Liberty, change O2 sensors all together or not?

[Agro]

I can not imagine Poseidon will ever bring their sensors to the rest of the market. They have a great USP and they will keep it. There is hardly any reason to buy a Poseidon Seven - unless these great sensors.

I guess Poseidon does not produce their sensors by themselves, they buy them. And I guess they made a deal with the producer which does not allow him to sell them anywhere else. That's what I would do if I was Poseidon's CEO.

 

[Big-swede]

I can not imagine Poseidon will ever bring their sensors to the rest of the market. They have a great USP and they will keep it. There is hardly any reason to buy a Poseidon Seven - unless these great sensors.

How do you know discussions between brands not already in progress?
I think the biggest issue is that anyone who wants to use the ss will have to rewire and recertifie their products and that's a big project.

And as a reply to the last bit, I guess a lot of people just have to much money and bought a Poseidon rb with galvanic sensors just for fun.

 

[tbone1004]

The 18 month rule I got from my instructor. I do not know where he got this from.

Until now my cells lasted for 18 month. I had one exception, 1 cell died after 1 month. It worked fine for 1 month, then suddenly died from one day to the other.

Yes, changing them when necessary leads to staggering. Unless they survive 18 month, that's what they did until now.

So you are changing it based off of an unqualified person telling you? The manufacturer of the cell says 42 months, Divesoft says 12months OR 18months from date of manufacture *this is based off of the cells warranty period, not expected life*. Why replace good cells just because someone else said so?

I can not imagine Poseidon will ever bring their sensors to the rest of the market. They have a great USP and they will keep it. There is hardly any reason to buy a Poseidon Seven - unless these great sensors.

I guess Poseidon does not produce their sensors by themselves, they buy them. And I guess they made a deal with the producer which does not allow him to sell them anywhere else. That's what I would do if I was Poseidon's CEO.

Shearwater already has the cells as an FYI, and this is the company that makes them. There is an exclusivity agreement, though for how long I am not sure.
PyroScience GmbH

 

[beldridg]

The difference with the Liberty though is you can manually vote a cell out. Say you're diving EAN32 dil and diving to 30m/100ft. The left O2 board failed and you only have the 2 cells from the right. You do a dil flush to make sure everything is OK like you are supposed to and you get 1.27 on cell 1 and 1.01 on cell 2. Any normal CCR would average those two to 1.15 and try to maintain whatever setpoint you have.
In the other breathers you have to drop the setpoint and run it manually off of cell #1 and ignore cell #2. With the Liberty you go into the menu and tell it to disable cell #2. In the cell menu it will tell you excluded if it was voted out, or disabled if you turned it off.

That is a cool feature. Those Divesoft guys are pretty smart.

Just a note on this. I had an interesting experience that I thought others would find helpful (especially if you dive a rEvo configured like mine).

In most cases, @tbone1004 is correct that the computer would average the two cells if only two are connected.

I dive a rEvo with three cells connected to my Petrel controller and two connected to a NERD2.

In October, I had one of the cells fail in the NERD2 during a dive. Not a big deal at all.

The thing I noticed is that my TTS was much greater on the NERD than the Petrel so I started to investigate to figure out why. It makes sense that it would be since the one cell was reading low, but it was a bigger difference than intuitively made sense to me and it was growing quicker than made sense to me.

On a Shearwater, in one of the screens, you can see what PO2 the computer is using for tissue calculations and it is usually the average of the cells connected (as @tbone1004 said).

In this case, it was the using the PO2 of the lowest cell for tissue calculations and NOT the average.

It obviously didn't know which one was "right" or "wrong". I knew because I had the PO2 of the three other cells on the Petrel to use as reference and the likelihood of 4 cells being bad (more on that in a minute) and one correct is very, very low. Especially since I perform checks every time I assemble my unit.

After returning home, I referenced the NERD2 manual and found this for the two cell mode:

'PPO2 display will alternate with the message “VOTING FAILED”. The lower PPO2 value will be used for decompression calculations. The higher PPO2 value will be used for CNS calculations."

That makes total sense -- yet another reason I like diving Shearwater computers.

Sorry for the somewhat off-topic post but I thought folks would find it interesting -- especially if you are using a computer with two cells connected.

Back on topic:

Because I have five cells and I like to always have a spare (or two), I tend to rotate my cells out and use the spare (so it doesn't age out beyond usefulness) and then get a new spare. I don't do it on a set schedule. It usually ends up being 12-18 months but is really based upon how the cells are behaving. If you average that to 15 months, it means one cell is getting replaced about every 3 months for a 5 cell system like I use.

