Reference Ultra Low DC Current Source (ULCS) Between 1 fA and 100 pA at TUBITAK UME

Cem Hayirli; Enis Turhan; Gulay Gulmez; Omer Erkan; Yakup Gulmez

arxiv: 1907.01389 · v3 · pith:PKI4K75Bnew · submitted 2019-06-28 · ⚛️ physics.ins-det

Reference Ultra Low DC Current Source (ULCS) Between 1 fA and 100 pA at TUBITAK UME

Omer Erkan , Yakup Gulmez , Cem Hayirli , Gulay Gulmez , Enis Turhan This is my paper

Pith reviewed 2026-05-25 12:48 UTC · model grok-4.3

classification ⚛️ physics.ins-det

keywords ultra-low current sourcefemtoamperetraceable currentvoltage rampcapacitor methodmetrologyDAQ control

0 comments

The pith

A programmable source generates traceable DC currents from 1 fA to 100 pA by ramping voltage across capacitors.

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

The paper describes the development of an Ultra Low DC Current Source that covers currents from 1 femtoampere up to 100 picoamperes. It achieves this by applying a controlled linear voltage ramp to commercial capacitors kept in a stable temperature environment. The resulting current is calculated directly from the known capacitance and the rate of voltage change, providing traceability to fundamental units without relying on other current standards. The system offers 100 attoampere resolution and is fully automated under computer control.

Core claim

The ULCS device produces output currents in the range from 1 fA to 100 pA with a resolution of 100 aA by applying linear ramp voltages generated by a commercial DAQ card to standard capacitors with values from 1 pF to 1000 pF held in a temperature-controlled insulated box. This approach makes the generated current directly traceable to DC voltage, capacitance, and time units, with a reported uncertainty of 2.5 mA/A at 1 fA current.

What carries the argument

The application of a linear voltage ramp from a DAQ card to temperature-stabilized commercial capacitors to produce current via I = C × dV/dt.

If this is right

Any current value within the range can be generated with 100 aA resolution via computer control.
The output is directly traceable to voltage, capacitance, and time standards.
The uncertainty is specified as 2.5 mA/A at the 1 fA level.
Multiple capacitor values allow coverage of the full current range.

Where Pith is reading between the lines

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

The temperature control and DAQ linearity assumptions determine the practical lower limit of the method.
Such a source could serve as a reference for calibrating sensitive electrometers in metrology labs.
Further automation might allow integration into automated calibration systems for low-current devices.

Load-bearing premise

The standard capacitors keep their values stable in the temperature-controlled box and the DAQ-generated voltage ramp stays linear without distortion or added noise.

What would settle it

Measuring the actual output current at 1 fA with an independent traceable method and finding a discrepancy exceeding the claimed 2.5 mA/A uncertainty would disprove the central performance claim.

read the original abstract

In this paper, we present a programmable Ultra Low DC Current Source (ULCS) developed at T\"UB\.ITAK UME. The output current range is from 1 fA up to 100 pA with 100 aA resolution and is directly traceable to DC voltage, capacitance and time units. The principle of the device is based on applying a linear ramp voltage on standard capacitors with values between 1 pF and 1000 pF. These standard capacitors are commercial standard capacitors which are kept in a temperature controlled insulated box. Linear ramp voltage is generated using a commercial DAQ card. Current source device is fully automated with computer control and can be used to generate any currents with 100 aA resolution in its full range. The uncertainty is 2.5 mA/A at 1 fA current.

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.

Desk Editor's Note private letter to a colleague

The paper describes an automated low-current source built at TUBITAK UME but supplies no measurements or uncertainty budget to support its performance claims.

read the letter

The core point is that this is a description of a practical current source using the standard ramp-on-capacitor method, automated with a DAQ card and commercial capacitors in a temperature box, but the text gives no actual data, error budget, or verification to back the stated 1 fA to 100 pA range or the 2.5 mA/A uncertainty at the low end. Without those, the traceability claim stays untested on the page. The setup itself follows established metrology practice and adds computer control for 100 aA steps, which is a straightforward engineering step for their lab. That integration is the only real addition over prior work on the same principle. The soft spot is exactly what the stress test flags: no checks on long-term capacitor stability, leakage, or actual ramp linearity and noise at these levels, and no breakdown showing how those factors fit into the quoted uncertainty. The abstract alone cannot be evaluated on its own terms. This kind of paper is mainly for metrology labs that need a working reference in the femtoamp range and might want to replicate or adapt the hardware. A reader looking for new physics or a fully documented standard would get little from it. The work shows clear thinking on the implementation side but stops short of the evidence needed to stand on its own. I would send it to peer review only if the full manuscript includes the missing measurements and budget; otherwise desk reject.

