USP General Chapter <41> Weights and Balance states a weighing device providing accurate weighing
for assay and test is to have MU of less than 0.1% of the reading and gives an example of 50 mg ± 50 :g as
acceptable. To qualify MU of a balance, an appropriate National Institute of Standards & Technology (NIST)
traceable weight within the weighing range of the balance is weighed 10 times or more. The resulting weights
are calculated so that three times the calculated standard deviation divided by the amount weighed should be
less than 0.001.
For different balance class designations and detailed information on weights and balance, the USP General
Chapter <41> is to be consulted.
