Realization of the SI mass unit through the Planck constant
bilancia elettrostatica INRIM

The most relevant change of the SI is the redefinition of the kilogram which now is based on the stipulated value of the Planck constant. This revolution paves the way for the realization of novel instruments to implement the unit “kilogram” without the need of a direct comparison with the international prototype. The solution adopted by most NMIs is the so-called “Kibble balance” which compares electrical and mechanical powers. At INRIM we decided to exploit the electrostatic force which, being “weaker” than the electromagnetic one, is more suitable for small masses and makes possible a more simple and compact realization. The INRIM electrostatic balance is based on the force generated between the plates of a parallel plate capacitor that is proportional to the derivative of the capacitance vs displacement. Preliminary experiments showed promising results. PISANI et al.: SIMPLE ELECTROSTATIC BALANCE FOR THE MILLIGRAM RANGE IEEE Transactions on Instrumentation and Measurement 68 6 (2019).


Marco Pisani