My own O2/CO analyzer

[HeXx]

As in another discussion about Undepleatable oxygen sensors I think it would be more appropriate to continue the topic here.
Previous posts on this thread: Thread

So I finally got to order some parts for my first prototype.
A bit different from the initial project but I can start simpler and then work my way up.
The first prototype will be with a simple galvanic cell. on/off switch and cal/extended functionality button.
Micro USB rechargeable battery and user replaceable (LiPo)
In its basic functionality, it will be able to measure PPo2 based in its last calibration parameters and show MOD for 1.4 and 1.6 PPo2.
Entering extended mode, by pressing the button while turning on activates communication with a phone via WiFi (APP).
In extended mode you can do a single step (air) calibration with parameters of temperature, RH, and pressure to account for calibration at altitude.
Will also be possible to do a two point calibration where you can set the second point to calibrate with a known oxygen mixture between 50 and 99.9%.
Lastly, it will be possible to measure presence of CO in the gas under test (minimum 10ppm, value might be lower after testing and tuning)

Ideas and suggestions are welcome.

Cheers

 

[JohnN]

Given the lack of any hard science behind maximum PPO2/MOD or what is a “safe” dive profile, isn’t factoring in temperature, RH, and altitude a bit like “measuring with a micrometer, marking with chalk, and cutting with an axe”?

 

[GJC]

This is specifically for the Analox O2EII sensor. I suspect that a galvanic sensor may have a different table.

 

[GJC]

You eliminate the humidity factor if you calibrate your sensor using a tank filled with air. Tank air should have almost all humidity removed when filled (from most shops but maybe not all).

 

[kelemvor]

I'd consider a different CO sensor. 10 is really high, the sensor in my tester works between 0 and 20ppm and reports in units of 1ppm. The one time I got a contaminated fill, it was only registering 1ppm.

A sensor whose low range starts at 10ppm would be good for monitoring room air when you travel. I want much earlier detection for scuba since I will be breathing that gas at more than one atmosphere.

 

[Subcooled]

The first prototype will be with a simple galvanic cell.
[...]
Lastly, it will be possible to measure presence of CO in the gas under test

Interesting. It would combine two devices, then.
Can you detect and measure CO2 accurately and reliably in a humid environment, too? It would be great!!!

 

[HeXx]

Hello.
I have been busy for the last few months and haven't had the opportunity to give feedback on my project.
Today I finished my 2nd prototype of the simplest type of analyser, plain O2 with measurement with given mod at ppO2 of 1.4 and 1.6.
It is a simple but apparently reliable analyser and tested accurately to 40% O2 comparing with measurement made with a "commercial" analyser.
Tomorrow I will be testing with 100% O2.
In the meantime here are some photos.

Display and software to still be tweaked but suggestions are always appreciated.

Cheers

 

[Alurpal]

What is the tank valve mating surface made of? I was thinking of 3d printing one with TPU if I get around to building an analyzer.

 

[HeXx]

What is the tank valve mating surface made of? I was thinking of 3d printing one with TPU if I get around to building an analyzer.

PLA as the rest of the case. You can see it in the first picture. I printed it in white because it was the filament I had

 

[HeXx]

Just another update.
Measure of 100% oxygen successful.

Cheers