Even making your own sensors, the oxygen meter still costs a pretty penny so usually we only have one, and we've only invested in the single channel unit, again because of costs. The challenge arises when you want to use a single meter, but measure using several sensors or several sensor spots. The measurement software is only able to hold one calibration at a time, but you really need to have a calibration for each sensor as they tend to be slightly different depending on their age, the amount of use they've gotten, etc. Entering new calibration values every time you switch sensors is not feasible when you're trying to measure from multiple respirometers at the same time.
Even then its a rather tedious process to convert phase to % saturation you have many 100's of measurements and so I wrote quick R function to convert the phase and temperature into % oxygen saturation (shown below). The function is written from an old Excel file that Presens nicely sent me many years ago when I first started using their products. Using the Excel sheet was rather slow, however, so I converted it to this R function (also available here on Github).