Magnetic Uncertainties for Compact Kibble Balances: An Investigation

TL;DR

This paper investigates how magnetic uncertainties in Kibble balances scale with size, highlighting that smaller systems face increased systematic effects, especially thermal effects, which require careful thermal design.

Contribution

It provides a detailed analysis of how magnetic effects scale with magnet size, emphasizing the importance of thermal management in small Kibble balances.

Findings

Systematic effects increase as magnet size decreases.

Thermal effects become dominant in small magnets.

Proper thermal design is crucial for accuracy.

Abstract

The Kibble balance has become one of the major instruments for realizing the mass unit, the kilogram, in the revised international system of units (SI). Researchers at about a dozen national metrology institutes are actively working with Kibble balances that are capable of weighing masses with nominal values from 10g to 1kg. In the future, the design of smaller Kibble balances will play a more significant role. Smaller Kibble balances require smaller magnet systems, and here we investigate the scaling of systematic uncertainties with the size of the magnet system. We describe the size dependence of three magnetic effects: the coil-inductance effect, the yoke nonlinear effect, and the thermal effect. The analysis shows that the relative systematic effects become increasingly larger with smaller sizes. For small magnets the thermal effects become dominant and, hence, a good thermal design is imperative.