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arxiv: 2605.04090 · v1 · submitted 2026-04-25 · ⚛️ physics.ins-det

Recognition: unknown

Recent Advances in Tabletop Kibble Balance -- KBmini

Nanjia Li , Weibo Liu , Kang Ma , Elsayed E.E. Qupasie , Wei Zhao , Songling Huang , Shisong Li
Authors on Pith no claims yet

Pith reviewed 2026-05-09 20:55 UTC · model grok-4.3

classification ⚛️ physics.ins-det
keywords Kibble balancemass calibrationtabletop metrologyvelocity profileinduced voltagemagnetic field characterizationspring constantE2 accuracy
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The pith

A tabletop Kibble balance reaches near-constant velocity over 180 micrometers with an induced-voltage flat-top exceeding 1 volt.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper advances the KBmini, a compact Kibble balance intended for E2-accuracy mass calibration up to 1 kg. The authors map the Bl(z) interaction by manual magnet positioning, select the field extremum as the weighing location, and measure the local spring constant of the weighing cell. They then install a coil with more turns and apply multi-harmonic excitation to produce nearly constant coil speed across a 180-micrometer travel distance while generating a strong, flat induced-voltage signal above 1 V. These elements together are presented as the necessary preparation for subsequent force-balance experiments that compare electromagnetic and gravitational forces on a mass.

Core claim

With a coil having a larger number of turns and a multi-harmonic excitation technique, the KBmini produces a near-constant velocity profile across a 180 μm range, resulting in an induced-voltage flat-top region exceeding 1 V. The Bl(z) profile is characterized by manual magnet positioning to select the extremum as the weighing position, and the spring constant of the weighing cell is measured around this point. These developments lay the groundwork for upcoming experiments aimed at E2-accuracy mass calibration up to 1 kg.

What carries the argument

The multi-harmonic excitation technique applied to a coil with increased turns, which maintains constant velocity and high induced voltage over the required displacement range.

If this is right

  • The 180 μm constant-velocity range supplies sufficient travel for practical electromagnetic force measurements.
  • The induced voltage above 1 V improves signal strength and reduces the relative contribution of noise.
  • The pre-characterized weighing position and spring constant allow direct integration into force-balance procedures.
  • The overall setup provides the motion and signal stability required for repeated mass comparisons at the target accuracy.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • A successful demonstration of mass calibration with these components would show that short-range constant-velocity operation suffices for tabletop Kibble balances.
  • The multi-harmonic drive approach could be tested in other precision instruments that require smooth coil motion inside magnetic fields.
  • Automating the Bl(z) mapping step instead of manual positioning would reduce setup time and improve repeatability in future versions.
  • If the velocity profile remains stable under loaded conditions, the same hardware could support comparisons between multiple masses without mechanical readjustment.

Load-bearing premise

The measured Bl extremum position, spring constant, and demonstrated velocity and voltage profiles will combine to deliver E2-accuracy mass calibration when used in actual weighing experiments.

What would settle it

A full mass calibration experiment performed with the KBmini that yields an uncertainty larger than the E2 target when using the reported weighing position and motion profiles.

Figures

Figures reproduced from arXiv: 2605.04090 by Elsayed E.E. Qupasie, Kang Ma, Nanjia Li, Shisong Li, Songling Huang, Weibo Liu, Wei Zhao.

Figure 1
Figure 1. Figure 1: CAD model of the KBmini. source (Keithley 6221). The high Bl value, in the meanwhile, allows an induced voltage exceeding 1 V in the moving phase. III. EXPERIMENTAL PROGRESS A. Bl Measurement The Bl(z) profile was determined through weighing mea￾surements conducted by moving the magnet to various vertical positions z. The origin of the z-axis is defined at the center of the magnet, with the positive direct… view at source ↗
Figure 2
Figure 2. Figure 2: Measurement result of Bl(z) profile. 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0 0.01 0.02 0.03 z/mm F/ N measured data linear fit [PITH_FULL_IMAGE:figures/full_fig_p002_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: F(z) curve of the weighing unit. resulting F(z) curve is shown in Fig.3. The linear fit indicates a good linearity, yielding a spring constant of the weighing unit k = 277.8 N/m. C. Multi-harmonic Excitation Measurement The multi-harmonic excitation method [9] is employed to generate a near-constant velocity profile by injecting odd-order harmonic currents into the drive coil. For the new coil, the optimiz… view at source ↗
read the original abstract

This paper presents recent advances in the KBmini Kibble balance, a tabletop system for E2-accuracy mass calibration up to 1 kg. The $Bl(z)$ profile is characterized by manually setting the magnet at different vertical positions, and the extremum point is selected as the weighing position. The spring constant of the weighing cell around this point is measured. With a new coil of a larger number of turns and a multi-harmonic excitation technique, a near-constant velocity profile over a moving range of 180 $\mu$m, producing an induced-voltage flat-top region exceeding 1 V, is achieved. These results establish a foundation for subsequent mass calibration experiments.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The manuscript reports recent experimental advances in the KBmini tabletop Kibble balance for E2-accuracy mass calibration up to 1 kg. It describes characterization of the Bl(z) profile via manual vertical positioning of the magnet, with the extremum selected as the weighing position; measurement of the weighing cell spring constant around this point; and implementation of a new coil with increased turns together with multi-harmonic excitation to produce a near-constant velocity profile over 180 μm that yields an induced-voltage flat-top region exceeding 1 V. These outcomes are presented explicitly as preparatory results establishing a foundation for subsequent mass calibration experiments.

