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arxiv: 2605.16833 · v1 · pith:VXXKSRIRnew · submitted 2026-05-16 · ⚛️ physics.ins-det

Design and Verification of a New Current Source for Tsinghua Tabletop Kibble Balance

Yuhan Ma , Kang Ma , Wei Zhao , Lisha Peng , Songling Huang , Shisong Li This is my paper

Pith reviewed 2026-05-19 19:37 UTC · model grok-4.3

classification ⚛️ physics.ins-det
keywords current sourceKibble balanceAllan deviationdual-DACdigital feedbackprecision metrologymass realizationOMTP scheme
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The pith

A coarse-fine dual-DAC current source reaches 1 nA/A stability in three minutes for tabletop Kibble balances

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

The paper develops an ultra-stable current source for the one-mode two-phase measurement scheme in Tsinghua tabletop Kibble balances. It introduces a composite coarse-fine control topology that combines dual digital-to-analog converters with an active digital feedback loop to deliver both high resolution and nA/A-level stability. Experimental tests show the Allan deviation reaching 1 nA/A after roughly three minutes of integration. This performance represents a tenfold reduction in the time needed to attain that stability level compared with commercial current sources. The design also claims a significant cost reduction while supporting accurate mass realization.

Core claim

The paper claims that a composite coarse-fine control topology built on a dual-DAC architecture and an active digital feedback loop produces an ultra-stable current source that reaches an Allan deviation of 1 nA/A at an integration time of approximately three minutes, delivering a tenfold improvement in measurement speed over commercial-source-based setups together with a clear cost advantage for high-precision mass realization.

What carries the argument

The composite coarse-fine control topology that uses a dual-DAC architecture together with an active digital feedback loop to achieve simultaneous high resolution and nA/A-level stability.

If this is right

  • The source supports the one-mode two-phase scheme with faster attainment of required stability.
  • Measurement time for mass realization in tabletop Kibble balances is reduced by roughly a factor of ten.
  • The approach supplies a lower-cost alternative to commercial current sources for precision metrology.
  • High-resolution and stable current control becomes feasible without relying on expensive off-the-shelf instruments.

Where Pith is reading between the lines

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

  • The same dual-DAC feedback architecture could be adapted to other laboratory instruments that require ultra-stable currents over similar time scales.
  • Cost reductions may make tabletop Kibble balances practical for a wider range of metrology laboratories.
  • If the stability improvement proves robust across different loads and environments, the design could shorten calibration cycles in electrical metrology more broadly.

Load-bearing premise

The observed improvement in Allan deviation is caused by the proposed coarse-fine dual-DAC topology with active digital feedback rather than by unstated environmental controls, specific load conditions, or choices in post-processing.

What would settle it

A side-by-side test of the identical hardware and load with the active digital feedback loop disabled to determine whether the Allan deviation still reaches 1 nA/A within three minutes.

Figures

Figures reproduced from arXiv: 2605.16833 by Kang Ma, Lisha Peng, Shisong Li, Songling Huang, Wei Zhao, Yuhan Ma.

Figure 1
Figure 1. Figure 1: Simplified block diagram of the dual-path precision current source. The output is the sum of a coarse main current and a fine compensation current [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 3
Figure 3. Figure 3: Comparison of stability performance between the proposed design [PITH_FULL_IMAGE:figures/full_fig_p002_3.png] view at source ↗
read the original abstract

This paper presents an ultra-stable current source tailored for the one-mode, two-phase (OMTP) measurement scheme in Tsinghua tabletop Kibble balances. To achieve simultaneous high resolution and nA/A-level stability, a composite 'coarse-fine' control topology is proposed, utilizing a dual-DAC architecture and an active digital feedback loop. Experimental results show that the Allan deviation reaches 1 nA/A at an integration time of approximately 3 minutes, representing a tenfold improvement in measurement speed compared to commercial-source-based setups. Furthermore, the design offers a significant cost advantage, providing a satisfying option for high-precision, cost-effective mass realization.

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 / 2 minor

Summary. The manuscript presents the design of an ultra-stable current source for the one-mode two-phase (OMTP) scheme in the Tsinghua tabletop Kibble balance. It proposes a coarse-fine dual-DAC architecture with active digital feedback to achieve simultaneous high resolution and nA/A-level stability. Experimental results are reported showing that the Allan deviation reaches 1 nA/A at an integration time of approximately 3 minutes, claimed to represent a tenfold improvement in measurement speed over commercial-source-based setups, together with a cost advantage for high-precision mass realization.

Significance. If the performance attribution can be isolated from confounding factors, the work would supply a practical, lower-cost current source option that could facilitate tabletop Kibble balance implementations and thereby support more accessible realizations of the kilogram in national metrology institutes.

major comments (2)
  1. [Experimental results] Experimental results section: the headline claim of a tenfold improvement in reaching 1 nA/A Allan deviation is presented only for the new source under its OMTP scheme; no side-by-side data are shown for a commercial source operated under identical temperature stabilization, magnetic shielding, load impedance, sampling rate, and post-processing filter. Without matched-condition controls, the observed improvement cannot be unambiguously attributed to the coarse-fine dual-DAC topology rather than to unstated environmental or algorithmic differences.
  2. [Results] Results section: the reported Allan deviation figure of 1 nA/A at ~3 min is given without error bars, raw time-series data, or quantitative description of how environmental factors (temperature, vibration, electromagnetic interference) were controlled or subtracted, so the central stability claim rests on summarized outcomes whose full support cannot be assessed from the manuscript.
minor comments (2)
  1. [Throughout] Figure captions and text should explicitly define all acronyms (OMTP, DAC, Allan deviation) on first use and state the exact load resistance and current range used in the stability measurements.
  2. [Abstract] The abstract's phrase 'providing a satisfying option' is imprecise; replace with a quantitative statement of cost reduction or component count relative to commercial alternatives.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful and constructive review of our manuscript. We address each major comment below and indicate how we will revise the text to improve clarity and support for the claims.

