Please upgrade dive planner in the next Firmware.

[brysonjk]

This weekend I was planning a dive on my computer. Not a deep dive, or even a long dive.

The dive was to 130ft, for 30 min. Primary gas was 21%, deco was 32%.

Now I know that this isn't a typical deco mix, but that shouldn't matter. When I go to the dive planner, and run the profile, it has me doing the total dive on the 32%, and doesn't seem to have a way to for the computer to use the 21% instead. I think if possible in the next firmware release, there should be an option to specify what depth you will be making the switch. If I could put that I planned to switch at 70' then the dive planner would have run the correct profile.

I understand that this is planning the best dive on the best mix that I have programmed in my computer, but the dive planner is useless if you cannot specify certain variables. It is useless to have a planner, plan a dive for you that has you using 100 cf of a certain gas when you only have 40 cf, and not touch the 200 cf of the other gas you have.

Hopefully something can be adjusted in the next firmware release. Other then that, it has proved to be a fantastic computer, and with every firmware release, it just gets better, and better.

Jeremy

 

[DA Aquamaster]

I usually use 32% as a travel gas on trimix dives and I've noted that at on ascent at 130' my Predator wants me to switch to 32% when my actual planned deco schedule (using GAP) wants the fisrt stop on 32% at, for example, 110'. My Predator does not know that it may still be a working portion of the dive rather than just deco, but I also don't expect it to know that, it just knows that the PO2 on ascent is now under 1.6 for the next richest gas.

I have also noted that it offers only one SAC, so if I want ball park accurate gas planning, I need to run it twice - once using my bottom SAC and noting the back gas used and once using my deco SAC, and then noting the deco gas used. But it is not very time consuming to do that so it's no big deal.

What strikes me as very odd and very problematic with your scenario is that your computer seems to be ok with you doing the entire dive at a PO2 of 1.58.

I am at work, but I want to run that plan on mine when I get home tonight and play with some of the settings to see what it might be looking at to decide it is happy with the bottom portion of the dive being done at 1.58. That just does not make sense when 21% would be available for the bottom portion of the dive normally done at a PO2 of 1.4 or less.

 

[garyd54220]

The Shearwater dive planner will calculate your dive and deco based on the gasses that are active at any given time. The V32 release notes include the following:

The Predator Dive Planner makes the following assumptions:
• Ascent and descent rates are 33ft/min (10m/min).
• For OC, the gas in use will be the gas with the highest PPO2 less than 1.61.
• For CC, the gas in use will be the gas with the highest PPO2 less than 1.05.
• Last stop is 10ft (3m).​

As you noted it does not allow you to dictate at what depth a gas is included or excluded in the gas list. While this would be nice, the current mode is how it will perform during the dive and the planner needs to reflect the actual dive. There is a work-around during the dive: Turn gases off and on when you want them to be included in the calculation. Not sure how to do a work-around in the planner...that would take some thought and playing with the computer. Anyone know the answer? I love the planner but its certainly not perfect...personally I wish the last stop depth could be changed to 15 or 20 feet but I just do the stop there and stay the extra minute or 3. Your issue is more problematic and no doubt more complicated for the programming.

The gang at Shearwater has been very receptive to feedback but are commited to maintaining the simplicity and intuitiveness of the product. Let them know your issue directly in case they don't see it here and I'm sure they will consider it. I have to say this though...after diving a Vr3 for years (and unlike some, I liked it a lot) I welcome the ease of use of my Predator.

Gary

 

[tcoen]

Hi,

I am a firmware developer at Shearwater Research.

I appreciate the suggestions and will definitely try to improve this in the next release.

The two possibilities I see are using a lower PPO2 threshold (say 1.4) to choose the gas for the bottom segment, or allowing the user to enter the maximum PPO2 for the bottom segment. During the ascent the planner would still pick gases based on a PPO2 of 1.61.

I prefer the first option (fixed PPO2) because it is simpler and also because some users may get confused if they have to enter a PPO2 in OC mode.

The Predator dive planner was intended as a basic, easy-to-use dive planner for simple dives. There are so many possible variables for dive planning, that a dive computer planner can never replace a good desktop dive planning program.

Also, I found this thread by accident, but in the future please feel free to email us directly with any suggestions.

Best regards,
Tyler Coen
Shearwater Research

 

[DA Aquamaster]

Thanks Tyler,

It's interesting to note that it is assuming a PPO2 of 1.6 for the bottom gas.

I played with my shearwater just now and with Jeremy's profile, you can get a psuedo semi-close profile by either:

1. Entering 36% instead of 32% for the deco - with obvious implications for doing the deco on the lower 32% mix - not the best approach, or

2. Assuming a max depth of 134' rather than 130' resulting in a PPO2 of at least 1.61 at the bottom, ensuring it kicks over to 21%. It ends up being lightly conservative with the slightly greater depth but it gives you a reasonable profile.

In thinking about it I am not not really concerned with this profile, as it would be rare for a diver to use a deco mix that has a PPO2 less than 1.6 at the max depth for the dive.

But it is a little alarming that it *allows* a PPO2 of 1.6 for the bottom gas. I'd prefer to see it use 1.41 for bottom mixes and reserve 1.61 for deco mixes.

I understand the concern about potential confusion for the user having to select a PPO2 for the bottom gas. But...you need to look at it differently. If you have a diver using a mutigas computer capable of using nitrox or trimix, then they need to be responsible enough to be certed for the gasses they are going to dive and if they have even a nitrox cert, they should understand PPO2 and MOD.

More importantly, if they are too stupid to understand that, then they are also too stupid to understand the potential problem of using a PPO2 of 1.6 on the working portion of the dive. The difference is that the way it is set up now, the planner will happily let a nitrox diver plan to use 32% at 130 ft for however long their gas will last - with no warning of the potential oxtox issues. I think that leaves you very exposed from a liability perspective, more so that with a user selectable PO2 for the bottom gas as at least the user selection puts the user in the loop and places the responsibility for good decision making on the user.

 

[brysonjk]

I agree with DA Aquamaster 100%. You would like to think that everyone has common sense, and knows/been trained for what they are doing, but it isn't always that way.

I have only used the built-in dive planner 2 times now. The first time it was great. I was using 50% deco, so when I got to 70 feet, the computer and I were on the same page. This weekend was the 2nd time, and I just had what was left of the 50% topped with 21%, just so I could practice gas switches and such. That is when I noticed the limitation of the planner. This limitation is by no means a deal breaker. How often would someone be using something like 32% as a deco gas.

I just wanted to restate that I wasn't discrediting shearwater or anything, Just throwing out there a potential feature, that might do some good in the future.

 

[CyprusSeb]

To allow the user to input when planned gas changes are would be a nice feature. I think keeping in mind that the dive planner was designed to be simple, I think it should stay that way. For simple dives with standard deco mixes I still use it to write up my backup tables. For multiple stage/deco dives with travel gases it just doesn't cut it and I'm perfectly ok with that.