Those who are divers and have at least a Nitrox certification will know the value of analysing the gas you will be breathing (and there are many, myself included, who would argue that ALL divers should know about this). For diving shallower than about 40 metres all that is generally needed is to check the oxygen content. But, for deeper dives helium is often added to reduce the density of the gas and reduce nitrogen narcosis - this is then known as Trimix.

Gas analysers that measure helium as well as oxygen tend to cost well over £500 which is fine if that’s what it needs to be (this is safety critical stuff). But, on the way back from a dive show I was chatting with some friends about what it would take to do something as accurate and reliable, but at a LOT lower cost that might mean more people would be able to have one. On some very back of envelope thinking we thought we could get to something like £150. That this isn’t quite like for like since if I buy an analyser I am paying for CE type certifications, sales tax, their support, and the lack of hassle. And, I’ll probably spend more designing, testing and making one than it would cost me to just buy it, even before I allow for my time … but where’s the fun in just buying stuff! So this repository is to hold the thinking and supporting designs / code for an open source trimix analyser.

ABSOLUTELY NO WARRENTY IS GIVEN TO ANY PART OF THE MATERIAL HERE, OR ANY DEVICE MADE USING IT

Well, the thought experiment so far feels like enough to make it worth a bit of playing. The helium side is the key, so the next step is probably to get hold of some thermal pelistors and ultrasonic transmitters/receivers, and have a test-bench play