Diving Nitrox and oxygen analyzer

[Jimmer]

VBD is right, they will settle over time, especially in doubles. I have gotten different readings out of each outlet on my doubles, but let them sit over night and they were right on the mix I was aiming for.

 

[ClayJar]

anyways, whatever the dynamics(maybe heat etc) ive known the % changing

I can handle it that way.

VBD is right, they will settle over time, especially in doubles. I have gotten different readings out of each outlet on my doubles, but let them sit over night and they were right on the mix I was aiming for.

I believe if you run the numbers you'd find the amount of diffusion through the manifold to be insufficient to allow significant mixing overnight, which would support the statement that the initial mixing was sufficient.

What I'd be interested in knowing is what sensors were giving these results. Also, were they calibrated with scuba air immediately prior to analyzing the mix? Obviosuly, there is some mechanism at work. The first thing that jumps out would be temperature-dependent effects in the sensor. (Some literature states that certain sensors are sensitive to temperature effects, but I have not found any specific, verifiable measurements.)

If it is a temperature-dependent effect of magnitude significant enough to throw off readings by up to several percent, it would be quite useful to know should one be working with MODs and best mix calculations.

 

[Jimmer]

The sensor was an Analox O2 EII, and we used 2 of them to confirm, and yes both were calibrated prior to use. It wasn't a significant difference between outlets, something like 1.3% but by morning both read the same.

 

[Jimmer]

Temperature could affect the sensor I suppose, but if I just calibrated it with air, turned around and checked an nitrox tank, there would be no issue, as the sensor was calibrated in the same temperature and conditions.

 

[ClayJar]

Temperature could affect the sensor I suppose, but if I just calibrated it with air, turned around and checked an nitrox tank, there would be no issue, as the sensor was calibrated in the same temperature and conditions.

I'm in over my head there. I haven't read up on the temperature dependence of oxygen sensors (or the "patented temperature compensation circuitry" involved). I'd have to study more to be able to discuss logically.

Anyway, it'd be interesting to study.

 

[jwalko]

This sort of confirmed what I thought...that it probably a good idea it have my own.

I was thinking about the El CheapoII...mainly because I like to build things and there is some satisfaction to knowing that I built it.

I probably won't be getting one before this next trip, but it will be moved to the top of my to buy list.

John

 

[Ice9]

Hmm...

Any soldering required to build the El Cheapo II?

 

[Jim Lapenta]

I've also looked at the El Cheapo and am probably going to get one since it looks like I'm going to be doing some classes with another shop after my Florida trip. That and the fact that I'm going into doubles and will be using mixes other than standard make it almost a must. Just wonder what the TSA goons would say about it. I mean a homemade black box with a battery and wires with a digital readout? I can see getting pulled out of line for a good check. I also wish they'd make a cheapo analyzer that would do He mixes since one of the classes I'll be doing is my heliotrox.

 

[ClayJar]

Any soldering required to build the El Cheapo II?

IIRC, desoldering one resistor and replacing it with the leads to the calibration knob's variable resistor is about all the soldering that's been mentioned.