Misalignment recognition of mass pan in joule balance

Joule balance is one of the precise instruments to measure the Plank constant for redefining the kilogram. During the measurement of the joule balance, two electrified coils produce an electromagnetic force to balance the gravity of a standard mass on the mass pan. However, if the mass pan is in a misalignment state, it will waggle and change the posture of the suspended coil during the mass exchanging progress. Then the alignment errors will be induced. In joule balance, the posture of the mass pan cannot be directly measured, which however can be decoupled by measuring the posture of the suspended coil. In this paper, the recognition method of the mass pan misalignment status will be discussed. By measuring and calculating the positon changing of the suspended coil, the alignment states of the mass pan can be evaluated.