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.
