Semi-DIY O2 and CO analyzer

[rmssetc]

I'm convinced of the benefit of analyzing tanks for O2 percentage and presence of CO (carbon monoxide).

I was a kickstarter supporter of Cootwo, and still think it was a great concept and form factor. I was unhappy with the lack (and tone) of support from Divenav in the past. On my last dive trip I found that my Cootwo was giving really wonky readings (O2 randomly off by 5~10%, despite having a good sensor, recent calibration, etc) and the CO sensor was due for replacement/calibration. With Divenav out of business (or at least, out of the business of hardware products -- maybe they still have a presence with their apps), I began looking for alternatives.

I decided to use off-the-shelf O2 and CO devices, packaging them to use the same gas supply in order to simultaneously analyze for both gases. There are a couple of great threads on true DIY builds for an analyzer ( Nitrox/Trimix & CO analyzer and DIY Touch Screen Trimix Analyser), and either of those would probably be a better solution than my hack, but that's never stopped me before from building my own Frankenstein.

My solution was to add a way to reduce the gas pressure and flow. Here's the finished product, which I'm calling Frankenstein Ugly Carbon-monoxide Kit & Oxygen Reader, but I may need to change the acronym for marketing purposes:

The Frankenstein Ugly Carbon-monoxide Kit & Oxygen Reader has now evolved to MarkII, with the Forensics Detector CO sensor and nicer packaging inside an old mask box. I chose the Carbon Monoxide Super-Meter model because it reads at 0.1PPM -- not that I'm concerned about the significant digits, but because I want a detector that will be (more) accurate <10PPM, which is about the initial trigger for many (lower cost) models meant for industrial/environmental use.