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Summary

Resistance standards traceable to NIST provide references for measurements of current at levels from 3000 A to below 20 fA and are used to support a wide variety of impedance, temperature, strain, and power measurements. This project develops the technology of quantum electrical measurements including the world's best high resistance standards and superconducting quantum interference device (SQUID) based scaling techniques. We have maintained close working relationships with researchers in other leading national institutes and successfully completed bilateral and key comparisons with the Bureau International des Poids et Measures (BIPM) and other National Metrology Institutes (NMI), serving as the pilot laboratory for several of these comparisons. This leadership has resulted in collaborative research on cryogenic current comparators (CCCs) and improved resistance standards, development of low current and high current measurement techniques for reduced uncertainty of measurements based on resistance metrology, and staff being called upon to provide expert peer review of NMIs and evaluating other labs while performing resistance and current comparisons.

Description

metrology of the ohm team

Metrology of the Ohm staff and associates.  From left to right: Dean Jarrett, Shamith Payagala, Albert Rigosi, Mattias Kruskopf (Univ. of MD, JQI), Rand Elmquist, and Alireza Panna.

Credit: NIST

The Metrology of the Ohm Project has been a leader in providing internationally consistent resistance standards that are readily available to support the scientific and industrial foundations of the U.S. economy. Through this very broad customer base, the activities of the project enable cost-effective electrical measurements at NIST and at more than 250 U.S. sites, leading to improved performance of products and services in a competitive world environment. The resistance calibration service brings a yearly income to NIST of several hundred thousands of dollars as well as supporting over a dozen other calibration areas. Project staff provide extensive customer contact and consultation on topics including low current measurements (for photodetectors, aerosol electrometers, ionizing radiation measurements) the characterization processes used with resistive shunts at very high current levels, and power loading measurements. Project scientists work in the U.S. and international communities, including support for comparisons at low, moderate, and high resistance levels and development of improved standards and techniques for better agreement between primary references.

Graphene QHR Arrays
Graphene QHR Arrays: RK/26 ≈ 992.800287 Ω These arrays can be used at high currents, for room-temperature bridges and for development of the NIST electronic kilogram mass standard at other levels.

The project collaborates in research on low current measurements, ac impedance, and active participation with the Quantum Conductance project that aims to develop quantum Hall resistance (QHR) devices from graphene. We provide ongoing support for the electronic kilogram experiment as well as pursuing scientific breakthroughs to maintain accurate local representations of the unit (conventional standards) and to develop improved quantum metrology, such as the introduction of resistive-winding cryogenic current comparators (CCCs) that enable stable SQUID operation with improved current sensitivity.

Major Accomplishments

  • Graphene quantum Hall resistance implemented for dissemination of the ohm. Gold Medal received from the U.S. Department of Commerce in 2018 (along with the Quantum Conductance project) for this pioneering work.
  • Development of an innovative approach that links ionization chamber (IC) current measurements in radioactivity to the Quantum SI. Bronze Medal received from the U.S. Department of Commerce in 2020 (along with Radiation Physics and Nanoscale Device Characterization Divisions) for this innovative work.
  • Piloted SIM Key Comparisons at 1 Ω, 1 MΩ, and 1 GΩ; developed analysis to link SIM NMIs to the international community
  • Developed CCCs for scaling up to 1 GΩ with multiple links to the QHR standard; disseminating the measurement techniques to three other NMIs
  • Developed standard resistors, transfer standards, and bridges for scaling up to 100 TΩ.
  • Low current capability down to 20 fA traceable to quantum standards through high resistance and voltage.
  • High current measurement techniques for current range extenders and resistance standards from 1 A to 3000 A.

Recent Publications

Created November 21, 2008, Updated April 20, 2021