Reviving a 3-month old thread here, figured I'd mention that I am making my own Oxygen analyzer to analyze my Nitrox fills at home using an Arduino Uno. Basically, I'm just replacing the digital meter in most of the DIY O2 sensor schematics with an Arduino that writes to a fancier display. The Arduino will read the O2 sensor about 10 times, average the results to increase accuracy, then write the Oxygen concentration that it just measured to a nice looking display that I'll stick on the wall.
Arduino isn't programmed (by the user) in C. It's programmed it in a higher-level language, called ArduinoC. ArduinoC is C-based, and will most certainly help make the transition to C when you're bored with Arduino. C is can be used to program "real" microcontrollers, such as made by Atmel, and do things extremely quickly and efficiently as opposed to the limited capabilities of Arduino. However, the Arduino platform is still very powerful.
As an example, an Arduino could easily measure the real-time tank temperature during partial-pressure blending, to provide a real-time correction factor for Oxygen pressure when the tank being filled gets warm. This way, the person blending needn't wait for the tank to cool off to know exactly how many PSI of air to top the tank off with, to get to exactly EAN36 or whatever.
After filling the scuba tank 95% of the way, the Arduino could calculate the difference between the ACTUAL tank O2 concentration, and the TARGET O2 concentration, AT temperature. It could then instruct a proportional valve to let "X" flowrate of air in for "Y" time period to get to "Z" target O2 concentration.
For most people this isn't necessary, but if you are in the business of making filling stations...
Microcontrollers will change your World if you let them.
For the O2 analyzer, the code should be extremely simple. I'll be using one of the on-chip Analog to Digital Converters (ADC's) to read the amplified O2 sensor output voltage, digitize it, then write to the display. I might write a little calibration routine in there.