Design of a Miniature Kibble Balance for Kilogram-Scale Mass Calibration -- KBmini

TL;DR

This paper introduces a tabletop Kibble balance designed for precise mass calibration from 1 g to 1 kg, featuring innovative multi-harmonic excitation to enhance measurement accuracy and linearity.

Contribution

The paper presents a novel miniaturized Kibble balance with a multi-harmonic excitation method to improve coil motion linearity and measurement precision.

Findings

Achieves a velocity flatness of Δv/v<5% over 60% of the cycle.

Design meets E2-accuracy class with <0.27 ppm uncertainty for 1 kg.

Introduces multi-harmonic excitation to enhance coil velocity uniformity.

Abstract

Tabletop version Kibble balances are a significant developing trend for mass realizations following the revised International System of Units. A key innovation through the miniaturization of the Kibble balance from a large-scale instrument into a tabletop device is making the quantum-based realization of mass accessible to a wider range of calibration laboratories and industries. This paper presents a tabletop Kibble balance design at Tsinghua University targeting E2-accuracy class mass calibrations from 1 g to 1 kg. For calibrating a mass of 1 kg, for instance, the required relative standard measurement uncertainty must be below 0.27 ppm to meet E2-accuracy class. Major components and features of the proposed system are discussed. A novel method of multi-harmonic excitation is proposed to improve the coil-motion linearity during velocity measurement. We show that injecting odd-order harmonics into the motion-driving current can significantly improve the uniformity of the coil's moving velocity, while the second-order component can address the asymmetry between upward and downward movements. This achieves a flat velocity $\Delta v/v< 5\%$ over 60% of the motion cycle.