Question about the Perdix AI

[CWK]

Hi Guys,

First some background info. I purchased my Perdix AI in July this year and have done 48 air and nitrox dives with it in recreational OC mode as I explore and become familiar with its functionality. I have now purchased one transmitter and have turned T1 on. The bottom row is set to display tank pressure and GTR. Everything appears to working as expected but I have yet to dive with it.

Assuming that I'm diving with two gases, air and EAN32, and the transmitter is on the tank of air. What will the computer do when I switch the gas from air to EAN32? I can only presme that it will show Nx32 on the bottom left. What will it display in the bottom centre and right fields? I just wanted to know what to expect before I do this during a dive.

Thanks

 

[Stoo]

Just be sure I understand... are you diving with two tanks? One has the transmitter and air in it, and the other has Eanx 32 but no transmitter?

If that's the case, then even when you change gases, I would think the pressure will still read the pressure in the air tank. To read the pressure in the second tank, you would need to have a second transmitter on it.

I think I might be misunderstanding you though... this would be an odd configuration of gasses!

 

[CWK]

Yes. Two tanks - one with air and the second with EAN32. Transmitter is on the tank of air.

I would have expected the computer to display what I had set the bottom center and right fields to before I enabled AI (ie setting for non AI). This was: bottom centre set to PPO2 and CNS, and bottom right set to TTS.

 

[Stoo]

The display will reflect whatever gas you choose and the "related" information... pO2, CNS and deco obligation. What it WON'T do is give you the second tank pressure... You need a transmitter for that.

Are you using the 32 for deco? Or are you carrying air to get a little deeper than the 32 allows? As I said, it's an odd combo of gasses to carry.

 

[CWK]

The display will reflect whatever gas you choose and the "related" information... pO2, CNS and deco obligation....

Would I need to turn off the air and purge the regulator to deactivate AI, or does it recognise this from the change of gas?

Carring air to go deeper than EAN32 will allow. Nitrox being carried for deco. May be a richer mix.

 

[Stoo]

I don't use AI, but I would think you would either need to turn off and purge (which seems like a bad idea as you lose your redundancy) or "disconnect" the transmitter. These computers only know what you tell them, so it will continue to read the air tank.

 

[CWK]

The redundancy remains. All that is required is to turn the air back on.

I don't think Shearwater covers this point as it allows 3 gases to be defined but has the ability to use only 2 transmitters.

 

[Stoo]

In tech mode, it will accommodate 5 gases but you are correct, it will only read pressures in tanks with transmitters, and that's limited to two.

I don't think most tech divers use AI and stick to SPGs. I think there's less likelihood of confusion.

Are you rigging this as a side-mount configuration?

 

[CWK]

This will be either side mount, sling tank or stage tank. It's still up in the air. The dive is the wreck in Pulau Weh. The resort is suggesting air and EAN32. For me, two tanks of air plus a stage tank of nitrox is the best option. What I'm trying to figure out is how the Perdix AI is going to behave when I switch gases with only 1 transmitter.

 

[Stoo]

The computer isn't magic. It will "behave" in the way you tell it too. It can only read the pressure in the tank that has the transmitter. There is no other possible way it can do that.

I suggest the transmitter go on the bottom gas as that supply is most critical and then be sure that whatever gasses you are using for deco have SPGs.

I am not familiar with that area. What is the max depth you will be diving on it?