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Scuba Forum / General / September 2004O2 Analyzer
Any recommendations, warnings, issues, concerns with O2 analyzers? I've been Nitrox certified and looking to acquire my own for all the obvious reasons. Just curious to know and learn from others who have been in a similar situation. Thanx In Advance... > Any recommendations, warnings, issues, concerns with O2 analyzers? I've been > Nitrox certified and looking to acquire my own for all the obvious reasons. > Just curious to know and learn from others who have been in a similar > situation. I had one but decided not to keep it because the cartridge needs to be replaced regularly and it's expensive. Everywhere I dive nitrox has an analyzer. It was perhaps more convenient and safer to have my own, but not cost-effective. A note on convenience: I had to find an air tank to use for calibration and that was sometimes difficult to do when almost everyone uses nitrox and the divers on air might be reluctant to have you "tampering" with their tank. Jeanne >I had one but decided not to keep it because the cartridge needs to be >replaced regularly and it's expensive. Everywhere I dive nitrox has an [quoted text clipped - 5 lines] > >Jeanne You might be safer setting up a "calibration tank" using 40 percent 02...because generally speaking its the O2 possibly being higher than you think it is that is a danger in diving... You want to make sure any O2 meter you use will ACTUALLY show a high O2 level if thats what it is exposed to...that fact it shows 21 percent when exposed to 21 percent isnt nearly as an effective test.... And Ive been under the impression that when O2 meters crap out, they tend to fail first by not showing high o2 levels when in fact they exist.... Just my opinion take care Blll Any of the O2 analyzers out there will work. Some are a bit easier to use than others. For an inexpensive one try Oxycheq's "El Cheapo". You can also build your own. The analyzer is really nothing more than a voltmeter. Plans are available from "The Oxygen Hacker". Most people calibrate with atmospheric air - usually close enough. Think about how accurate you need to be. How much will an error of .5% affect your dive plan? How about 1% ? What about a 2% error? If you want to calibrate to compressed air it will be more accurate because most of the water is eliminated. You can also measure the amount of water in the air (humidity) and apply a correction to the reading. Using a "calibration tank" of EAN40 would only increase your accuracy if you could analyze the "calibration tank" at a significantly higher level of accuracy. The errors would be additive. Checking your sensor on pure O2 (or high oxygen EAN) will let you know if your sensor is failing, because they fail at the high end first. Calibration of O2 analyzers to pure oxygen is sometimes recommended, but raises a problem. Since most analyzers have only single point calibration capability, it is better to calibrate them at a point close to the where you will be actually be taking readings.  SignatureSafe diving, Dale Bennett Captain Dale's, Inc. Enterprise Marine, Inc., Dive Charters > >I had one but decided not to keep it because the cartridge needs to be > >replaced regularly and it's expensive. Everywhere I dive nitrox has an [quoted text clipped - 22 lines] > > Blll >Using a "calibration tank" of EAN40 would only increase your accuracy if you >could analyze the "calibration tank" at a significantly higher level of >accuracy. The errors would be additive. Checking your sensor on pure O2 >(or high oxygen EAN) wi Yeah...your right that pure 02 "might" be a better calibration tank than 40 percent 02....and yes your calibration is harder (at least in theory) for using 40 percent because its hard to get "exactly" 40 percent..... But the whole point isnt to get an exact calibration...its to make sure that the oxygen sensor hasnt gone tits up and isnt giving WAY wrong readings....particularly at 02 levels that are likely to be in the range of the mix you plan to use... which reminds me of these fools who think you can calculate deco to a precision of few percent and think it really means anything..... So, it really comes down to whether you want to fool with getting pure 02, or just get a 40 percent nitrox tank measured with a couple different sensors at the time of the fill....or just mixed carefully by the partial pressure method... Reminds me of something someone posted here a few years ago....they were on a commercial dive boat....someone grabbed a tank and did a deep dive only to find out that it was 40 percent! Well, the story ended up with the dive operator screaming about having nitrox in "air" tanks, yet the dive operator ended up having air in the boats "nitrox" tanks on the boat as well...or maybe the "air" tank filled with nitrox was one the diver brought but someone else grabbed..... Whose the fool(s) here? :) trust but verify :) take care Blll >But the whole point isnt to get an exact calibration...its to make sure that >the oxygen sensor hasnt gone tits up and isnt giving WAY wrong >readings....particularly at 02 levels that are likely to be in the range of the >mix you plan to use... .. This bothers me. I would think that any sane diver would start with a tank that contains a KNOWN O2 level. Checking it again with another sensor is a double check. If it doesn't match closely the correct resonce is to not dive with that tank untill you know what went wrong and why. In other words, if the sensor has gone "tits