Calibration is an important step in keeping your equipment functioning properly. We recommend using at least two points of calibration on a monthly basis to allow the sensors to provide the most accurate reading possible. Using 4.01 and 7.01 single use packets achieves this calibration process. It is helpful to order enough packets to get through 6 months of calibration. Calibration packets can be stored in a cool dry area for up to 1 year.