Design and Initial Test of the Weighing Unit for Tsinghua Tabletop Kibble Balance

TL;DR

This paper introduces a specially designed weighing unit for the Tsinghua tabletop Kibble balance, featuring a high-resolution sensor and a novel control strategy, achieving high accuracy and stability for mass measurement.

Contribution

The paper presents a new weighing unit with a capacitive sensor and a modified PID control loop, enhancing performance for high-precision mass metrology in Kibble balances.

Findings

Repeatability better than 0.1 mg in air for 1 kg mass exchanges

System demonstrates high static stability and fast dynamic response

Validates potential for high-accuracy mass measurements

Abstract

This paper presents a customized weighing unit developed for the Tsinghua tabletop Kibble balance. The system is based on a flexure hinge mechanism sourced from a commercial weighing cell, with a major modification to the feedback control loop. The redesigned loop incorporates a capacitive displacement sensor for high-resolution position detection and a novel PID control strategy that ensures both fast dynamic response and high static stability. Initial characterization results demonstrate a repeatability better than 0.1 mg in air for 1 kg mass exchanges, validating the system's potential for high-accuracy mass metrology in Kibble balances.