up" (what a term!) and gives a way wrong readign -- well the dive should know something is wrong because the tank does NOT show the O2 level it is supposed to have. SignatureCharlie Hammond -- Hewlett-Packard Company -- Ft Lauderdale FL USA (hammond@not@peek.ssr.hp.com -- remove "@not" when replying) All opinions expressed are my own and not necessarily my employer's. > This bothers me. I would think that any sane diver would start with a tank > that contains a KNOWN O2 level. Checking it again with another sensor is [quoted text clipped - 4 lines] > way wrong readign -- well the dive should know something is wrong because > the tank does NOT show the O2 level it is supposed to have. Absolutely! I have nine sets of doubles and I don't know how many singles. I don't even dive air until I have analyzed it before the dive. I once lent another diver a 40 CF stage with EAN50 (70 FT) and when I got it back it had 100% O2 in it with no change in markings. I analyzed it before using it and was quite surprised as the reading kept climbing. I checked it again with a second meter just to make sure. Needless to say, I was none too happy. SignatureSafe diving, Dale Bennett Captain Dale's, Inc. Enterprise Marine, Inc., Dive Charters > I once lent another diver a 40 CF stage with EAN50 (70 FT) Awful lot of liability there, "captain". Signature"We're going to rush the hijackers." -Jeremy Glick, aboard United Airlines flight 93, September 11, 2001 > Awful lot of liability there, "captain". Oh, what a pithy comment. It shows such a depth of understanding. SignatureSafe diving, Dale Bennett Captain Dale's, Inc. Enterprise Marine, Inc., Dive Charters > > Awful lot of liability there, "captain". > > Oh, what a pithy comment. It shows such a depth of understanding. Yup. When the subject is you, I'd call our understanding "total", or perhaps "complete". Aren't you do at your dive store? Oh, wait... Signature"We're going to rush the hijackers." -Jeremy Glick, aboard United Airlines flight 93, September 11, 2001 >? I once lent another diver a 40 CF stage with EAN50 (70 FT) > >Awful lot of liability there, "captain". Why? If the tank was correctly labelled, I see no problem with it at all. -- SignatureKarl Denninger (karl@denninger.net) Internet Consultant & Kids Rights Activist http://www.denninger.net My home on the net - links to everything I do! http://scubaforum.org Your UNCENSORED place to talk about DIVING! http://divegearregistration.com REGISTER DIVE GEAR TO PROTECT AGAINST THEFT > If the tank was correctly labelled, I see no problem with it at all. Yes, we know. Signature"Let's roll!" -Todd Beamer, aboard United Airlines flight 93, September 11, 2001 >>€ I once lent another diver a 40 CF stage with EAN50 (70 FT) >> >>Awful lot of liability there, "captain". > Why? > > If the tank was correctly labelled, I see no problem with it at all. You would take that chance? I wouldn't. >>>? I once lent another diver a 40 CF stage with EAN50 (70 FT) >>> [quoted text clipped - 5 lines] > >You would take that chance? I wouldn't. Huh? If I gave it to you, I'd know what was in it before I did. If you are dumb enough to trust the label and dive it without analyzing it yourself, well, Darwin is a waitin' for 'ya. If you have the ability to use a stage-rigged AL40, you damn well ought to know how to read a contents label and verify it yourself. Besides, you'd need the appropriate reg to hook on to it, etc - if you've got all that sorted out (necessary to use the tank in the first place) I bet you've got the rest sorted out too. -- SignatureKarl Denninger (karl@denninger.net) Internet Consultant & Kids Rights Activist http://www.denninger.net My home on the net - links to everything I do! http://scubaforum.org Your UNCENSORED place to talk about DIVING! http://divegearregistration.com REGISTER DIVE GEAR TO PROTECT AGAINST THEFT >In other words, if the sensor has gone "tits up" (what a term!) and gives a >way wrong readign -- well the dive should know something is wrong because >the tank does NOT show the O2 level it is supposed to have. Uhhh and thats the reason for a calibration tank, whether it be air, 40% or pure O2 or whatever the heck is your "standard"... Somehow you've read nearly exactly the opposite of what I was trying to say...and Im too lazy right now to figure out if its me or you.... take care Blll The sensors are fuel cells. They are thus both temperature and humidity sensitive. Some sensors have temperature compensation in them, but none have humidity compensation. For best accuracy, calibrate on compressed air (which should have low humidity) and both calibrate and measure on tanks that have cooled to ambient temperature. Your O2 analyzer, if you're mixing your own gas, is a CHECK on your mixing. It is NOT a primary tool. If you PP mix you should know what's in there before you use the analyzer - you do not want a single failure to result in you taking hits off a tank full of 50% O2 at 130'! This is one of the dangers, by the way, of "stick" mixing - often no confirmatory check is done after the fill. This is extremely dangerous - if the inline sensor is out of whack and reads low, you could easily be breathing a "richer" mix than you think you are. - SignatureKarl Denninger (karl@denninger.net) Internet Consultant & Kids Rights Activist http://www.denninger.net My home on the net - links to everything I do! http://scubaforum.org Your UNCENSORED place to talk about DIVING! http://divegearregistration.com REGISTER DIVE GEAR TO PROTECT AGAINST THEFT >Any of the O2 analyzers out