European and international standards for statements of uncertainty

To make measurements comparable it is necessary to state the quality of a measurement in terms of the uncertainty of measurement. The ISO-BIPM ´Guide to the expression of uncertainty in measurement´, usually referred to as the GUIDE or the GUM, was published in 1993 and proposed a unifying method for evaluating and stating measurement uncertainties. This method is accepted by nearly all calibration services in the world and has become a quasi-standard in the field of metrology. This paper describes the fundamental aspects of the method, which also has entered the EAL-R2 requirement document edited by the European co-operation for Accreditation of Laboratories