Diamond Magnetometer Enables Accurate Room-Temperature AC/DC Current Comparison

Accurate measurement of both alternating and direct current ratios underpins modern electrical power systems, yet current comparators traditionally rely on separate technologies for each signal type. Hidekazu and colleagues at the National Metrology Institute of Japan, in collaboration with the University of Tokyo, now demonstrate a single device capable of measuring both AC and DC currents with unprecedented precision. Their compact, room-temperature current comparator integrates a diamond-based magnetometer, achieving an accuracy of 10-8 for both signal types and a bandwidth up to 300 Hz. This unified approach, which eliminates the need for complex cryogenic cooling, represents a significant advance over existing technology, offering ten-fold higher accuracy than typical AC comparators and matching the performance of state-of-the-art DC devices, ultimately broadening its application to electrical standards and resistance measurements.

Accurate Current Ratio Measurement for Power Systems

Accurate measurements of alternating current (AC) and direct current (DC) ratios are fundamental to electric power systems, underpinning applications like power quality monitoring, harmonic analysis, and energy metering. The increasing complexity of modern power grids, driven by renewable energy sources and power electronic devices, demands more accurate, robust, and efficient current measurement techniques. Quantum-based current measurement offers a potentially disruptive technology, promising significant improvements in accuracy, stability, and dynamic range compared to existing techniques. This research explores the feasibility of realising a highly accurate current measurement system based on nitrogen-vacancy (NV) centres in diamond, leveraging their sensitivity to magnetic fields.

By precisely measuring the magnetic field generated by a current-carrying conductor, the current value can be determined with unprecedented accuracy. The research aims to demonstrate the potential of this technology for achieving significantly improved current measurement performance, specifically targeting an accuracy of 10⁻⁶ at 1 kHz and a dynamic range exceeding 10⁴. This work focuses on the development and characterisation of a prototype quantum current sensor based on NV centres in diamond, establishing a pathway towards a practical, quantum-enhanced current measurement system for industrial and scientific applications.

Diamond NV Center Current Sensing System

This research details the development of a highly sensitive current sensor based on a diamond nitrogen-vacancy (NV) center, and its application to precision current comparison using a current comparator. Traditional methods for precise current comparison often rely on complex setups, and this research offers a more compact, robust, and potentially room-temperature solution. Key findings demonstrate high sensitivity, achieving a DC magnetic field sensitivity of sub-10 pT Hz -1/2, and successful integration into a current comparator setup. Diamond sensors offer potential advantages in terms of robustness and compactness, with a wide dynamic range and the ability to simultaneously measure temperature and magnetic fields, improving accuracy and reducing noise. A closed-loop control system was implemented to enhance the sensor’s stability and accuracy.

Diamond Magnetometer Measures AC and DC Currents

Researchers have developed a new current comparator capable of measuring both alternating and direct electrical currents with unprecedented precision and versatility. This device, based on a diamond-based magnetometer utilising nitrogen-vacancy centers, allows for measurements with an accuracy of one part in ten million for both AC and DC signals, a significant improvement over existing AC comparators and comparable to the best DC instruments. The system operates at room temperature, eliminating the need for bulky cryogenic cooling systems, and demonstrates a bandwidth of up to 300 Hertz, enabling accurate measurement of rapidly changing currents. It achieves nanoampere-level sensitivity, capable of detecting extremely small currents, while maintaining high precision. This unified approach simplifies electrical standards and calibration, improving traceability and expanding possibilities for applications like precision DC resistance bridges.

Diamond Magnetometer Enables Precise Current Ratio Measurement

This research demonstrates a new current comparator capable of measuring both alternating and direct currents with an accuracy of 10⁻⁸, all at room temperature. By integrating a diamond-based magnetometer utilising nitrogen-vacancy centers, the device offers a unified solution for current ratio metrology, overcoming the need for separate technologies and bulky cryogenic systems traditionally required for AC and DC measurements. The system achieves a minimum detectable current of 50 nanoamperes and surpasses the performance of typical AC comparators, while matching the precision of state-of-the-art DC comparators. This innovation simplifies current ratio measurements and offers a pathway towards improved electrical standards and calibration.