Finite element simulation of the effect of surface roughness of coaxial electrodes on small mass and force measurements using a voltage balance apparatus

Abstract

For the accurate measurement of small masses and forces in a traceable manner to the new definition of the kilogram, a voltage balance apparatus that uses electrostatic force between coaxial electrodes has been developed at the National Metrology Institute of Japan (NMIJ). In the voltage balance measurements, the coaxial electrodes of the apparatus are mechanically aligned by measuring the capacitance to achieve accurate small mass measurements. In this work, we investigated the effect of surface roughness on mechanical alignment of coaxial electrodes for voltage balance measurements using the finite element method (FEM). The results indicate that misalignments caused by surface roughness alter the capacitance gradient but do not significantly increase unwanted lateral forces in the mass measurement compared to that in the ideal condition.