Q.I have heard that "uncertainty" is needed to ensure the traceability of weighing. What is this?
A : JIS Z8103 defines uncertainty as "an assessed range in which the true value for the measured value exists." "Uncertainty" is a new scale that was formulated for unifying the assessment of the reliability of measurement data due to the lack of coherency in conventional concepts of "error" and "accuracy" in various different fields of technology and countries. For example, let's assume a weight of 100.00000 g. If we were to trace back to the source of the chain of comparisons (traceability) for the mass of a weight used for calibration, we must reach national standards. However, the mass of weights will always contain an error as long the mass "100.00000 g" of that weight is a measured value. This is why the "uncertainty" is provided. This statistically expresses the range in which the true value for measurement of "100.00000 g" really exists. If we assume that the uncertainty of this 100.00000 g is ±0.000015 g, then this would mean that the true value of this weight exists between 99.999985 to 100.000015 g with an approximate probability of 95.4%. (assuming that the coverage factor (also called "expanded uncertainty") = 2)
Furthermore, "uncertainty" is always listed in the JCSS Calibration Certificate.