DIY 02 sensor

cstmwrks · 3rd October 2006, 14:45

Well on the long list of nearly forgotten projects was making polarographic 02 sensors for a modern version of the Electrolung. Has anyone else given these sensors much study? Enough to understand the basic curcuit? I have forgotten most of that I had learned from years ago but as I recall the sensor has to have power to work unlike todays fuel cell sensors.
I recall a posting on the web about some one who had got there hands on an old Elung and after a good clean up, new batteries and making a fresh batch of KOH ( I think ) the system powered up and worked!
Does anyone remember the basic concept of the polarographic sensor? Was it a variable risistor affected by the amount of 02 molicules? Any details on how fast they would react to drops or increases in 02? I recall they could take a full flood and keep on working... right down to reading the 02 content of the water.

Bill

Marc T · 3rd October 2006, 17:57

Quote: (Originally Posted by cstmwrks)

Well on the long list of nearly forgotten projects was making polarographic 02 sensors for a modern version of the Electrolung. Has anyone else given these sensors much study? Enough to understand the basic curcuit? I have forgotten most of that I had learned from years ago but as I recall the sensor has to have power to work unlike todays fuel cell sensors.
I recall a posting on the web about some one who had got there hands on an old Elung and after a good clean up, new batteries and making a fresh batch of KOH ( I think ) the system powered up and worked!
Does anyone remember the basic concept of the polarographic sensor? Was it a variable risistor affected by the amount of 02 molicules? Any details on how fast they would react to drops or increases in 02? I recall they could take a full flood and keep on working... right down to reading the 02 content of the water.

Bill

Not totaly off topic but just an interesting link for who dont know this ancestor
Electrolung Rebreather

teknosofen · 6th October 2006, 11:38

Quote: (Originally Posted by cstmwrks)

Well on the long list of nearly forgotten projects was making polarographic 02 sensors for a modern version of the Electrolung. Has anyone else given these sensors much study? Enough to understand the basic curcuit? I have forgotten most of that I had learned from years ago but as I recall the sensor has to have power to work unlike todays fuel cell sensors.
I recall a posting on the web about some one who had got there hands on an old Elung and after a good clean up, new batteries and making a fresh batch of KOH ( I think ) the system powered up and worked!
Does anyone remember the basic concept of the polarographic sensor? Was it a variable risistor affected by the amount of 02 molicules? Any details on how fast they would react to drops or increases in 02? I recall they could take a full flood and keep on working... right down to reading the 02 content of the water.

Bill

Hi Bill!

So you have refound the old thread, the sensors I sent you might have dried out by now but you can test them anyway.

In a way it is a resistance measurement, the principle is that you apply a polarisation voltage (ca 0,6V in the platinum sensors you got) and then the resulting current will be proportional to the PO2 (or rather the flow of O2 through the membrane which will be dependent on temp and PO2)

The current will be very low, << microamps but will depend on the design of the cell.

If you really want to get it started, I might be able to dig out the theory and practical papers for you.

As mentioned earlier, the old (but good) electrolung schematic is a good start.

Regards // Åke

AD_ward9 · 6th October 2006, 12:07

It is described under Prof. Clark's biographies and work, such as HERE.

The dissolved oxygen sensors are readily available, such as from HERE and many similar sources: you do not have to make them, though replacing the membrane with Zitex A-105 gives a product more suited to diving.

The key issue is response time: almost always too slow (30s to 1 min), so during ascent the PPO2 level would fall. A response time of under 10seconds (90%) is needed for use in a CCR. If you manage that cheaply, it would replace galvanic sensors. It is a tall order. Sol-gel sensors are a better bet: faster response, cheaper to make, but sensing is more involved (a one-off cost).