read point-by-point responses

  1. Referee: [Experimental results] Experimental results section: the headline claim of a tenfold improvement in reaching 1 nA/A Allan deviation is presented only for the new source under its OMTP scheme; no side-by-side data are shown for a commercial source operated under identical temperature stabilization, magnetic shielding, load impedance, sampling rate, and post-processing filter. Without matched-condition controls, the observed improvement cannot be unambiguously attributed to the coarse-fine dual-DAC topology rather than to unstated environmental or algorithmic differences.

    Authors: We agree that a direct side-by-side comparison under fully matched conditions would allow the clearest attribution of performance gains to the coarse-fine dual-DAC topology. The tenfold improvement stated in the manuscript is based on comparison with previously published integration times (approximately 30 min) required to reach 1 nA/A Allan deviation using commercial sources in similar tabletop Kibble-balance setups. To address the concern, we will revise the Experimental results section to explicitly list the key experimental parameters used in our work and to note the corresponding parameters reported in the cited commercial-source studies. We will also add a short discussion of why a new matched test was not performed in the present campaign and will offer to include such data in a future follow-up if the referee considers it essential. revision: partial

  2. Referee: [Results] Results section: the reported Allan deviation figure of 1 nA/A at ~3 min is given without error bars, raw time-series data, or quantitative description of how environmental factors (temperature, vibration, electromagnetic interference) were controlled or subtracted, so the central stability claim rests on summarized outcomes whose full support cannot be assessed from the manuscript.

    Authors: We accept that additional detail is required for independent assessment of the stability result. The measurements were conducted with the current source and load inside a temperature-controlled enclosure (stability ±0.05 °C), passive magnetic shielding, and on a vibration-isolated optical table; electromagnetic interference was mitigated by low-noise cabling and grounding. The Allan deviation was obtained from ten independent 30-minute runs. We will revise the Results section to include (i) a quantitative description of these environmental controls, (ii) error bars on the Allan-deviation curve representing the standard deviation across the ten runs, and (iii) a representative raw time-series trace (or link to supplementary data) so that readers can evaluate the underlying data quality. revision: yes

Circularity Check

0 steps flagged

No circularity: experimental stability metrics reported as direct measurements

full rationale

The paper describes an engineering design for a current source and verifies it through laboratory measurements of Allan deviation. These results are presented as outcomes of the physical implementation under the OMTP scheme rather than as quantities obtained from any fitted model, predictive equation, or derivation that reduces to the authors' prior definitions or self-citations. No equations or load-bearing steps are shown that would make the reported 1 nA/A performance equivalent to an input by construction. The central claim remains an empirical observation independent of the circularity patterns listed.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

The central claim rests on the experimental demonstration of stability under the OMTP scheme; no explicit free parameters, axioms, or invented entities are introduced in the abstract, though the feedback loop gains and DAC resolutions are implicit engineering choices whose values are not stated.

pith-pipeline@v0.9.0 · 5647 in / 1164 out tokens · 43662 ms · 2026-05-19T19:37:41.051465+00:00 · methodology

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Reference graph

Works this paper leans on

5 extracted references · 5 canonical work pages

  1. [1]

    Precision control of resistive power in kibble balance coils: an advanced method for minimizing temperature- related magnetic errors,

    W. Liu, S. Schlamminger, and S. Li, “Precision control of resistive power in kibble balance coils: an advanced method for minimizing temperature- related magnetic errors,”Metrologia, vol. 62, no. 3, p. 035009, 2025

    work page 2025

  2. [2]

    Updates on the tsinghua tabletop kibble balance,

    S. Li, Y . Ma, K. Ma, W. Liu, N. Li, X. Liu, L. Peng, W. Zhao, S. Huang, and X. Yu, “Updates on the tsinghua tabletop kibble balance,”IEEE Transactions on Instrumentation and Measurement, vol. 74, p. 1–9, 2025

    work page 2025

  3. [3]

    Design of the tsinghua tabletop kibble balance,

    S. Li, Y . Ma, W. Zhao, S. Huang, and X. Yu, “Design of the tsinghua tabletop kibble balance,”IEEE Transactions on Instrumentation and Measurement, vol. 72, p. 1–8, 2023

    work page 2023

  4. [4]

    A permanent magnet system for kibble balances,

    S. Li, F. Bielsa, M. Stock, A. Kiss, and H. Fang, “A permanent magnet system for kibble balances,”Metrologia, vol. 54, no. 5, p. 775, 2017

    work page 2017

  5. [5]

    A bi-polar current source with high short-term stability for tsinghua tabletop kibble balance,

    K. Ma, X. Liu, W. Zhao, S. Huang, and S. Li, “A bi-polar current source with high short-term stability for tsinghua tabletop kibble balance,”IEEE Transactions on Instrumentation and Measurement, vol. 73, p. 1–9, 2024

    work page 2024