Evaluation of vertical movement precision of the exciting coil along the gravity direction in Joule Balance NIM-2

The vertical movement precision of the exciting coil is very important for the mutual induction measurement in Joule Balance NIM-2. In order to assure the vertical movement precision of the exciting coil along the gravity direction, the error sources are identified according to the connections between the key components, such as the metrology frame supported by the vibration isolator, the guide rail and the exciting coil. Then, a multi-body error propagation model of the exciting coil is established and the vertical movement deviation error from the gravity direction is estimated. Experiments are conducted to verify the built model. Measurement and theoretical results show that the multi-body error propagation model can be used to effectively evaluate the vertical movement precision of the exciting coil in Joule Balance NIM-2.