The science behind AIM-EF
Extending SI-traceable impedance measurements across a broad frequency range — from 100 mHz to 2 MHz — to meet emerging industrial and scientific needs.
Overview
Why impedance, and why now?
Electrical impedance is a far more complicated quantity than DC resistance: it is a multi-complex parameter with real and imaginary parts, both of which typically vary with frequency, and can be expressed in terms of resistance, capacitance, inductance or any combination of these. Impedance measurements therefore offer deep insight into the static and dynamic properties of materials and interfaces, networks and circuits, and even electrochemical solutions and biomolecules.
Although impedance can theoretically span some 22 orders of magnitude, today’s commercial impedance meters cover around 13 (roughly 10 µΩ to 100 MΩ). Crucially, traceability for the highest-accuracy four-terminal-pair (4TP) standards is typically only available in the audio frequency range — in some institutes only around 1 kHz. The rapid evolution of emerging technologies demands traceable, accurate and reliable impedance measurements over a much wider frequency range.
Overall objective: significantly advance existing world-leading impedance metrology in Europe by extending traceability across a broad range of frequencies — improving the traceability chain for impedance meters, analysers and electrochemical impedance spectroscopy (EIS) instruments, and developing a pathway towards a universal Quantum Impedance Standard (QIS) based on quantum Hall devices operating up to 2 MHz.
Excellence
Specific objectives
Five specific objectives structure the scientific and technical ambition of the project.
Optimise impedance bridge methods
Enable efficient and robust optimisation of new and existing impedance bridge methods and topologies by deepening understanding of existing impedance standards — through rigorous validation of uncertainty budgets across 100 mHz to 2 MHz, using practical models and advanced simulations. (WP1)
Calibrate commercial instruments
Enable accurate calibration of commercial impedance meters, analysers and EIS systems over the extended frequency range by optimising calculable impedance standards and coaxial bridges. Target uncertainties (k = 1) at 2 MHz: 10 µF/F for 10 pF capacitance, 10 µΩ/Ω for 1 kΩ resistance, and 30 ps for time-constant standards. (WP2)
Advance quantum Hall devices
Investigate and develop GaAs- and graphene-based quantum Hall devices and associated cryomagnetic setups over the extended frequency range, with target measurement uncertainty of 20 µΩ/Ω (k = 1) at 2 MHz, and outline a pathway towards a universal quantum standard for impedance. (WP3)
Strengthen European infrastructure
Strengthen and expand the European measurement infrastructure for advanced impedance techniques over the extended frequency range, supporting the development of new Calibration and Measurement Capability (CMC) entries and robust traceability chains. (WP2, WP4)
Demonstrate uptake & impact
Demonstrate an integrated European metrology infrastructure for impedance and facilitate take-up by the measurement supply chain (calibration laboratories, instrument manufacturers), standards developing organisations (IEC/ISO, CEN-CENELEC, IEEE) and end users. (WP4, WP5)
Implementation
Work packages
The project is delivered through six interlinked work packages.
Impedance bridge methods
Advancing impedance bridge methods for the extended frequency range: reviewing the state of the art, developing impedance standards and optimising coaxial, digital and Josephson bridges.
Traceable measurement methods
Accurate and traceable measurement methods for impedance in the extended frequency range, including transfer standards and calibration of impedance meters towards both higher and lower frequencies.
Quantum Hall effect devices
Investigation of quantum Hall effect devices over the extended frequency range — bridge components, cable parameters, GaAs and graphene devices, and measurement with calibrated impedance meters.
Infrastructure & use cases
Integration of new capabilities into the pan-European metrology infrastructure, demonstrated through grid impedance and electrochemical impedance spectroscopy use cases.
Creating impact
Dissemination and communication, exploitation and uptake — engaging stakeholders, standards committees and end users to maximise the project's impact.
Management & coordination
Project management, meetings and reporting, ensuring the consortium delivers on time and to the standards required by EURAMET.
Need for the project
Building on a strong European foundation
By addressing the needs of calibration service providers and the electrical industry, AIM-EF builds on the successful outcomes of previous projects, including EMRP JRP SIB53 AIM QuTE, EMPIR JRPs 18SIB07 GIQS and 17RPT04 VersICaL, and Metrology Partnership JRP 23FUN07 QuAHMET for classical, quantum-enhanced and quantum impedance metrology.
The need spans many fields: accurate impedance measurements from hundreds of kilohertz to a few megahertz are essential in the electronics industry for characterising capacitors and inductors in switching converters; precise electrochemical impedance spectroscopy is increasingly key for battery performance and safety; and accurate knowledge of power-grid impedance from 9 kHz to 500 kHz supports the integration of renewables and protects power line communication technologies. The 2025 blackout on the Iberian Peninsula underlined the urgent need for precise methods to characterise grid performance.
Across all of these, the common requirement is the same: traceable, accurate and reliable impedance measurements over an extended frequency range.
Discover the consortium
Eighteen national metrology institutes, universities and companies from across Europe bring world-leading expertise to AIM-EF.