Building an O2 analyzer, anyone else need?

[guruboy]

I would like to see a picture of one completed unit to see how it looks and have you report that it actually works before I buy a kit and have it sent to you. Is that reasonable?

I don't know that I could make a CO sensor for much cheaper than the one linked in another thread, especially for that level of build quality. Definitely on my list of things to probably maybe do...

I'm sure others on this board have El Cheapo already so I would be interested in seeing/hearing from them. Otherwise, I'll let you know once I get mine.

FWIW, I have a MSEE degree and I design and build circuit boards for a living. The hardest part for me is probably any cutting that has to be done to the plastic housing.

But I also have access to a full soldering bench at work, so that probably helps.

 

[Tortuga68]

The 10 turn pot will give you MUCH better resolution

It doesn't change the resolution, it decreases sensitivity

As far as rounding up goes, since you're rounding the oxygen you're effectively rounding down the N2, which is why people are saying it's a bad idea

 

[NAM001]

I have been giving this rounding thing a lot of thought , and i think it has become a moot issue.

table divers... 45 avg depth and a boune to 52 ft for total time 33 min. you use the table as if it were 60 ft for 40 min.You get a double whammy on cutting ther ndl in the direction of safety. If you hit ndl and go into deco you are actually not even into deco time. To further ssave us we do a 3 min stop at 20 ft. (safety stop) The nitrox tables are the same because the mechanics of them are the same. So that if you did this profile on n32, the only difference would be the time to ndl being longer. Still your table time cuts you off early like before.

Enter the cmoputer... There are so many variables here but for sake of discussion the computer does one of 3 things.

1. Gives honest data. Probably the more technical computers sherewater ect. not many use them as far as this issue goes. ( tech vs rec diving)
2. The computer pads all the input info ( rounds up the depth and time ) for the most conservative NDL calculations. No problem NDL alarm goes off and you are truely not yet in deco.
3. The computer calculates an honest ndl and has the alarm padded togo off x minutes early and says deco when you are not. Once again you are not truly in deco.

There is little difference in the calculated depths/times ect because of the issue of dangerous rounding up or down because of FO2. Far greater errors in safetys behalf are already occuring.

Once hitting NDL and 30 ft'/min accent occurs you will clear any deco obligations before you hit the safety stop depth

It is possible that somewhere a newby rev diver is packing double heiser 4500psi 160 cuft tanks. But it is not probable and to be honest i would like to see the diver that can physically carry such a rig.


So it still seems reasonable to proceed with the notion that if you are not at MOD then NDL is the controlling factor. If at or past MOD toxisity would be formost controlling.

One thing for sure is that the computer (BY DESIGN) will always compute with errors in the direction of safety/ liability exposure such that round up found down should become a moot issue.

In short computer programmers have already taken into account the possibility of FO2's being rounded up. In the world of rec diving all training is set up to prevent us from the conditions that these FINE points of rounding would be of consecuence to us. Its cool to have the car that can do 180, but on main street you can only drive 25.

 

[PfcAJ]

1% left or right of the actual value does not matter at all (for oxygen or nitrogen). These analyzers aren't precise enough to even worry about 1%.

 

[NAM001]

I believe that is correct, Any problem with such an error woill be built into the computer to correct for the the worst case scnerio.

1% left or right of the actual value does not matter at all (for oxygen or nitrogen). These analyzers aren't precise enough to even worry about 1%.

 

[charlesml3]

I have called it for 20.9 set it down on a table, taken a sample and after sampling find that setting it down it then read 21.2.

OK, but so what? You'd still set your computer for 21% anyway.

1% left or right of the actual value does not matter at all (for oxygen or nitrogen). These analyzers aren't precise enough to even worry about 1%.

That's exactly right. Most of you are stressing over a .2% difference in an analyzer reading. You're making WAY to big a deal out of this.

On a liveaboard I'll buy the "Nitrox for the week" option where they pump 32%. Any tank that's 31 to 33% is 32. I set the computer at 32 and leave it. A 1% difference is irrelevant.

-Charles

 

[guruboy]

So back to the OP, I plan to place an order this weekend.

If anyone is interested, please PM me for details. Thanks.

 

[guruboy]

Last call for anyone else that wants to get in on this build.

Will post pics later after I get the first batch ordered and built.