clear that this is where the problem is.

For what it's worth, I have the i300 computer. It didn't show average depth which was part of the reason I 'moved on' because I think calculating SAC is very important for dive debriefing. This is a pretty big oversight on the part of aqualung. I'd be interested to see if other i300c owners have the same problem.

edit: not sure how to make the table columns line up on the forum. the excel file I did the math in is attached.
I'm sure you got it! It has to be the total time from the beginning of the first dive, which is why the error keeps getting worse and worse. I can't believe I didn't pick that up. And of course a very easy programming error to make, especially since you could run a test dive and get the right answer, at least for the first dive. I bet the computer is probably fine, based on that. It's an obvious bug, I hope Aqualung fixes it, but more importantly, that they respond to their customers when they point stuff like this out. Feedback is a gift. Especially if you're selling life support equipment.
 

tursiops

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Gotta say, this thread shows the very best and the very worst of ScubaBoard.
Someone asks a question, and they get both an excellent answer and a (paraphrased) "why would you even want to know that?"
:thumbsup: :argument:
 

dannysporea

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I'm sure you got it! It has to be the total time from the beginning of the first dive, which is why the error keeps getting worse and worse. I can't believe I didn't pick that up. And of course a very easy programming error to make, especially since you could run a test dive and get the right answer, at least for the first dive. I bet the computer is probably fine, based on that. It's an obvious bug, I hope Aqualung fixes it, but more importantly, that they respond to their customers when they point stuff like this out. Feedback is a gift. Especially if you're selling life support equipment.

It's been more than 6 months and no answer from Aqualung, they are ignoring my emails. I went diving again last month and the error is still there. Unfortunately it looks like Aqualung does not care about these issues with their life support equipment... buyers beware.
 

tursiops

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It's been more than 6 months and no answer from Aqualung, they are ignoring my emails. I went diving again last month and the error is still there. Unfortunately it looks like Aqualung does not care about these issues with their life support equipment... buyers beware.
@John Bantin
 

dannysporea

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Since Aqualung is ignoring my emails, I have left a couple negative reviews for this computer and manufacturer online so others will be aware of the issues. Very disappointed with this manufacturer.
 
https://www.shearwater.com/products/peregrine/

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