build it yourself O2 analyzers

[Dave Lizdas]

depending on the design, you can store the sensor covered by a plastic sleave to minimize its exposure to oxygen.

also, if your going to get a kit - why not get two extra sensor heads? that way you have a replacement ready to go when it's used up.

In my experience, an old sensor will not level off after a few seconds, may fail to come back down to 20.9, and return low numbers on pure oxygen.

[crazyduck]

Please be careful when pulling a vacuum or purging the container with inert gas.
Oxygen cells are basically fuel cells and if pull a good vacuum you could damage the cell, membrane or other delicate components of the cell.

Flushing with inert gas can have other issues. If purging please be careful with pressurizing the case. This can affect the hydrophobic membrane.

If used regularly cells last for about a year.

It should be noted that multiple cells should not be changed out at the same time- IE rebreathers. Some competitors to Teledyne have complained that their design is leading to contamination problems in their oxygen cells; that results in a shorted life cycle of the cell. However- these are their competitors.

Rumor has it that we might see a new cell soon that runs for 5 years.
However, we’ll have to wait and see.

Best Regards, Andrew

[tanto]

I built the "El Cheapo" O2 analyzer, and it works fine. You can get a kit for it here (bottom of the page):

http://www.oxycheq.com/Oxygen_Analyzer_Main_Page.html

I need a second analyzer and this kit is a strong temptation at 105 bucks, however I'm concerned: will it be difficult to assemble?
They say it takes three hours, that would be ok, but what about the degree of skill required?
Can anyone tell me how difficult it was?
Thank you,
T

[tomhauburn]

Any homemade He sensors out there? I not quite there yet but I was just wondering.

[FW]

I built the "El Cheapo" O2 analyzer, and it works fine. You can get a kit for it here (bottom of the page):

http://www.oxycheq.com/Oxygen_Analyzer_Main_Page.html

I need a second analyzer and this kit is a strong temptation at 105 bucks, however I'm concerned: will it be difficult to assemble?
They say it takes three hours, that would be ok, but what about the degree of skill required?
Can anyone tell me how difficult it was?
Thank you,
T

It does take some soldering skill, but otherwise it is pretty easy to build.

[Dave Lizdas]

I've built five of those kits for me and my aquatic homies. they are easy to wire with 15-35 Watt soldering iron and a steady hand. cutting the box is the hard part. I used a Dremel and a jigsaw blade. I'm quite sick of building now.

Sometimes I got a new sensor that would not calibrate. It would level off after being broken in, but I didn't have enough travel in the knob to get it to 21. Say it was at 18 or so. I wired in another variable resistor (50K Ohm, panel mount) in series with the knob and used that as a "course adjustment." I compared it to the lab oxygen analyzers we have at work and it was fine.

Has anyone else had this issue?

[crazyduck]

Potentially it sounds like a current limited sensor.
There should be raw milli vote range for a new sensor.
If it does not make that range then you potentially have a defective sensor.
You could compare it to air, a known gas and Oxygen. Oxygen usually makes it harder for limited sensors to made the correct reading.
Chip- no thoughts?

I am not sure about helium but to my understanding you have to have a sample “on board” to do a comparison of the gas.
Patrick gives a pretty good explanation for his units.
Web example- http://oxycheq.com/Expedition_He.html

Andrew

[Dave Lizdas]

oh yes, I tested the sensors on air, something around 50%, and 100% O2. I ran the tests again some months later and still got good numbers. The sensor lasted a year.

they have an internal circuit for temp compensation. mabe something in there was offset a bit? Anyway, the mod worked, but I shouldn't have had to do that. BTW, this was not Oxycheq's kit and these were Analytical Industries sensors. I've heard of one other sensor doing this too.

Chip- no thoughts?

It could be a problem with the sensor.

I am not sure about helium but to my understanding you have to have a sample “on board” to do a comparison of the gas.
Andrew

I don't think you have to have a sample on board. Helium sensors now come packaged similar to oxygen sensors. A home built trimix analyzer is within reach. You can build it similar to an oxygen analyzer.

Any homemade He sensors out there?

I'm not sure about the specifics to build the actual helium sensor.

[FW]

Someone needs to write a "Helium Hackers Handbook"...