Comparison of the linear and non linear methods for the evaluation of measurement uncertainty

The main method recognized by the metrologists for the evaluation of measurement uncertainty is de facto the Guide to the Expression of Uncertainty in Measurement (ISO Guide). Due to some limitations of the proposed method by ISO Guide however, ISO has developed a supplementary method for evaluating the measurement uncertainty based on the propagation of probability density functions using the Monte Carlo method (ISO-S1). The present paper discusses these methods for the quantification of measurement uncertainty. We review the literature, in particular the main papers presenting these modern approaches. We also discuss the merits and the limitations of the ISO Guide and ISO-S1 approaches. Furthermore, a comparative study between these two methods was carried out in two case studies. The obtained results show that it is necessary to evaluate the influence of the degree of non linearity in order to estimate the measurement uncertainty before either method is chosen.