Flexure-based mechanism for a Kibble Balance

The redefinition of the kilogram in 2019 has emphasized the need for precise measuring instruments such as the Kibble Balance, which directly compares an electromagnetic force to the weight of a test mass. This work investigates the development of a flexure-based mechanism for use in a high-precision Kibble Balance. The central requirement is that the mechanism can deflect over several millimeters (> 20mm) whilesupporting a heavy load (> 10kg). Particular challenges arise in implementing flexure pivots, which are already used in weighing cells for mass comparators to overcome limitations in precision of knife edge pivots. The novel mechanism enables increased sensitivity as a force sensor through stiffness compensation. Experimental results of a prototype also show that the anelastic aftereffect of the flexures can be compensated to provide stable reference force values for the weighing phase of a mass realization based on a Kibble Balance. The design paves the way for future simplifications in Kibble Balance development and allows the precise realization of test masses of 100 g with a relative measurement uncertainty of 2x10-8.