o2 meters

[blacknet]

Hello,

Since there's no computer/meter forum I felt this forum would work.

I am curious as to which o2 meter everyone is using for nitrox/etc. What is the good/bad things you like that that meter?

Personaly I have the analox mini o2 DII meter. I can calibrate it easily and no hookup and instantly reads the levels.

Ed

 

[roakey]

You can build one for about half, if not more than you can buy one for. The greatest inaccuracy you'll encounter is in the sensor itself, so the DIY meters are just as accurate as the ones you can buy. There's even an argument that DIY meters are more accurate for Nitrox than commerically available units. The argument goes like this: Because of liability, most commercial analyzers use a medical rather than a industrial sensor. Catch is, medical sensors are more accurate near 100% O2 (where they're called upon to measure the most), whereas industrial sensors are more accurate mid range, where our Nitrox and Trimix lies.

To specifically answer your question, a DIY with a DMD-3500 panel meter, some Radio Shack parts and a MaxTec MAX-250E, soon to be Teledyne R-17D (36 month, 6 second response sensor).

Here's a cut-and-past of some mail I sent off to a friend just a few days ago...

================================

"The Oxygen Hacker's Companion" Everything about O2, how to get it, grades, cleaning and building analyzers. "The Divelight Companion" how to build canister lights, where to find parts, etc. "SCUBA Regulator Maintenance and Repair" home repair and maintenance of your regulators. And for the adventuresome, "Improvised and Low Cost HP Gas Boosters." how to build a Haskel. Well, not quite, but some interesting stuff nevertheless.

http://www.airspeedpress.com/

Spend some time on this page, especially the links section, there's some great stuff. One warning about the Divelight Companion: I don't know why but it's filled with typos. Hopefully they've fixed many of them, but the book I have is almost painful to read. Quite different from the O2 Hackers. However, the information is accurate.

More O2 analyzer information:

http://oxycheq.com/
http://users.erols.com/bee2/O2Meter/text.htm

Great DIY page, click on the tools link for more O2 analyzer plans (spend some time checking out this page, too):

http://www.cisatlantic.com/trimix/

Sources for sensors and analyzer information:

http://oxycheq.com/
http://www.maxtecinc.com/
http://www.oxygenanalyzer.com/

Roak

 

[The Chairman]

An old oxy meter being disposed of by the Chemistry dept... does not give me a decimal point, but I can't put a decimal point in my Cobra anyway. I go to Oxycheq.com for my sensors. IF I had to do it all over again, I think I would try this one out...

http://oxycheq.com/Expedition_nn4.html

 

[SDAnderson]

Just put together an El Cheapo II from OxyCheq. Took a couple of hours and minimal tools/skills. If you've never soldered anything electronic, I wouldn't try it, but if you have a long and inglorius history as a geek, you'll probably enjoy it like I did. They'll also sell you one that's already assembled for twice the price. Still cheaper than most off the shelf models.

Couple of friends have them and they work well. The key to all of these toys is the sensor and there just isn't much difference from one to another.

Steven

 

[blacknet]

NetDoc,

Interesting. That photo is the identical layout to my DII. I wonder if it IS the same meter but packaged for another company.

FYI, here's the link for my meter. http://www.analox.net/pages/products/miniO2DII.html
Ed

 

[The Chairman]

Through them thar gloves... The oxycheq picture is pretty clear, and since you own one, you should know! For $190, it makes me think I will let my old used meter sit as a backup and go with the Oxygheq Expedition... BTW, Patrick Duffy of Oxycheq is a member of the SCUBABoard...

 

[blacknet]

Hello,

My analox DII is very nice. No hookups to the bottle at all. Does both din AND yoke with no seperate attachments. Air loss is something like 5 psi (that's just a guestimate as it's very difficult to measure that small amount). Can use the baggie method and save even more gas.

Some meters I looked at takes about 2+ mins for it to 'level' with an accurate reading. This meter take something like 4-5 seconds to level.

Ed

 

[Patrick]

Just to clarify some info, not all sensors are the same. Some are faster than others and some are more stable over their lifespan.

The stuff about using an industrial sensor for mix and medical for nitrox (or whatever) is not accurate.

There are minor differences between a medical, industrial and diving (rebreather) sensors. They can all be used in analyzers for what a diver needs them for. The differences are very minor, but sometimes needed (or wise) depending on the application. A sensor is basically a battery that produces mv output when exposed to oxygen. The higher the O2 percent, the higher the mv output. When you calibrate your analyzer to air, and then expose it to a higher percentage of oxygen (nitrox), your analyzer reads a higher number and that is the result of the increased mv output of the sensor. The hard part of building a sensor is consistency.

The Expedition looks very similar to the Analox, but it is smaller, and gas is measured the same way. It really ends there. The Expedition has a gasket sealed panel meter, the Analox uses silicone. The Expedition has a different circuit using a low mv sensor, where the Analox uses a high output sensor. Low output sensors are not as expensive and from my experience, seem to last longer. The Expedition has an on/off/on with backlight, the Analox does not. The Expedition has a much nicer (and smaller) carrying case. When you open the back of the Expedition, the back is completely separated from the front half of the case. The Analox has wires connecting the back to the front. The Expedition uses 3 AAA batteries that will last twice as long as a 9v. The Expedition's sensor is threaded into the case and has an o-ring seal. The Analox uses a "proprietary" stovepipe connector and has foam on the bottom of the sensor to protect the board from being smashed into the bottom of the case (this was a trade off to have a proprietary sensor in an attempt to force you into buying replacement sensors only from them). Not too cool if you ask me. They are upset with OxyCheq for figuring out a method to use another sensor. We noticed that on the older Analox analyzers the SS bolts began to get some rust stains. This was likley due to getting the analyzer wet and putting it in the box (the water pooled up in the head of the bolts). We put our bolts on the bottom. There are a few other items, but I think I mentioned enough that you can see there is a big difference between the two.

The Expedition was on sale for $190, but is no longer. Dealers do not like it when I have a web site offering the units less than they sell them.

However, I will always try to take good care of past customers and friends of OxyCheq.

Even though the Expedition has only been out for two weeks, it is already 1/2 done with the NOAA approval/testing (which is expected) and the USN approval will follow shortly thereafter.

I know I have already mentioned some of the info above, but I figure if I say it enough, you guys might be able to say it for me.

Regards,

Patrick
--
OxyCheq ... the diver's source for oxygen analyzers and oxygen sensors
http://oxycheq.com

 

[blacknet]

Patrick,

First let me say welcome to the board!

It is always nice to see someone post some very thoughtful and informative. I was going to call the company and ask but never made it yet.

I assume you have some ties with the company right?

Ed

 

[roakey]

Thanks for joining us Patrick.

I couched the medical-vs.-industrial sensor statement carefully since the data I had heard was inconclusive; thanks for the information.

However, I am unclear if you're saying that for mid-range accuracy that commercial units use industrial grade sensors or that they do use a medical grade sensor and they're just as accurate as industrial sensors in the mid-range?

Back when I built my analyzer the CAG-250E from Ceramatec (now Maxtec) was the hot ticket. Back then they had a medical 250 and an industrial 250 and all the recommendations floating about the web were for the industrial sensor.

Nowadays Maxtec has a MAX-250E (industrial) and a MAX-13-250 (medical). I know this isn't a product you carry, but do you know what the difference is? Are the two products simply binned and if so, on what basis?

Sorry about all the questions, I’ve had these floating around in my head for awhile!

Roak

Ps. After all this Maxtec talk, to make you feel better, my latest sensor is the Teledyne R-17D