Establishment Of Measurement Standard For AC/DC Digital Instruments And Evaluation Of Uncertainty In Calibration Results

National Metrology Department has issued the latest edition of technical wood standards for assessment of measurement standards and evaluation and expression of uncertainty in recent years,and has replaced them with the calibration standards of digital multimeter and multi-functional standard source.For the long-term use of the verification rules,the construction of standards and calibration work put forward higher requirements.At present,the research data about the calibration equipment of AC and DC digital instrument are basically compiled and evaluated according to the old edition.There confusion and divergence,which can not meet the requirements of new edition.Therefore,it is necessary to study the evaluation method of the uncertainty of the calibration standard and the calibration results according to the latest requirements,so that the calibration of AC and DC ditigal instruments is not accurate.It is of great practical significance and use value to unify and standardize the method of rating evaluation.This paper takes the newly-built calibration device of digital multimeter as the research object,applies the latest promulgation off JJF1033-2016 Examination Specification of Measuremet Standards,JJF1587-2016 Calibration Specification of Digital Multimeter,JJF1638-2017 Calibration Specification of Multifunctional Standard Sources and JJF 1059.1-2012 Evaluation and Expression of Uncertainty in Measurement and so on,based on the Metrology Management,Metrology and measurement uncertainty theory,this paper analyses and studies the process of establishing standard and the evaluation method of measurement uncertainty.From the aspects of scheme design,working principle analysis,stability assessment,repeatability test and uncertainty evaluation and verification of calibration results of digital multimeter calibration device,it expounds how to apply the new version of measurement technical specifications to establish the design.The source of uncertainty component and the general method an process of uncertainty evaluation in calibrating ditigal multimeter are summarized.At the same time,it is recognized that the relevant measurement technical specifications are only the general rules and basic requirement of all metrology specialties,and there are some deficiencies that need to be perfected and supplemented inpractical application.In view of these deficiencies,and combined with the author's actual work,the corresponding solutions are given,mainly follows:the design flow chart of the configuration scheme of metrology standards is proposed,which solves the problem of how to select and select standards.The result of the nuclear analysis shows that the technical index of the verification standard in the stability assessment should be equal to or higher than that of the assessed standard.Through analysis and verification,it is proposed that the uncertainty component of the higher-level measuremet standard should include the influence of the higher-level measurement standard when the value is tansferred.Finally,the application of degree of freedom,coverage fator selection,resolution and repeatability,as well as the choice of sources of uncertainty,which are closely related to uncertainty,are discussed and explained,and the ambiguity in understanding is eliminated.It makes the establishment of standards and evaluation of uncertainty more standardize and complete,facilitates the exchange and comparision of calibration results,and achieves the purpose of correctly using the new version of measurement technical specifications.The method used in this paper has certain reference value and Enlightenment for establishment of standards and the evaluation of uncertainty of other similar metrological standards.