Shearwater Perdix AI

[stuartv]

I should also add that while I'm tempted to remove my SPG, I haven't done it and at this point I don't think I will, as the two warnings are a great time to cross check with my SPG to make sure both are in agreement.

After doing that enough, wouldn't you start to trust the AI? And if they disagree, don't you think it's most likely the SPG that is wrong? I believe that AI is not known for giving erroneous readings. Generally, it either gives you an accurate reading or no reading at all.

 

[Pullmyfinger]

If you take the Anti AI sentiment on SB, I'm sure they'll be a ton of buyers who want a Perdix without that pesky AI cluttering up the computer.

AI is not for me, so I will take advantage of those antiquated non-AI versions that are showing up in the classifieds.
I have a Predator. I love the screen, but not the size of it.
I had a Perdix briefly, but my wife thought it was the prefect computer and quickly took it from me. LOL!

I may pick up one of those 'old relics' later on.

 

[stuartv]

during our testing, the testers (Shearwater engineers who know the product very well) frequently made setup mistakes when using multiple tanks that resulted in inaccurate GTR. For this reason, when deco is needed, GTR is not shown (since we feel GTR is a tool for no-stop diving).

This kind of sounds like, either, it was engineers who are familiar with SW products, but not so much with diving with AI, OR, they were trying to solve the GTR problem for the most complex case and decided it was too complicated and so they gave up and made it too simple, instead. I do think there is a useful middle ground. At least, GTR for people doing deco on back gas only - and including any and all stops the computer is going to call for - mandatory or optional.

 

[tcoen]

The way SW has done it means that if you do a gas switch to a second cylinder with a transmitter, you have to do the gas switch on the computer AND switch which cylinder is being displayed as the tank pressure. Otherwise, you'll be breathing from one cylinder and seeing the tank pressure of a different cylinder.

Hi Stuartv,

This is not quite correct. With our implementation, you can see pressure from either transmitter at any time. Either transmitter can be placed on the main screen, or two right button presses (one step past the compass) brings up an AI line, that doesn't time out back to the main screen. You can see a bit of this in a video we posted.

Not linking the transmitter to a specific gas results in a simpler system that is more flexible. The downside is GTR being limited to one gas. Although we find 1 gas GTR is ideal anyways. We tested more complex GTR with multi-tanks, and the setup required to cover different scenarios properly is too high. Our test engineers made frequent mistakes or forgot to change settings, which resulted in incorrect GTR. I hope to cover the rational for our design decisions in a future video.

We appreciate all the interest, discussions, and ideas. Many of us are at DEMA now, but we will provide more information once back in the office.

Best regards,
Tyler Coen
Shearwater Research

 

[scubadada]

Craig,

I personally never use the GTR feature of my AI computer. I do however utilize the mid and reserve tank pressure warnings. And I don't think I use them like most people do.

For example, I enter my mid pressure warning as my turn pressure. Tank pressure minus reserve divided by two = mid pressure warning. I do not set my reserve warning as my reserve, but rather my ascent pressure warning.

Aside from the convenience of heads up tank pressure display, I find the warnings are an excellent safety measure for task heavy diving. I normally am anticipating the warning, especially my ascent pressure warning as it's typically right about the time my tank shifts in trim due to buoyancy changes, but it's a nice reminder that says, "Hey buddy, stop what you're doing, don't chase that fish and head up!"

Hi James,

I have never used my turn pressure warning, I have always had it disabled. I do use the final pressure warning, and generally ascend some number of minutes after it has hit zero. My diving is mostly drift and I have free accss to the surface.

Good diving, Craig

 

[CuzzA]

Hi Stuartv,

This is not quite correct. With our implementation, you can see pressure from either transmitter at any time. Either transmitter can be placed on the main screen, or two right button presses (one step past the compass) brings up an AI line, that doesn't time out back to the main screen. You can see a bit of this in a video we posted.

Not linking the transmitter to a specific gas results in a simpler system that is more flexible. The downside is GTR being limited to one gas. Although we find 1 gas GTR is ideal anyways. We tested more complex GTR with multi-tanks, and the setup required to cover different scenarios properly is too high. Our test engineers made frequent mistakes or forgot to change settings, which resulted in incorrect GTR. I hope to cover the rational for our design decisions in a future video.