The way to make polarographic sensor work for a CCR is to get a 30s sensor work by convolving the output with the inverse filter, i.e. the sensor acts like a low pass filter, so you add a matching inverse high pass filter digitally with enough gain so the overall response looks flat, and hey presto, a reliable 10s sensor. The problem is with such a lot of gain, the noise is amplified as well, so SNR reduces by the same amount as the boost. Given the small signal to start with, this ends up with an expensive solution. Some of the other variants, like the optical sensing, are worth looking at, such the RBO device HERE.

Cheers

Alex

DanFountain · 6th October 2006, 12:45

Bill,

Take a look at Kanwisher's patent Publication Images.
It describes the sensors he and Starck used in the Electrolung.

Dan

Quote: (Originally Posted by cstmwrks)

Well on the long list of nearly forgotten projects was making polarographic 02 sensors for a modern version of the Electrolung. Has anyone else given these sensors much study? Enough to understand the basic curcuit? I have forgotten most of that I had learned from years ago but as I recall the sensor has to have power to work unlike todays fuel cell sensors.
...

Does anyone remember the basic concept of the polarographic sensor? Was it a variable risistor affected by the amount of 02 molicules? Any details on how fast they would react to drops or increases in 02? I recall they could take a full flood and keep on working... right down to reading the 02 content of the water.

Bill

Dutchy · 6th October 2006, 13:03

And then there' still the hearing aid battery. The silver oxide ones take their oxygen from he air. That's why you can keep them in heir package for very long. They start to deteriorate once opened as oxyen enters the cell and starts the reaction. They have been used in chemistry classes as a poor mans oxygen detector. Their voltage is high which makes them less susceptible to noise but they obviously have their own set of drawbacks or we would all be diving with them at less than $0,10 per dive right? Right, their voltage drops with age and they too are slow. Oh and they are likely to be non-lineair because of their construction. The non lineairity is not necessarily a problem an I just wondered whether anyone has considered using the principle in another construction...

cstmwrks · 7th October 2006, 04:07

Thanks! I'll have to check out some of the links. As it is I do have the patent drawings and even spoke with the man who invented the Electrolung sensor. He did not seem very interested in sheading any light on the design other than purity of the silver, platnum and KOH used was a big issue. He also held the additude that one needed a collage degree to dive a rebreather. No kidding.
The whole idea ( in my mind ) was even if it cost $400.00 to buld the sensor it would be worth it for its near unlimited life. We will see.

Bill

**Dave Sutton** · 7th October 2006, 13:43

Rip Quinby did a lot with air/zinc batteries a bunch of years ago. See here:

The Zinc-air O2 sensor debate

Funny that he's a local guy here and now works professionally rebuilding a certain antique airplane, the North American Navion (which I happen to own a sample of as my family cruiser....) Small world. AFAIK he's not working with rebreathers now.

The time response being long in the sensors as described is not a huge issue.... the loop PP02 does not vary enough in the short term for long response to be an issue. Bottom line: Over the 30 second period *who cares* what the PP02 is, as long as it's viable? With normoxic diluents and a basic setpoint of 0.7 (the old Electrolung PP02) it's REALLY hard to get into trouble in the 30 second time frame. Who cares if the solenoid fires a few extra times in that period? "Maybe" the PP02 will rise to 0.9.......Electrolung designer Walter Stark used what he had.... and he did damned good. He's forgotten more than most of us know, and simply smiles and does not answer when asked. He's the one who taught me that if you cannot design and build it without help, you ought not to be diving it.

Bill Sewall did some experiments after reading Rip's work and he can comment. Come on cstmwrks! We know who you are, destroyer of oil-saturated pony bottles, diver of arctic lung, and vulcanizer of counterlungs and all.... ;-)

For those who never were a part of the "old" NW Rebreather list, when there were just a few of us as part of the family, here's the sort of debate that we enjoyed:

+++++++++++++++++++++++++++++++++++++++++++++++++

Will Smithers writes:

