Some balances are equipped with internal motorized calibration function for an easy calibration by one touch. Internal calibration can be even easier if the balance is equipped with the isoCAL feature, where internal calibration will be launched automatically when environmental conditions change. This feature is very convenient to have in a micro, semi-micro, analytical or precision balance. Depending on the balance readability, usually for 4-, 5-, 6- and 7-digit balances it is launched every four hours, for lower resolution balances it is every six hours. However, time to time, external calibration is recommended as well. External calibration required more effort on the balance user. In case the calibration may need to be traceable for ISO purposes or to meet other requirement, certified weight should be used to calibrate the balance. A traceable calibration can be done through service from the balance manufacturers (calibration certification), or it can be done by the balance owner if they buy a certified weight which will be used in the calibration process.