Solid State O2 Sensor

[REVAN]

This came across my desk today; new solid state O2 sensors from Poseidon. I thought it was worth sharing. I've been impressed with this tech when I first saw it being developed/used by SeaBear (at least that is the first I place where I saw it). As far as I know, this is pretty new stuff, and to me, looks to have a lot of advantages over the traditional galvanic sensors.

I've always been intrigued with rebreathers but don't dive them myself as it would be total overkill for the type of diving I like to do these days. But, I'd like to hear what the experts have to say about it. When they get simple and reliable enough, maybe I'll make the transition (though I'd probably have to do some customization first ).

Solid State Sensor | Poseidon

 

[rjack321]

Given the finicky and temperamental nature of their automated CCR I will let someone else try it first.

 

[UnixMarine]

Will certainly be interesting. Use them on anything critical for a while myself though.

 

[fnog]

That is a bit short for such an interesting topic, so I thought I would revive it. I am, just like the OP, and OC diver who is just interested to know whether the technology on RB is moving forward these days, but not involved.

From the basic wikipedia info on zirconium O2 sensors, it seems these are typically used in a differential mode. That would mean that they compare the sensed gas to a reference gas pocket (either dil or 100%O2) all the time during their operation. That looks at first sight more reliable than the "calibrate three heads and hope for the best in the coming hours" approach. Plus the response time is in the milliseconds range, so it also seems these could be modulated or some signal theory magic done to improve their signal over noise.

Do you RB divers follow-up on this development with interest ? Do you know word of mouth on how this O2 sensor performs or fails in the field (of kelp) ?

 

[manni-yunk]

I have nothing real to add - other than that as a CCR diver, I am hoping that this new sensor technology evolves and proves as useful as we hope. Im sure the other sensor manufacturers are a little nervous. Im also cautious and even if my unit eventually gains compatibility with this sensor - Ill wait a few years until its more proven.

 

[fnog]

Alright... It seems I got things mixed up a bit. Again. If this new sensor is identical in principle to the one developed in Austria, I was wrong to assume a Zirconium sensor. The Seabear sensor has a completely different functioning principle. It is based on the way molecular oxygen (O2) diffuses into a paint or a gel made of some aromatic organo-metal material, and then modifies its' fluorescence. Oxygen has those funny doublets of electrons on the outside and does somehow find a way to interact with the excited organic molecule without really getting into a chemical reaction that would consume it. That de-excites the organic molecule that was previously pumped up by LED light, thus modifying the fluorescence.

For more info on that, one can look at the slides from Arne Sieber at Rebreather Forum 3.0, and then further keywords/reference guys: "fluorescence quenching" "franck-condon" "stern-volmer" "jablonski diagram" "Hans Kautsky" . (And, no, I have no idea if the Jablonskies are related).

Still, has anyone heard through the grapevines about how these new sensors from either Seabear or Poseidon perform in real life ?

 

[REVAN]

It looks like I'll be going to DEMA Show this year. I'll try to get to the Poseidon booth to learn more about this. I believe this is the fluorescing tech in these new SS sensors. I'll try to confirm this and it's connection to the Seabear technology, if any. I'm not a rebreather diver, so I'm not the best person to investigate, but I'll have the access and will do what I can. So, if anyone has any specific questions they want me to ask Posiedon, let me know. Hopefully, I'll have some new information by late November.

 

[JohnnyC]

The interesting thing will be if they can reduce the size of the components so that the sensor is a direct swap for the current galvanic reaction-based sensors on the market. These won't get traction unless there's a way for current rebreather owners, who are already heavily invested in their units, to replace their current sensors without costly modification.

 

[REVAN]

My impression was that these solid state sensors are a plug-and-play replacement for the galvanic sensors; that this was what Poseidon had done with the tech.

Seabear used the fluorescing tech in parallel redundancy to the galvanic sensors in a separate O2 sensing component. This was a measure taken when the tech was very new and they did not want to rely on this alone until it had been through proper sea trials.

The advancement here, I'm thinking, is that this tech has advanced to the point of being a solid state replacement for the galvanic tech. If this is the case, it seems it should be a more reliable sensor than the old method of getting O2 feedback. I'll try confirm all this at DEMA Show, but this was how I read Poseidon's press release.

 

[JohnnyC]

No, that would require a power source on-cell. These require a digital interface of some sort, and a power source. Galvanic oxygen sensors CREATE electricity through their natural galvanic reaction. These require juice from the handset. Current non-digital electronics extrapolate PO2 based on the mV reading they get from the galvanic cell. A direct plug-and-play replacement would need to output similar readings in order to be backwards compatible.

If they could put a rechargeable battery and the circuitry required to directly replace galvanic cells, I'd happily switch and deal with having to charge the cells provided they are the same standard footprint of normal cells.

You still in Tucson? I'll happily give you an old cell that you can play around with. Hook it up to a multimeter and feed it some O2 and you can see how it reacts. If you've got a pressure pot it's a more useful exercise.