Ripley, I am doing my best not to be snide here, but your enthusiasm and emphaticism has wasted over 20 hours of my time at this point, and I'm not wasting much more on this topic, which has now been exhaustively covered, as far as I'm concerned. But, because I am willing to grant you some small margin of doubt, I will waste up to three more hours on this subject. Please fax me your drift-compensating circuit, and I will run a series of chamber tests using your own design.-Will

And Will has now fairly well refuted the theory and backed up his results. And Rip replies:
Sincerest Apologies Bill, I spent over 600 hours of my time developing a reliable Rebreather which works quite well for me. You've got a lot of hours to go. Keep experimenting, you'll get there. Anyone who believes that verification of research is a waste of time is himself a waste of time. Sorry to have hampered your social life. Regards, Rip

At this point, Lee sums up Rip with the following:
Arrogant sucker, isn't he?. . . Lee

And the final word.....
Who's the dumb Fu** that recommended the zinc air batteries? This is the single stupidest thing I have seen on here, and that is saying something!!!

++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++

Sheesh..... who else but Bill and myself remember these circa 1998 debates? Rebreather Tinkering has come a long way since those days, when the total "non-government owned" CC Rebreather population was probably sub-100 worldwide with 30-ish of those being Mark-15's built up by Kevin. I sure do miss 'em..... I cannot swing a cat now without hitting a new rebreather "expert".

Dave (defying death by bad-gas since 1979)

bgpartri · 7th October 2006, 18:00

One of the unfortunate things about that is that the archives appear to be gone. Due to a hard drive crash, I only have a copy back to early 2000. The one on the rebreather list site has headings only. The messages aren't there. As I flip through a couple of discussions in the middle of December 99 and look at the names beside the posts, I would love to re-read them.

I've emailed Paul a couple of times, but he either can't or won't restore them.

I know Gordon Smith used to have a complete copy at one time, but I have no idea if it still exists.

It's unfortunate because it was history in the making. A lot of the principles that are taken for granted now were argued with hundreds of messages back then.

On the other hand, I don't remember check flushes at 20 feet being discussed back then, and I think they're an important part of my survival now.

**Dave Sutton** · 7th October 2006, 20:27

Well, Bruce I'm sure you tried here:

Mailing list archives

Featuring all of the old timers, us included.

Names only, sad to say, the messages are all gone. Many old friends there, and noticably several are now dead.

Bruce is right, this material defines the early history of Rebreather diving. There are no new rebreather discussions, only new rebreather divers....

We ought to prevail on Paul Elliot to get the achives re-done, as the material is priceless.

