So what solid state sensors are out there at the moment?

[RedSeaDiver2]

I thought it might be time to pool the knowledge from around the world on what solid state sensors are currently available?

Known ones are

- the one that Poseidon uses (can't remember the manufacturer name) - requires a power source so not a simple straight swap for galvanic cells

- the Oxygen Scientific ones - are a straight swap for galvanic cells - just need to be aware that they are about 2mm larger in diameter so need to check your head carefully to make sure will fit.

- any others?

 

[makar0n]

(...)
- the one that Poseidon uses (can't remember the manufacturer name) - requires a power source so not a simple straight swap for galvanic cells

-made by Pyro Science GmbH, 10 year life, appears to be cleared for dive/medical/life support use. Offered in two distinct flavors:
a) With Poseidon firmware - only works with Poseidon rebreathers, currently 850 Euro (incl. VAT; unsure what rate?) on Poseidon site

Solid State O2 Sensor | Poseidon

Voting logic is not always logical and traditional O2 sensors have a short shelf life and are prone to failure. For that reason, we have created the Solid State O2 sensor. This factory calibrated sensor is absolute and delivers unsurpassed operating life, as well as calibration stability. In a...

www.poseidon.com

b) With a non-Poseidon firmware - works with anything but Poseidon, currently 435 Euro (incl. 19% VAT) on Tecme site; also offering full conversion kits for different rebreathers:
TecMe.de - O2 Solid State Cells - (Look for "O2 Solid State Cells" section on the left menu)

- the Oxygen Scientific ones - are a straight swap for galvanic cells - just need to be aware that they are about 2mm larger in diameter so need to check your head carefully to make sure will fit.

-made by Oxygen Scientific GmbH - 5 year life, works with anything, appears to have integrated battery source and a DAC converter, hence can work with analog rebreathers potentially as a drop in replacement of an analog sensor (note the 2mm difference in diameter mentioned above!). Seems to be cells that KISS Go and Halcyon (Oxygen Scientific) Symbios rebreathers will use.
Currently appears to not be certified for any dive/medical/life support usage, has no CE mark neither. Cannot be sold legally in EU.
There is one shop selling those "for demo purposes" though (some legal wriggling) - Dive2.me at 675 Euro (incl 19% VAT)
Dive2.me - Solid State Sensor Sauerstoff



Now as for the power source - from my understanding and talk with some folks, both need power - in case of PyroScience ones that is usually provided from an external source, while Oxygen Scientific seems to have an integrated battery. PyroScience ones potentially could be still used using the usual 9V already built in in most rebreathers (with some extra cable) but battery life would be shorter for example estimate was that Choptima 50 hours rated usage would be cut to 25 hours with 2 solid state sensors. Otherwise one just need to add an extra "solid box" - seems to be pretty simple mod, box is like Choptima ones - more info on Tecme website.

The second consideration is DAC conversion - solid state is a digital technology sending 1/0's (and no longer mV) - for Pyro Science you need a DAC converter to get those 1/0's to mV rebreather can read. However the best option would be to use these with DiveCAN system (5 pin), which is also digital, at which case you would need no converters at all (not even the ADC currently integrated in the likes of Choptima to convert mV to 1/0's) - however that needs Shearwater releasing a firmware that would allow for the cells to talk to their computers.
OxygenScientific appears to have DAC integrated, hence 1/0's are converted to mV and can be used on any analog system. Would not be a great fit for DiveCan model, as then you would convert 1/0's to mV then back to 1/0's.

 

[Scuba-Lad]

-made by Pyro Science GmbH, 10 year life, appears to be cleared for dive/medical/life support use. Offered in two distinct flavors:
a) With Poseidon firmware - only works with Poseidon rebreathers, currently 850 Euro (incl. VAT; unsure what rate?) on Poseidon site

Solid State O2 Sensor | Poseidon

Voting logic is not always logical and traditional O2 sensors have a short shelf life and are prone to failure. For that reason, we have created the Solid State O2 sensor. This factory calibrated sensor is absolute and delivers unsurpassed operating life, as well as calibration stability. In a...

