Research On Evaluation Of Uncertainty In Measurement And Its Application In Mechanical Measurement

With the development of social market economy and science technology, the importance of metrological verification/calibration is increasing. The laboratory approved by the National Laboratory can be engaged in measurement calibration and detection in corresponding professional field. According to the requirement of metrological verification, the uncertainty evaluation has its corresponding regulations. The acreditatin criteria of national laboratory ISO/IEC17025:2005sets:the laboratory must evaluate the uncertainty of test items.Some physical parameters such as mass、force value、torsion、rigidity、pressure and impact are included in mechanical measurement.The uncertainty evaluation of mechanical measurement project is the reference of the calibration,《Guide to the Expression of Uncertainty in Measurement)) provides quantized index and basis for its assessment. The paper introduces the assessment of uncertainty in mechanical measurement. During the calibration process, in order to evaluate the indication error’s uncertainty of the associated equipment in the calibration laboratory of Zhoushan Institute of Calibration and Testing for Quality and Technology Supervision, for instance:material tester、torque spanner、hydraulic jack、rockwell apparatus、fuel dispenser, experiments are designed, and then build mathematical model, analyse the origin of uncertainty. Afterwards, the uncertainty components are evaluated from type A and type B evaluation. Based on each uncertainty component, combined standard uncertainty can be confirmed, then expanded uncertainty. Finally, the uncertainty report is given.Via the theoretical and experimental study of the uncertainty of measurement, some confusable measurement concepts are explicit. It also resolves the rectification of uncertainty ENOB (Effective Number of Bits) and standardization of its presentation. In the assessment of B type uncertainty, the estimate of DOF (Degree of Freedom) and the confirm of coverage factor are deeply discussed. It analyzes the dangers during the uncertainty evaluation for some neglectful factors. The achievements can be widely used in practical work, and provide reference for the research of uncertainty evaluation in the following mechanical measurement. It also has actual guiding significance of uncertainty evaluation for mechanical measurement calibration laboratory in our institute.