Many modern electronic scales offer the user a choice of calibration weights. For instance a 100.g capacity scale may allow the user to select either a 100.g calibration weight or a 50 gram calibration weight, a 200.g capacity scale might allow 3 different weights, such as 50.g, 100.g, or 200g. In almost all instances the calibration weight that equals the full scale capacity of the scale will produce the best calibration.

There are scales that have internal calibration weights and calibrate themselves in accordance with algorithms in their software, usually by detecting temperature changes and/or the passage of time. The internal calibration weights are held to the same tight tolerances as external calibration weights, and their exact weight, which need not be a round number, is fed into the scale’s memory for use in calibration. These scales provide high level accuracy on a continuous basis. While these scales do not require calibration they should be checked periodically to see that nothing has failed and that they are indeed calibrated.

Calibration weights require special handling and should be stored carefully. The use of lint free white gloves when handling these weights will keep them free of fingerprints. They should be stored in a container that prevents dust from settling on them. Static electricity can be another problem and result in clinging particulate. The documentation that verifies the calibration weights traceability to certified standards should be stored carefully, and many people store the paperwork with the weight.

It is far more sensible to calibrate the scale more often than may be required, but to have the peace of mind of knowing that that a great deal of work, effort, and time are not going to be lost because the results are distorted by an out of calibration scale. Be sure to calibrate the scale when it is in a stable state (has been turned on long enough, sitting in a stable environment long enough, and not been moved recently).