www.poseidon.com

b) With a non-Poseidon firmware - works with anything but Poseidon, currently 435 Euro (incl. 19% VAT) on Tecme site; also offering full conversion kits for different rebreathers:
TecMe.de - O2 Solid State Cells - (Look for "O2 Solid State Cells" section on the left menu)




-made by Oxygen Scientific GmbH - 5 year life, works with anything, appears to have integrated battery source and a DAC converter, hence can work with analog rebreathers potentially as a drop in replacement of an analog sensor (note the 2mm difference in diameter mentioned above!). Seems to be cells that KISS Go and Halcyon (Oxygen Scientific) Symbios rebreathers will use.
Currently appears to not be certified for any dive/medical/life support usage, has no CE mark neither. Cannot be sold legally in EU.
There is one shop selling those "for demo purposes" though (some legal wriggling) - Dive2.me at 675 Euro (incl 19% VAT)
Dive2.me - Solid State Sensor Sauerstoff



Now as for the power source - from my understanding and talk with some folks, both need power - in case of PyroScience ones that is usually provided from an external source, while Oxygen Scientific seems to have an integrated battery. PyroScience ones potentially could be still used using the usual 9V already built in in most rebreathers (with some extra cable) but battery life would be shorter for example estimate was that Choptima 50 hours rated usage would be cut to 25 hours with 2 solid state sensors. Otherwise one just need to add an extra "solid box" - seems to be pretty simple mod, box is like Choptima ones - more info on Tecme website.

The second consideration is DAC conversion - solid state is a digital technology sending 1/0's (and no longer mV) - for Pyro Science you need a DAC converter to get those 1/0's to mV rebreather can read. However the best option would be to use these with DiveCAN system (5 pin), which is also digital, at which case you would need no converters at all (not even the ADC currently integrated in the likes of Choptima to convert mV to 1/0's) - however that needs Shearwater releasing a firmware that would allow for the cells to talk to their computers.
OxygenScientific appears to have DAC integrated, hence 1/0's are converted to mV and can be used on any analog system. Would not be a great fit for DiveCan model, as then you would convert 1/0's to mV then back to 1/0's.

There's some really interesting stuff on the website you linked, including Co2 monitoring...

So we have the sensors, but with the likes of Choptima, what is stopping us from using them - simply that Shearwater currently do not support digital input?

 

[Mobulai]

simply that Shearwater currently do not support digital input?

that's one reason -- the Shearwaters that would be able to support it are the ones that have DACs (from what I understand that is the set of variants that have CAN bus capability), the alternative is integrating into the system (the RB) a power supply and DAC boxes (like the stuff that TECME offer)
I have not used a diveCAN and don’t know how they work exactly with galvanic cells, but I can imagine the basic version of it — a CAN bus is the same anywhere: Digital, asynchronous, and redundant (failing gracefully if designed with that in mind)

Shearwater just has to either write code to deal with it, or make their os opensource so that other makers can do it(not likely)

CO2, whole other thing there -- the sensing tech isn't as... mature, probably a chemical engineer can shed more light on that tho.
All I know is moisture is even more problmatic there, among other factors.

Eventually it all boils down to testing the system as a whole (think more QA less QC):
The more inputs/variables/states/components/controlled variables a system has, the harder it gets to test it -- exponentionally, in the sense that you verify that it would do what it's intended/designed to do. Various techniques and methods are used for this -- far more than I would like to bore everyone with.

But here is a very simple example:
you add one more "signal" that has 2 possible values to a system that already has 2 signals with 2 possible values each.
The possible combinations of values grew from 4 to 8, to 16 and so on with each extra binary signal we add.

you need (for QA/QC) reasons to test that under all various possible inputs that the system (software/HW...) and that it would respond as designed. And if you give it "invalid" inputs it wouldN#t behave in a way that the designer didn't intend (think high ppo2 > open solenooid and add o2)

Now moving back to real life; ppo2 is not a binary signal, it's a float (virtully infintie possibilities), a converted from digital to analog buffer(or alike) is also an extra signal; in computer terms that means a ton of possibilities, a ton of testing, and a ton of edge/corner cases that the ssytem logic might overlook and misbhave in.