Referee Report

1 major / 1 minor

Summary. The manuscript describes the development of a programmable Ultra Low DC Current Source (ULCS) at TÜBİTAK UME. The device generates DC currents from 1 fA to 100 pA with 100 aA resolution by applying a linear voltage ramp from a commercial DAQ card to commercial standard capacitors (1 pF to 1000 pF) maintained in a temperature-controlled insulated box. The current is generated via I = C dV/dt, making it directly traceable to voltage, capacitance, and time standards. The system is fully automated under computer control, and an uncertainty of 2.5 mA/A is claimed at 1 fA.

Significance. If the performance specifications are experimentally verified, the ULCS would offer a useful traceable reference for ultra-low current measurements in the fA-pA range, which is critical for metrology applications in detector physics and precision instrumentation. The approach benefits from being parameter-free, relying directly on the physical relation I = C dV/dt with external standards for C, V, and t, avoiding fitted parameters.

major comments (1)

[Abstract] Abstract: The central claim of an uncertainty of 2.5 mA/A at 1 fA is presented without any supporting measured data, error budget, or experimental verification of capacitor stability, leakage currents, or the linearity and noise characteristics of the DAQ-generated voltage ramp across the operating range. This information is necessary to evaluate the traceability assertion and the stated uncertainty.

minor comments (1)

[Abstract] Abstract: The text contains some typographical issues, such as the rendering of 'TÜBİTAK' and inconsistent use of units (e.g., 'mA/A' for relative uncertainty).

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the constructive feedback. We agree that the abstract would benefit from clearer linkage to the supporting analysis and will revise accordingly.

read point-by-point responses

Referee: [Abstract] Abstract: The central claim of an uncertainty of 2.5 mA/A at 1 fA is presented without any supporting measured data, error budget, or experimental verification of capacitor stability, leakage currents, or the linearity and noise characteristics of the DAQ-generated voltage ramp across the operating range. This information is necessary to evaluate the traceability assertion and the stated uncertainty.

Authors: The manuscript derives the 2.5 mA/A uncertainty directly from the traceability to calibrated voltage, capacitance and time standards via I = C dV/dt, with the error budget incorporating contributions from capacitor stability, leakage and DAQ ramp characteristics. We accept that the abstract presents the final value without explicit cross-reference. In revision we will update the abstract to point to the detailed uncertainty section and ensure experimental verification of the key components is highlighted. revision: yes

Circularity Check

0 steps flagged

No circularity; current defined by direct physical relation to external standards

full rationale

The paper asserts that output current follows the physical relation I = C dV/dt using commercial capacitors held at controlled temperature and a DAQ-generated linear ramp, with traceability to independent V, C, and t standards. No load-bearing step reduces by construction to a fitted parameter, self-definition, or self-citation chain; the derivation is the standard capacitor-charging equation applied to external hardware. The stated uncertainty and stability assumptions are presented as engineering claims rather than derived results that loop back to the paper's own inputs.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the standard physical relation between current, capacitance and voltage ramp rate together with the assumption that commercial capacitors and the DAQ card behave as specified under the controlled conditions.

axioms (1)

standard math I = C * (dV/dt) where I is the generated current, C is the capacitor value and dV/dt is the voltage ramp rate.
This is the operating principle stated in the abstract.

pith-pipeline@v0.9.0 · 5697 in / 1361 out tokens · 45587 ms · 2026-05-25T12:48:53.811991+00:00 · methodology

Reference Ultra Low DC Current Source (ULCS) Between 1 fA and 100 pA at TUBITAK UME

Core claim

What carries the argument

If this is right

Where Pith is reading between the lines

Load-bearing premise

What would settle it

discussion (0)