- brett

 

[broncobowsher]

I had a failure like that. One cell wasn't playing nice so I moved it to the NERD and went for a dive. The Petrel controller was happy, had 3 good cells. The NERD, not so happy. 1 cell matched the others in the Petrel. The other cell started running really hot, sky high PPO2. A little DIL flush confirmed the cell was not happy. Finished the dive. CNS was something like 250% on the NERD.

Now I knew I had a bad cell and really dug into it. It was a bad board on the cell. Put some strain on the board and the output changed. Swapped cells one more time, issue followed the cell and not the connection. New cell fixed it. It was also my only cell to have gone bad.

 

[Divermikey]

That is a cool feature. Those Divesoft guys are pretty smart.

Just a note on this. I had an interesting experience that I thought others would find helpful (especially if you dive a rEvo configured like mine).

In most cases, @tbone1004 is correct that the computer would average the two cells if only two are connected.

I dive a rEvo with three cells connected to my Petrel controller and two connected to a NERD2.

In October, I had one of the cells fail in the NERD2 during a dive. Not a big deal at all.

The thing I noticed is that my TTS was much greater on the NERD than the Petrel so I started to investigate to figure out why. It makes sense that it would be since the one cell was reading low, but it was a bigger difference than intuitively made sense to me and it was growing quicker than made sense to me.

On a Shearwater, in one of the screens, you can see what PO2 the computer is using for tissue calculations and it is usually the average of the cells connected (as @tbone1004 said).

In this case, it was the using the PO2 of the lowest cell for tissue calculations and NOT the average.

It obviously didn't know which one was "right" or "wrong". I knew because I had the PO2 of the three other cells on the Petrel to use as reference and the likelihood of 4 cells being bad (more on that in a minute) and one correct is very, very low. Especially since I perform checks every time I assemble my unit.

After returning home, I referenced the NERD2 manual and found this for the two cell mode:

'PPO2 display will alternate with the message “VOTING FAILED”. The lower PPO2 value will be used for decompression calculations. The higher PPO2 value will be used for CNS calculations."

That makes total sense -- yet another reason I like diving Shearwater computers.

Sorry for the somewhat off-topic post but I thought folks would find it interesting -- especially if you are using a computer with two cells connected.

Back on topic:

Because I have five cells and I like to always have a spare (or two), I tend to rotate my cells out and use the spare (so it doesn't age out beyond usefulness) and then get a new spare. I don't do it on a set schedule. It usually ends up being 12-18 months but is really based upon how the cells are behaving. If you average that to 15 months, it means one cell is getting replaced about every 3 months for a 5 cell system like I use.

- brett

Interesting post, thank you. I also dive a rEvo with petrel controller and recently changed from a nerd1 to a nerd2. The only difference is I use a splitter on cell 3 so both computers display 3 cells. I assume with 3 cells on the nerd2 it would behave like my petrel if I had a cell failure?

 

[beldridg]

Interesting post, thank you. I also dive a rEvo with petrel controller and recently changed from a nerd1 to a nerd2. The only difference is I use a splitter on cell 3 so both computers display 3 cells. I assume with 3 cells on the nerd2 it would behave like my petrel if I had a cell failure?

It should.

Since the NERD2 and the Petrel don't know about the splitter, the NERD2 thinks it has three independent cells. From memory, the voting logic on a Shearwater with three cells is that if one is out of range, it will vote it out and average the remaining two. So, it will NOT act like the NERD2 I gave in my example.

Again, a bit off-topic, but I think an interesting discussion is whether or or not to split the cell and add a 3rd to the NERD2. I'll start a new topic on that since I think it could be an interesting discussion. Also, the weather here is turning and no dive in site for the next week.

- brett

 

[broncobowsher]

I run the NERD on 2 sensors. The 3rd position is the display for AI (Dil + O2)

 

[beldridg]

I run the NERD on 2 sensors. The 3rd position is the display for AI (Dil + O2)

Yes, I do the same.

 

[Scuba Client]

I can not imagine Poseidon will ever bring their sensors to the rest of the market. They have a great USP and they will keep it. There is hardly any reason to buy a Poseidon Seven - unless these great sensors.

I guess Poseidon does not produce their sensors by themselves, they buy them. And I guess they made a deal with the producer which does not allow him to sell them anywhere else. That's what I would do if I was Poseidon's CEO.

CCR manufacturers have to pay royalties if they want to use solid state sensors.