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This article provides best practice to avoid errors in weighing by difference caused by buoyancy and drift.
Weighing samples and standards is a fundamental analytical operation. It is such a familiar laboratory operation, usually digitally displayed and captured, that one tends to intuitively believe that the numbers from balances are error free, or at least have such a small uncertainty that any errors will be negligible. On many occasions, this may well be true but not always. Modern electronic balances rely on a load cell. As force is applied to the loadcell or transducer by calibrated masses, the response is measured. The responses from the loadcell are transformed into a mass calibration function supported by digital averaging, smoothing, and rounding firmware, which leads to the displayed mass on the balance. The purpose of this article is to look at the uncertainties in terms of their source, and provide one best practice to avoid errors in weighing by difference caused by buoyancy and drift.
Chris Burgess is managing director, Burgess Analytical Consultancy Limited, Barnard Castle, Co Durham, UK.
Volume 46, Number 5
When referring to this article, please cite it as C. Burgess, "Weighing Isn’t an Uncertain Process, Is It?," Pharmaceutical Technology 46 (5) (2022).