RESEARCH AND DEVELOPMENT OF SMALL FORCE STANDARDS AT NIM

With the development and industrialization of micro- and nano- technology, small force measurements are widely applied in many fields such as advanced materials, bio-technology, aerospace and so on. For realizing traceable small forces and founding small force metrology hierarchy in China, NIM has launched a research project on small force metrology in 2011. 2 methods for small force realization at the scale of nano-Newton to micro-Newton are applied: electrical force based method and mass based method. The initial prototype of small force standard, which is based on the electrostatic force realization and adopts a coaxial cylindrical capacitor, has been developed and experimented. 2 kinds of micro force transmission mechanism are applied to the prototype: a parallelogram mechanism with 4 flexure hinges, and a lever-type force measurement system based on an elastic torsion bar. The structure and key units of 2 schemes are described in detail, the experiment results are demonstrated. The system stiffness of torsion bar scheme is smaller than that of flexure hinges scheme. In addition, structure of the initial prototype will be improved, and the environment conditions will be controlled strictly in our further experiments to minimize the creep of our system.