We appreciate all the interest, discussions, and ideas. Many of us are at DEMA now, but we will provide more information once back in the office.

Best regards,
Tyler Coen
Shearwater Research

Tyler,

Great to see your participation here. If I could make a suggestion, and I think this goes for all manufactures producing transmitters, perhaps a different color than black would be a good idea to avoid accidentally lifting a tank by the transmitter. They look so much like tank valve knobs.

I'd suggest red, but perhaps Shearwater Blue for SW customers.

 

[CuzzA]

Hi James,

I have never used my turn pressure warning, I have always had it disabled. I do use the final pressure warning, and generally ascend some number of minutes after it has hit zero. My diving is mostly drift and I have free accss to the surface.

Good diving, Craig

Sounds like we're doing about the same thing and not setting the reserve warning as our reserve, but rather an ascent warning. Makes the most sense to me. What's the point of a reserve warning when you're probably already on the surface at that point.

We don't have the current over here so we typically drop, head out, turn, come back and ascend. Makes sense not to have the mid warning for a drift dive. It would be rather pointless.

 

[Pullmyfinger]

Tyler,

Great to see your participation here. If I could make a suggestion, and I think this goes for all manufactures producing transmitters, perhaps a different color than black would be a good idea to avoid accidentally lifting a tank by the transmitter. They look so much like tank valve knobs.

I'd suggest red, but perhaps Shearwater Blue for SW customers.

Good observation. I wonder if it's happened before.
On that note.......it could make for an interesting valve drill experience if one were new to valve drills. This assumes that the transmitter were oriented the same way as the valve knob.

 

[scubadada]

Sounds like we're doing about the same thing and not setting the reserve warning as our reserve, but rather an ascent warning. Makes the most sense to me. What's the point of a reserve warning when you're probably already on the surface at that point.

We don't have the current over here so we typically drop, head out, turn, come back and ascend. Makes sense not to have the mid warning for a drift dive. It would be rather pointless.

I've done many dives in Grand Cayman, Little Cayman, Turks and Caicos, Bonaire, Curacao... and have used the turn pressure principle without using the computer alarm. The principle works perfectly fine, just don't need the alarm.

 

[tcoen]

This kind of sounds like, either, it was engineers who are familiar with SW products, but not so much with diving with AI, OR, they were trying to solve the GTR problem for the most complex case and decided it was too complicated and so they gave up and made it too simple, instead. I do think there is a useful middle ground. At least, GTR for people doing deco on back gas only - and including any and all stops the computer is going to call for - mandatory or optional.

Hi Stuartv,

In handling multi-tank GTR, there are a lot of complexities. The killer for us though, was simply the need to properly setup tank size for each tank.

In the 1 tank situation, the GTR can simply be based on SAC, which is a measure of the rate of change of pressure. For this, the tank size is unknown and doesn't matter. However, the SAC isn't transferable to to another tank, which may be of a different size.

So to handle 2 or more tanks, the GTR must be based on RMV. Calculating this requires having proper information on tank sizes. In the imperial system this requires entering both capacity (e.g. 80 Cuft) and rated pressure (e.g. 3000 PSI) correctly. In the metric system only the tank size in liters (e.g. 10 L) needs to be entered. Technically, the calculations are simple, as was the user interface to enter the information. However, in practice, it is too easy to forget to change this, resulting in incorrect GTR values.

There are other drawbacks to multi-tank as well. Having to associate transmitters to gases is a pain and easy to make mistakes or forget as well. Also, covering situations where multiple tanks are used for the same breathing mixture adds additional complexity.

We feel that the solution we are launching with is a good solid starting point. The main utility of AI is having the pressure available at a glance on the wrist. Logging of pressures for post-dive analysis is also useful. Features like the GTR and real-time SAC are nice, but our current opinion is they best suited for single-tank, no-stop diving.

We are paying attention to comments and feedback, and may make changes as long as we feel adequate usability can be maintained.

Best regards,
Tyler Coen
Shearwater Research