Best,

Dave

3rd October 2006, 14:45	#1 (permalink)
cstmwrks The old ways still work. Current Rebreather/s: Home Build Other Rebreather/s: Not Bought Yet Home Build Join Date: Sep 2006 Location: Boise Idaho Posts: 238	DIY 02 sensor Well on the long list of nearly forgotten projects was making polarographic 02 sensors for a modern version of the Electrolung. Has anyone else given these sensors much study? Enough to understand the basic curcuit? I have forgotten most of that I had learned from years ago but as I recall the sensor has to have power to work unlike todays fuel cell sensors. I recall a posting on the web about some one who had got there hands on an old Elung and after a good clean up, new batteries and making a fresh batch of KOH ( I think ) the system powered up and worked! Does anyone remember the basic concept of the polarographic sensor? Was it a variable risistor affected by the amount of 02 molicules? Any details on how fast they would react to drops or increases in 02? I recall they could take a full flood and keep on working... right down to reading the 02 content of the water. Bill
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3rd October 2006, 17:57	#2 (permalink)
Marc T hell is in the details Current Rebreather/s: RB80 / Clone Home Build Other Rebreather/s: Not Bought Yet RB80 / Clone Home Build Join Date: Sep 2005 Location: FRANCE Carcassonne Posts: 498	Re: DIY 02 sensor Quote: (Originally Posted by cstmwrks) Well on the long list of nearly forgotten projects was making polarographic 02 sensors for a modern version of the Electrolung. Has anyone else given these sensors much study? Enough to understand the basic curcuit? I have forgotten most of that I had learned from years ago but as I recall the sensor has to have power to work unlike todays fuel cell sensors. I recall a posting on the web about some one who had got there hands on an old Elung and after a good clean up, new batteries and making a fresh batch of KOH ( I think ) the system powered up and worked! Does anyone remember the basic concept of the polarographic sensor? Was it a variable risistor affected by the amount of 02 molicules? Any details on how fast they would react to drops or increases in 02? I recall they could take a full flood and keep on working... right down to reading the 02 content of the water. Bill Not totaly off topic but just an interesting link for who dont know this ancestor Electrolung Rebreather
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6th October 2006, 11:38	#3 (permalink)
teknosofen Rebreather diver... Current Rebreather/s: Other CCR Other SCR Home Build Other Rebreather/s: Not Bought Yet MK 15.X Other CCR Other SCR Home Build Join Date: May 2005 Location: Sweden Posts: 9	Re: DIY 02 sensor Quote: (Originally Posted by cstmwrks) Well on the long list of nearly forgotten projects was making polarographic 02 sensors for a modern version of the Electrolung. Has anyone else given these sensors much study? Enough to understand the basic curcuit? I have forgotten most of that I had learned from years ago but as I recall the sensor has to have power to work unlike todays fuel cell sensors. I recall a posting on the web about some one who had got there hands on an old Elung and after a good clean up, new batteries and making a fresh batch of KOH ( I think ) the system powered up and worked! Does anyone remember the basic concept of the polarographic sensor? Was it a variable risistor affected by the amount of 02 molicules? Any details on how fast they would react to drops or increases in 02? I recall they could take a full flood and keep on working... right down to reading the 02 content of the water. Bill Hi Bill! So you have refound the old thread, the sensors I sent you might have dried out by now but you can test them anyway. In a way it is a resistance measurement, the principle is that you apply a polarisation voltage (ca 0,6V in the platinum sensors you got) and then the resulting current will be proportional to the PO2 (or rather the flow of O2 through the membrane which will be dependent on temp and PO2) The current will be very low, << microamps but will depend on the design of the cell. If you really want to get it started, I might be able to dig out the theory and practical papers for you. As mentioned earlier, the old (but good) electrolung schematic is a good start. Regards // Åke
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6th October 2006, 12:07	#4 (permalink)