Significance. If the reported profiles can be integrated into a complete Kibble balance measurement chain, the work would advance the development of compact, accessible systems for high-precision mass metrology. The concrete experimental achievements—the 180 μm near-constant velocity range and >1 V flat-top voltage obtained with the new coil and multi-harmonic technique—constitute tangible progress in controlling the moving mode. The direct characterizations of Bl(z) and the spring constant provide useful system-level data. The manuscript does not yet demonstrate E2 accuracy or include validation against standards, so the ultimate metrological impact remains prospective.

major comments (2)
  1. [Results section (velocity and voltage profiles)] Results section (velocity and voltage profiles): the description of the 'near-constant velocity profile' over 180 μm and the 'induced-voltage flat-top region exceeding 1 V' provides no quantitative metrics of constancy or flatness (e.g., maximum deviation, RMS variation, or percentage tolerance across the range). Without these, it is not possible to assess whether the achieved profiles meet the requirements for subsequent E2-accuracy mass calibration.
  2. [Bl(z) characterization] Bl(z) characterization: the manual positioning of the magnet at different vertical positions to map Bl(z) and select the extremum lacks any report of the number of sampled positions, the repeatability or precision of the manual adjustments, or uncertainty estimates on the measured Bl values. This information is load-bearing for justifying the chosen weighing position.
minor comments (1)
  1. The manuscript would benefit from inclusion of error bars or repeatability data on the reported velocity, voltage, and spring-constant measurements to allow readers to evaluate experimental reliability.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their thorough review and valuable feedback on our manuscript. The comments have helped us improve the clarity and completeness of the presented results. We have revised the manuscript to incorporate quantitative metrics for the velocity and voltage profiles as well as additional details on the Bl(z) characterization. Our responses to the major comments are provided below.

read point-by-point responses

  1. Referee: Results section (velocity and voltage profiles): the description of the 'near-constant velocity profile' over 180 μm and the 'induced-voltage flat-top region exceeding 1 V' provides no quantitative metrics of constancy or flatness (e.g., maximum deviation, RMS variation, or percentage tolerance across the range). Without these, it is not possible to assess whether the achieved profiles meet the requirements for subsequent E2-accuracy mass calibration.

    Authors: We agree that quantitative metrics are important for assessing the profiles' suitability for E2-accuracy mass calibration. In the revised manuscript, we have added the maximum deviation, RMS variation, and percentage tolerance for both the velocity profile over the 180 μm range and the induced-voltage flat-top region. These metrics are calculated from the experimental data shown in the figures and are now reported explicitly in the Results section. We discuss how these values support the foundation for future mass calibration experiments, while acknowledging that complete E2-accuracy demonstration is beyond the scope of this preparatory work. revision: yes

  2. Referee: Bl(z) characterization: the manual positioning of the magnet at different vertical positions to map Bl(z) and select the extremum lacks any report of the number of sampled positions, the repeatability or precision of the manual adjustments, or uncertainty estimates on the measured Bl values. This information is load-bearing for justifying the chosen weighing position.

    Authors: We acknowledge that the description of the Bl(z) characterization was incomplete. The revised manuscript now includes the number of sampled positions, the estimated precision of the manual adjustments using the positioning stage, and uncertainty estimates on the Bl values based on repeated measurements. These additions provide the necessary information to justify the selection of the extremum point as the weighing position. revision: yes

Circularity Check

0 steps flagged

No significant circularity; purely experimental characterization

full rationale

The paper contains no derivations, predictive models, or fitted parameters presented as outputs. All reported results (Bl(z) profile characterization by manual positioning, spring-constant measurement, and achieved velocity/voltage profiles via new coil and multi-harmonic excitation) are direct experimental observations. These are explicitly framed as preparatory data establishing a foundation for subsequent mass calibration, with no internal reduction of any claim to its own inputs by construction, self-citation, or renaming. The central achievement is a measured physical profile, not a derived prediction.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The reported work relies on standard electromagnetic induction and mechanical spring behavior with no new free parameters, axioms beyond domain standards, or invented entities.

axioms (2)
  • standard math Electromagnetic induction produces voltage proportional to velocity and Bl product in a moving coil
    Invoked when characterizing Bl(z) profile and induced voltage flat-top.
  • domain assumption Weighing cell behaves as a linear spring near the selected position
    Used when measuring spring constant around the Bl extremum.

pith-pipeline@v0.9.0 · 5425 in / 1206 out tokens · 43128 ms · 2026-05-09T20:55:41.139172+00:00 · methodology

discussion (0)

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Reference graph

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