Research report: Simplifying the calibration of current measurement instruments with diamond quantum sensing technology

A compact current comparator based on diamond quantum sensing can evaluate both alternating-current and direct-current ratios with the same device configuration, according to an experimental study led by Japan’s National Institute of Advanced Industrial Science and Technology (AIST). Researchers from AIST, the Institute of Science Tokyo and the National Institutes for Quantum Science and Technology demonstrated that a sensor detecting the magnetic flux generated by electric current could measure both kinds of ratio with stated type-A uncertainty at the 10^-8 level. The comparator’s central section was less than one-third the size and less than one-tenth the mass of conventional current comparators, offering a route to simpler calibration systems for electrical power infrastructure.

Current comparators help determine the ratio between the large current carried by power systems and the smaller value measured after conversion by a current transformer. Transformers are needed in power generation, transmission and distribution facilities, where currents may reach several hundred amperes and cannot be fed directly into measuring instruments. Accurately establishing the relationship between the original and converted currents is therefore important for operating, maintaining and expanding those facilities.

Conventional AC comparators rely on electromagnetic induction, which can measure alternating-current ratios but not direct-current ratios. As a result, AC and DC measurements have conventionally required different instruments, measurement principles and calibration arrangements. The new design replaces that division with a diamond quantum sensor that detects magnetic flux associated with current.

Using one setup, the researchers evaluated both AC and DC current ratios with high precision. They also eliminated the detection coil based on electromagnetic induction that is normally used in conventional AC ratio measurements, allowing them to reduce the size and mass of the comparator’s central component. The study was published in Scientific Reports on 11 August 2026 under the title “Current comparator for both AC and DC ratio measurements with 10-8-level type-a uncertainty.”

The results demonstrate high-precision ratio measurements with the same comparator configuration for AC and DC current, rather than performance across every possible operating condition. The research was an experimental demonstration by a team working across three Japanese research organizations. Its scope was the evaluation and design of a current comparator; the supplied report does not present the device as a complete national calibration standard or as an immediate replacement for conventional comparators.

Researchers describe the diamond-sensor comparator as a foundational technology for combining calibration systems that were previously separated into AC and DC arrangements. By using one device configuration, the approach could reduce duplication in instrument configurations and simplify the management of measurement data. That possibility is relevant to power networks in which AC and DC coexist, including next-generation grids shaped by the growing use of renewable energy sources.

The reported findings support the feasibility of unified current-ratio calibration, while broader adoption and standardization remain future steps rather than demonstrated outcomes of the experiment.

Subject of Research: Diamond quantum-sensor current comparators for unified AC and DC calibration of electrical measurement instruments

Article Title: Simplifying the calibration of current measurement instruments with diamond quantum sensing technology

Article References: Simplifying the calibration of current measurement instruments with diamond quantum sensing technology. Original publication (Bibliographic details unavailable.)

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Keywords: diamond quantum sensing, current comparator, AC calibration, DC calibration, power-grid metrology, magnetic-flux sensing, current transformers, measurement uncertainty, electrical power systems, Scientific Reports, Simplifying, calibration