AD_ward9 RBW Member Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jun 2005 Location: Scotland Posts: 2,011	Re: DIY 02 sensor It is described under Prof. Clark's biographies and work, such as HERE. The dissolved oxygen sensors are readily available, such as from HERE and many similar sources: you do not have to make them, though replacing the membrane with Zitex A-105 gives a product more suited to diving. The key issue is response time: almost always too slow (30s to 1 min), so during ascent the PPO2 level would fall. A response time of under 10seconds (90%) is needed for use in a CCR. If you manage that cheaply, it would replace galvanic sensors. It is a tall order. Sol-gel sensors are a better bet: faster response, cheaper to make, but sensing is more involved (a one-off cost). The way to make polarographic sensor work for a CCR is to get a 30s sensor work by convolving the output with the inverse filter, i.e. the sensor acts like a low pass filter, so you add a matching inverse high pass filter digitally with enough gain so the overall response looks flat, and hey presto, a reliable 10s sensor. The problem is with such a lot of gain, the noise is amplified as well, so SNR reduces by the same amount as the boost. Given the small signal to start with, this ends up with an expensive solution. Some of the other variants, like the optical sensing, are worth looking at, such the RBO device HERE. Cheers Alex Last edited by AD_ward9 : 6th October 2006 at 12:34. Reason: Putting in the links.
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6th October 2006, 12:45	#5 (permalink)
DanFountain This is my custom title! Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: Dec 2005 Location: Lake Superior Posts: 113	Re: DIY 02 sensor Bill, Take a look at Kanwisher's patent Publication Images. It describes the sensors he and Starck used in the Electrolung. Dan Quote: (Originally Posted by cstmwrks) Well on the long list of nearly forgotten projects was making polarographic 02 sensors for a modern version of the Electrolung. Has anyone else given these sensors much study? Enough to understand the basic curcuit? I have forgotten most of that I had learned from years ago but as I recall the sensor has to have power to work unlike todays fuel cell sensors. ... Does anyone remember the basic concept of the polarographic sensor? Was it a variable risistor affected by the amount of 02 molicules? Any details on how fast they would react to drops or increases in 02? I recall they could take a full flood and keep on working... right down to reading the 02 content of the water. Bill
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6th October 2006, 13:03	#6 (permalink)
Dutchy Rene Warries Current Rebreather/s: Sport Kiss Other Rebreather/s: Join Date: Apr 2006 Location: Nieuwegein (The Netherlands) Posts: 844	Re: DIY 02 sensor And then there' still the hearing aid battery. The silver oxide ones take their oxygen from he air. That's why you can keep them in heir package for very long. They start to deteriorate once opened as oxyen enters the cell and starts the reaction. They have been used in chemistry classes as a poor mans oxygen detector. Their voltage is high which makes them less susceptible to noise but they obviously have their own set of drawbacks or we would all be diving with them at less than $0,10 per dive right? Right, their voltage drops with age and they too are slow. Oh and they are likely to be non-lineair because of their construction. The non lineairity is not necessarily a problem an I just wondered whether anyone has considered using the principle in another construction... __________________ = This post is environmentally friendly. It is composed of 100% recycled electrons only. =
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7th October 2006, 04:07	#7 (permalink)
cstmwrks The old ways still work. Current Rebreather/s: Home Build Other Rebreather/s: Not Bought Yet Home Build Join Date: Sep 2006 Location: Boise Idaho Posts: 238	Re: DIY 02 sensor Thanks! I'll have to check out some of the links. As it is I do have the patent drawings and even spoke with the man who invented the Electrolung sensor. He did not seem very interested in sheading any light on the design other than purity of the silver, platnum and KOH used was a big issue. He also held the additude that one needed a collage degree to dive a rebreather. No kidding. The whole idea ( in my mind ) was even if it cost $400.00 to buld the sensor it would be worth it for its near unlimited life. We will see. Bill
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7th October 2006, 13:43	#8 (permalink)
Dave Sutton Diveshop of Horrors Current Rebreather/s: Sport Kiss MK 15.X rEvo Other CCR Azimuth Home Build Other Rebreather/s: Evolution Megalodon rEvo Other CCR Azimuth Home Build Join Date: Jun 2006 Location: Narragansett, Rhode Island and Hackettstown, New Jersey Posts: 2,907	Re: DIY 02 sensor Rip Quinby did a lot with air/zinc batteries a bunch of years ago. See here: The Zinc-air O2 sensor debate Funny that he's a local guy here and now works professionally rebuilding a certain antique airplane, the North American Navion (which I happen to own a sample of as my family cruiser....) Small world. AFAIK he's not working with rebreathers now. The time response being long in the sensors as described is not a huge issue.... the loop PP02 does not vary enough in the short term for long response to be an issue. Bottom line: Over the 30 second period who cares what the PP02 is, as long as it's viable? With normoxic diluents and a basic setpoint of 0.7 (the old Electrolung