How often do I recalibrate
No hard and fast answer can be given to this question. Like cleaning, the frequency at which pH electrodes should be calibrated can be determined only by experience.
However, the rule of thumb has proven itself in practice:
When working with new media, it is advisable to re-calibrate the sensor as often as possible. If no significant variation in value is found, the calibration interval can be correspondingly increased e.g. weekly.