Analytical balances typically have several "tolerances" that need to be addressed when you calibrate one.
Here is a sample specification set:
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Readability is the resolution of the balance. This is not a tolerance.
Repeatability is derived by making a series of measurements of the same mass at the same location on the pan.
Linearity is performed by using test weights from the minimum reading to the balance capacity.
Most analytical balances also have a tolerance for off center balance:
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Here you would take a test weight, measure it at the center of the pan, and then measure the same weight at the edge of the pan in all four quadrants.
Some labs combine all of the tolerances into an "accuracy" specification, but this is extremely poor practice.