there will work. Some are a bit easier to use >than others. For an inexpensive one try Oxycheq's "El Cheapo". You can [quoted text clipped - 50 lines] >> >> Blll All O2 analysers are basically the same, they all comprise of a digital voltmeter attached to an oxygen sensing 'cell'. This cell will produce a voltage which is proportional to the percentage concentration of oxygen passed across it; however it is sensitive to changes in temperature and humidity. Correct calibration of the O2 analyser requires a known source of O2, usually 100%, or in actuality 99.999% (which can be treated as 100% as this is well within the tolerance accuracy for the O2 cell and the other components, especially the DVM as it is normally only .1% accurate); and a source of 100% Nitrogen or helium as the 0% scalar (inert for these purposes). There are several types of O2 cell available, from companies such as Teledyne see http://www.oxycheq.com/sensors.html, and the Oxycheq complete analysers are probably some of the most rugged and fast reacting. I built my own analyser from a design by Dave Cordes a couple of years ago with no problem. Oxycheq also do one in kit form if you fee confident. I don't rely on shop analysers, partly because I do my own Nitrox blending (own compressor & supply of 100% O2, which is also useful for calibration of O2 analyser), and partly so that I can re-check a mix a few hours later when its settled. <snip> >I don't rely on shop analysers, partly because I do my own Nitrox blending >(own compressor & supply of 100% O2, which is also useful for calibration of >O2 analyser), and partly so that I can re-check a mix a few hours later when >its settled. By "settled" do you mean once the temperature has dropped? Signaturedillon When I was a kid, I thought the angel's name was Hark and the horse's name was Bob. > By "settled" do you mean once the temperature has dropped? No, he probably means once he's rolled his tanks up and down the dock a couple times. Signature"We're going to rush the hijackers." -Jeremy Glick, aboard United Airlines flight 93, September 11, 2001 >> By "settled" do you mean once the temperature has dropped? > >No, he probably means once he's rolled his tanks up and down the dock a >couple times. That is what I feared. Signaturedillon When I was a kid, I thought the angel's name was Hark and the horse's name was Bob. > I don't rely on shop analysers, partly because I do my own Nitrox blending > (own compressor & supply of 100% O2, which is also useful for calibration > of > O2 analyser), and partly so that I can re-check a mix a few hours later > when > its settled. But once you crack the valve to analyze the mix, doesn't it get all stirred up again? >Any recommendations, warnings, issues, concerns with O2 analyzers? I've been >Nitrox certified and looking to acquire my own for all the obvious reasons. >Just curious to know and learn from others who have been in a similar >situation. Take a look at the Analox O2EII. It's a lot tougher than most. Easy to use. They were bouncing one off the floor at DEMA. About $280. Sensor life +/- 4 years. Sensor warranty 3 years. I bought one, we use one at the shop and we sell every one we get in stock. Something must be good about it :) Look at your local dive shop. Later- bj Chicago The one I hate is the O2 Stick. I've never been able to get consistent readings off the same tank, minute to minute, with one. They prompted me to get my own to take on dive boats. SignatureChuck Tribolet triblet@garlic.com http://www.almaden.ibm.com/cs/people/triblet Silicon Valley: STILL the best day job in the world. > Any recommendations, warnings, issues, concerns with O2 analyzers? I've been > Nitrox certified and looking to acquire my own for all the obvious reasons. > Just curious to know and learn from others who have been in a similar > situation. > > Thanx In Advance... >Any recommendations, warnings, issues, concerns with O2 analyzers? I've been >Nitrox certified and looking to acquire my own for all the obvious reasons. >Just curious to know and learn from others who have been in a similar >situation. Know which end of a soldering iron to hold? www.oxycheq.com El-Cheapo. Mine has been going strong for 3 years (using the Sensor Saver). --- Rich http://richlockyer.tripod.com/ >Any recommendations, warnings, issues, concerns with O2 analyzers? I've been >Nitrox certified and looking to acquire my own for all the obvious reasons. You don't need one...for all the obvious reasons. safe diving, bullshark >Any recommendations, warnings, issues, concerns with O2 analyzers? I've been >Nitrox certified and looking to acquire my own for all the obvious reasons. >Just curious to know and learn from others who have been in a similar >situation. > >Thanx In Advance... I built one - about $100, with most of the cost being the sensor ($70 or so.) The sensors are good for 2-3 years with reasonable care. It checks against 100% and air, and has been in service for a couple of years now without any problems at all. My sensor is just starting to get a bit towards the end of its useful range; I'll probably change it out this winter. -- SignatureKarl Denninger (karl@denninger.net) Internet Consultant & Kids Rights Activist http://www.denninger.net My home on the net - links to everything I do! http://scubaforum.org Your UNCENSORED place to talk about DIVING! http://www.spamcuda.net SPAM FREE mailboxes - FREE FOR A LIMITED TIME! http://genesis3.blogspot.com Musings Of A Sentient Mind |
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