Step-by-Step Guide for Testing Processes According to the New USP Chapter 41
To determine a balance’s operating range, Sartorius recommends one test weight of roughly half of the balance’s maximum capacity. Examples: For a 220 g analytical balance, use a 100 g weight; for a 500 g balance, use a 200 g weight. It is highly recommended NOT to use several weights to perform the repeatability test.
The measurement uncertainty of the weight must be less than ±0.03 g. It is therefore sufficient to use a class F2 weight for the tests.
The balance must be warmed up, leveled and adjusted before starting.
Set the display of the balance to zero by pressing the “Tare” key.
Position the test weight on the center of the weighing pan (if necessary open the draft shield door and close it after positioning the test weight).
When the display has stabilized, please check and write down the weight displayed.
Repeat steps 1 through 3 nine times (repeatability test).
Calculate the standard deviation of all ten measurements. Multiply by 2 and then by 1,000. The resulting weight is the starting point of the operating range of the balance.
Use the first measurement of the repeatability test for the accuracy test. The difference between the displayed and the actual weight of the test weight must not be greater than ± 0.10%. For example, if the test weight is 100 g, the weight displayed must be between 99.9000 and 100.1000 g. If this is the case, the balance meets the USP accuracy requirement.