Recommendation for a scuba oxygen analyzer

[Octopusprime]

I am looking into scuba oxygen analyzers and was hoping for a recommendation. I see then for $200-500. I would like it to be durable enough to take with on a charter and easy to use. Also do they require and maintenance / parts? I did not know if they have to be tested or have replacment sensors.

 

[Jim Lapenta]

I built mine from a kit. Keep it in a small pelican case so it's practically bullet proof. OxyCheq - EL Cheapo II Analyzer Kit
Took roughly 45 minutes with a dremel and soldering iron.
You do have to replace sensors and the battery when each gives up the ghost. My sensors normally last 2 years or so. Battery depends on the quality of it. Sensor life depends on brand, how you store it, how much use, etc. I had one last just over a year but that seemed to be a fluke.

 

[tbone1004]

No maintenance other than replacing sensors when they go bad, every 1-2 years, instantly if they get exposed to water. The Oxycheq DIY kit is a pretty good one but a PITA if you are doing it without a reg on the tank. Analox is good for tank use.

O2EII Pro Nitrox Analyzer - Dive Right in Scuba
That would be first choice

 

[SubAquatix]

Oxy cheq for me. They cost a ~$100. Unfortunately, for me, sensors rarely last 1 year and almost never 2, so I always keep a spare. I test and mix a lot of gas, though. Easy as pie to use on a charter if you buy a BC flow restrictor. Just hook up your regulator, and plug into the bc connector, then turn on the tank. Spend the extra $20 for the multiturn pot and you will save yourself a lot of effort.

 

[kensuf]

I use an Oxycheq. It's not that fancy, but does the job, and I think it cost me less than $180. Considering a sensor is about $75, that's not too bad.

If you're poor but good at basic algebra, you can just buy an O2 sensor and use a voltmeter. You'll need a calculator, I bet your cell phone has one.

The sensor puts out voltage in mV. The voltage will skew as the sensor ages, but typically a brand new sensor will spit out a number like 11.2mV when you calibrate it with air. Calibrate first, then run the sensor in the flow of a nitrox tank and take the new reading. Use the following formula to figure out the voltage:

(cgFO2 ÷ cgmV) • ngmV

cgFO2 is calibration gas FO2.
cgmV is calibration gas voltage.
ngmV is nitrox gas voltage.

So.. If you calibrate in air, and get 11.2mV as the calibration voltage, and when you analyze your nitrox mix you get 17.4mV your nitrox % would be..

(0.21 ÷ 11.2) • 17.4

32.6%

Ta da!

BTW -- the Oxycheck kit is basically just a panel volt meter with some electrical doodad wizardry to essentially start the mv output somewhere close to 21%, and then a potentiometer to adjust the output during calibration. They even have a "do it yourself kit" that is all the parts and you can assemble it yourself.

---------- Post added February 13th, 2015 at 05:43 PM ----------

And someone posted the link to the build it your own kit while I was typing my book.

 

[KevinNM]

Boats with compressors that produce nitrox will pretty much always have an oxygen analyzer. Pretty much any store that fills tanks with nitrox will pretty much always have one too. If they are well run you will need to analyze and log the results. Writing it on a label on the tank is a good idea too. If they don't have an analyzer you might want to rethink using them.

The time you really need one yourself is when you have a tank that got filled some time ago and you pull it out of the trunk at a dive site. Don't trust old labels. Don't trust your memory. People die doing that.

You also need one if you are mixing your own nitrox.

 

[DiveNav]

I am looking into scuba oxygen analyzers and was hoping for a recommendation. .....

If you don't mind using your smartphone to test a tank, you might be interested in our Nitroxbuddy Smartphone Oxygen Analyzer.

..... Also do they require and maintenance / parts? I did not know if they have to be tested ......

In general Oxygen Analyzers are considered "Comparative Instruments" (instead of Absolute ones). This means that they need to be calibrated against a reference gas (usually air) before each use.
They also have a battery .... that needs to be changed once in a while.

..... or have replacment sensors.

An Oxygen sensor is like a mini battery and as such it has a finite life. More Oxygen gets in contact with the sensor and more it gets "discharged".
Typical life for an Oxygen sensor is 12 to 18 months.

 

[Octopusprime]

Thanks for all of the input... The DIY I find interesting... I would expect the LDS doing nitrox would test but I would like to confirm or be able to varify if label was damaged or rubbed off. Would not be the first time the carpet in the back of the SUV rubbed a sticker or sharpie marker off a tank.

---------- Post added February 13th, 2015 at 08:52 PM ----------

Looks like they just give you the O2 % but does not give you other percentages. So they wil
not give you Co2 % ( not that a good shops would have this prob) not that I'm going to be doing trimex anytime soon but is there differnt tester for trimex?

 

[KevinNM]

Co2 isn't typically a problem. CO requires a different test cell, and is usually a different analyzer. Helium analyzers are out there, but I don't do that. Iirc, they are pretty expensive.

 

[tbone1004]

Helium is quite expensive to analyze, but unless you are diving trimix there is no point to checek it unless you suspect it has been put in there, but if the shop has helium they'll have an analyzer for that. CO2 is a nonissue, but CO requires a separate sensor as mentioned above. Analox just discontinued their CO sensor which is unfortunate.