O2 sensors

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O2 sensors

Postby Packhorse » Thu Jan 31, 2008 7:06 pm

OK I have been working on a PPO meter/ HUD and have the electronics sorted.
So now I need to build a case and purchase some O2 sensors.
Rebreather world store seem to sell the cheapest with oxycheck being close behind.
Anyway which O2 sensors do you prefer and why?
Where do you get them from?
Do you need anymore as we may save a few $$ buying/ mailing in bulk

Here Is some of RBW's ones
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Postby Andy » Thu Jan 31, 2008 10:40 pm

I think the ones I use are Teledyne ones, but there just for my analyser. I get them from wherever has them in stock at the time I need them!
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Postby silent solutions » Fri Feb 01, 2008 2:53 pm

sensors are in a very different enviorment inside a rb compared to a analyser!!!!There is no perfect cell regardless of brand yet .Now assuming you have designed a set of electronics that is accepting of the same mv range as the common cells in use.I would choose the same type of cell that is common to your dive buddies easier for spares when they fail.Try a coax cell less connection problems.The ends are available pre wired which should make life easier unless you like soldering.Diverite express are not a bad place for cells quick turnaround 4 days on my doorstep when I last ordered.I have given up on rbw sending my last order.
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Postby Andy » Fri Feb 01, 2008 8:49 pm

silent solutions wrote:sensors are in a very different enviorment inside a rb compared to a analyser!!!!T


I guess a breather is the ultimate analyser!!! :lol: :lol: :lol:
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Postby Gregv » Sat Feb 02, 2008 5:55 pm

I've used Analytical Industries Mini-Jack and Molex, IT / DiveTek molex and Teledyne MiniJack and Molex sensors.

I've had all three brands fail in a variety of ways, some DOA, some within a week of first use, and others after a month. Some went high, then low, a couple were current limited out of the box, a few others completely dead. The ones that were stable beyond the initial month or so have lasted beyond 18 months, though I rotate them out of the rebreather at about 12 months.

AI sensors (DiveriteExpress, and before that, RC Technologies) have been as reliable as the Teledynes (or vice versa, depending on your bias).

I'm due for another set in a few months, and will likely get them from DiveRiteExpress. As Gibbo says, they're quick and reliable. Patrick at Oxychek is a good guy and also reliable. Bulk buying is made difficult as a single set of 4 is under the $400 goods+shipping GST exempt limit, but any more in a single order puts it over, generally offsetting any savings on shipping.

Sensors are the weakest part of any rebreather design. Use more than one, calibrate carefully and switch them out regularly.

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Postby Packhorse » Sat Feb 02, 2008 7:43 pm

My PPO meter has been tested on a 8mv sensor (R17D) and has more than enough adjustment for a 25mv sensor.
Im am in two minds about building a double or tripple display.
I think I will go with a double dispaly. I think this is all you really need for a 30meter mCCR. Although the sensor housing will have space for 3. I can then either build a second independant display or when I win Lotto buy a VR3 and hook that up to the 3rd. 8)
I guess a breather is the ultimate analyser!!!

I like to think of them as the ultimate continuous blending system. :lol:
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Postby silent solutions » Sun Feb 03, 2008 8:38 am

Packhorse the way you are trying to do this on the cheap concerns me a little.You say this is all I need for a 30m rebreather these things are very capable at taking your life in 6m or 125m of water.The issue of a two cell rebreather or three has been discussed on rbw my opinion is for a minium of three and I currently run 4 cells the forth being through the vr3.I cant stress enough that rbs are a tool to do a job if I wasnt doing the type of diving I am then I would be back to oc in a flash.Alot of the questions you ask are covered on any good generic rb course and you have a very experinced rb instructor up there phone him.If you skimp on money now are you the type of person that will push there cells just one more month past there use by date because there not in the budget this month??.Just little things like this will compound problems on a set of electronics that arent voting a cell out or due to the divers limited experience it is not recognized.Sorry for the rant and dragging of topic but back to cells :)
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Postby Packhorse » Sun Feb 03, 2008 1:25 pm

silent solutions wrote:You say this is all I need for a 30m rebreather these things are very capable at taking your life in 6m or 125m of water.
Perhaps I should have said No decompression dives and less than 30meters. ie; being able to abort the dive at any time.

