Is purchasing an analyzer really necessary?

[BelchFire]

I'm new to Nitrox, but I was taught that the flow rate of the gas across the sensor was critical to an accurate measurement. For that reason, I was taught to always use an air tank rather than ambient air as the flow of EANx would be MUCH greater than "flow" (if you will) of just waving it around in the air. Was I taught wrong?

 

[John_B]

I'm new to Nitrox, but I was taught that the flow rate of the gas across the sensor was critical to an accurate measurement. For that reason, I was taught to always use an air tank rather than ambient air as the flow of EANx would be MUCH greater than "flow" (if you will) of just waving it around in the air. Was I taught wrong?

No you weren't "taught wrong", but you do need to understand the issues with some of your assumptions. If you are absolutely certain that the air tank you are calibrating off of is 20.9% O2 then that is a better method than waving the analyzer around in air. But how do you know the air in the air tank really has 20.9% O2? (How do you know what you don't know?) In that case, you do know that the air you are breathing is pretty close to 20.9% and the sensor will read that slightly low, so its at a minimum a good check after you've analyzed that you get a reading a few tenths of a percent low from 20.9%.

FWIW, I saw a guy in Fla. calibrate his analyzer off of a 6 cu ft bottle of 100% O2 he had brought with him. Being naturally curious I asked him about the accuracy at calibrating with 100% O2, since I would've thought calibrating against 21% would have been closer to the standard nitrox mixes that divers use; in my case that's 32%. Unfortunately its pretty much impossible to travel by air with your own 6 cu ft bottle of 100% O2 (as well it should be) so that's only an option for someone driving their dive gear from point A to point B. Still, it made me consider whether a similarly sized tank filled with known 20.9% would be useful to have at a resort, on a liveaboard, etc.

Then again, I always overthink this stuff...

 

[Web Monkey]

No you weren't "taught wrong", but you do need to understand the issues with some of your assumptions. If you are absolutely certain that the air tank you are calibrating off of is 20.9% O2 then that is a better method than waving the analyzer around in air. But how do you know the air in the air tank really has 20.9% O2?

If I don't have any known 20.9% air, I'll calibrate from room air. Even my measurement is off, it's generally only off by a few tenths of a percent, which really doesn't bother me.

If I have a tank that's supposed to be 32% and analyzes as "31.7%", that's just fine with me. I analyze so I don't plan the dive for 32% when it's actually 50% or 80% or 10%. With the proliferation of all sorts of mixed gases, there's really no guarantee that you have a breathable mixture, unless you analyze it.

Terry

 

[DandyDon]

Ok, this thread got me to check, and my 4 year old Analox O2EII Nitrox Analyzer has a 3 year sensor. Hardly been used, but - really need to change it?

Know where I can find a sensor for under $100...?

 

[aowi]

Hello...

My question is really for when I travel to foreign countries in the Caribbean and Asia. If I'm using EANx and getting my fills from a dive shop in a foreign country, should having my own analyzer be a must or can I trust the dive shop's analyzers?

I know its one of those depends on the shop question... but I guess I'm just wondering if its a good idea to invest in one. I plan to travel maybe once or twice outside of the country for diving. Majority of my dives will be here so I know I can trust my local dive shop. I just hate to throw another $400+ or so for an equipment I probably won't use more than a couple of times a year.

Thanks!
cmk

Yes, you are very correct, it depends on the dive operation. However, do you want to trust even the slight possibility of CNS O2 Toxicity, because someone else's equipment is faulty? Spend the money and buy your equipment

 

[oldtimerbob]

My LSD fills EANX tanks from a bank of prefilled cylinders which provides a perfect mix. While diving abroad, I use some caution and am very critical of the analyzer in use. When in doubt, I use air.

 

[BabyDuck]

don, depending on the sensor you're using, edd at cave adventures is having a sale on them...

 

[oldtimerbob]

Ok, this thread got me to check, and my 4 year old Analox O2EII Nitrox Analyzer has a 3 year sensor. Hardly been used, but - really need to change it?

Know where I can find a sensor for under $100...?

Typical O2 sensors function by a reaction to an ablative "reactive" coating on the sensor. Keeping the unit from constant air contact is important. Your sensor should be fine although I would check it against a known good sensor typically found at the LDS for accuracy. The oxygen reacts with this coating to create a weak electrical charge from the destruction caused by the reaction between the two elements. Its "life expectancy" is in direct relationship to its frequency of use and is advertised as typical My .02.

 

[DandyDon]

don, depending on the sensor you're using, edd at cave adventures is having a sale on them...

Thanks! Nice prices on everything else. Not my sensor for the O2EII but I sent him an email asking nonetheless...

Typical O2 sensors function by a reaction to an ablative "reactive" coating on the sensor. Keeping the unit from constant air contact is important. Your sensor should be fine although I would check it against a known good sensor typically found at the LDS for accuracy. The oxygen reacts with this coating to create a weak electrical charge from the destruction caused by the reaction between the two elements. Its "life expectancy" is in direct relationship to its frequency of use and is advertised as typical My .02.

I've kept it airtight in the Pelican box virtually all the time and it still reads out. I'll compare readings next time I get a chance to check Nitrox.

Would it be good to get a sealed sensor now for when I need to replace, or do they aged even sealed...?

 

[scubadobadoo]

... Your sensor should be fine although I would check it against a known good sensor typically found at the LDS for accuracy...

But isn't this why we should all carry and rely only on our own??? Just being a smarty pants.