All about Oxygen O2 Analyzers, including DIY

[svs3]

Dr. Deco and List,

Perhaps this is best posted in the general equipment discussion area but am starting this thread here anyway.

I'm doing alot Nitrox diving and will be trained in the use of trimix by the end of summer. I'm getting to the point where I need an analyzer. What the most important features I should look for? What should I avoid? Are some designs inherently better than others? Are there some that should be avoided at all cost?

I'm just begining my research in this area, so any and all input and real world experiences would be very welcome.

Thanks,
Sam

 

[Rick Murchison]

The Mini-Ox is fine, expecially with a flow regulator off an LP hose; I use the "stick" directly off the tank, but to be accurate with it takes some practice.
You should always use two analysers before you trust any reading.
Rick

 

[Atomox]

Sam,

The most important aspect of a galvanic cell O2 analyzer is repeatable and reproducible results (this is the same for any analytical instrument). To get this performance you need to be able to control the flow rate. There are a number of ways to control the flow rate. The easiest is to get a flow restrictor from Dive Rite, Maxtec or other. A needle valve and flow meter (from McMaster-Carr and Dywer respectively) will also work. Feathering a valve is not a good method and is not recommended.

A galvanic O2 cell will provide a reading of the partial pressure of the oxygen. You can use this reading as a direct measure of the percentage of O2 if the meter was zeroed at the same flow rate with a known source (typically done with air). The type of cell used will determine the response time, the amount of error, and drift.

I strictly use meters I have built with the Teledyne O2 sensors. I use Teledyne because they are very linear over the range of O2 that I use, the response time is very quick, I have zeroed out the offset (much smaller with Teledyne vs. Maxtec) of the cell, and I know what the overall performance is. (I have a NIST traceable flow calibrator, and cylinders of nitrogen, oxygen, and helium in both zero grade and welding grade as part of my hobby/business that allow me to do this).

Vance Harlow’s Oxygen Hackers Companion has good information on oxygen analyzers and how to build one as well. Remember, you should be thoroughly familiar with the risks of using oxygen in diving applications. You should also know how to analyze and be familiar with different blending techniques. And you should know how an analyzer works, gives correct readings, recognize erroneous readings.

Brad

 

[neil]

Sam,
The analyzer must be able to show percentage O2 to the nearest 0.1%, most do.
It should be compact so you can carry it easily.
It should have, or you should buy separately, a device that will keep testing flow rate consistent.
It should be simple to calibrate.
The sensor should be fairly simple to replace.
The OMS unit is just fine for your needs. There are other brands as well, and yes, you can build your own. (What is your time worth :>) )
Neil

 

[Atomox]

Sam,

I don't know if you are aware of this site but it does contain some good information (about 95% good, 5% crap) and links:
http://www.cisatlantic.com/trimix/

Yes some of the designs are better than others. The analyzers that have temperature compensation are in general a little more accurate at varying conditions.

I would want a unit that you can get service and parts for. This is not a common need with analyzers but it does happen.

As I said before make sure that you have a device that can regulate the flow for accurate and repeatable analysis.


What I would do is:
1. Buy Vance Harlow's
THE OXYGEN HACKER'S COMPANION
http://www.airspeedpress.com/

2. Build an oxygen analyzer with a Teledyne cell

Brad

 

[algulfdiver]

Does anyone have info on where to get info on how to build a oxygen analyzer? I have read that you could purchase everything you need from radio shack.
Thanks for any info.

 

[Uncle Pug]

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

buy the kit or get the free plans and make your own buying parts at radio shack (for slightly more).....

Have two.... they work great....

 

[algulfdiver]

Uncle Pug thanks for info great site I willuse it.

 

[Lost Yooper]

Here's some more links, but I think the El Cheapo is the way to go too.

http://www.dcordes.freeuk.com/analyser.htm

http://users.erols.com/bee2/O2Meter/text.htm

Good luck.

Mike

 

[roakey]

http://www.cisatlantic.com/trimix/tools.htm

This has several "how to build an analyzer" links as well as a ton of other interesting links.

http://www.airspeedpress.com/

Follow the link to "The Oxygen Hacker's Companion." It has plans for an analyzer, but that's just a small part of the book. It has information on mixing, O2 cleaning, etc. An excellent reference.

Roak