Trying to calibrate a ph sensor

Hi , I am currently trying to build a Ph dosing system . I have never really written code before and thought i would give it a go . I am just trying to get the voltage reading from my ph sensor so i can properly calibrate it . I was wondering if anyone could see where i am going wrong in my code. Any help would be appreciated

Nice start. I am more of a hardware person and I would like to see a schematic showing all connections. I am not familiar with this device. I do not understand how you are reading the sensor. The documentation states it is a serial interface but I see no reference to any hardware that will perform this function in you sketch and if it is in the Library I missed it. Does the code actually compile? Also I found no defination of the messages.