DIY-ing O₂ analyzer is one of the simplest project you can do, for those of you who’s electronically literate will understand this after taking a look at a sensor’s data sheet. While when we mentioned this to other divers, they’ll say, “you’re making your own analyzer? You’ll die.”
So, I’ll split this into 2 parts. First is this post, I’ll basically just explaining data sheet and how the sensor operates. And I’ll go into the actual build, BOM, source code, etc. in part two. I’ll use my own sensor as an example, it is the cheapest one that checks all the boxes for it to be scuba oxygen analyzer. Let me know if you found anything cheaper 😜
Pictured above is the technical specs from the sensor data sheet. From the data sheet we know that if you expose the sensor to gas, it’ll spit out mV out of the other end. With the only caveat it being in the most ideal conditions, hence the calibration button. As mentioned in there, the numbers will drift over time, and humidity will affect the numbers too.
Let’s use the pic above as example, We know “air” is 20.9% oxygen, so 9mV = 20.9% we use this as the baseline, the calibration value if you will. From that, if we were to expose the sensor to EAN32, it’ll spit out 13.8 mV. 13.8 / 9 * 20.9 = 32.05
That’s it! All you really need is a millivoltmeter really, and you can math it out. But ideally, you’d want a screen that display the actual oxygen percentage to simplify a lot of things. As mentioned, I’ll get into the how to in part 2.