It is possible for the calibration on a balance to drift, that is no longer read accurately. All balances can do this, it is not a reflection on the quality of the balance. When the calibration on a balance does drift you have to have some way to correct it (make it accurate again). There are 3 methods.
External Calibration
This requires the use of a use of an external calibration weight – this must be certified. Once the calibration routine has been activated the balance it will request the external calibration weight be put on the pan. The balance will then compare the reading of the balance against the known value of the weight – if the balance reading differs from the weight it will adjust to match the weight.
Internal Calibration
This performs the same function as external calibration except an external weight is not required. The weight used to adjust the balance is built into the balance itself. When the user wishes to adjust the calibration they simply press a button on the key pad, this activates an internal motor which lowers the internal weight onto the weighing mechanism. When the adjustment is complete the weight is returned to its parked position in the balance. This is a recommended feature, which we suggest is activated before each sequence of weighings.
Automatic Calibration
This is the same as internal calibration but with one key enhancement. If the balance detects a change in temperature or after a certain amount of time elapses (both key factors that can cause drift) the balance will automatically activate the internal calibration. The internal calibration can also be activated manually.
