Test mass alignment using overlapped-flexure hinge in NIM-2 joule balance

To solve the test mass misalignment problem in NIM-2 joule balance, a new suspension system with an overlapped-flexure hinge is proposed. The overlapped structure of this flexure hinge can guarantee the forces to act on the same pivot point, so the first type error torque caused by deviation of the weighing pan can be eliminated without any adjusting process. In addition, to eliminate the transmission of the second type error torque caused by tilt of the weighing pan, a mathematic model is established to analyze the stiffness requirement of the overlapped-flexure hinge. The overlapped-flexure hinge is designed based on the above calculated stiffness, and new suspension system have been assembled. Finite element simulations and experiments are used to prove the effectiveness of this new suspension system. The results show that by meeting the stiffness requirement of the overlapped-flexure hinge, the test mass alignment error can be eliminated effectively.