Nitrox Analyzer

[Grantt]

Definitely overkill, but I use a Divesoft. I wouldn't worry about getting one off the bat.
If you are going on charters through dive shops, they will have analyzers and will get you sorted out. If they don't have an analyzer, don't calibrate it or don't let you check your tanks...then don't dive with them.

 

[greeniguana]

MSA MiniOx 3000. Cheap medical surplus units on ebay.

 

[Ulfhedinn]

Oxycheq

This is what I use and have for a couple of decades.

This is what I have coming in the mail as we speak. Picked it up from Golem Gear as they had the lowest price.

 

[mwerle]

One thing to watch is age. The oxygen cell has a fixed life. Figure 2-3 years. That life is from date manufactured, not date purchased or first used. Really doesn't matter how much you use it in that time, they just age out.

Not entirely true - oxygen cells are packaged in an inert gas and while yes, over very extended periods of time the chemicals probably do break down, the actual reaction which is used to measure oxygen content doesn't start until you break the packaging open. So the cells only start "aging" from that point onwards.

You _could_ also try to extend their life by re-packing the cell (or entire analyser) in an airtight bag and suck the air out if you won't be using it for an extended period. The cell will use up the remaining O2 and then stop.

Overall though, yes, cells will only last a couple of years, some longer, some shorter. Once they take an excessive amount of time to settle on a value or become current limited they need to be replaced.

 

[Divin'Papaw]

The Analox has a ‘sensor saver’ cap you can buy that seals off the sensor when not in use and thus extends the life of the sensor.

Also, the life expectancy of the Analox sensor is rated at 4 yrs.

 

[Wibble]

It's a standard galvonic oxygen sensor. These are effectively little batteries that generate a few millivolts in proportion to the amount of oxygen they're in. The sensor saver simply seals the sensor face such that the oxygen levels reduce as it's consumed in the reaction.

Eventually they will all expire.

You can pay the full price for a replacement OEii sensor, or search out equivalent sensors for half the price.

 

[Divin'Papaw]

It's a standard galvonic oxygen sensor. These are effectively little batteries that generate a few millivolts in proportion to the amount of oxygen they're in. The sensor saver simply seals the sensor face such that the oxygen levels reduce as it's consumed in the reaction.

That’s what I said

 

[Wibble]

That’s what I said

Edited post.

 

[PBcatfish]

I've been using an analox. I've had no problems with the unit. I bought it new, less than 4 years ago, so the sensor is not expired. The sensor was in the sealed bag when I bought it.

I was going to make a flow restriction system with adjustable needle valve to use a pony of air as a cal reference because I was told that just waiving the thing around in the room to calibrate the baseline, gives a false reading due to humidity. In practice, the readings I get off mine & the readings I get off a dry air cal system in a shop are pretty close & a chart exists if I want to do humidity variance calculations, so I scrapped the idea of making my extra gizmo.

An issue I HAVE noticed, is that if I get partial pressure fills, the reading I get at home is very different when compared to what I checked at the shop, if I don't roll the tanks around a bunch before checking them at the shop. I've seen differences of several percent, which is enough to cause trouble. After the home check, if I go back to the shop, the second shop check is pretty close to my home reading. The ride home seems to mix things up well enough.

 

[Divin'Papaw]

An issue I HAVE noticed, is that if I get partial pressure fills, the reading I get at home is very different when compared to what I checked at the shop, if I don't roll the tanks around a bunch before checking them at the shop. I've seen differences of several percent, which is enough to cause trouble. After the home check, if I go back to the shop, the second shop check is pretty close to my home reading. The ride home seems to mix things up well enough.

As you mention, that is a mixing issue not an analyzer issue. If you get a fill at a shop using partial pressure blending, unless that tank has sat for quite awhile, or been rolled around as you mentioned, the analysis in the shop is pretty meaningless. Thankfully all of the shops I use bank nitrox.

I use the humidity/temperature adjustment table myself. Doing that mine gets a reading consistent with what I get in the shop.