OMS Oxygen analizer ????

[Scott M]

OK, I need some advise or at least some clarification if possible.

I just read the directions for the OMS O2 sensor. According to the directions the unit has to be calibrated to a "known" source prior to each use???? And it should be calibrated to a source close to that which is to be tested???? Does this make any sense what so ever???

Where do you get a "known" source each and every time you want to check your fill? You can not get it from your LDS if that is the same air in your tanks. You would be calibrating it to "their" level. What good is that?

Do you have to search out a certified O2 dealer to calibrate every time you use the unit? What a pain that would be. Not to mention finding one with the same % of O2.

What about if you where on a dive boat? Where are you going to get a "known" source???

Any ideas or am I just stupid?? You don't have to answer the second part of that question, I think I already know the answer.

Scott

 

[Capt Jim Wyatt]

If measuring EAN32 or similar gas use air -- it is known to be 21% -- use it to calibrate, then measure the unknown gas.

If measuring higher % mixtures use 100% O2 to calibrate

 

[Scott M]

Capt Jim Wyatt once bubbled...
If measuring EAN32 or similar gas use air -- it is known to be 21% -- use it to calibrate, then measure the unknown gas.

If measuring higher % mixtures use 100% O2 to calibrate

OK, I get that part as far as air is 20.9% and the EAN32%/34% and all that, but......where do I get the "known" air source? I have two AL80's with air in them in my garage right now. How do I "know" that it is actually 20.9%? Where do I get "known" air to calibrate the unit so I can test the tanks?

The only feasable answer would be to go to a medical supply facility to calibrate the unit, which I am sure they only have 100% O2. I would have to do this each and every time I wanted to test my fills? If the they would even let me do that.

Scott

 

[MechDiver]

Scott M once bubbled...

OK, I get that part as far as air is 20.9% and the EAN32%/34% and all that, but......where do I get the "known" air source? I have two AL80's with air in them in my garage right now. How do I "know" that it is actually 20.9%? Where do I get "known" air to calibrate the unit so I can test the tanks?

The only feasable answer would be to go to a medical supply facility to calibrate the unit, which I am sure they only have 100% O2. I would have to do this each and every time I wanted to test my fills? If the they would even let me do that.

Scott

Air is air dude, and will be 20.9%. I'm not familiar with the OMS unit, but I just wave my Oxycheq Expedition in open air and let it stabilize, then set if necessary. As Jim said, if using high EAN mixes, then you need a source of pure O2.

Have you had a nitrox class? This all should have been explained in the class.

MD

 

[Capt Jim Wyatt]

MechDiver suggested...
Air is air dude, and will be 20.9%.
MD

and I agree. The air in your scuba tanks will suffice. Have you been certified as a nitrox diver yet?

if not, the class will help immensely. If yes..then I suggest restudying the book.

 

[Scott M]

MechDiver once bubbled...


Air is air dude, and will be 20.9%. I'm not familiar with the OMS unit, but I just wave my Oxycheq Expedition in open air and let it stabilize, then set if necessary. As Jim said, if using high EAN mixes, then you need a source of pure O2.

Have you had a nitrox class? This all should have been explained in the class.

MD

I am scheduled for the Nitrox class this January.

The OMS is a x-mas present from my wife that I..ehhh... opened a little early, shhhhhh.

I was thinking to calibrate it, it had to be under pressure to be calibrated. Waving it works, duh. Thanks.

Now for the 100%. I'm sure I could figure out some way to get that locally for calibration purposes but what about on a dive boat?

I'm pretty sure they will not let me tap into there oxygen safety kit to calibrate my tester. Can it be calibrated prior to leaving on a trip? Or possibly setting to the standard 20.9% by waving then read the nitrox?

Thanks Mech and Capt. It's starting become clear now.

Scott

edited for typo

 

[Capt Jim Wyatt]

Scott M said...

I was thinking to calibrate it, it had to be under pressure to be calibrated. Waving it works, duh. Thanks.

Now for the 100%. I'm sure I could figure out some way to get that locally for calibration purposes but what about on a dive boat?

It is a more accurate calibration if you flow the proper volume over the sensor. Generally about 2 LPM. The analyzer may have come with a flow restrictor that connects to your BCD inflator hose that ensures that rate of flow. There are other pieces of hardware that ensure proper flow across the sensor as well.

Waving it the air is likely to be as accurate as you need for EAN32 and the like. However, when oxygen % is more critical as in the case of trimixtures flowing at the prescribed rate is far superior.

Generally you will not be analyzing tanks on the boat. Typically those measurements are done at the shop before the boat leaves the dock to ensure you get the gas you asked for.

The shop should be able to provide you with 100%.

As an note: I calibrate my Oxycheq to air regardless of the mixes I am analyzing & that calibration provides the accuracy that we need, even with mixes like 16/40.

 

[MechDiver]

Scott M once bubbled...

Now for the 100%. I'm sure I could figure out some way to get that locally for calibration purposes but what about on a dive boat?

I'm pretty sure they will not let me tap into there oxygen safety kit to calibrate my tester. Can it be calibrated prior to leaving on a trip? Or possibly setting to the standard 20.9% by waving then read the nitrox?

Thanks Mech and Capt. It's starting become clear now.

Scott

edited for typo

For basic nitrox diving you'll be limited to 40% or less, with 32 and 36 being common mixes. Just calibrate the meter to air for these mixes. I would also, if possible, analyze your mixes prior to getting on the boat so you know they're correct before you board. Also, anything taken on a boat will get wet. Rule No. 21.3 IF you take the meter on a boat, make sure its in a drybag or waterproof box.

Good luck with the class, and shame for opening presents early

MD

 

[Scott M]

Capt Jim Wyatt once bubbled...


It is a more accurate calibration if you flow the proper volume over the sensor. Generally about 2 LPM. The analyzer may have come with a flow restrictor that connects to your BCD inflator hose that ensures that rate of flow. There are other pieces of hardware that ensure proper flow across the sensor as well.

Waving it the air is likely to be as accurate as you need for EAN32 and the like. However, when oxygen % is more critical as in the case of trimixtures flowing at the prescribed rate is far superior.

Generally you will not be analyzing tanks on the boat. Typically those measurements are done at the shop before the boat leaves the dock to ensure you get the gas you asked for.

The shop should be able to provide you with 100%.

As an note: I calibrate my Oxycheq to air regardless of the mixes I am analyzing & that calibration provides the accuracy that we need, even with mixes like 16/40.

Thats the kind of info I was looking for. The directions are not the most informative I have ever seen. A small section on obtaining known air sources would have done the trick.

I submitted the same questions to OMS and am waiting on their reply. It will be interesting to hear.

Thanks again
Scott

 

[Scott M]

MechDiver once bubbled...


For basic nitrox diving you'll be limited to 40% or less, with 32 and 36 being common mixes. Just calibrate the meter to air for these mixes. I would also, if possible, analyze your mixes prior to getting on the boat so you know they're correct before you board. Also, anything taken on a boat will get wet. Rule No. 21.3 IF you take the meter on a boat, make sure its in a drybag or waterproof box.

Good luck with the class, and shame for opening presents early

MD

This unit is water "resistant" but I agree a drybag/box would be prudent.

LOL....If I don't get caught it didn't really happen now did it?

Thanks for the help
Scott