CIPM MRA COMPARISON REPORTS

The ongoing on-site comparison BIPM.EM-K12 is part of the BIPM program implemented to verify the international coherence of the primary resistance standards. It allows National Metrology Institutes (NMIs) to validate their implementations of the Quantum Hall Effect (QHE) for dc resistance traceability by comparison to the reference maintained at the BIPM.

The realization of the ohm from the QHE-based standard of the NMIs at 100 Ω is compared with that realized by the BIPM from its own transportable quantum Hall resistance standard (QHRS). This comparison is usually completed by scaling measurements from 100 Ω to 1 Ω and 10 kΩ through the measurement of the resistance ratios 100 Ω/1 Ω and 10 kΩ/100 Ω, respectively.

In November 2025, a new BIPM.EM-K12 on-site comparison was carried out at the Centro Español de Metrología (CEM). It was the first time the CEM participated in this comparison program.

Measurements of the 100 Ω transfer standard in terms of the ohm realized from the QHE-based standards of the CEM and the BIPM agreed to 3.4 parts in 10⁹ with a relative combined standard uncertainty U_c = 3.6 × 10⁻⁹. Measurements of 10 kΩ/100 Ω and 100 Ω/1 Ω ratios agreed to −2.0 parts in 10⁹ with U_c = 3.1 × 10⁻⁹ and to −4.7 parts in 10⁹ with U_c = 4.7 × 10⁻⁹, respectively.

Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.

The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).