Oxygen tester????

[NoVA_Agent]

Just wanted to add a quick 2 cents . . . I bought a used O2 analyzer and got a new sensor for it. After calibrating it to air @21%, I used it at a dive site on nitrox tanks and it gave readings about 5% higher than what the mix should have been. The LDS tested the tanks with theirs and found the mix to be as marked on the tanks.

This posed a dilemma for me, is my analyzer right or theirs? The best way to calibrate is supposed to be off of pure O2 but how am I going to do that?

I chose to compute my limits based on the higher O2 reading (mine) because I know the sensor was new and using the lower reading (if it was false) would have been bad ju ju.

When you get your analyzer, you may want to check it against some readings in your LDS to see if they agree.

Happy diving!

 

[Capnsnott]

That is the first place I'm going. The owner and his wife each use one to test, so I think I can get a pretty good feeling for the accuracy of mine.

Just as an FYI, I sent my money via Pay Pal to Patrick (Oxy Cheq), I got a return email from him with the tracking number withing a few minutes. VERY GOOD CUSTOMER SERVICE!!!!!!!!!!!!

 

[SDAnderson]

That is the first place I'm going. The owner and his wife each use one to test, so I think I can get a pretty good feeling for the accuracy of mine.

Just as an FYI, I sent my money via Pay Pal to Patrick (Oxy Cheq), I got a return email from him with the tracking number withing a few minutes. VERY GOOD CUSTOMER SERVICE!!!!!!!!!!!!

I built an OxyCheck analyser a few years ago and highly recommend them, both the analyser and the company.

Take your time when you get the kit, plan carefully and you'll do just fine. The directions aren't written for a novice, so read carefully, understand fully and if you don't have any experience soldering low voltage electronics you might want to practice a bit before you try the real thing.

Otherwise, a dremel will make it easier to cut and trim the box. Get yourself a small Pelican box with padding to store the thing in and be sure you have a flow regulator and the various adapters you'll need for your tanks.

 

[dc4bs]

Just wanted to add a quick 2 cents . . . I bought a used O2 analyzer and got a new sensor for it. After calibrating it to air @21%, I used it at a dive site on nitrox tanks and it gave readings about 5% higher than what the mix should have been. The LDS tested the tanks with theirs and found the mix to be as marked on the tanks.

This posed a dilemma for me, is my analyzer right or theirs? The best way to calibrate is supposed to be off of pure O2 but how am I going to do that?

I chose to compute my limits based on the higher O2 reading (mine) because I know the sensor was new and using the lower reading (if it was false) would have been bad ju ju.

When you get your analyzer, you may want to check it against some readings in your LDS to see if they agree.

Happy diving!

Compare yours (and the shops if possible) against a third tester to see which ones come closest to agreement.

--

Without 100% O2 available, the 2nd best bet to calibrate is a known 'air' filled tank.

Hook up the tester EXACTLY as it is used on a nitrox tank and run air through it. Set the calibration to 20.9 and then use it to check your nitrox tanks. The flowrate and pressures will be the same as at calibration that way. Of course, this requires you have a tank with air available to do this...

I have an old AL12 pony bottle that comes out for nitrox class demonstrations and even shows up at divesites sometimes (it was nice to find a use for the thing... ).

 

[fdog]

As a member of our Fire Department's HazMat team, we maintain and repair our "fleet" of gas detectors, roughly 50 units, with about 25 of those being 4-gas meters that detect Oxygen. So, I've gotten to see alot of their little quirks.

First off, the sensor cell is a consumable item, just like tires on a car. From the time it's manufactured it has a lifespan. In the best of cases, the best oxygen cell I've seen, manufactured by CitiCell (British) will last about 2 years.

There's lots of things that reduce that lifespan. Use is a big one; using a meter twice daily for about 15 minutes per use will cut life in half. Some meters that are used heavily I have seen beyond span limits in 6 months. Another is contaminates; exposure to a variety of acids, bleach or other oxidizers such as hydrogen peroxide can poison the sensor cell.

Calibration of the meter is important. The most commonly used calibration gas is atmospheric air. We use synthetic air, hideously expensive at $240 per 200 cu. ft. cylinder, at exactly 20.095%. Oddly enough, we can calibrate a meter to this standard, then walk outside in the winter and see 20.1% in the atmosphere. This is from the inversion layer we often get here. And at a class where everyone looked and acted sleepy, we pulled out a meter...19.6% Oxygen! No wonder people were nodding off. So the moral is, be sure of where you calibrate the meter.

Since the sensor cells operate by how much oxygen drive (partial pressure) exists, the sensing conditions are pretty important, too. We use calibrated flow meters to deliver gas. You can turn the knob from 1 lpm to 2 lpm and watch the O2 % change. There are other variables we control for calibration, also, such as temperature and humidity. Not to mention battery voltage.

The good news is that we have seen, with careful maintenence and calibrations, meters that reliably produce repeatable readings with accuracy +- 0.05% over months.

Yes, it's worth your life to have your own meter. Just give it the maintenence and care in use you would have for any other piece of life support equipment.

All the best, James

 

[Capnsnott]

I got my meter on Thursday, talk about FAST shipping. It took me about an hour to get it all together, I have all the cool tools (table top scroll saw, exacto for the holes). I tested it out and it works great. The OX sensors are $64.00 from Patrick, who bye the way is one of the only Teledyne sellers in the US. I also checked on buying the stuff from a supplier, it only saves me about $20.00. So it isn't worth the hastle or time.

I was told to store spare sensors in the fridge (in a bag), has anyone heard of this?

thanks
Greg

 

[fdog]

We used to store ours in a ziplock baggie under a shot of Nitrogen. The manufacturers' technicians have indicated in the past that storage in a refrigerator will increase the storage lifespan by some indeterminate amount, but will not arrest the slow degredation the sensor cell has over time. Just slows it down.

We were told to avoid storage in a freezer. The sensor cells are essentially little cans with a liquid chemical inside. To make them stable, the liquid has a gelling agent, and is held inside by a Gore-Tex membrame. Freezing causes ice crystals that expand and rupture the Gore-Tex, causing the lifespan (when thawed) to be dramaticaly shorter.

For us, it has been more cost-effective to watch span values, and just order new cells when the sensors are close to going bad.

Hope this helps.

All the best, James

 

[SDAnderson]

I got my meter on Thursday, talk about FAST shipping. It took me about an hour to get it all together, I have all the cool tools (table top scroll saw, exacto for the holes). I tested it out and it works great. The OX sensors are $64.00 from Patrick, who bye the way is one of the only Teledyne sellers in the US. I also checked on buying the stuff from a supplier, it only saves me about $20.00. So it isn't worth the hastle or time.

I was told to store spare sensors in the fridge (in a bag), has anyone heard of this?

thanks
Greg

Storage in an airtight container will reduce the oxygen exposure - increasing the sensor life. Likewise, storage in a cool environment will help slow any reactive activity - increasing the sensor life. I don't keep a spare sensor, it's fast and easy to buy a new one when it's needed.

 

[TTSkipper]

The sensor that comes with the El Cheapo II kit fits great in an old film canister. I write the date I opened the bag for the sensor on the sensor itself and the canister so I know how old it is.

 

[Snowbear]

The sensor that comes with the El Cheapo II kit fits great in an old film canister. I write the date I opened the bag for the sensor on the sensor itself and the canister so I know how old it is.

Great idea - thanks