Why do we need to calibrate a pH probe?

All pH electrodes cannot be produced with identical characteristics. This difference between the theoretical and actual behaviour of a pH probe must be compensated for. A calibration is required to match the pH meter to the current characteristics of the pH probe. These characteristics constantly change throughout a pH probe's life, so, Bluelab recommends calibrating every 30 days. However, the more a pH probe ages, the more frequent a calibration will be required.