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According to:

  • “Expression of the Uncertainty of Measurement in Calibration” (EA-4/02),
  • “Guide to the Expression of Uncertainty in Measurement” (BIPM, IEC, IFCC, ISO, IUPAC, IUPAP, OIML),

the statement of the result of a measurement is complete only if it contains both the value attributed to the measurand and the uncertainty of measurement associated with that value.

The uncertainty of measurement is a parameter, associated with the result of a measurement, that characterises the dispersion of the values that could reasonably be attributed to the measurand.

The measurands are the particular quantities subject to measurement, in calibration or in testing. Each measurand or output quantity Y depends upon a number of input quantities Xi (i = 1, 2 ,. . ., N) according to the functional relationship: Y = f(X1,X2, ...,XN)

The model function “f” is in most cases an analytical expression, but it may also be a group of such expressions which include corrections that cannot be written down as one function explicitly.

The uncertainty of measurement associated with the input estimates is evaluated according to either:

  • Type A evaluation of standard uncertainty, i. e. the method of evaluating the uncertainty by the statistical analysis of a series of observations,
  • Type B evaluation of standard uncertainty, i. e. the method of evaluating the uncertainty by means other than the statistical analysis of a series of observations; in this case the evaluation of the standard uncertainty is based on some other scientific knowledge.

CEQMAS provides solutions for both Types of evaluation.

The "cequnc" software performs automatically the Type B evaluation of uncertainty of measurement in a variety of applications for Testing and Calibration. Operating in the Excel environment, it approaches the 2nd order evaluation. The case here reported relates to the Example "1" in Guide to the Expression of Uncertainty in Measurement.