Couldn't agree more, Railroader. Oddly, this seems to be a common question:
reddit. com/r/arduino/comments/sforee/measure_the_ph_a_comparison_of_the_various_mehtods/hva0ekw/?context=3
OP is there a point? I mean its a fine project but you're delusional if you think you're going to build a measurement device (that's not a tape measure), that'll never, EVER need calibration, especially for measuring ph.