Accuracy of use
Since the calibration of a balance represents a snapshot in time, a statement must be made about how the measuring instrument behaves in use at the place of use and to what extent the measurement uncertainty changes. This is because the measurement uncertainty increases due to various influences during daily use of a balance. These influences must be recorded and classified.
...and this is how it works:
Assuming the same environmental conditions (e.g. draughts, vibrations, etc.) as those prevailing at the time of calibration at the scale's installation site and estimated room temperature fluctuations of X Kelvin (°C) with a temperature coefficient (X•10-6 / K) assigned to the scale, a certain accuracy of use is obtained. This accuracy of use is determined in accordance with EURAMET cg-18.