The issue of a two cell rebreather or three has been discussed on rbw my opinion is for a minium of three

I based my choice of 2 sensor display on the logic of this artical here...
http://www.airheadsscuba.com/sensors.html
The way I see it if the displays differ I end the dive. Being a no deco dive I can do that at any stage.
Also a double display is 1/3 smaller than a tripple and I think I would preffer a second totally independant display holding the 3rd sensor when I deem it neccasary. EG if I ever use it for deco or convert it to eCCR.

Packhorse the way you are trying to do this on the cheap concerns me a little.
If you skimp on money now are you the type of person that will push there cells just one more month past there use by date because there not in the budget this month??.

The choice of 2 sensors vs 3 was not a finacial one. And I cant see anything wrong with shopping around for sensors.
I have seen them for 65 pound UK vs $50US. Are the ones at 65pound better because they cost more? Are the ones at $50US crap or not? I dont know. Thats why I asked. One thing I know for sure is that just because something costs more does not mean it is better.


Sure I know many of the question I ask can be answered buy a RB instructor, But im the type of person that likes to learn as much as I can before the course so I can learn more during the course.
I understand your post was made out of concern and I thank you for it.
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Postby silent solutions » Sun Feb 03, 2008 3:45 pm

Sensors regardless of price and brand can and do fail for no reason or age.Just my opinion but three sensors is the minimum i would feel comfortable with for verification of a dodgey cell or gas flush.
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Postby Andy » Sun Feb 03, 2008 8:02 pm

silent solutions wrote:Sensors regardless of price and brand can and do fail for no reason or age.Just my opinion but three sensors is the minimum i would feel comfortable with for verification of a dodgey cell or gas flush.


If three was the minimum, presumably you'd prefer four?

If there were three, and two gave one reading and the third different, presumably you'd trust the two?

If you had four, and had a two and two situation, what's the call?

Just curious!
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Postby Packhorse » Sun Feb 03, 2008 10:42 pm

Andy wrote:
If there were three, and two gave one reading and the third different, presumably you'd trust the two?!
If you had four, and had a two and two situation, what's the call?

Just curious!



Flush the loop with dilutant (or blow dilutant accross the face of the sensors if your unit can) then compare the readings with what the PPO should be based on your present depth and your dil mix..????

Thinking about it more perhaps 3 sensors should be a minimum in my set up. At least this way if (when) one fails I could still dive it with only 2.
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Postby Xman » Mon Feb 04, 2008 7:59 pm

Packhorse wrote:Thinking about it more perhaps 3 sensors should be a minimum in my set up. At least this way if (when) one fails I could still dive it with only 2.


Let me start by saying that I am definately NOT qualified in any way shape or form on rebreathers, and am just commenting from a common sense point of view.

Surely it would be foolish to plan to dive a faulty rebreather, regardless of how many sensors you are running. Your life is worth more than that.....
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Postby Packhorse » Mon Feb 04, 2008 8:35 pm

Let me also say I am not qualified either. I am still definatly in the learning stage and I tend to post questions (and statements) in an atempt to learn more and further shape my ideas and opinions. Nothing is set in stone.
Having said that....

Did you read the artical X? Is there something you disagree with?

I wasnt talking about a faulty rebreather I was talking about 1 faulty sensor out of 3.
Surely the reason for having 3 or 4 sensors is so you can continue a dive if 1 goes bad. As long as you know the sensor is bad and you disregard it and you accept and agree with the logic in the artical what is the problem?
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Postby silent solutions » Mon Feb 04, 2008 9:39 pm

There is a lot of rebrether experts on the internet some credible some not.You are designing a breather on these experts advise that you may not have meet or dived with.Talk to pete or greg and see if they had the choice would they everbother homebuilding .so far you have been stopped jumping onto a cold scrubber on a rg for deco from oc and desiging po2 moitoring with only one or two cells. Pony up do a course with a real instructor and actual time on a unit where you are not looking over your shoulder for it to kill you and ejoy the experience.only then you will see the shortcomings of what you intend.Time tinkering is time that you could be in the water.
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Postby Packhorse » Mon Feb 04, 2008 10:30 pm

Sorry SS but I like tinkering. Its how I learn best. Its what I do. Its what I have always done.
PM him self said the best way to learn about RB's is to build one.
[quote="PeteM"]If you want to learn about rebreathers - my advice is build your own!! I couldn
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