The National Institute of Metrology, China (NIM) is the nation’s highest research facility of measurement science and legal metrology technical agency. Its responsibilities are to study, formulate, keep, maintain and utilize the national primary standards and measurement standards of various measurement units; carry out dissemination of the value of quantity, verification, calibration and testing, and ensure the traceability of Chinese quantity values. NIM represents China to take part in international comparisons of quantity values, ensuring its international comparability and uniformity. It also undertakes the formulation of metrological technical regulations, type evaluation of domestic and imported measuring instruments, metrological arbitration of import and export trade and examination of measurement standards, etc. Measuring and testing technologies are studied to solve fundamental and common technical problems faced by enterprises in measurement and testing practice, thereby improving the product quality and international competence of Chinese enterprises.
The Mass Laboratory and the Force and Torque Laboratory affiliated to the Division of Mechanics and Acoustics Metrology under NIM are internal laboratories of the OIML Issuing Authority, China. Since 1999, China has signed mutual recognition agreements on type evaluation test reports of “non-automatic weighing instruments” (NAWI), “automatic weighing instruments” (AWI) and “load cells” with NMi in the Netherlands, PTB in Germany, NMO in the United Kingdom and METAS in Switzerland successively, with the Mass Laboratory and the Force and Torque Laboratory jointly participating in these agreements as laboratories appointed by the Chinese party. In addition, these two laboratories used to engage in the certificate system of OIML MAA before the implementation of new OIML-CS, which means they have a long history of participation in the international cooperation of legal metrology.
The Mass Laboratory carries out studies related to the maintenance and dissemination of mass-related values of quantity. As an internal laboratory of the OIML Issuing Authority, China, its capability scope covers OIML R 76, R 50, R 51, R 61, R 107 and R 134.
The Mass Laboratory owns complete OIML test equipment needed for NAWI and AWI, including a temperature and humidity test device specially used for loaded tests of large weighing instruments, anechoic chamber with dedicated immunity, and pulse train, surge and voltage drop test devices, in addition to four-station durability test devices and high-precision mass standards. The laboratory has independently developed an internationally recognized type evaluation test device for weighing instruments. Its self-developed management system won a second prize in the 2013 Awards for Promoting Inspection by Science and Technology organized by the former Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China (AQSIQ) and the self-developed automatic loading system of weighing instrument type evaluation won the “Award of Excellence” in the 16th China Patent Awards.
The temperature and humidity test device specially used for loaded tests of large weighing instruments tests the metrological performance of large weighing instruments under brutal temperature and humidity conditions, which is significant to the quality of weighing instruments. The device also provides the best measuring capability for the large weighing instruments in China, with a world-leading maximum measuring ability of 3 tons. It can perform continuous tests with any combinations in the scope of 300kg-3000kg and allow temperature cycle tests under high temperature: 20℃ and 40℃, and low temperature: -10℃ and 20℃. Working temperature scope: -10℃ to 40℃, maximum relative humidity 85%. In the meantime, all measuring processes can be controlled by the self-developed software, with data collected automatically.
The characteristics of the mass standards adopted for weighing instrument tests are: large quantities and high individual mass value. Large quantities mean that many weighing instruments used in bulk cargo trade settlements, e.g., belt weighers and hopper weighers used at port and electronic scales used for automobiles on highways, have to use a large number of 20kg weights for traceability. Therefore, the Laboratory developed a set of 3D manipulators to move precisely with three DOF under the control of the self-developed software, and conduct automatic centering loading and automatic undisturbed mass measurement of 20kg mass standards, with the help of a mass comparator, so as to improve the precision and efficiency of daily big mass tracing work. The device has a double-deck weight holder to realize high-precision and high-stability mass tests. There are 14 mass standard place areas, enabling the test of 13 weights to be completed at one time.
What’s more, based on the advanced equipment, sophisticated quality system and outstanding team of talents, the Mass Laboratory has provided strong technical support and guarantee for the establishment of the first OIML training center in China. It has also helped national administrations hold several training sessions on various international weighing instruments concerning the Countries and Economies with Emerging Metrology Systems (CEEMS), giving a significant boost to China’s right of speech in the field of international legal metrology.
The Force and Torque Laboratory, one of the earliest laboratories of NIM, focuses on force values and torque measurement studies. It is responsible for establishing and maintaining the national primary standards and measurement standards for force value and torque, formulating national metrology verification regulation and technical regulation of force and torque, ensuring the accuracy, consistency and reliability of domestic force and torque quantity values, establishing force and torque primary standards and measurement standards with international equivalence and consistency, and guaranteeing the international comparability and equivalence of Chinese force and torque quantity values. Up to now, the Laboratory owns 8 primary standards and 13 standards. The measuring scope of force value primary standards and measurement standards is 0.01N-20MN; the measuring scope of dynamic force standards is 500N-1MN; the measuring scope of torque primary standards and measurement standards is 0.1Nm-30kNm; and, the measuring scope of measuring cell standard facilities is 20N-60MN.
The Force and Torque Laboratory undertakes the testing work for OIML R 60 certificate of load cells issued by the issuing authority. The Laboratory has acquired OIML MAA approval, CNAS approval and ISO 17025 recognition, and is capable to complete performance tests of Class B, C and D digital and analog load cells with the maximum weighing capacity of 100t according to the requirements of OIML R 60.
It also undertakes the work of force value and torque testing, calibration and dissemination of the value of quantity through the country, provides precise testing measures for industries like aerospace, metallurgy, construction, transportation, railway and ships, solves reliable measurement and calibration problems of force and torque quantity values, and ensures the accuracy, consistency and correct dissemination of force and torque quantity values in China.