It’s a lot of test cases, and I’d assume you’d have a lot of them qith pressurized components for sanity/integration testing — that’s gonna keep that CE rating and and acceptance by (compliance departments of) training agencies further away from reach

It's money and liabilty that keeps us where we are.

----
Cards on the table: I WANT to design such a system, and work on adding further automation there (+ the required testing); If any on the RB makers out there is seeing this -- give me a hawody

 

[makar0n]

There's some really interesting stuff on the website you linked, including Co2 monitoring...

So we have the sensors, but with the likes of Choptima, what is stopping us from using them - simply that Shearwater currently do not support digital input?

Well "nothing" really - Oxygen ones could be used straight away (but appear to have no validation/certification of any kind and since the Halcyon deal, there appears to be sourcing issues and seems unclear if these will even be sold in a non-Halcyon version (aka the Poseidon treatment)...plus price is just silly), Pyro at the very least would need some cable modding and an ADC converter...and battery (kind of optional but useful if want to keep more than 2 and not have battery runtime cut in half in Choptima) - Martin @ Tecme did lots of those conversions for various rebreathers over the years.

Now on the "nothing" part - in an ideal world yes, Shearwater would upgrade their firmware, then, at least for Choptima and DiveCAN, you could have a fully digital system (well that is after removing the current ADC converter for analog cells) - no more ADC/DAC conversions, possible support for other features like checksums and so on. And with Pyro sensors would be a perfect combo as tried and tested with 10 year life and decent price. But so far silence on the Shearwater radio continues...and a chance for Shearwater releasing firmware as open source is rather non existent.

 

[makar0n]

There is also an interesting mention here:

What is DiveCAN® and why should I care?

Digital communications are clearly replacing analog communications in computer based devices. As more digital communication becomes integrated into rebreathers, Shearwater went in search of the best digital solution. We looked at basic serial and at higher level serial like HDLC and SDLC as well...

shearwater.com

It is relatively easy to add two more wires and provide power on the bus. This means that power sources don’t have to be in the same place as power. It also allows for backup power schemes and batteries outside the loop powering devices inside the loop.

Another alternative to an additional solid-box with extra power could be moving away from the AA/9V setup and replacing those with things like Li-Ion batteries but guess that would require a bit more engineering...

 

[RedSeaDiver2]

There is also an interesting mention here:

What is DiveCAN® and why should I care?

Digital communications are clearly replacing analog communications in computer based devices. As more digital communication becomes integrated into rebreathers, Shearwater went in search of the best digital solution. We looked at basic serial and at higher level serial like HDLC and SDLC as well...

shearwater.com

Another alternative to an additional solid-box with extra power could be moving away from the AA/9V setup and replacing those with things like Li-Ion batteries but guess that would require a bit more engineering...

I am now aware of one rebreather manufacturer that is actively working to do the necessary redesign work to their head to enable the solid state cells that Poseidon used to be used in that rebreather. It would be appreciated if all Divesoft Liberty owners and potential owners could keep asking Jakub to hurry up with this so as they throw the resources at it to get it done!

 

[makar0n]

I am now aware of one rebreather manufacturer that is actively working to do the necessary redesign work to their head to enable the solid state cells that Poseidon used to be used in that rebreather. It would be appreciated if all Divesoft Liberty owners and potential owners could keep asking Jakub to hurry up with this so as they throw the resources at it to get it done!

Now this is awesome news! Not on Liberty myself, but if one major air freshener manufacturer jumps on this, hopefully the rest follows the suit (looking at you Dive Rite )

 

[RedSeaDiver2]

Now this is awesome news! Not on Liberty but if one major air freshener manufacturer jumps on this, hopefully the rest follows the suit (looking at you Dive Rite )

Divesoft have the advantage that the Liberty is their own proprietary electronics so as they can make the decision and do all the work in house - they don't have to persuade Shearwater to do some of the work for them!

 

[makar0n]

Divesoft have the advantage that the Liberty is their own proprietary electronics so as they can make the decision and do all the work in house - they don't have to persuade Shearwater to do some of the work for them!

Yeah that is definitely a plus....no need to wait for a certain Canadian company to do something And I really do not understand the delay there - first they create a great digital ecosystem, then, when the last missing piece to make it fully digital finally appears, suddenly everybody seem to look the other way