In anticipation of the redefinition of the kilogram and to avoid
a parallel non-SI dissemination system for mass, an alternative
approach to mass measurement is being developed at NIST.
Magnetic levitation is utilized to create a mass comparison
system in which a test mass artifact in air can be directly
compared to a standard mass artifact in vacuum using the same
high precision comparator balance. Due to the extreme
sensitivity of this comparator balance (in the order of 10 μg),
any change in temperature near the balance may affect
measurement results. Therefore, permanent magnets will be used
in this project to achieve the levitation. A solenoid is added
to the system to stabilize the magnetic levitation. To test the
feasibility of this project, a levitation system has been
constructed as shown in Figure 1. This is a photograph of the
proof-of-concept apparatus. For simplicity, the proof-of-concept
apparatus was constructed with both masses in air at atmospheric
pressure. Two attractive permanent magnets a