PP02) it's REALLY hard to get into trouble in the 30 second time frame. Who cares if the solenoid fires a few extra times in that period? "Maybe" the PP02 will rise to 0.9.......Electrolung designer Walter Stark used what he had.... and he did damned good. He's forgotten more than most of us know, and simply smiles and does not answer when asked. He's the one who taught me that if you cannot design and build it without help, you ought not to be diving it. Bill Sewall did some experiments after reading Rip's work and he can comment. Come on cstmwrks! We know who you are, destroyer of oil-saturated pony bottles, diver of arctic lung, and vulcanizer of counterlungs and all.... ;-) For those who never were a part of the "old" NW Rebreather list, when there were just a few of us as part of the family, here's the sort of debate that we enjoyed: +++++++++++++++++++++++++++++++++++++++++++++++++ Will Smithers writes: Ripley, I am doing my best not to be snide here, but your enthusiasm and emphaticism has wasted over 20 hours of my time at this point, and I'm not wasting much more on this topic, which has now been exhaustively covered, as far as I'm concerned. But, because I am willing to grant you some small margin of doubt, I will waste up to three more hours on this subject. Please fax me your drift-compensating circuit, and I will run a series of chamber tests using your own design.-Will And Will has now fairly well refuted the theory and backed up his results. And Rip replies: Sincerest Apologies Bill, I spent over 600 hours of my time developing a reliable Rebreather which works quite well for me. You've got a lot of hours to go. Keep experimenting, you'll get there. Anyone who believes that verification of research is a waste of time is himself a waste of time. Sorry to have hampered your social life. Regards, Rip At this point, Lee sums up Rip with the following: Arrogant sucker, isn't he?. . . Lee And the final word..... Who's the dumb Fu that recommended the zinc air batteries? This is the single stupidest thing I have seen on here, and that is saying something!!! ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++ Sheesh..... who else but Bill and myself remember these circa 1998 debates? Rebreather Tinkering has come a long way since those days, when the total "non-government owned" CC Rebreather population was probably sub-100 worldwide with 30-ish of those being Mark-15's built up by Kevin. I sure do miss 'em..... I cannot swing a cat now without hitting a new rebreather "expert". Dave (defying death by bad-gas since 1979) __________________ "Silent Diving with No Bubbles and No Politics".... www.nobubblediving.com** Last edited by Dave Sutton : 7th October 2006 at 14:08.
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7th October 2006, 18:00	#9 (permalink)
bgpartri CEO-Shearwater Current Rebreather/s: Megalodon Other Rebreather/s: Inspiration Classic Sport Kiss Classic Kiss Titan Join Date: Apr 2005 Location: Vancouver, Canada Posts: 423	Re: DIY 02 sensor One of the unfortunate things about that is that the archives appear to be gone. Due to a hard drive crash, I only have a copy back to early 2000. The one on the rebreather list site has headings only. The messages aren't there. As I flip through a couple of discussions in the middle of December 99 and look at the names beside the posts, I would love to re-read them. I've emailed Paul a couple of times, but he either can't or won't restore them. I know Gordon Smith used to have a complete copy at one time, but I have no idea if it still exists. It's unfortunate because it was history in the making. A lot of the principles that are taken for granted now were argued with hundreds of messages back then. On the other hand, I don't remember check flushes at 20 feet being discussed back then, and I think they're an important part of my survival now. __________________ http://www.shearwaterresearch.com Good judgment comes from experience. Experience comes from bad judgment.
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7th October 2006, 20:27	#10 (permalink)
Dave Sutton Diveshop of Horrors Current Rebreather/s: Sport Kiss MK 15.X rEvo Other CCR Azimuth Home Build Other Rebreather/s: Evolution Megalodon rEvo Other CCR Azimuth Home Build Join Date: Jun 2006 Location: Narragansett, Rhode Island and Hackettstown, New Jersey Posts: 2,907	Re: DIY 02 sensor Well, Bruce I'm sure you tried here: Mailing list archives Featuring all of the old timers, us included. Names only, sad to say, the messages are all gone. Many old friends there, and noticably several are now dead. Bruce is right, this material defines the early history of Rebreather diving. There are no new rebreather discussions, only new rebreather divers.... We ought to prevail on Paul Elliot to get the achives re-done, as the material is priceless. Best, Dave __________________ "Silent Diving with No Bubbles and No Politics".... www.nobubblediving.com Last edited by Dave Sutton : 7th October 2006 at 20:38.
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