build it yourself O2 analyzers

[oldguy]

Do any of you distinguished dudes (and dudettes) have any experience with the O2 analyzer kits that are available? Would like to know if they are accurate. I have some electronics component assembly experience, ham radio, etc. but I do not assemble circuit boards. Thanks for your input. Safe diving.

[Jason B.]

Oh yes, I have built many myself.

http://ncdivers.com/cpg133/albums/us...inside%7E0.jpg

http://ncdivers.com/cpg133/albums/us..._analyzers.jpg

[curtschu]

Check with TDL just to make sure you can't get a deal on one for just a little more than the kit, unless of course you are just a DIY kinda guy.

Curt

[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

[aw]

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

Me too. Works fine. I've since bought the Diverite He/O2 analyzer. They are both very close to each other in O2 readings.

[OutlawCaver]

For the more techie types you can do the following:

Use the oxygen sensor and a digital voltmeter with at least 1 millivolt resolution. This allows you to obtain 3 calibration values. You need a source of 100% O2, air and 100% helium or argon (any inert gas will do). The sensor will provide decreasing voltages levels as PO2 decreases. Input the 3 points (PO2 vs voltage) to a calculator such as a TI83 and perfrom a linear regression (built-in function).

NOW you can test any concentration of oxygen in a gas mix more accurately not just those close to 21% . With the linear regression equation found, simply input the voltage obtained from the unknown gas into the calculator and out comes your PO2.

The benefits gained from this over a single point calibration analyzer, is you can calibrate measurements over the full scale 0-100% oxygen range of the sensor and not just at 21%. You can further determine if the calibration points are linearly correlated (basically a straight line slope) to determine if the sensor response is linear. I like to perform this analysis when my mix is getting away from a single 21% calibration point such as mixes between 10 & 16% O2 or a 50/50 mix.

Remember, most inexpensive O2 sensors, like the galvanic cell Teledynes, are sensing PO2 and not percentage so flow rates, temperature and pressure are an issue. As long as you keep them all constant it doesn't really matter. Typically, off the back of the truck, I just use a single calibration point analyzer calibrated without flow using ambient air. Back at the garage for trimix analysis I do the 3 point method and maintain constant flow for all gases. I also use multiple sensors.

Once again, this is for the more technical types who like to fiddle.

[Alan Garrett]

I built one from parts a few years ago and it works extremely well. I used the plans from a source in the "Oxygen Hackers' Handbook". The only difficulty I had was de-soldering some of the tiny SMD resistors off the board on the digital panel meter and soldering on some jumpers and contacts for the test leads, but I managed to get it done without too much fuss and I saved a lot of money. Everything except the panel meter and O2 sensor was available locally off the shelf (Radio Shack), and I was able to order those two items on-line. I got the O2 sensor from Oxycheq and the panel meter from some electronics supply house that I can't remember right now. Mine reads within 1/10th of a percent of any other analyzer I have ever compared it to, regardless of how much it cost. I suggest you go for it! You'll have fun doing it and you'll have the money you saved to spend on something else really cool. 8)

[aainslie]

The one thing that sucks about Patrick's Oxycheq "El Cheapo" kit is the hard plastic container he puts it in. The plastic is hard to deal with and you end up spending more time carefully dremeling the holes than any other part of the process. I mounted two of his kits into an old video box I had lying around - much softer plastic, and actually it's easy to open and close for maintenance. In general a softer box is easier to work with. I also used a single switch and battery on mine as I use two on a CB trimix station.

It's hard to beat his price. I'd recommend just buying his kits.

[Alan Garrett]

I ended up using one of the little black electronics project boxes from Radio Shack. It only cost a few dollars and the plastic was pretty easy to drill and work with. I'm kind of a "gadget-man" anyway and I enjoy building stuff for myself, so I purposely opted to build everything from parts, which definitely isn't something everyone enjoys. But if a persons' goal is simply to get a good O2 analyzer without spending a lot, and if they have some basic skill for following instructions and assembling things for themselves, I also think the "kit" would be the way to go. I admit it would have been pretty nice to have been able to open a single box and have everything I needed right there in front of me without having to go on the scrounge. But then again, I have to say I enjoyed that part of it too.

[D1V3R]

Another good project for the DIY guy that i've heard about is building a air tight inclosure out of a pelican case that you can purge with argon, so you can store your O2 sensors in inert gas and make them last longer
(i guess they burn out after a while, i really have no idea, lol)