Reproducibility: A Major Source of Uncertainty in Weighing

Balance confirmation tests usually include eccentricity, linearity, and repeatability. The latter is a measure of the random variability of the instrument. Further, repeatability is usually based on 10 consecutive measurements of a mass standard in a short period of time. The test results are used to verify the balance performs within manufacturer's specifications. These test results are often used in calculating an estimate of the uncertainty in measurements made with the balance. Uncertainty estimates, used to quantify the quality of measurements, must accurately estimate the magnitude of these errors. Does the repeatability test provide a realistic estimate of the random variation in the weighing process? The authors had concerns that it may not. The reproducibility estimate of the balance needs to be determined for the variables that will change between measurements of the same material while the other parameters are held constant by procedures and training