How often does the AquaSensor need to be calibrated?

The AquaSensor is calibrated at the factory but can also be recalculated at the customer's site. When calibrating the AquaSensor, it has to be brought into contact with a known level of saturation (saturation level standard) and the displayed value compared to the known one. We recommend calibrating the AquaSensor at least once a year. 
The available HYDAC AS Calibration and Adjustment Set (stock no. 3122629) is supplied with two saturation levels standards (11.3% and 75.5%).